Hi all, I’m back once again with another post, however, this time I am going to dig a little deeper into the 1938 hurricane season as I have been observing some recent similarities to that year & I’ll offer some historical perspective on that year as well. I’ll also give an update on the tropics & how my current hurricane season predictions and analogs stack up thus far.
Look at the CMC ensemble 6-10 day 500 millibar height analogs from well over a week ago, notice years like 1979 (one of my hurricane season analog years), 2006, 1990, 1998, 1959, 1955, 2002 and 1994.
The GFS ensemble 6-10 day analogs shows many of the years the CMC ensemble shows, although there are a few different years like 1961, 1995, and 1989.
Now, interestingly, look at the hurricane seasons of those Julys being shown in the CMC & GFS ensembles like 2006, 2002, 1998, 1995, 1994, 1990, 1989, 1979, 1961, 1959, 1955, and 1954, and the vast majority of those years were quite active in July & many of them featured a long track Cape Verde storm in the month of July, much like what I have been predicting since June 20th.
Tropical Storm Barbara into the central Gulf
Tropical Storm Brenda, like Barbara in 1954, also goes into the central Gulf coast
Hurricane Cindy, which developed along a stalled frontal boundary under a classic trough splitting situation, where due to the abnormally small jet stream wavelengths, with the trough over the eastern US that was in place being as deep as it was, the shorter wavelengths eventually forced a piece of the trough to split off. In the wake of the trough, higher than normal pressures built in, and this region of high pressure to the north of the developing tropical system that would become Cindy prevented the storm from harmlessly escaping out to sea while at the same time with air spreading out from all directions under regions of high pressure, forced convergence directly to its south into this storm system. Along with the warm waters off the southeast coast from the Gulf stream this storm intensified into Hurricane Cindy and moved slowly westward under the rather strong subtropical ridge to its north, however, with the next oncoming trough, the storm was quickly swept out to sea. Unlike this year, this storm was rather beneficial to an ongoing drought in the Carolinas & other areas of the mid-Atlantic, but something that is very intriguing about Cindy is it seems to closely resemble Hurricane Gaston of 2004 (a hurricane season analog to this year).
Hurricane Cindy’s rainfall
Hurricane Gaston (2004)
Speaking of 2004, here’s a few infrared satellite loops of the 2004 hurricane season
Here are my hurricane season analog years of 1960, 1969, 1979, 2004, 2010, and 1996 storm tracks in the month of July. One thing to note is for the most part, the storms are relatively weak in nature, however, 1996’s hurricane Bertha is a clear exception being a category 3 hurricane at its peak intensity north of the eastern Greater Antilles. What you should also notice is there seems to be some sort of congregation of storm tracks around the northeastern Caribbean islands & of course also notice how there are absolutely no storms east of 70 degrees west, a testament to not only how climatology naturally favors the Azores-Bermuda high being farther to the south in July, which enhances the northeasterly trade winds that forces surface divergence that can severely disrupt surface circulations that are necessary to form & maintain a tropical cyclone. The strong northeasterly trade winds also drag in dry air & dust from the Sahara Desert which promotes subsidence & limits convection & thunderstorm activity that are the building blocks for tropical cyclones.
This is a combination of my hurricane analog years & the 500 millibar analogs in the GFS & Canadian ensembles. (included storms that formed in the first week of August as well to expand the timeframe being studied as well as use this extra data to offer further perspective on this July’s activity, & you should take note of the anomalous storm tracks of Hurricanes Connie & Diane, which were back to back hurricanes that hit North Carolina in August 1955, both storms officially formed before August 7th, thus their entire paths are shown in the picture below.)
You should notice in this picture above as well that there is a large congregation of storm tracks near and just to the northeast of the northern Leeward & Virgin Islands and Puerto Rico, which is the same area I put under the “Greatest Risk” in my hurricane season forecast map that was released in April.
The tracks of these storms abnormally far to the west is also at testament to how generally favorable the pattern is in the Atlantic for landfalling tropical cyclones. Look at my hurricane analog years mean 500 millibar pattern for the month of July, notice the +NAO signature in place (I put that region in a box) with lower than normal pressures towards Iceland, higher than normal pressures towards the Azores. This +NAO forces the Azores-Bermuda high to be stronger than normal, and also because in the summer time with longer solar wavelengths, the jet stream wavelengths are very short and rather erratic in nature, this forces the associative pressure rises with a +NAO also farther to the north over the North Atlantic and when pressures are generally higher over the north Atlantic, this naturally will block the progression of tropical cyclones out to sea and this naturally raises the threat of tropical cyclone landfalls on the US coast.
You can see since May 1st, that the 500 millibar pattern has been rather persistent with blocking located generally near and to the east of Atlantic Canada, which is a very ominous position for a region of high pressure as it forces any storm in the southwestern Atlantic to turn northwest & perhaps even north, but it makes the turn out to sea to the northeast next to impossible, thus this significantly raises the threat level of tropical cyclone landfalls on the US coast as a result.
In fact, the 500 millibar pattern since July seems to resemble the track orientation of storms from 2004, with some early Cape Verde recurvatures, but for the vast majority of storms which got caught far enough to the west to go under the influence of the stronger than normal Bermuda high sitting off the US east coast.
This begs the question, can you look at May-July 500mb height anomalies to try and predict tropical cyclone landfalls on the US coast?
Well, let’s start with last year, & you can see this pattern already is much different than what has been observed this late spring & summer with plentiful amounts of blocking showing up near Greenland, helping to force a large trough over the central Atlantic that forced many storms out to sea, but we still had Sandy & Isaac, & Sandy’s track makes a little sense just by looking at this pressure pattern, with low pressure out to sea generally indicative of Sandy’s eastward movement out to sea, & the slightly enhanced ridge near the midwest & Great Lakes indicating that the eastern edge of that ridge may have been strong enough to catch the storm, overall looking at the May-July pressure pattern wasn’t a bad idea as many of the storms which made landfall on the US coast seemed to comply with the overall set-up. Also, the track of Alberto & Beryl makes sense as they became stuck underneath the stronger than normal high pressure near the Great Lakes, thus generally moving in a retrograde motion westward & then the troughiness over the Atlantic forced them to take relatively sharp turns northeastward out to sea.
You can even see how the overall track of 2012’s storms seemed to closely resemble this 500mb pattern in May-July with a large amount of storms over the NE Atlantic & towards the Azores where the core of the troughiness was located months before & during the early part of the hurricane season.
I think you get the general idea of what I’m trying to tell you here, with blocks of high pressure shown in shades of green, yellow, orange & red, with focuses of brighter colors within the overall band of high pressure indicative of locally stronger high pressure, & of course in shades of blue & purple, they’re indicative of troughs which tend to capture storms & send them along the journey poleward.
Here’s 2011, you can see there is a favorable landfall set-up with ridging over Atlantic Canada & into southeastern Canada, however, the ridge extends throughout much of eastern North America, acting as a barrier against storms & with the trough out in the central Atlantic & close to bermuda, one can see why so many storms recurved & why Bermuda was affected by several storms. Notice the trajectory of Irene up the eastern seaboard goes right in line with the shape of the ridging along the eastern seaboard & we had a few other developments in the Gulf which didn’t amount to a whole lot, including tropical storms Don & Lee.
Notice in the overall track of the storms in 2011,how many of them seem to go along with the 500mb May-July pattern with a vast number of storms curving out to sea in the central Atlantic close to Bermuda exactly where a trough of low pressure was located in the pre-season & first few months of the hurricane season.
The 2010 May-July 500mb pattern looked a little different than 2011 & 2012, although there was still a formidable amount of blocking towards the Greenland & Canadian Arctic, & in spite of the Bermuda high being stronger than normal across the subtropics, the trough that was centered towards Atlantic led to unfavorable landfall set-up for the US coast, as there was also a region of high pressure near the east coast that deflected storms away, including hurricane Earl & Igor, both of which interestingly went onto strike Atlantic Canada as category 1 hurricanes, thus the 2010 hurricane season was quite a memorable one in that region. Also note with the position of the region of high pressure near the east coast, this left an opening for activity to come into the Gulf, which was where the greatest US landfall impacts were felt in 2010.
Once again, you can see the hurricane tracks that season, with some suppressed thanks in part to the high over the Atlantic being further south than normal & other storms going out to sea as the region of high pressure was thinner than normal & with a trough near Atlantic Canada this allowed for an easy out-to-sea route for many systems.
2009 hurricane season, remember which had a -IOD that helped to give support to 2 major hurricane developments in the deep tropics despite it being an el nino, (Bill & Fred), & it’s something that hasn’t been observed since 2010. With the 500 mb pattern observed in 2009, if that season had not been an el nino year, with the blocking in Atlantic Canada such a pattern would have likely led to a dangerous hurricane landfall year on the US coast, thankfully only on significant storm even came close to threatening the US coast, Bill.
In 2008, the 500mb May-July pattern connection to US tropical cyclone landfalls doesn’t work at all, with troughiness showing up over much of the north Atlantic along with a -NAO suggesting an easy out to sea route for storms.
The 2008 hurricane season had other ideas than having storms turning out to sea, with a very active landfall hurricane landfall year observed, especially in the Gulf of Mexico with storms like Fay, Gustav, Hanna, & Ike.
I think 2008 requires a bit closer inspection that the other years, looking at the troughing pattern over the North Atlantic, you can see that between the abnormally strong low heights over the Great Lakes & another low pressure center towards Iceland, there is a noticeable break in the strength of the low pressures, which although would suggest stronger than normal troughiness given the low heights, it also implies that there would be some sort of transient high pressure feature in this area, & it’s this high pressure which helped to force systems like Hurricane Ike further to the south & east than they would have otherwise, In spite of this, it still looks as if the storms which did eventually enter the mid-latitudes, their curvatures into the mid-latitudes were rather sharp in nature which does comply with the 500 mb May-July 500mb height pattern.
2007 May-July 500 mb
I moved the analysis all the way down into the deep tropics for 2007 as we had 2 category 5 hurricanes, Dean & Felix which traversed the Caribbean under the influence of the stronger than normal Azores high. With a + tilted trough near the US eastern seaboard, thus suggested that there would be storm tracks generally paralleling the east coast in a northeasterly fashion, & with troughiness also extending back into the Gulf coast, this also helped to attract storms like Erin & Humberto.
The 2006 May-July 500 mb pattern looked very dangerous with lower than normal heights over the southeastern US surrounded by stronger than normal pressures over much of Canada & Atlantic Canada, a generally favorable landfall set-up for the US coast, however, given the record breaking season of 2005 before which likely worn out & used up much of the available fuel near the US coast, this was likely a contributing factor as to why 2006, although which was hyped up & for good reason, didn’t live up to the high standards it was given.
Some hurricane forecasts from 2006, which show that given the steering pattern set-up & the recent devastating 2005 hurricane season, there was plenty of good reason for why many were concerned 2006 would be a bad landfall set-up, but with limited fuel to support such a dangerous pattern, 2006 clearly under-performed.
Sometimes, seeing forecasts like this for 5 hurricane hits & actually going back and looking at how there weren’t any hurricane landfalls sometimes makes me laugh, how could forecasts like this be so inaccurate?
This chart helps to show the over-hyping of the hurricane forecasts that occurred preceding the 2006 hurricane season, with just about every major forecasting agency way too high in just about every department as far as tropical storms, hurricanes, & major hurricanes go
This picture below helps to explain the reason as to why the 2006 season under-performed, a few of which include but aren’t limited to an oncoming, relatively unexpected el nino, higher than normal wind shear as a result of the el nino, stronger westerlies over the North American continent which would help to steer many storms out to sea & the cool SST in place courtesy of the previously record-breaking 2005 hurricane season likely all contributed to the “bust” season of 2006.
The May-July 500mb pattern before the historic 2005 hurricane season showed an infamous blocking set-up over southern & Atlantic Canada usually associated with high hurricane landfall years on the US coast as the high pressure area blocks the natural northerly & northeasterly progression of tropical cyclones coming out of the tropics & forces pressures to fall directly to their south, enforcing convergence that favors tropical cyclone genesis & intensification. You should also notice looking at the pattern below the decent trough of low pressure that set-up over the central-eastern Gulf coast, exactly where the barrage of hurricanes & tropical cyclones struck that season, including Cindy, Dennis, Katrina, Rita, & Wilma. You should also see the trough out in the central Atlantic & not surprisingly if you compare to the actual tracks of the storms in the 2005 season, you’ll be able to see how closely this matches up with the pressure pattern in the pre-season & early parts of the hurricane season. Despite a record hurricane season in terms of numbers, damages, etc., there was a relative lack of tropical cyclones in the deep tropical Atlantic (south of 20 north, east of 60 west, generally east of the Lesser Antilles all the way to Africa, & this was detectable given the higher than normal pressures in this area of the tropics in the months preceding the “meat” of the hurricane season.
The 2005 hurricane season tracks show this close relationship to the May-July 500 mb pattern in the Atlantic to where many of the storms hit land & where many of them coalesced over the North Atlantic, with very few in the deep tropics corresponding to above normal pressures there.
The 2004 May-July 500mb pattern preceding that devastating hurricane season which demolished Florida looked like this, once again this correlation between storm tracks & the 500mb pattern in the months preceding the peak of the hurricane season works quite well.
2004 storm track comparison to the May-July 500mb pattern shows how great this works in predicting overall storm tracks and behaviors for a particular season
2003 May-July 500mb pattern
2003 storm tracks & representation of the May-July 500mb pattern
The 2002 500 mb pattern feature a stronger than normal & further south than normal Bermuda-Azores high which extended into North America, & with the high further south than normal, this kept the trade wind belt also further south than normal into the deep tropics, which essentially helped to promote surface divergence and dry saharan air that claimed numerous tropical waves that season, & for the most part, if any systems developed in the deep tropics, it was further to the west where the sea surface temperatures and Tropical Cyclone Heat Potential was much higher, & thanks also in part to the warm 400m temperatures near the US coast, this forced many systems to develop in close to the US coast, which raised the amount of storms that made landfall that year, most of which ended up in the Gulf because of the stronger than normal ridging off the southeast US coast & strong Bermuda high forcing many systems further south & west.
2002 storm tracks show the results of this 500mb pattern in May-July stronger than normal trade winds force very few storm formations in the deep tropical Atlantic, while the minor break in the ridging near the Gulf of Mexico, particularly towards Louisiana & Texas results in a significant amount of storm landfalls there, including Tropical Storms Bertha & Isidore, & of course hurricane Lili. Also, the erratic track of hurricane Kyle is somewhat explainable given it developed underneath a strong ridge of high pressure where steering currents are naturally weak. Whatever storm systems did form in the western Atlantic had trouble hitting the US due to the ridge of high pressure that spanned across much of the US, & with a trough in Atlantic Canada, forced many systems even that were near the east coast to go out to sea.
The 2001 May-July 500mb pattern is probably one of the best you could possibly ask for as far landfalling patterns on the US coast, high-latitude blocking over northern Canada & into the Greenland arctic leading to a -NAO along with a large trough in the northeastern Atlantic & weak Bermuda high allows for just about every storm system in the Atlantic, except for the systems that develop in the Gulf of Mexico to go out to sea & avoid the US coast.
2001 hurricane season tracks nicely reflect the May-July 500mb pattern before that season, a large trough in the NE Atlantic & weak Bermuda high allows for easy storm recurvatures & with a -NAO in plac with blocking over the Canadian Arctic, it’s generally not a favorable set-up for US landfalls, however, “homegrown” development in the Gulf or perhaps a late season system that develops in the western Caribbean, like Hurricane Michelle would be the only concerns.
2000 May-July 500mb heights show a relatively weak Azores-Bermuda displaced to the north with a trough in Atlantic Canada and a stronger than normal ridge over the Rockies, such a set-up allows for a relatively easy pattern for storm recurvatures. Also, the high displaced to the north forces the trade wind belt also to the north, allowing for lower pressures & cyclonic vorticity to be promoted in the deep tropical Atlantic, thus an overall favorable pattern for deep tropical activity in the Atlantic. In general, this pattern generally does not favor hurricane landfalls on the US coast, & that’s exactly what transpired in 2001.
The pattern at 500 mb, although slightly more favorable for tropical cyclone landfalls on the US, was generally not supportive with a “Texas Death Ridge” evident over the southern plains forcing some storms into central America & Mexico to the south, while keeping any storms that developed in the Gulf at bay from Texas. Also, the relatively weak high, displaced further north than normal allowed for easy storm recurvatures.
1999 May-July 500mb pattern, with overlaid US impacting storms & you can clearly see over Atlantic & southeastern Canada the very persistent high pressure zone that prevented storms that approached the eastern seaboard from turning out to sea, & with the region of high pressure in this location, it also helped to focus convergence in the southwest Atlantic that only helped to intensify storms like Dennis, Floyd, & Irene. The central Atlantic trough allowed for some early recurvatures, & with the focus of high pressure over southeastern Canada as opposed to Bermuda, it allowed for the trade winds to be relatively light in nature, & allowed for low pressures & latent heat to build over the deep tropical Atlantic, promoting an overall favorable environment for tropical cyclone genesis in the deep tropical Atlantic.
The storm tracks really do match up nicely once again with the 500mb pattern in May-July, the high over southeast Canada forcing storms into the eastern seaboard, a central Atlantic trough allowing for early recurves & even a stronger than normal trough in the Rockies helping to drag storms out of the western Gulf, like Bret northward into Texas.
1998 500mb pattern from May-July reveals a relatively nice pattern that would imply for few hurricane landfalls with the Gulf of Mexico experiencing higher than normal pressures as well as much of the deep tropical Atlantic except for the eastern Atlantic, & with a trough off the east coast & near normal heights in Atlantic Canada the pattern was generally slightly less conducive than normal for us landfalls, however that doesn’t mean storms couldn’t hit the US coastline, and there certainly were numerous systems which did so that hurricane season
What seems to be somewhat off when I looked at the 1998 hurricane season was that normally when you see ridging over much of the deep tropical Atlantic & even into the Gulf of Mexico, this would imply for lower than normal hurricane activity, however, this doesn’t appear to be the case for 1998. I think this is attributed to the fact that in 1997-98, we were still coming off of the strong el nino & the atmosphere does take time to respond to changing oceanic conditions, thus it does seem plausible as to why the deep tropical Atlantic still was facing higher than normal pressures given that when you have an el nino, this forces warmer water west of South America in the equatorial Pacific and focuses upward motion over there as well, causing air to effectively sink towards the Atlantic. However, by later in 1998 & especially towards 1999, this el nino was quickly waning & likely by the time the peak of the Atlantic hurricane season arrived, the pressures may have fallen some in relation to average, over the Atlantic to slightly enhance the overall environment comparatively speaking for later in the season. However, the effects of dry air in the Atlantic in the pre-season & early months of the hurricane season still took their tool as drier than normal air naturally begets cooler than normal temperatures at 400 millibars promoting cold air in the atmospheric column compared to normal as their is a definitive lack of latent heat release, which is unfavorable to tropical cyclone genesis. Also, the lack of storm activity would have promoted dry air which would have been a hinderance to tropical cyclones, overall, not a generally conducive nor completely unfavorable environment for tropical cyclones in the deep tropical Atlantic. However, once the Pacific did cool as the summer progressed & the fall approached, this began to focus upward motion away from the Pacific & at least induce more rising air to be focused over the Atlantic, which in combination with the higher than normal observed surface pressures in the Gulf of Mexico & surrounding areas leading to a piling up of air in the western Caribbean is a likely reason as to why we saw hurricane Mitch in October, which of course is among one of the strongest & deadliest Atlantic hurricanes on record.
1997 May-July 500 mb height anomalies probably one of the beast looking patterns you’ll ever see if you don’t like hurricane landfalls, lots of troughing all across the north Atlantic from North America to Europe meaning just about every storm is going to recurve & do so sharply because with el nino in the eastern Pacific, it forces the westerlies to be stronger & further south than normal in the Atlantic. This occurs because when you have the warmest waters over the eastern Pacific, this is where upward motion is going to be focused & thus with a mean mass of thunderstorm & convective activity going off there, considering that winds in the upper levels of the atmosphere in the tropics & mid-latitudes go westerly, while surface winds in the tropics generally are out of the east, convection located to the west of the Atlantic would enforce higher than normal shear, not to mention higher than normal pressures, all of which are detrimental to storm formation. That’s not to say though that storms will no form, as when you have this kind of pattern, you can get homegrown development & you always have to watch the Gulf of Mexico, where in this case any system would generally move northeastward into the mean trough over eastern North America, & this makes perfect sense after observing hurricane Danny threaten the eastern Gulf of Mexico.
1997 storm tracks & analysis.
1996 gets more interesting though, normally when I see a trough at 500mb over Atlantic Canada I can breathe a sigh of relief when it comes to the pattern, however, a few things do seem to offset this & this is why you should intend to look at the overall pattern as opposed to just one factor when trying to determine storm tracks based on the May-July 500mb. For one, this area of low pressure goes all the way into the Canadian & Greenland arctic, inducing a slightly +NAO, which normally is an indicator of a stronger than normal Azores-Bermuda high because the trough into that area forces the northern & northeastern sides of the high to flatten out, thus forcing the ridge to retreat & build southwestward into the subtropics & in towards the western Atlantic where its precarious position from this +NAO could lead to issues in landfalling storms. This does seem to be the case with 1996 as the slightly +NAO appears to override the Atlantic Canada trough, thus enforcing a region of stronger than normal pressures off the US eastern seaboard & into the north Atlantic, while also having a trough out in the eastern Atlantic allowing for some systems to take an early out-to-sea route into the north Atlantic. Although this region of high pressure isn’t too terribly strong it’s strong enough to the point to where it can attract systems that generally get a little ways west of Puerto Rico & steer then dangerously close to the US eastern seaboard. Also, the “Texas Death Ridge” was stronger than normal & as a result, many systems were kept at bay from the western Gulf of Mexico & with relative troughiness near the US eastern seaboard, this implied for storm tracks, if any in the Gulf of Mexico to be directed towards the eastern side of the Gulf.
The 1996 storm tracks line up quite nicely with the May-July 500mb pattern with many Cape verde systems initially being drawn slightly towards the north by the eastern Atlantic trough, which also reduced the trade winds in this area & allowed for air to pile up in the lower levels, allowing it to rise & leading to thus an overall favorable environment for eastern Atlantic tropical cyclones. Also, with a stronger Bermuda high & a strong Texas ridge, this forced a break in the two highs near the eastern seaboard, which is where many of the storms that season ended up going as they were able to “feel” the Atlantic Canada trough to the north
The last May-July 500mb pattern I’ll look at for this analysis considering that is was the first year in the overall warm AMO multi-decadal phase where the behavior of Atlantic tropical cyclones are most similar. It is also well within the reliable satellite record that began in the mid-late 1970s, & if I had continued this study before the satellite record, slightly less reliable & inaccurate observation of the atmosphere as well as accounts of tropical cyclones were made, thus with those parameters considered, 1995 will be the last of the 500mb May-July analogs I will use.
1995 May-July 500mb pattern reveals a generally favorable pattern for recurving tropical cyclones, especially systems that form in the deep tropical Atlantic with a large trough centered over Atlantic Canada. What seems to grab my attention here in looking at this pattern is I seem to notice that there is a large region of troughiness extending through much of the mid-latitudes that tends to favor recurving storms. Remember back in my previous post how I talked about 1997 in that the troughiness, which compared to 1995 isn’t as strong still reveals relatively powerful westerlies in much of the Atlantic that can be thanked in part by the Pacific Ocean being in its warm cycle. However, in the case of 1995, the Pacific enters it’s cool state while the Atlantic is cool, in a general sense the overall warm PDO still favors stronger westerlies in the Atlantic as convection from the eastern equatorial regions helps to enhance that region’s upper level divergence, that only forces stronger westerly winds especially aloft. If the Atlantic was colder than normal overall, it would usually force sinking motion over the Atlantic & even if the Pacific briefly cooled into a la nina state. Thus, when the Atlantic is generally cold while the Pacific is warm, you tend to get this kind of pattern. Notice the lower than normal pressures over Greenland down into Atlantic Canada, indicative of an overall +NAO. Such a set-up is generally caused by the Pacific being warmer & with the Atlantic in its cold cycle, forces the mid-latitude westerlies to be stronger in the Atlantic and when the westerlies are stronger than normal, this forces cold air to bundle over the arctic, inducing low pressure, particularly near Greenland & Iceland that leads to +NAOs.
Look what happened when the Atlantic ocean warmed in 1995, the pressures rose over Greenland because of the reduced influence of the westerlies from the Pacific, with slower westerlies, the pressure gradient was effectively reduced over the Atlantic, & high-latitude arctic blocking began to take over near Greenland, which also effectively lead to decreasing arctic sea ice.
This effect of increasing arctic blocking was further enhanced when the Pacific went into its cold mode in 2007 & most of the years since then have had a large amount of arctic blocking
With this considered here are the 500mb heights for May-July 1995, and you can see that although there was a flip in the AMO into its warm cycle at this time, there was an abnormally strong trough of low pressure near Atlantic Canada which favored many storms which developed in the deep tropical Atlantic to turn out to sea & you can also see the stronger than normal heights over Greenland & Iceland indicative of a -NAO, which we’ve had for the last several years & is a good reason as to why the US coast has been lucky the last several years to avoid major & significant hurricane landfalls.
The storm tracks for 1995 match up very well with the 500mb May-July pattern with a band of storms recurving out to sea thanks to the trough in Atlantic Canada providing a substantial weakness to allow tropical cyclones to go on their naturally progression up into the mid-high latitudes & other storms hitting the southeastern US, mainly from close-in formations such as Hurricane Erin in the Bahamas & hurricane Opal in the extreme southern Gulf of Mexico in October 1995.
Now, what does this year’s May-July 500mb pattern tell us about he this year’s upcoming hurricane tracks & potential areas which may be at risk? Well, this year’s May-July pattern so far, (it’s pretty much set in stone at this point with just a few days left to be analyzed by NOAA ESRL), has been one that when you compare to these other patterns above, it looks extremely dangerous. For one, the very strong blocking which extends from southeastern Canada to Europe is something that has not been seen in any of the hurricane season patterns since 1995, in fact this kind of blocking is very concerning not only for how strong it is but how just a large area it covers, with no significant troughs or weaknesses evident in ANY region of the Atlantic. This should be an automatic red flag that this hurricane season is going to be one where we witness very few & far in between recurving storms, if any at all. Also, given the very strong start to the hurricane season with 4 named storms observed so far, 2 of them developing in the eastern Atlantic before August, a feat that only a handful of hurricane seasons since 1950 have been able to accomplish. Now, you can also see the troughiness that has set up near the central Gulf coast, which tells me already that there is a weakness in this area of the Atlantic & we are likely to see some tropical system which comes through the Caribbean & head straight into this region, much like my analog hurricane seasons’ storms like Hurricane Frederic, Camille, and Ivan, which are some of the most historic storms on record to strike the central Gulf coast areas of eastern-central Louisiana, Mississippi & Alabama. As far as the eastern seaboard goes, this looks like a very destructive year, I’ll provide more evidence to support this, but times in which you see considerable blocking over the Canadian Maritimes are usually seasons where the east coast, in particular the northeastern US & New England face hurricane strikes. Considering we are also in a period of warm AMO, cold PDO like the 1890s & 1950s when east coast hurricanes were running rampant, this year shouldn’t be much different from those seasons. Here is the May-July pattern this year so you can see for yourself just how dangerous this pattern really is.
Now, looking into some of the most recent dangerous hurricane hit years on the US coast like 2004, 2005, & 2008, we share an interesting similarity to those years in that we have a considerable block of high pressure situated over New England & into the Canadian Maritimes, a signature in July 500mb patterns that seems to preclude significant hurricane landfall seasons.
2004’s July 1-27 500mb pattern, note the stronger than normal pressures (shown in green, yellow, & orange) over the Canadian Maritimes.
2004 of course is one of my hurricane season analogs that I’ve had since March and that was a devastating hurricane season on the US coast with hurricanes Charley, Frances, Ivan, & Jeanne absolutely wrecking Florida.
The 2005 hurricane season July 1-27 500mb pattern, you can see once again there is a lot of blocking over Atlantic Canada & the Maritimes, much like the devastating 2004 hurricane season before it. Many of us also vividly remember what happened in the 2005 hurricane season, with major hurricanes Dennis, Katrina, Rita, & Wilma causing havoc & devastation on the US coast.
The 2008 hurricane season isn’t one of my analogs, but it sure was probably one of the last really destructive seasons on the US coast, which shouldn’t take away from hurricanes Irene & Sandy as they were deadly in their own right, but as far as the overall pattern goes 2008 was really the last time the US coast was under siege by tropical cyclones. Looking at that pattern, it’s no surprise to see that much like the 2004 & 2005 seasons, there’s a lot of blocking over Atlantic & Maritime Canada and near New England.
Compare those patterns to this year & you can see the striking similarities this year shares with the large amount of blocking near Atlantic Canada & New England in July.
You can can clearly see that this season is much like those devastating hurricane seasons of 2004, 2005, & 2008 in that we share the commonality of blocking near New England & Atlantic Canada. Take another look at this 500mb May-July pattern so far this year, notice the corridor of storm tracks near the eastern seaboard & the “greatest risk” zone that I put out for the central Gulf coast, which is completely in line with my official hurricane season map I put out in April based on ideas I had set out back in March.
My hurricane season forecast, I’m amazed at this point just how close my hurricane season forecast lines up with the current pattern, quite amazing, with the focus of hurricane tracks into the central Gulf coast analogous to the trough over that area & the “greatest risk” region near the NE Caribbean where the rebuilding Atlantic ridge to the north forces storm systems farther to the west & closer to Hispaniola & Puerto Rico.
Now, If there was ever a year in which Georgia & northern Florida were to face a significant hurricane landfall, this season could be it. Taking into account how we can correctly use the May-July 500mb pattern to give us an idea where & exactly how storms may track. Now, looking at the most available version of the NOAA ESRL 500mb height anomalies upon me writing this part of the post (through July 29th), you should notice the very large & expansive high pressure area from Canada to Europe, which will put a very big limit on “fish” storms this upcoming season & thus we should already know that storms are going to be very hard pressed to go out to sea this year & are much more likely to hit landmasses farther west, like the US coastline. In fact, if you look at the storm tracks thus far this season, you can start to get the idea that by looking at Chantal & Dorian that storms will be less inclined to move northward & safely out to sea until they get very close to the US coast or Caribbean, which by then, it’s generally too late for the system to avoid land.
2013 hurricane season so far
The aspect about our current May-July 500mb pattern that seems to grab my attention the most is the upper level low pressure feature near the northern Gulf coast states with a strong high to the northeast near Atlantic Canada & New England creating a west-northwest, to northwest alleyway for storms to come into the eastern seaboard & southeastern US.
Now, where I have seen this pattern before? Hurricane Hugo in 1989, check out that system’s 500mb pattern & you can see a fairly similar pattern, although the pressure gradient is in an orientation that implies for a storm to go more northwestward in nature, as opposed to this year where the ULL axis is orientated more east-west, implying for potentially a track that could bring this more westward in track than Hugo.
Hurricane Hugo 500mb pattern several days preceding landfall
For comparison, here’s the pattern of Hurricane Isabel, which like hurricane Hugo, took an anomalous track to the NW at the end of its journey into the US coastline, however, in this case, with the mean ULL & associative trough axis centered over the Ohio Valley instead of near the Gulf coast states, Hurricane Isabel’s track would be further to the north, closer to the mid-atlantic.
Another good example of an anomalous northwest track into the coast is the 1933 Chesapeake-Potomac hurricane.
In fact, this 1933 Chesapeake-Potomac hurricane became a category 4 hurricane before weakening to a category 1 at landfall in Virginia, & it produced a wind gust at Cape henry near 82 mph, with storm surge nearing up to 6-9 feet on the area in the right front quadrant of the storm. a storm surge of over 11 FEET IN WASHINGTON DC on the Potomac River, which flooded numerous cars on the Washington DC-Baltimore road when the little Patuxent River overflowed it’s banks. An even more significant, 12-foot storm surge was observed in Alexandria, VA, that helped to put the Washington-Richmond roadway (known as US highway 1 today) completely unbelievable.
This is what it looked like in Norfolk on Granby Street on August 23, 1933 following the 1933 Chesapeake-Potomac Hurricane, completely flooded much of the city with several feet of standing water left in the aftermath.
This hurricane absolutely drenched the mid-atlantic & Delmarva peninsula area including cities like Philadelphia, Atlantic City, Baltimore, Washington DC, Dover, & Norfolk.
WIth the way the 500mb pattern is shaping up, there is concern from me that a storm may hit the east coast from the southeast, which is much more dangerous than a storm that takes the classic “C” curve up the eastern seaboard because for one, the system coming in from the southeast comes in more perpendicular to the coast & has more potential to drive a much larger storm surge onto the shoreline & up into water bodies like the Chesapeake Bay, somewhat reminiscent of what we observed with hurricane Sandy when it came in perpendicular to the coast in central NJ. Also, a storm that comes in more perpendicular to the coast generally has less time to weaken than a storm that rides the coast, because they don’t have to deal with the increasing frictional effects of land & plus have a much more limited amount of time to suck in dry air of the continent into their circulations & enforce weakening. Another thing that will obviously play a big role than just steering for such a storm, just look at the water temperature anomalies off the northeastern US coast, & even though they usually are cool thanks to the Labrador current and are considered detrimental to hurricane intensity, this year, thanks in part to the very persistent Bermuda high feature allowing for higher than normal pressures in these areas that promotes generally more incoming solar radiation, the southwesterly flow on the eastern edge of the high has allowed for large scale downwelling to occur along much of the northeastern US coast, which has forced water temperatures well into the upper 70s to near 80, which compared to normal conditions where waters are in the mid to even low 70s, these warmer waters will make it naturally even more difficult for a potential hurricane to weaken on its way to this region.
Atlantic SST anomalies
You can see the 26 degree centigrade line (in yellow) generally showing the 80 degree F line is very far to the north this year, much closer to the northeastern US coastline, giving hurricanes generally less time to weaken over the cooler waters near the coast.
My official hurricane landfall risk forecast for the US, the reason why this wan’t released earlier was because I didn’t have the May-July 500mb pattern available for reliable guidance to which areas seemed more at risk this year than others. Notice this forecast, unlike so many others which I’ll show below, boldly puts the coast of northern Florida & Georgia under the “greatest risk” this year for a hurricane landfall, of course these areas have been relatively unscathed over the last several decades & their most significant hurricanes haven’t occurred since the 19th century, but that could all change this season. Given the AMO/PDO cycle relationship, ULL pattern, the fact that this area hasn’t seen a devastating hurricane in a long period of time, & the similarities to the 1890s US landfall pattern in which although the east coast was the prime target like in the 1950s, the Gulf Coast didn’t get left out of the action & I expect that to be the case this season.
My landfall forecast
28storms.com landfall risk
A forecast from one of my earlier posts
Hurricane Alley landfall predictions
Dale Link’s hurricane landfall forecast, I strongly agree with this forecast, think he has the general ideas right.
Already, we’ve observed storms in my “greatest risk” areas in my official hurricane season prediction, including Andrea near the “greatest risk” area in the central-eastern Gulf of Mexico.
Tropical Storm Andrea
Chantal & Dorian near the NE Caribbean islands.
Tropical Storm Chantal
Tropical Storm Dorian
Now, I’m going to add this information to further support my landfall forecast for the US eastern seaboard in giving that area a relatively high risk of landfall this year from SW Florida to Long Island. I have noticed that going back into the hurricane record, hurricane landfalls on the eastern seaboard tend to come in what we call a “series”, or a general 3-6 year period in which hurricane landfalls on the east coast are favored, with definitive break periods in between each series.
Starting back since the beginning of the official hurricane record from 1851, & some of the data in the 1800s may not be as conclusive, thus although this correlation in east coast hurricanes & their associative “series” may not be noticeable here in the beginning, that may be due to relatively inconclusive data & a lack of reliable records of hurricanes.
1854 hurricane three
1857 Hurricane Two
1858 hurricane three
1861 hurricane five
1861 hurricane eight
1865 hurricane seven
The first real definitive “series” doesn’t develop until 1867 & lasts until 1872, with a break year of 1868 observed, which is quite common in an east coast hurricane “series”
1867 hurricane one
1869 hurricane nine
1869 hurricane 10
1870 hurricane 6
1871 hurricane three
1871 hurricane four
1872 hurricane five
1874 hurricane 6
Another “series” is evident from 1876 to 1881
1876 hurricane 2
1876 hurricane five
1878 hurricane five
1878 hurricane 11
1879 hurricane 2, or also known as the “Great Beaufort Hurricane”
1880 hurricane 4
1880 hurricane 6
1881 hurricane 5
1881 hurricane 6
1883 hurricane three
1885 hurricane two
1885 hurricane 4
1888 hurricane three
1888 hurricane six
Another “series” started in 1891, with a break year of 1892, that was later followed by the very historic 1893 hurricane season, which for its time, was the deadliest hurricane season on record with 3 significant hurricane strikes on the US eastern seaboard. This series of hurricanes on the eastern seaboard lasted until 1894.
1891 hurricane three
1893 NY hurricane “midnight hurricane”, one of only two hurricanes, the other being the 1821 Norfolk hurricane to pass directly over downtown NYC & Manhattan.
1893 Sea Islands hurricane
1893 Charleston hurricane
1894 hurricane 4
1894 hurricane 5
The next “series” of hurricanes began in 1896 & ended in 1899, with storms like the San Ciriaco hurricane, that holds the record for an individual storm for producing the most ACE (Accumulated Cyclone Energy) in the Atlantic basin.
1896 hurricane 2
1896 hurricane 4
1898 hurricane two
1898 Georgia hurricane
1899 San Ciriaco hurricane
1899 hurricane nine
Another “series” began in 1901 & was finished in 1904.
1901 hurricane three
1903 hurricane three
1903 NJ hurricane
1904 hurricane 2
After 1905 being inactive, hurricanes once again returned to the east coast in 1906, with a break year of 1907, before the series of hurricanes lasted 2 more seasons to 1909.
1906 hurricane two
1906 hurricane five
hurricane 8 1906
1908 hurricane 2
1908 hurricane 3
1909 hurricane 11
In the early half of the 1910s, thanks to the AMO dipping well into its cold state, hurricane “series” on the east coast became very ill-defined, which makes sense anyway given that for one, the Atlantic Ocean is the smallest on the globe with the lowest energy budget & is thus, especially in its cold cycle at the mercy of the mighty Pacific, when the Atlantic is in its warm mode, it still can be a struggle, however, the Atlantic can somewhat overcome the adverse effects of a warm Pacific.
1911 hurricane three
1913 hurricane 4
1913 hurricane 5
In 1915 another “series” of hurricanes on the east coast started which lasted until 1920, with a break year in 1917.
1915 hurricane one
1916 hurricane 3
1916 hurricane four
1918 hurricane 3
1919 Bahamas-Gulf hurricane
1920 hurricane three
A new “series” of east coast hurricanes began in 1926 & ended in 1930
Hurricane one 1926
1926 Great Miami hurricane
1926 hurricane ten
1928 hurricane one
1928 Lake Okeechobee hurricane
1929 hurricane two
1930 hurricane 2
After a few year’s break, east coast hurricanes came roaring back to life in a big way in the 1933 hurricane season & this “series” of hurricanes on the east coast went out in fury & violence with the 1935 Labor Day hurricane.
1933 hurricane 5
1933 Chesapeake-Potomac hurricane, the storm which drove an absolutely unbelievable 11-12 foot storm surge up the Potomac river into the Washington DC metro area.
1933 hurricane 11
1933 Outer Banks hurricane
1934 hurricane seven took a track that seems very reminiscent of hurricane Bob in 1991.
1935 Labor Day hurricane, no explanation can really describe the magnitude of this storm, pressure near 900mb, 200 MPH winds, gusts up to 230 MPH, & the fact that the weather bureau let this one slip from their grasp and many citizens had no idea the storm was coming (likely because the hurricane itself was probably what we call a “vortcane”, just a hurricane, many times which are very powerful, however a generally much smaller than a typical hurricane, instead of being hundreds of miles across, this one may have been 100-150 at best. This storm being a vortcane in would help to explain its rather rapid intensification as smaller system tends to take better advantage of its environment & with the surrounding landmass of Cuba known to force dry air entrainments into larger hurricanes, smaller systems like 1935 Labor Day would likely be less susceptible to dry air. Dr. Steve Lyons of the Weather Channel helps to better explain these phenomena, the term “vortcane” was one he coined & one I have learned over the years.
1935 hurricane seven
The next “series” began in 1938 with the very historic Long Island Express “Great New England hurricane” & ended in 1941.
1939 hurricane 2
1940 hurricane 3
1941 hurricane five
1944 hurricane three
1944 Great Atlantic Hurricane
That hurricane severely damaged the east coast, this is what was left of Cape May, NJ after the storm, very devastating, especially considering they were on the weaker western eyewall of the storm. In fact, at Cape Henry, VA a wind gust of 156 MPH was recorded out of the north, meaning that this wind was on the weak side of the hurricane & winds may have been even stronger on the eastern side, which suggests this storm may have still been a category 4, possibly even category 5 hurricane while passing Virginia, absolutely unbelievable as very few storms can maintain that kind of strength so far north. Cape Henry at Virginia Beach during the Great Atlantic Hurricane of 1944 recorded a sustained wind speed of 134 MPH, an all-time Virginia state record that still stands today. Just remember, this was on the western (weaker) side of the storm, just imagine what winds were like on the east side of the hurricane.
Seaside heights, NJ after the Great Atlantic hurricane of 1944, as you can see left severely damaged with a house completely flipped over in the distance.
Here’s what was left of the Atlantic City boardwalk in Atlantic City, NJ, absolutely nothing, the debris of what was left of what was once a very nice & thriving boardwalk were pushed all the way back to Baltic Avenue (you would probably know the magnitude of that if you’ve ever played Monopoly.)
Despite this storm moving very fast to the northeast, it produced still very heavy rain amounts, with a bullseye of over 10 inches of rain in Newark, NJ, NYC, & New Haven, CT, likely leading to flooding in many of the surrounding areas.
Hurricane hunters investigating the storm reported sustained winds of 140 mph, & the turbulence of the storm was so great that the plane was losing control & it was feared the plane would be completely ripped apart, when the hurricane hunters returned to their base, 150 rivets were found on one wing of the plane alone, amazing. NYC reported sustained winds at 81 MPH with gusts of about 100 MPH in the downtown area. The minimum barometric pressure measured at Cape Hatteras, NC of 947 mb, just for comparison is just 7mb higher than what the maximum intensity of hurricane Sandy was last year at 940mb, & also remember, like much of the east coast, Cape Hatteras was on the weaker side of the storm, so the storm was likely to be even stronger than that further east offshore.
This already devastating hurricane “series” started in 1944 continued in the years following up until 1950.
1945 hurricane one
1947 Ft. Lauderdale hurricane, the first official category 5 hurricane since the 1938 Long Island Express 9 years earlier.
1947 hurricane eight
1948 hurricane seven
1948 hurricane eight
1949 Florida hurricane
1950 hurricane King
Then, another “series” of east coast hurricanes began in 1952 with hurricane Able into SC, similar track overall to the Sea Islands hurricane in 1893.
1953 Hurricane Barbara
1953’s hurricane Carol, struck near Eastport, ME as a category 1 storm.
The 1954 & 1955 hurricane seasons both featured a trio of trouble on the east coast with Carol, Edna, & Hazel in 1954 then Connie, Diane, & Ione in 1955 into NC.
1954 hurricane season
1955 hurricane season
That hurricane series from 1952-55 came to a halt in 1956 & 1957, then a new “series” of storms came starting in 1958 & lasting into the early 1960s.
1958’s hurricane Helene, a particularly intense storm near the NC coast, likely a category 4 storm on its closest approach to southeastern NC.
hurricane Cindy 1959
1959 Hurricane Gracie
Hurricane Donna 1960, the only hurricane in known history to produce hurricane force winds in EVERY state along the eastern seaboard.
Hurricane Esther got within miles of the southern New England coast as a major hurricane in 1961
1962’s hurricane Alma got within miles of the NC Outer Banks as a strengthening minimal hurricane.
Another “series” of hurricanes began in 1964 that lasted until 1966 after a brief hiatus in 1963, although hurricane Ginny in that season came very close on many occasions to hitting the east coast.
Hurricane Cleo 1964
Hurricane Dora 1964
1964 hurricane Isbell
1965 Hurricane Betsy
Hurricane Inez 1966
A new series of storms began in 1968 with hurricane Gladys getting extremely close to NC which lasted until 1971, by then the AMO had become deeply entrenched within its cold cycle.
1969’s Hurricane Gerda, hitting eastern Maine as a rare category 2 storm for that region.
1971’s Hurricane Ginger
Given the cold AMO, hurricane activity in the mid-late 1970s was very sporadic & not well organized, only hurricanes Belle & David made landfall
1976 hurricane Belle
1979 Hurricane David
By the mid 1980s, another “series” of hurricanes began in 1984 with hurricane Diana off NC & ended in 1987 with Floyd.
1984’s hurricane Diana
1985 hurricane Bob
1985’s Hurricane Gloria gave NYC & the surrounding areas quite a scare & was a very close call, could have been much worse.
Hurricane Charley 1986
1987’s hurricane Floyd
Another “series” began in 1989 with hurricane Hugo & lasted until 1992, ending with the devastating hurricane Andrew.
1989’s hurricane Hugo
This “series” of hurricanes took a break in 1990, then resumed in 1991.
1991 hurricane Bob
1992’s hurricane Andrew
Then, in 1993 hurricane Emily came close, but no cigar, the next “series” of storms that usually last 3-6 years, usually longer, more defined & stronger in warm AMOs began in 1995 with the start of the warm AMO.
1995’s hurricane Erin
Once a “series” of hurricanes gets going in the warm AMO cycle, its hard to stop it, 1996 proves why this is the case with hurricanes Bertha & Fran.
1996’s hurricane Bertha
1996’s hurricane Fran
1998’s hurricane Bonnie
1999’s hurricane Floyd
1999’s hurricane Irene
The next 3-6 year “series” of storms on the east coast began in 2003 with hurricane Isabel
2004’s hurricane Charley
2004’s hurricane Frances
2004’s hurricane Jeanne
This “series” of hurricanes came to an end with hurricanes Katrina & Ophelia on the southeast US coast
2005 hurricane Katrina, category 1 hurricane landfall in south Florida
2005’s hurricane Ophelia
Now, with hurricanes Irene & Sandy and considering that we are in the warm AMO cycle, it appears we are now within a new “series” of east coast hurricanes.
2011 hurricane Irene
2012 hurricane Sandy
With this information taken into account, if we are indeed in a 3-6 year “series” of hurricane landfalls on the US east coast, then if history serves us right, its almost a guarantee that a hurricane this year is going to strike somewhere on the US east coast from the Florida Keys to Maine. A few other things to consider as well is that in the warm AMO (Atlantic Meridional Oscillation), like what we’re currently in now….
AMO, as you can see with predominantly red since 1995, we are in the middle of the warm cycle now.
In all of the hurricane “series” since 1900, those that were in the warm AMO, ALL of them had at least one major hurricane of category 3 intensity or greater make landfall on the eastern seaboard, most had at least one category 4 hurricane make landfall on the US east coast. Now, think about this & consider that although you could possibly argue that Sandy & Irene were in their own rights, major hurricanes, they weren’t according to the Saffir-Simpson hurricane wind scale, they were both ONLY category 1 hurricanes. In fact, in ALL series, whether they be in the cold or warm cycle of the AMO have always featured at least one storm of category 2 intensity on the east coast of the US, we have yet to see that. Also, the last time we were in a similar pattern of AMO & PDO like what’s being observed now was in the 1950s, when the east coast experienced 8 major hurricane landfalls, we have none now. Don’t you think we’re going to catch up to that at some point. Well, the conditions at hand & history say we will, so for the eastern seaboard the next several years, as long as the AMO remains warm with a cold PDO, there will be a “minefield” of hurricane threats, once we see the Atlantic cool, the east coast hurricane hit pattern will grind to a halt & shift into the Gulf of Mexico like it did in the 1960s.
As if this evidence wasn’t enough for you, there’s even more. Looking at typhoon Soulik which made landfall in Taiwan as a typhoon last month.
Here’s radar out of Taiwan prior to Typhoon Soulik’s landfall, notice the double-eye wall structure of the storm, which is common for storms of this intensity that were once very organized, more compact & stronger systems, usually land interaction & dry air intrusions which disrupt but don’t completely destroy the inner core of these powerful cyclones, leave a remnant inner eye wall, which in the case of Soulik was hanging on by a thread, & eventually if this storm had not run into Taiwan, the inner eye wall would have completely collapsed from the subsidence being generated by the more dominant & large outer eye wall.
Even as Soulik was a powerful storm, you can see the northwest quadrant of the sorm appeared flat & the heaviest convection appeared weighted towards the south & east sides of the storm thus eventually when an eye-wall replacement cycle took place, this left the storm open to dry air intrusions into the circulation that would cause severe disruptions in its intensity.
I also looked into other seasons that had a landfalling typhoon in Taiwan in July & looked at those hurricane season’s mean 500mb steering pattern, this gave me 20 years to look at. It’s amazing to see that once again, this offers more evidence to support that a particularly dangerous hurricane season may be on the way with a considerable amount of blocking in southeastern Canada, Atlantic Canada & extending back all the way to the Azores. Also, notable in the pattern is the +NAO signature I’ve talked about which is dangerous for the US coast because of how the stronger than normal Icelandic-Greenland vortex associated with cold air bundling forces the jet upstream near SE Canada & over the extreme northern Atlantic to buckle, forcing a high pressure ridge to form in this area, & when you have high pressure in this area, it blocks the natural northeasterly progression of tropical cyclones into the mid-latitudes, especially storms which approach the SW Atlantic, which due to this strong high are forced further west & closer to landmasses like the United States.
500mb pattern following typhoon landfall in July in Taiwan for the peak of the Atlantic hurricane season.
Even recently, this ominous steering pattern shows virtually no signs of slowing down, and the last 10 days since the start of July, the 500 millibar pattern continues with abnormally strong blocking all across the north Atlantic from eastern North America to the west coast of Europe. The +NAO signature with lower than normal pressures over the Canadian & Greenland Arctic continues, denoted by the shades of blue & purple) & what does seem intriguing about this pattern is the cut-off low signature over the south-central US. This as well is not a good signature for hurricane season as any powerful tropical cyclones that happen to traverse the Caribbean sea, considering that these systems become strong & are thus more influenced by any weakness in the pattern to send them poleward are much more likely to impact the US, especially the Gulf coast with a trough of low pressure sitting over that region ready to direct any systems in the northwestern Caribbean or ones that may be nearing central America northward into the US coast.
Also, a weather headline that made news earlier this summer has been the abnormally strong Alaskan heat that has been occurring due to the rather unusual jet stream undulation, in fact, look a closer look at the overall jet stream pattern reveals this is in line with many of the connections & certain oscillations I have to big hurricane landfalling seasons on the US coast. Notice the large trough in eastern Asia, this helps to pick up any storms over the western Pacific and bring them near the east Asian coastline, setting up the east Asia, typhoon-eastern seaboard hurricane landfall connection. This pattern is set-up as a trough of low pressure near the east coast of Asia sets up, drawing storms from the deep tropics in the western Pacific poleward, helping to intensify a region of low pressure over extreme eastern Russia. This low pressure, thus in turn, much like a rock in a stream forces air flow to slow down as it approaches the anomalous region of low pressure, and as the air slows down it loses inertia. Thus with this loss in inertia, the air has a greater ability to change directions, thus a subsequent buckling of the jet stream is forced downstream of this low pressure area near Alaska. This high pressure ridge forces temperatures to warm underneath it over Alaska, helping to create the abnormally warm conditions currently being observed over this area. In response to the higher than normal pressures found over Alaska, a region of lower than normal pressures is forced towards the Canadian & Greenland Arctic, thus a +NAO is created. This +NAO signature helps to force the Azores-Bermuda high to strengthen & retreat northward because of the short jet stream wavelengths in the summer, forcing pressure falls or rises in a relative sense, much closer to the regions of anomalous low or high pressure as opposed to the winter, thus the Azores-Bermuda high is stronger than normal, but also located farther north than normal.
Remember in an earlier post back in May, I provided various reasons as to why the NAO would enter into its positive phase as we approached the summer, one of those being the solar cycle connection to the NAO in that years, like this one, in the extremities of the solar cycle, featured lower than normal pressures towards Iceland & Greenland, a signature of a +NAO.
Compare this to the highest hurricane landfalling years on the US coast, and you can see once again, the +NAO is evident, helping to force pressure rises towards Atlantic & southern Canada, which helped to lead to the rather large number of hurricane landfalls on the US coast in those hurricane seasons.
The NAO since mid April has been predominantly in its positive mode, verifying my predictions for a +NAO to develop.
Interestingly, if you look at my hurricane analog package you can clearly see that this also has the Alaskan heat
Hurricane analog years mean June Temperature in Alaska
Looking a little deeper into this pattern, I’ve recently noted a few similarities between this year & the 1893 hurricane season.
Looking into the tropics,
95L (which later became Tropical Storm Chantal) reminds me of Hurricane Ernesto last year & Dean in 2007 as it was a tropical wave over the east Atlantic.
Hurricane Dean (2007) videos showing it from formation to its death, & note how the appearance of that storm in its formative stages does resemble in some ways 95L, especially in how the storm has much of the convection associated with it towards the southern side of the circulation into the ITCZ, a statement to how unusually dry conditions are in the early half of the season in the eastern Atlantic due to large amounts of SAL (Saharan Air Layer- or “Saharan Dust”). However, the main difference in the case of Hurricane Dean & 95L is how as the summer progresses, due to the high heat content of the ocean relative to the land creating a rather slow response in heating, this means that even after the official summer solstice occurs in late June, the ITCZ continues to push northward, thus getting farther away from the equator, where now these systems may have an easier time spinning up as the Coriolis Effect is notably stronger, especially north of 10 degrees North latitude.
Looking at this objectively, I took a gander at CMC ensemble 8-10 day 500 mb analogs & was quite surprised to see these analogs popping up (the top 5) 2000-07-28 (July 28th), 2008-07-23 (July 23rd), 2007-07-24 (July 24th), 2005-07-11 (July 11th), & 1990-07-27 (July 27th). The analog in 2000 is just before Hurricane Alberto formed off west coast of Africa.
Hurricane Alberto 2000 near its peak intensity, this image from the Sea-viewing Wide-Field-of View Satellite
This image of Hurricane Alberto from NOAA HRPT
In 2008, the July 23rd analog in the 8-10 day CMC 500 mb height pattern was when TS Cristobal was moving away from US east coast.
Tropical Storm Cristobal radar animation from its berth of the US southeast coast to its death just to the south of Nova Scotia.
Tropical Storm Cristobal Satellite July 19th, 2008
TS Cristobal track
However, Hurricane Dolly, which was initially a tropical wave that entered the Caribbean several days earlier, however because of the general theory based on trade wind tendencies in which storms that don’t develop when they reach the Lesser Antilles won’t do so until they get into the western Caribbean, meant Dolly had to wait until she got past the longitude of Jamaica to develop, & this is exactly what transpired. This storm on July 23rd was nearing landfall on the coast of South Texas under a rebuilding ridge as a strengthening category 2 hurricane.
Hurricane Dolly radar animation shows the storm approaching Texas on July 23rd, most notably, the northeastern semi circle of the storm seems to completely fall apart, likely due to dry air intrusion from Texas, however, at the same time, much like Hurricane Gaston in 2004 & Hurricane Isaac last year among countless other storms, the interaction with land & the differences in the amount of friction from the land to water forced Dolly’s circulation to tighten up, thus the storm was allowed to intensify up to landfall.
Hurricane Dolly track
Seeing Hurricane Dolly’s northern & northeastern semi-cricle fall apart in terms of precipitation reminds me a lot of what happened to hurricane Katrina as it was passing over south Florida & due to a rebuilding ridge, this forced Dolly & Katrina to go on a more westerly to even west-southwesterly course. In response to the rising pressures to the north of both storms, this forced a lot of the precipitation & the rain bands to the north to weaken or even fall apart completely & interaction with land only further complicated matters.
Hurricane Katrina south Florida radar
Speaking of 2005, that analog being depicted in the CMC ensembles is quite notorious, it was when Hurricane Dennis was bombing out in the east Gulf into a category 4 monster, while being picked up by a trough of low pressure in E US & of course waiting in the wings was Hurricane Emily, & the wave that helped to form Emily led to its development developed on this day just east of the Antilles. (wasn’t a hurricane though, at least not yet).
Image of hurricane Dennis as it was making landfall on the Florida Panhandle in July 2005
This image of hurricane Dennis in 2005 reminds me of Hurricane Frederic, which also hit a similar region of the Gulf in 1979, and of course 1979 is also one of my analog years for this upcoming hurricane season.
Hurricane Frederic (1979)
Here’s an awesome video of radar loops of hurricane Frederic as it approached the coast of Alabama & Mississippi, note the eye wall structure looks as if there are two eccentric eye walls within the overall circulation, with the inner eye wall that was once associated with Frederic as it was a strong category 4 hurricane over the Gulf of Mexico to the new developing outer eye wall that is becoming dominant. This is fairly typical for weakening, but still strong tropical cyclones, as they tend to uncoil like a snake, thus as Frederic was seeming to undergo an eye wall replacement cycle that would eventually conclude in a larger but relatively weaker hurricane, however, Frederic did not have enough time to complete this process as it slammed into the northern Gulf coast.
Hurricane Dennis satellite near its peak intensity as a category 4 hurricane with winds of 150 MPH & a minimum central pressure of 930 millibar (a record for July for any storm in the Atlantic basin, of course this would be broken just days later by Hurricane Emily.)
One of my favorite hurricane videos, this one The Weather Channel’s coverage of hurricane Dennis and in this video you can see when they show the satellite loop of the storm how the eye of Dennis pops out of the central dense overcast (CDO) & this sudden intensification is likely due to a number of factors, one of the most obvious being the fact that it passed over the Gulf Loop current or perhaps even a gulf loop current eddy that broke off from the main flow that is usually present in the southern Gulf of Mexico.
This image below shows the Gulf loop current & eddies in a hypothetical situation, showing the possibility that hurricane Dennis may have encountered a Gulf loop current eddy, an isolated pocket of slightly warmer water & Tropical Cyclone Heat Potential values, which along with other favorable conditions at hand can lead to sudden intensification of tropical cyclones, which is exactly what was observed with hurricane Dennis & hurricanes Katrina & Rita that would follow the same season.
This picture helps to give further representation of the Gulf Loop Current & Eddies and the processes involved, which show that this loop current is much like a river on land in that the current, although trying to go into straight lines, can not do so to do obstacles involving landmasses & other topographic changes in the sea floor as well as even surface current changes that can be induced by changes in the local weather pattern. Thus, the loop current does not go in straight lines, rather has many twists and turns & especially over the Gulf of Mexico where the loop current occasionally will split off eddies, which are reminiscent of Oxbow lakes observed with rivers on land.
You can see the oxbow lake in the picture below evident by the “horseshoe” ring of water cut-off from the main river flow.
The processes involved to form an oxbow lake are fairly similar in some ways to that of the processes involved in the Gulf Loop Current & associative eddies.
However, it does appear that in the case of Dennis, a much more notable factor is a difference in wind shear in the vicinity of Dennis as a trough of low pressure is dragging the storm northward, & under this kind of set-up Dennis faced where higher in its path ahead of the storm, relative to the environment it was embedded in, this higher shear ahead of the cyclone promoted upper level divergence which is favorable for tropical cyclone formation as it allows for faster escape of air in the upper levels outwards, thus forcing more air to pile up at the surface, which promotes more surface convergence, a lowering of surface pressures & hence a stronger tropical cyclone.
Out of pure curiosity, I looked at other historic hurricanes in the Caribbean, & one storm in particular has caught my attention, Hurricane Allen of 1980. I looked into the 500 mb pattern for this storm’s formation & discovered just how similar this is to the current pattern over the Atlantic. The picture below is of Hurricane Allen’s 500 mb pattern at its formation, with a rather deep trough over the eastern Atlantic leaving a piece behind (remember this is reminiscent to what we observed early in July with the upper level low approaching the Bahamas) underneath a strong ridge over the western Atlantic & some weakness in this ridge & the other one located towards the Rockies & the Plains is also noticeable over the eastern US.
This sounds a lot like the current pattern set-up. Look at the picture below from CIMSS showing mean steering analysis, & its this analysis that can help to easily reveal the strength & location of ridges & troughs that are vital to the steering of tropical cyclones. In this picture, the large areas of spin going in clockwise motion are regions of high pressure, whereas the areas that go in counter-clockwise motion or are generally indicated by what appear to be large “U’s” are troughs of low pressure.
In this picture I overlayed the ridges & troughs so you could get a better idea of what I was talking about here & I want you to notice how similar this appears to the set-up in the formation of the infamous hurricane Allen in that there is a generally strong region of high pressure over the western Atlantic & in the eastern Atlantic with a positively tilted trough of low pressure (means a trough orientated southwest-northeast) in the central Atlantic which due to the short jet stream wavelengths in the summertime, it is forced to leave a piece of energy behind in the subtropics, which in this case is in the form of an upper level low.
You can see this upper level low over the Bahamas on the satellite imagery with some cyclonic spin noted & it’s producing a relatively small region of showers & thunderstorms to the north of the Greater Antilles.
Another look at this upper level low pressure system at the 200 millibar level (typically where upper level anticyclones & upper level low pressure systems are located just underneath the tropopause) shows a region of strong vorticity (in orange, red, & white) just to the north of Puerto Rico & Hispaniola, indicative of this upper level low pressure feature that was spawned by the positively titled trough over the central Atlantic.
What;s interesting about this particular upper level low in relation to Chantal is because of the strong high pressure system near the US east coast forcing the ULL to move rapidly to the east, this system is generally backing away from 95L in the central Atlantic & as a result, when you look at the shear tendencies map, much of the higher than normal wind shear in association with this upper level low is also moving away with it, leaving a relatively low shear environment with which Chantal can thrive in on its way to the Lesser Antilles.
What is important here though about backing upper level lows is that they provide a generally favorable environment with which tropical cyclones can thrive in but why is this the case? Well, an upper level low pressure system itself is a generally unfavorable set-up for a tropical cyclone that is near the relative location of the upper level low and the TUTT (Tropical Upper Tropospheric Trough) We can take for example, Hurricane Isabel in 2003 that faced features such as backing upper level lows.
Hurricane Isabel (2003)
I really like this picture, which shows the “pinwheel” like eye of hurricane Isabel, which implies that the intense circulation of the storm itself is not just one area of rotation, rather in this case, it’s multiple vortices & knowing the swirl ratio, which denotes that with increasing mass being forced around a given circulation, if that mass is too great to properly evacuate, the circulation will break-down into multiple vortices in order to compensate for this, thus when you see a hurricane showing signatures of multiple vortices rotating around each other near the eye, that should be a big red flag that intensification is likely occurring.
Track of hurricane Isabel from unisys, showing the storm from its berth to death, with a very unusual track to the northwest noted all the way to its landfall in the mid-atlantic after the storm attained category 5 status a third time east of the Bahamas (one of only a few storms, like Hurricane Allen (1980) to do so)
Such a track is very reminiscent of the infamous hurricane Hugo in 1989 that struck South Carolina as a category 4 hurricane, it too took a similar & very unusual northwest track inland into the US.
Hurricane Hugo (1989) track
The track also seems reminiscent of the 1933 Chesapeake-Potomac hurricane
Such a track is highly unusual for tropical cyclones leaving the tropical easterlies & entering into the mid-latitude westerlies, as there actually would be more of a tendency for such storms to turn northwest, but to keep turning, northward & eventually northeastward at some point, however, this was not the case with hurricanes Hugo & Isabel. If you look at the patterns of both storms as they are coming ashore, you can see that to the west-southwest of both storms there is an upper level low pressure system. Considering that both areas are regions of low pressure, despite one being lower level low pressure while another (the upper level low) is centered in the upper levels of the troposphere, the “fujiwhara” effect still applies here. The fujiwhara effect in of itself is an process that tries to offer an explanation for the interaction of two cyclones in close proximity of each other. The fujiwhara effect is essentially dictates that in the northern hemisphere, that two cyclones will rotate around each other in a counter-clockwise motion towards a common center (“barycentre) or ” the mean region of low pressure between the two systems.
Yet in the case of the interaction of an upper level and lower level low is much more complicated than that & rather than the lower level low rotating into the upper low, like a lower level cyclone would if it encountered another lower level cylone, it rotates around the upper low in a counter-clockwise fashion because the upper low naturally induces more in the way of sinking motion at the surface that leads to surface high pressure, this would naturally deflect the cyclone around it, thus in the case of Hurricanes Hugo & Isabel with the juxtaposition of an upper level low to their west-southwest, cyclonic flow generally around this upper low would force these storms to rotate generally in a northwest motion on the northeastern sides of the upper low.
This interaction between a tropical cyclone & an ULL in such a juxtaposition that forces the storm to go northwestward is demonstrated nicely in this archived satellite loop of hurricane Isabel.
Looking at the satellite presentation of Hurricane Isabel as it was over the open Atlantic on September 9th, 2003, just before its rapid intensification cycle into a category 5 hurricane within a few days, the appearance of the storm is one of a very powerful Cape Verde hurricane with a well-established inner core & outflow channels in many quadrants of the storm. However, the one thing that looks strange is how Isabel appears to be somewhat cut-off on the northwestern side of its circulation & this is due to wind shear coming out of an trough of low pressure located near Atlantic Canada with air flowing into an upper level low just to the west of Africa, thus cutting across the northwestern side of Isabel, & imparting unfavorable upper level winds. However, what you should notice in the satellite presentation is despite this storm encountering unfavorable wind shear to the northeast of the system, you should note the very expansive & well defined outflow to the southeast of the storm, indicative that upper level conditions ahead for this storm are going to be improving & that was certainly the case with Isabel.
I really like this video on the coverage of Hurricane Isabel, especially when Dr. Steve Lyons talks about why Hurricane Isabel became so strong north of the northeastern Caribbean, as it had two outflow channels to evacuate air in the upper levels of the atmosphere, one into a ridge of high pressure centered over the central Atlantic, and another into an upper level low directly to the south of this region of high pressure. Also, you should note he talks about a backing upper level low in the face of hurricane Isabel, & with an upper level low generally moving in tandem with the storm, this allowed for Hurricane Isabel to stay remarkably strong for an extended period of time as a strong category 4 or 5 hurricane.
Despite the storm also moving unusually slow to the north of the Caribbean, usually a good indication of a storm that would tend to turn out to sea as the slower movement of the tropical cyclone & with it being intense, Isabel would tend to be able to “feel” a weakness in the subtropical ridging & get steered harmlessly out to sea, that didn’t happen in this case, & a lot of this had to do with the very persistent area of high pressure over southeast Canada, which I’ve mentioned before as a signature of significant hurricane landfalls on the US coast.
Isabel by far though, is my favorite hurricane, especially in terms of looks, what an absolute buzzsaw. This storm was able to be so strong for such a long period of time also due to it being what we like to call an “annular” hurricane, which are storms that are very symmetric in nature with large eyes, they tend to have the looks of a buzzsaw, well those storms tend to change very little in intensity aren’t as easy to weaken & deteriorate compared to a hurricane of similar strength that has a different overall structure.
Looking at the satellite presentation of an earlier image of Chantal, it seems to look a lot like Tropical Storm Dolly in 2002. Note the convective banding features with both systems, the dry saharan air to the north & west of both systems indicated by the fair weather cumulus clouds & the most striking similarity would seem to be the band of clouds extending northeastward from both systems, acting as a boundary between the relative moist & “primed’ air left in the wake of both systems & the dry/stable air to the north & west. The main difference in this case is that Chantal is forming in the early stages of July, while Tropical Storm Dolly occurred near the peak of the hurricane season in late August & early September, which is a testament to hoe favorable the overall conditions at hand are this year for tropical development in the deep tropical Atlantic.
An earlier image of Chantal at 10 am Monday
Tropical Storm Dolly 2002
Tropical Storm Dolly’s track in 2002
Notice how Tropical Storm Dolly, although a fairly decent tropical cyclone over the central Atlantic faded away as it turned north into the heart of the North Atlantic. The picture I posted below is the mean 500 millibar height pattern into the demise of Tropical Storm Dolly in 2002, & one notable feature that has been fairly prevalent this year is the considerable blocking located near and just to the north of Atlantic Canada. However, there were a few reasons as to why this pattern was not as devastating as other hurricanes seasons that also featured a large amount of blocking into Atlantic Canada. One reason is the location of the blocking itself, you should notice how the high pressure area (shown in shades of green, yellows, & red (increasing strength with the warm colors mentioned) ) is centered somewhat farther to the north closer to the coast of Labrador & north of Newfoundland as opposed to being centered directly over these areas. What this does, is with the high pressure blocking located so far to the north, it allows mid-latitude troughing to build in underneath into the subtropics, which allows for an easy-out to sea route for many of the tropical cyclones in the 2002 season. Also, the ENSO index was weighted towards el nino in this year, which increased wind shear in the deep tropics. Also, 400 millibar temperatures (400mb level is important because as opposed to the 500 mb pattern which is used in the mid-latitudes, the 400mb level is used for the tropics because the tropopause layer is much higher in the tropics than in the mid-latitudes due to the increased spin of the earth at the equator compared to areas farther away fro the equator, leads to a higher tropopause level (the tropopause is the boundary between the lowest level of the atmosphere, the troposphere, to the stratosphere directly above it & it is here at the tropopause where upper level anticyclonic motion is induced over cyclones as air tends to spread out at this level because it can not go through into the lower stratosphere because the temperature gradient actually increases with height in the stratosphere, thus, once the warmer air reaches the boundary to the stratosphere, it can’t rise any further & must be forced to spread out, thus inducing high pressure in the upper levels of the troposphere, which helps to ventilate tropical cyclones.)
(400 mb temps) in the preseason leading up to the start of the 2002 hurricane season were colder than normal, which promotes drier than normal air in the deep tropics & severely hinders the latent heat release of associated with tropical cyclones, thus a cooler atmospheric column in the deep tropics isn’t favorable for tropical cyclone activity.
The 400 mb temps leading up to the 2002 hurricane season reveal in the deep tropical Atlantic, throughout the MDR (Main Development Region) temperatures were colder than normal, which naturally hinders tropical cyclone formation, but you should also notice that temperatures at this level were actually warmer than normal closer to the US coast, indicative that although storms would for the most part remains weak on their way westward, they would have a better opportunity to strengthen farther west, thus with such a set-up storms would naturally be much closer to landmasses farther west, increasing the threat of hurricane landfalls on the US that season.
You can see comparing to the 2002 hurricane season, that most of the storms were weighted close to the US coast, where 400 mb temps were warmest.
Here is a radar animation of Tropical Storm Chantal as it is passing through the Lesser Antilles, you can see clearly despite the rather ragged satellite presentation, Chantal has a surface circulation, albeit a very weak one at best. You can also see that most of the intense rain bands (in yellows, oranges, & reds) are to the north of the center of circulation , which is also where the air force hurricane hunters found most of Chantal’s strong winds, which makes sense as it was going along with strong easterly trade wind flow in the eastern & central Caribbean.
With such a strong trade wind flow in place in the eastern-central caribbean, it would make sense as to why Chantal struggled so much with keeping its surface circulation in tact, not to mention the fast forward speed of Chantal that was up to 30 MPH which enforced wind shear into the system as the storm is moving so quickly to the west, & given it being very weak already, this makes it that much more difficult for Chantal to organize as a storm that’s moving around 25-30 MPH to the west requires at least 25-30 MPH westerly winds on the southern side of the circulation to even have the circulation closed, & if this is not possible, then the storm would open up into a tropical wave. This is why storms that move very quickly like Chantal have a much more difficult time organizing, especially storms that are weak in nature, which makes their surface circulations very fragile & more susceptible to unfavorable conditions in their outside environment.
Take a look at the mean 500 mb height pattern over the eastern-central Caribbean as Chantal was passing through this area from July 9th-11th. Notice how (shown in reds, yellows, & greens) pressures are above normal just off the east coast, while a persistent trough is in place over the central Atlantic forcing lower than normal pressures (shown in blues & purple). In such a set-up, on the backside of a trough of low pressure & in front of a region of high pressure (considering that weather moves from west to east in the mid-latitudes), pressures are going to rise, & in this case that rising region of pressures are going to be directly to the north of the east-central Caribbean right where Chantal is going. These rising pressures against the relatively low pressures from the ITCZ & South American monsoon to the south of Chantal create a pressure gradient, & thus with a pressure gradient comes wind, which under a region of rising pressures to the north, only grows stronger, & this kind of set-up leads to increasing easterly trade winds in front of Chantal, which means that air is divergent at the surface in front of Chantal, & thus with divergence at the surface, this leads to increased pressures that doesn’t allow air to properly pile up into Chantal, thus the system is going to struggle immensely with trying to keep itself together & likely will not intensify significant, if at all, & this was exactly the case with this storm as it opened up into a tropical wave in the central Caribbean.
Tropical Storm Chantal
Now, don’t imply just from tropical storm Chantal that every storm that enters the eastern-central Caribbean is going to struggle with increasing trade winds, in fact there are many instances in which the trade wind flow is actually very conducive for tropical cyclone genesis in this region & actually supports intensification of systems. Storms that come to mind which developed in the eastern-central Caribbean “graveyard” and intensified were…
Hurricane Fifi (1974)
Hurricane Iris (2001)
Satellite of Hurricane Charley as it came inland in southwest Florida in August 2004
Hurricane Ernesto 2006
Hurricane Dennis (2005)
Hurricane Gustav (2008)
Very beautiful satellite loop of hurricane Gustav as it passed through the northwestern Caribbean & into western Cuba, notice how right before Gustav’s eye cleared out near the Isle of Youth, a large convective blow-up of thunderstorms occurred over the center, which means that as the storms went off near its center, they forced a significant drop in surface pressures which likely began a period of rapid deepening of the storm before it hit Cuba. You’ll also notice how this storm quickly weakens in satellite appearance in passing over western Cuba & even before it reaches the island, you should notice a warming of the cloud tops near its center, which indicate that the environment in which the storm is moving into isn’t as favorable for intensification and this can likely be attributed to the storm entering a region of relatively shallow warm water, that may have effectively worn off before the center of Gustav reached the area. Also, notice how the coldest ring of clouds near the center didn’t completely rap around the center just yet & there was a definitive break just to the NNW west of the center, which suggests that the eyewall of Gustave may have been open or at the very least much weaker on its northwest side, thus once the storm made landfall in Cuba it entrained dry air into the circulation which is struggled with during the rest of its life over the Gulf of Mexico, had Gustav not ingested this dry air, there would have likely been a much different outcome on the north-central gulf coast where the storm only made landfall as a category 2 hurricane. However, the overall environment for Gustave was favorable for strengthening with the classic spreading out of the clouds poleward of the center, perhaps suggesting that there may have been wind shear in front of the storm, but with higher wind shear values in front of the circulation, thankfully for Gustav, with it being so strong, much of the latent heat release from its thunderstorms would have significantly lessened the shear values for when the storm actually reached that area. In general, type of set-up allows for proper ventilation of the storm in the upper levels that helps to enforce convergence at the lower levels which is good for hurricane intensification.
Now, Chantal certainly isn’t the first victim to suffer the death from enhanced trade winds in the eastern central Caribbean, there are numerous storms in the past that have suffered a similar fate, of course many of these systems also managed to come back once the trade winds slackened over the western Caribbean, which in fact is just another reason along with the usual exceptionally high TCHP (Tropical Cyclone Heat Potential) values that are found here because of how water tends to be forced to into downwelling in this region, may be just another reason as to why this area of the tropical Atlantic is so favorable to tropical cyclone genesis. This is because as the trade winds slow because they are either forced to turn more to the northwest in this area because the southwest edge of the Bermuda high is found here, also, the “squeezing” of the trade winds between South America & the Greater Antilles also slows, & this forces air to pile up in this region, in which air is then forced upwards, leading to surface convergence that is extremely favorable to tropical cyclones.
Hurricane Ernesto last year is a good example of a weak storm which comes into the Caribbean, yet due to trade winds, opens up into a tropical wave, however, reintensifies once it reaches the much more favorable western Caribbean.
Picture of Tropical Storm Ernesto as it entered the eastern Caribbean, notice how weak looking & rather disorganized the storm was, with a large expanse of thunderstorms aligned in a north-northwest to south-southeast fashion, indicative of how poor the overall structure of the storm was, & this also suggests given the random convective nature of the storm & how spread out it was, that Ernesto may in fact open up into a tropical wave, & this did in fact occur for a brief period of time in the central Caribbean.
Look at how Tropical Storm Ernesto in the central Caribbean, seemed to develop a “tail-like feature” at the front end of the system, much like Chantal did as it neared the Lesser Antilles. Such a feature is not indicative that the storm is strengthening, rather, that kind of look is indicative that the storm is about to open up into a tropical wave as the surface circulation is struggling to hold together & focus surface pressures in one particular region, thus they become spread out over a large area, inducing a tail-like feature that is much more typical of tropical waves.
You can also see this tail-like feature with Chantal as it was approaching the Caribbean, here in this picture below I give a detailed description of Chantal & its surrounding environment
This tail-like feature was also evident in Tropical Storm Colin before it opened up into a tropical wave.
Tropical storm Colin’s track, notice how it dissipates right after the image above into a tropical wave.
Here are a few other good examples of systems with tail-like features, or spread out tropical wave like structures evident before dissipating.
2009’s Tropical Storm Ana
A picture of Ana near its peak intensity as a minimal tropical system, you can see in the image below the banding features on the eastern side of the convective mass indicative that the circulation is displaced somewhat from the mean thunderstorm activity, indicative of strong easterly trade winds which were impacting the system, & given its small size, & interestingly reminiscent appearance to Tropical Storm Chantal (2013) & Tropical Storm Dolly (2002), both of which later dissipated before becoming much of anything, would imply that Ana as well was doomed to dissipate, and that’s exactly what occurred as the east-central Caribbean “graveyard” claimed yet another victim.
Here’s a satellite image of the western & central Atlantic about the time Ana was approaching the Lesser Antilles, & although it may not be as evident in this picture below, you can see that Ana is embedded within an overall tropical-wave like structure with a large tail extending all the way to the north of the storm. You may also note the system in the bottom left corner of the picture, this would become the very powerful hurricane Bill within a few days as it passed north of the Lesser Antilles & northeastern Caribbean.
1994 Tropical Storm Debby, although which had 70 MPH winds, you can see just by looking at the satellite image below this storm is very disorganized, with a north-south orientation in the cluster of thunderstorms reminiscent of a tropical wave, & you can actually see what appears to be an exposed low-level center of circulation well to the west of these thunderstorms, indicating how unfavorable the environment is & that fast trade wind flow is a likely cause for this storm’s disorganization.
1994’s TS Debby track, like so many other systems, dissipates in the central caribbean”graveyard”
1993’s Tropical Storm Cindy, although running into Hispaniola was a likely cause for this system’s demise, you can see by looking at a satellite picture of the storm that it was struggling immensely with fast trade wind flow.
Tropical Storm Arthur (1990)
Notice how Arthur was almost a hurricane with pressures down to 995 millibars at one point, however, even storms this strong can still struggle with fast trade wind flow, which also killed Arthur in the central Caribbean
In this picture of Tropical Storm Arthur I added a pink line to demonstrate how this storm resembles a tropical wave, the only difference is that Arthur has an embedded low pressure center within the wave axis.
Tropical Storm Danielle (1986)
Hurricane Dennis (1981)
Hurricane Beulah (1967)
In looking at these tropical systems, what is the difference between the storms which seem to thrive in the environment of the east-central Caribbean graveyard and storms that dissipate? Well, for one thing, systems which enter the Caribbean relatively weak with strength mainly below hurricane status are already at a disadvantage as their circulations tend to be weak & fragile & increasing trade winds in their path alone can be enough to completely rip the storm apart & force it to open up into a tropical wave. Also, many of these storms that are weak when they enter the Caribbean are generally small in nature because the environment from which they are born promotes generally high pressures as they are caught well within the easterly flow underneath the strong Bermuda-Azores High. Considering these circulations are small in nature means they are much more prone to changes in their environment & such systems have a tendency to fluctuate much more dramatically in intensity as opposed to storms that are large.
Looking specifically at the systems that form over the east-central Caribbean & tend to strengthen, you should notice that in the patterns involved with the formation of these storms generally features lower than normal pressures directly to the north of the east-central Caribbean, which is quite anomalous given that the Bermuda high is usually fairly strong in this area. Thus, with a weak pressure gradient between the South American Monsoon & ITCZ & the Bermuda high, trade winds naturally slow down, thus such a set-up allows for air to pile up at the surface which can lead to the formation and intensification of tropical cyclones in an area that’s usually not too favorable for weak tropical cyclones.
Also, something I noted was that the tracks of these tropical cyclones that tend to survive & even thrive in the trek through the east-central Caribbean have a tendency to move more meridional in nature, as opposed to storms that dissipate which tend to move more east-west in nature. A reason as to why a more north-south movement is more favorable for intensification of tropical cyclones in this area can be attributed to how if a storm is already moving in such a direction, this usually means that trade winds are generally weak, but they are still in place, thus a system which moves more perpendicular to the easterly trade wind flow will have a tendency to strengthen more so than a storm which moves along with the trade wind flow. That’s not to say though that every storm which moves generally along with the trade wind flow is going to weaken, in fact there have been very powerful hurricanes to take such a track through the Caribbean, many of which have been historically some of the strongest hurricanes on record. Take for example systems like…
Hurricane Allen (1980)
Hurricane Gilbert (1988), up until Hurricane Wilma in 2005, this was the strongest storm on record in the Atlantic basin.
Hurricane Emily (2005), the strongest July storm on record, and the only category 5 hurricane in the Atlantic to form during the month of July.
Hurricane Emily nearing its peak intensity as a category 5 hurricane late on July 16th & early on the 17th.
Hurricane Dean (2007)
I think something I mentioned on my other forecasting site would help to better explain why storms of such intensity, despite entering the naturally unfavorable caribbean “graveyard” are able to maintain intensity & even intensify
“Well, I thought about this, & I think that this “feast or famine” scenario where storms that aren’t fully developed don’t intensify, as opposed to hurricanes that are already quite powerful continue to intensify, sometimes rather rapidly in the central Caribbean, I think that storms that are fully developed have a quality about them that allows them to turn the seemingly unfavorable environment with stronger trade winds inducing surface divergence to a very favorable environment that can allow for rapid intensification. When you think about fully developed storms as opposed to systems that are still trying to close off surface circulations, their wind fields are much larger and more organized with westerly, northerly, southerly, & easterly winds over a much larger area. These well organized winds fields essentially are able to “bend” the strongly easterly trade winds around them into a tropical wave like structure where winds in the wake of the wave are out of the southeast & winds ahead of the wave are out of the northeast. Using what we know about tropical waves where thunderstorms and convective activity are usually favored along and behind the tropical wave axis, this means that if we consider the well developed tropical cyclone in the central Caribbean reminiscent of a tropical cyclone, this would lead us to conclude that the circulation of the tropical cyclone is in the middle of the wave axis, thus in a favored position of the tropical wave where convergence is favored as the easterly trade winds, especially on the southern side of the tropical cyclone, are forced to change direction from easterly to southerly and southeasterly & if you apply the concept of turning a sharp corner in a vehicle, where the vehicle’s inertia forces you to slow down once you reach the corner, the same concept can be applied to the trade winds in this case, which change direction as a result of the tropical cyclone, are forced to slow down and when air slows down over a distance, that leads to a piling up of air, which is then forced to rise, leading to surface convergence that is actually favorable for tropical cyclone development despite the central Caribbean naturally being a “dead zone” for tropical development due to enhanced easterly trade winds that severely disrupt surface circulations.”
Now, another thing to consider when dealing with storms which enter the Caribbean is climatology. Usually earlier in the season, the trade winds in the Caribbean are very strong because this is usually when the pressure gradient between the Panama-Columbian Low & Bermuda high is strongest, & this is another reason why el nino hurricane seasons usually don’t feature significant Caribbean hurricanes as the Panama-Columbian Low is stronger than normal, which only enhances easterly trade winds in the Caribbean making the environment more unfavorable than it already is.
Look at the July mean 500 mb pattern in the Caribbean, notice how strong the pressure gradient is in the Caribbean between the Panama-Columbian monsoon low & the Bermuda high. For this pressure pattern, I used all years since the start of the warm AMO in 1995.
July mean 500 mb height pattern
Look how by August, the pressure gradient decreases significantly, with less colors (area of equal pressure indicated by the same color) dominating the Caribbean, indicative that trade winds are naturally slower this time of the year.
Trade winds remain relatively weak even into September, at least compared to July
Notice how by October, the mean ridging usually begins to shift south, & this allows for lower pressures to build farther to the north, lowering the pressure gradient between the tropics & mid-latitudes, to the point to where in many instances ridging over eastern North America & the western Atlantic is actually a favorable pattern for tropical cyclone genesis, by forcing convergence into the deep tropics, which is usually beginning to become hard to come by as water temperatures cool, the ITCZ retreats & wind shear naturally begins to increase again.
However, for those storms which can develop in the Caribbean in October, they have a tendency to be quite strong & even historic.
Some good examples are
1921 Tampa Bay hurricane
1924 Cuba Hurricane
1926’s Hurricane 10
Hurricane 18 (1933)
1944 Cuba-Florida hurricane
Hurricane Five (1946)
1947 Hurricane 8
1948 Miami Hurricane
Hurricane King (1950)
Hurricane Hazel (1954)
Hurricane Hattie (1961)
Hurricane Mitch (1998)
Hurricane Wilma (2005)
Hurricane Tomas (2010)
Of course we can’t forget about Hurricane Sandy last year
Speaking of Hurricane Sandy, there’s something I need to mention about this storm. I’ve recently come across a study that makes an outrageous claim that this storm’s track was a “Once-in-a-700 year event”. (link to article) http://news.yahoo.com/hurricane-sandy-1-700-event-182934012.html
First of all, the only reason as to why anyone would want to make a statement such as this would be to promote the AGW agenda, & this statement clearly shows their ignorance of history & facts as for one, our “reliable” hurricane record only goes back to the civil war, giving us at most about 150 years of hurricane data, thus how can you possibly come up with a “700 year” figure when you don’t even have nowhere near the amount of data that even amounts to 700 years. Second of all, their statement that Sandy’s trajectory (referring to it’s bend westward, in that it came into the mid-atlantic & northeast coast from the east-southeast is unprecedented, and their bogus claim that this is a 700 year event is absolute garbage once you get a look at actual historical hurricane tracks which have made similar movements to Sandy. Remember, for starters you could see this pattern coming from a mile away, with cold 400 millibar temperatures in the deep tropics which led to shut-down in activity in the deep tropics for most of the year, thus allowing for the waters in the Caribbean & MDR to remain warm. Also, the MJO moved into a favorable octant for the Atlantic, & with high pressure building to the north of the Caribbean, this forced convergence into the deep tropics, which along with the MJO, would mean tropical activity would be heavily favored in October in the Atlantic, & given the fact that we are in a similar AMO/PDO set-up to the 1890s & 1950s when the Pacific was in its cold cycle, & the Atlantic was warm, this favors east coast hurricane landfalls, thus it would make sense for something to at least attempt to make landfall on the US east coast in October. Now, the pattern that forced Sandy west was interesting, because I recall there were those who were screaming this was a fish storm and was going out to sea based on the GFS, but let’s remember that the GFS has a significant poleward bias when it comes to the tracks of tropical cyclones & with a bowling ball low to the east of Sandy, how in the world can Sandy go out to sea, because unlike an open trough, a bowling ball low is much more isolated in nature & any subsequent pressure rises on the periphery of the low will be much closer, thus even if Sandy did come very close to the low, the higher pressures enforced by the bowling ball low pressure system would force Sandy to be deflected back to the west to wait for the next trough to pick up the storm. Unlucky for the US, the pattern of blocking which had dominated Greenland much of the summer & had led to many storm recurvatures out into the Atlantic broke down as the high pressure moved farther to the south towards Atlantic & southern Canada, an infamous position for hurricane landfalls on the US east coast.
500 mb pattern for hurricane Sandy’s landfall.
Now, with this information considered, although Sandy’s westward track into the US east coast was unusual, it’s certainly far from unprecedented in being a “700 year event”
Hurricane Sandy’s track
Here are some other storms that have hit the northeastern US & mid-atlantic from the eas-southeast
Tropical Storm 11 (1893)
1903 New Jersey hurricane
Tropical Storm Seven (1923)
1933 Chesapeake-Potomac Hurricane
Tropical Storm Seven (1943)
Hurricane Frances (1961), although it didn’t hit land, took a similar westward hook very far to the north, much like Sandy, & look at how this storm was a category 3 hurricane to the latitude of New Jersey, this means that someday a major hurricane will hit that region, just a matter of time.
Hurricane Doria (1967)
Hurricane Agnes (1972)
Tropical Storm Bret (1981)
Tropical Storm Dean (1983)
Enough of that rant, just wanted to show you evidence to expose the fallacy of some of the AGW claims about hurricane Sandy, & show you that although the storm was unusual, it’s certainly not without precedent and it is completely bogus to claim this as a once-in 700 year event when several storms since just since late 1800s (never even mind 700 years) have made the general turn into the mid-atlantic & northeast coast from the east-southeast like Sandy. Now, going back to my rules about Caribbean hurricanes & how this pertains to tropical storm Chantal.
Thus, here’s a general rule about storms which enter the Caribbean gathered from from the information given above, if trade winds are increasing ahead of a relatively weak tropical system, preferably below hurricane status & small in nature, the storm is likely to dissipate or open up into a tropical wave once it reaches the central Caribbean. One way you can tell a storm is about to open up into a tropical wave is by seeing a “tail-like” feature, reminiscent of a tropical wave, indicative that air is spreading out in front of the system & it’s very disorganized, thus more likely to weaken or open up into a tropical wave. Also, storms which tend to move along with trade wind belt from east-west are much more liable to be torn up by the trade winds, however, if a storm is a significant hurricane, then there’s an exception to this rule as the storm’s large & dominant wind field can change the unfavorable easterly winds that promote surface divergence into winds that promote surface convergence which is more favorable to the storm’s own development & with the storm being so well organized, it is also very difficult to destroy the cyclone, thus these storms have a higher likelihood to survive & even thrive in the east-central Caribbean “graveyard”. Although weak storms usually struggle in this area of the Atlantic, if trade winds slow down, this can lead to a much more favorable environment for tropical cyclones, & can allow even small and weak storms to survive the trek through this area of the Caribbean. Storms which tend to move more poleward in nature perpendicular to the trade wind belt also have a better chance of surviving & climatology favors storm survival late in the season, generally after the peak of the hurricane season & especially towards October when trade winds are much slower due more troughiness over eastern North America & a weaker panama-Columbian low.
However, look how once Ernesto reached the western Caribbean, where trade winds naturally slow down at the surface & force air to pile up, how organized Ernesto became, & luckily this storm ran into the Yucatan, because it was clearly undergoing a period of rapid intensification at landfall.
Look how though once we had Tropical Depression Five, which would become Ernesto the NHC forecasted it to become a hurricane near Jamaica, which was clearly overdone given that Ernesto would move into an area of increased trade wind flow, which did open up the system briefly into a tropical wave. It’s in situations like these where you have a weak tropical system entering into the increased trade wind belt of the eastern-central Caribbean, that you have to question the NHC’s intensity forecasts.
Hurricane Isidore (2002)
Infrared satellite loop of hurricane Isidore as it was near it’s peak intensity as a category 3 hurricane, making landfall on the north coast of the Yucatan Peninsula. Notice just how expansive the outflow is with Isidore especially to the east & south of the center, indicative of a very favorable upper level environment in which air is being properly evacuated in the upper levels to allow for more air to pile in at the surface and cause pressures in the storm to lower, thus leading to intensification. You should notice in looking at the satellite loop of this storm how outflow seems somewhat restricted to the north & northwest of the center, indicating that there’s a region of high pressure building in to the north of the storm, & this region of high pressure is what helps to force Isidore into the Yucatan Peninsula. If it wasn’t for this region of high pressure, Isidore would have likely continued to intensify further & would have likely caused extreme destruction on the US Gulf coast, luckily the storm only came into Louisiana as a tropical storm.
Hurricane Lili, thankfully, this system weakened from a category 4 storm to a one at landfall in Louisiana thanks to an incoming trough providing unfavorable southerly wind shear that disrupted Lili, & thus with a weakening system at landfall, the effects were significantly lessened along the west-central Gulf coast. Notice also how Lili came into the Caribbean as a fairly formidable tropical storm, yet because of the naturally enhanced trade winds in this area, the storm weakened dramatically & in fact opened up into a tropical wave briefly before intensifying once again into a significant hurricane once it reached the Gulf of Mexico.
Some historical perspective on Chantal for storms that develop in its general area west of 30 west, east of the Lesser Antilles & generally south of 15 degrees north for the month of July & even the first week of August (I included August at least for our sake as there aren’t very many cape Verde storms in July, but I won’t go deeper into August as conditions drastically change throughout the month, allowing for very different tracks & formations of tropical cyclones in this area, thus including the 1st week of August was a way to expand my data in this research showing historical track perspective on 95L.).
The first storm that pops up is Hurricane Ernesto which formed last year on August 1st.
Tropical Storm Colin (2010- a hurricane season analog)
Then we go all the way back to the historic 2005 Atlantic hurricane season to find the next tropical system that formed east of the Lesser Antilles in a relatively similar area as Tropical Storm Chantal
Hurricane Emily (2005)
Hurricane Irene (2005)
Tropical Storm Bonnie (2004- one of this year’s hurricane season analogs)
Tropical Depression two (2001)
1998’s Tropical Storm Alex
Hurricane Bertha (1996)-a hurricane season analog
Tropical Storm Bret (1993)
Tropical Storm Arthur (1990)
Tropical Storm Barry (1989)
Hurricane Dean (1989)
Tropical Storm Claudette (1979-one of my hurricane season analogs)
Tropical Storm Ana (1979), the only June storm in history to form east of the Lesser Antilles.
Tropical Storm Anna (1969-my #1 hurricane season analog for this year)
Tropical Storm Ella (1966)
Hurricane Arlene (1963)
Hurricane Anna (1961)
Hurricane Abby (1960)
Now, what is the significance of the development of these early Cape Verde systems like 92L observed in early June & currently 95L, what do they potentially mean for later in the hurricane season?
Well, I already showed you many of the storms which developed east of the Lesser Antilles in July, now we’ve had this year tropical storms Chantal & Dorian, 2 Cape Verde tropical cyclones before August, with at least one of those systems being a tropical storm, there were only a few select years to accomplish this feat since 1950, including 1966, 1969, 1979, 1989, & 2003 & 2005.
Tropical Storm Ella
Tropical Storm Anna
Tropical Depression 5
Tropical Storm Ana
Tropical Storm Claudette
Tropical Storm Barry
Hurricane Claudette (didn’t officially become designated as a tropical storm until the central Caribbean, likely thanks to the “John Hope Rule” & other rules I explained earlier in this post about Caribbean tropical cyclones, I suspect Claudette was at the very least a tropical depression east of the Lesser Antilles.
Tropical Depression 2
Tropical Depression 6
Hurricane Emily, the strongest hurricane in July history & the only category 5 hurricane to form in July.
The most interesting aspect about all of those hurricane seasons is that, these seemingly weak in some cases, storms early in the season are usually followed later by monster hurricanes, with many of these seasons except 2005 seeing a significant Cape Verde hurricane.
1966 Hurricane Faith, one of the longest lived Atlantic hurricanes on record
1966 Hurricane Inez
The 1969 hurricane season which like this year had two early Cape Verde tropical cyclone developments before August 1 featured the devastating & very historic category 5 hurricane Camille into the central Gulf coast.
Here’s the very famous satellite image of hurricane Camille on August 16th, & you can see just how compact & very tightly wound the eye of this storm appears, indicative of a very powerful hurricane as the smaller eye is indicative of faster winds, much like a figure skater drawing in here arms, the tighter the circle they make, generally, the faster they tend to spin, certainly was the case with Camille. You can also point out by judging by the upper level outflow in association with Camille that the storm is being pulled to the northwest, likely from the interaction of an upper level low, which are notorious for helping pull tropical cyclones on very anomalous tracks into the coast, & considering that the computer models struggle the most with upper lows because simply due to the fact of their complex dynamics and relative lack of observation in the upper levels of the troposphere, it’s hard for the models to accurately predict the track & even the strength (upper lows help to provide outflow channels for hurricane ventilation, which in turn leads to more surface convergence & lowering pressures that strengthen the tropical system) of tropical cyclones in such a set-up.
1979’s Hurricane David
Here’s a picture of hurricane David east of the Lesser Antilles during his relatively fast intensification phase as he began to strengthen to a major hurricane.
This picture of hurricane David following its passages over Hispaniola reveals a very disturbed core evident by what appears to be some dry air he’s attempting to mix out of his circulation & the fact that he crashed into Hispaniola as a strong hurricane means he’s going to survive, but come out the other side severely weakened, especially considering that such strong category 4 & 5 hurricanes which interact with land like this uncoil like a snake & although their inner core remains intact, it’s usually much larger & more broad in nature on the other side, which then makes it harder for the system to strengthen as quickly & makes them susceptible to dry air intrusions, among other things.
Another good example of a storm that was strong when it came into the Antilles, Hurricane Georges was definitely a beautiful hurricane, the storm system really liked to track over land & as a result, even though it was over the Gulf of Mexico for a large period of time, the very disturbed yet somewhat intact inner core didn’t allow hurricane Georges to take full advantage of its favorable environment it encountered after crossing the Greater Antilles .
This video on TWC coverage of hurricane Georges is very good & goes through a lot of the meteorological processes involved with hurricane Georges as it approached Puerto Rico.
Hurricane Frederic, as opposed to hurricane David interacted with the Greater Antilles as a weaker storm, which although would increase its chances of decay, the fact that no well-defined inner core was established implies that this system has much less to lose essentially by going over the islands & if it manages to come out the other side like David did, unlike that system which struggled to intensify because of it’s core being large & broad in nature, Frederic can start from scratch & develop a much tighter inner core that will allow it to take better advantage of its favorable environment at hand, thus this is why Frederic was able to become a category 4 hurricane in a relatively short period of time after emerging off Cuba as only a tropical Depression.
Following tropical Storm Barry & what was a developing tropical depression that would later become hurricane Dean in August in the eastern Atlantic, was hurricane Hugo, an absolute monster of a storm. It was because of this storm that helped to bring popularity to the weather channel.
This is a great video of John Hope describing hurricane Hugo as it was coming ashore into South Carolina, plenty of good information to learn about this storm & hurricanes in general from this video.
For those of you in the Carolinas, specifically in and around the Charlotte, NC area, this next video below is just for you, local news coverage & recap of the devastating hurricane Hugo which produced significant damage & widespread power outages throughout the Charlotte area as it still was a category 1 hurricane at the time of crossing through the city.
Hurricane Hugo was a category 5 Cape Verde hurricane & what helped make the storm so devastating was that not only did it cross over the warmer Gulf stream waters & its outflow was being aided by a digging trough off to its east providing a nice equatorial outflow channel, & the trough to the north providing yet another ventilation for the storm, but the fact that unlike many other storms like hurricane Floyd & Irene which paralleled the coastline for a long period of time hugo came in relatively perpendicular to the coast. With a storm that comes in perpendicular to the coast, like what we witnessed with Sandy, it helps to focus & enhance the coastal storm surge, but also this allows for the hurricane to maintain its intensity for a longer period of time. If you look at storms like Irene & Floyd for example, they appeared at one point very powerful in the Bahamas, both at some point were major hurricanes, yet when they reached land they weakened considerably, down to category 1 & 2 hurricanes. The reason for this is as the storm begins to approach land, although the frictional effects of land can help to tighten up a broad circulation briefly before landfall, the longer the storm stays near land, the more dry, continental air will get entrained into its circulation, usually bigger storms like Irene & Floyd with much larger circulations & storms that are undergoing eye wall replacement cycles near the coast are prone to dry air intrusions, and this helps to significantly weaken the storm.
Just take a look at this series of pictures of hurricane Floyd in 1999 from when it was over the Bahamas to as it was hitting the NC coast, you should notice significant weakening in overall appearance as it stays near land for an extended period of time, absorbing more dry air into its core, especially on the southern side of the circulation where the fast forward movement to the northeast into the trough near the east coast made this quadrant of the storm more vulnerable to dry air.
Hurricane Floyd near its peak intensity over the Bahamas as a strong category 4 hurricane
Hurricane Floyd as its passing by South Carolina
Hurricane Floyd at landfall in NC
This effect of sucking in dry air as a storm parallels the east coast is much more noticeable in hurricane Irene because it was an even larger storm than Floyd, thus it’s larger inner core is more susceptible to dry air intrusions & it was moving much slower than Floyd, thus it spent more time interacting with land, which caused the storm’s structure to deteriorate even more so than Floyd.
Hurricane Irene near peak intensity in the Bahamas
Look how Irene’s structure deteriorates thanks to its prolonged period of being too close to land, allowing for dry air to infiltrate on the western & southern sides of the storm.
Compare these storms to hurricane Hugo which unlike Irene & Floyd, came in perpendicular to the coast, if anything, Hugo’s structure actually improved compared to Floyd & Irene which had weakened.
Hurricane Hugo’s track
Continuing on with hurricane seasons that had 2 deep tropical developments before August 1, look at what followed the storms in 2003, the incredible hurricane Isabel, which I’ve talked about extensively earlier in this post.
Beautiful RGB satellite image from EUMETSAT showing hurricane Isabel relatively early on its life cycle as a developing hurricane
Following the early developments in 2005 of hurricanes Dennis & Emily, we know what came after that, the terrible trio of hurricanes Katrina, Rita, & Wilma.
An interesting statistic about these seasons like this year which had 2 tropical developments with at least one tropical storm forming east of the Antilles before August is that 5 out of those 6 hurricane seasons had a category 5 hurricane, something that hasn’t been witnessed since the 2007 hurricane season duo of category 5’s Dean & Felix. Now you might be thinking well, wouldn’t it be nice to have a category 5 hurricane, yet one that goes harmlessly out to sea & one we can watch from a safe distance? Well, really think about this statement & try and think back to the last time a category 5 hurricane turned harmlessly out to sea. You probably are having trouble thinking of one, so here are all of the category 5 hurricanes since 1924 so you can see for yourself when this occurred.
1924 Cuba Hurricane
1928 Lake Okeechobee hurricane
1932 Bahamas Hurricane
1932 Cuba Hurricane
1933 Tampico Hurricane
1935 Labor Day Hurricane
1938 Long Island Express
1947 Ft. Lauderdale Hurricane
1950 Hurricane Dog
1951 Hurricane Easy
1955 Hurricane Janet
1958 Hurricane Cleo
1960 Hurricane Donna
1960 Hurricane Ethel
1961 Hurricane Carla
1961 Hurricane Hattie
1967 Hurricane Beulah
1969 Hurricane Camille
1971 Hurricane Edith
1977 Hurricane Anita
1979 Hurricane David
1980 Hurricane Allen
1988 Hurricane Gilbert
1989 Hurricane Hugo
1992 Hurricane Andrew
1998 Hurricane Mitch
2003 Hurricane Isabel
2004 Hurricane Ivan
2005 Hurricane Emily
2005 Hurricane Katrina
2005 Hurricane Rita
2005 Hurricane Wilma
2007 Hurricane Dean
2007 Hurricane Felix
The last official time a category 5 hurricane turned out to sea was all the way back in 1958 with category 5 hurricane Cleo! In fact, looking at the official stats on category 5 hurricanes, the Atlantic has seen 34 category 5 hurricanes since 1924, & out of those 34 systems, 31 of them ended up hitting land, giving us a figure that about 90-95% of all category 5 hurricanes in the Atlantic basin end up hitting land, including the United States coastline, a staggering figure. Of all of these category 5 hurricanes, 14 of them formed in the eastern Atlantic (generally from 40 degrees west & points eastward, which would usually mean that the chances of such a storm turning out to sea is abnormally high. However, of these 14 storms, only two hurricanes Easy (1951) & hurricane Cleo (1958) turned out to sea, all other storms eventually went onto hit landmasses further west, giving us a percentage of about 85% of all category 5 hurricanes which form in the eastern Atlantic end up hitting land, another astonishing figure. The interesting aspect about these Cape Verde category 5 hurricanes is that their relative frequency is more closely associated with African Sahel rainfall.
The most interesting information I found out by looking at this picture above was that Sahel rainfall & category 5 Cape Verde hurricanes in general although they do correlate with periods of high & low rainfall, seem to be more closely related to rainfall in relation to the surrounding time period. This is especially true when looking at the period from about 1960 to the early 1980s, where although rain in the beginning was above normal there was a complete lack of category 5 Cape verde hurricanes, & this was interesting also given the fact that we had a higher frequency of category 5 Cape Verde hurricanes in the mid-late 2000s when Sahel rainfall was below normal. also, even the period in the late 1930s & into the 1940s when overall rainfall was still above the mid-late 2000s level, yet there weren’t any category 5 Cape Verde systems. What this information implies is that even though there is a correlate as a whole with increasing Sahel rainfall & generally more category 5 Cape verde storms, it appears that these systems are more closely associated with overall trends in rainfall, & this is evidenced by the decrease in rainfall from just after 1960 to the early 1980s resulting in the formation of only 2 Cape verde hurricanes (David & Allen) & resulting in a 19-year lull in category 5 Cape verde hurricanes, the longest on record since the 1920s. Also, the 9-year lull in category 5 Cape Verde storms from 1938 following the Long Island Express to 1947’s Ft. Lauderdale hurricanes correlates with a notable, but less significant decrease in Sahel rainfall during this time period. The general trend upwards in Sahel rainfall since the 1980s has resulted in several formations of category 5 Cape Verde hurricanes, with 3 occurring in the mid-late 2000s (Isabel, Ivan, & Dean), despite overall rain being below normal. What all of this data implies is that yes Sahel rainfall is correlated to the formation of category 5 Cape Verde hurricanes, but is more closely associated with rainfall trends in a given period, with downward trends, even in periods of relatively high rainfall resulting in fewer storms, while increasing rainfall, even in times of overall drier than normal conditions on the Sahel results in more storms. Given this information, it is important to note that since the 1990s & 2000s, Sahel rainfall is on the increase and given that we haven’t seen a category 5 Cape verde hurricane in 6 years under increasing Sahel rainfall, suggests that given history, we should soon see a category 5 Cape verde hurricane. Also knowing that our rainfall is on the increase, we are going to likely see an increase in category 5 Cape verde hurricane frequency over the next several years & decade or two, despite the AMO likely entering its cold phase by then.
Further evidence that supports this idea for a category 5 Cape verde hurricane this year is that if you go back to those years I mentioned earlier which had 2 tropical developments in the eastern Atlantic before August 1 (although CSU just came out with their forecast & it has a few different years), 3 out of those 6 years had a category 5 Cape Verde hurricane!! (1979’s David, 1989’s Hugo, 2003’s Isabel).
Now, where potentially would this category 5 Cape Verde hurricane track? Just look at history & the 14 storms which were Cape Verde category 5 hurricanes, which by my definition formed at or east of 40 degrees west, where naturally the chances are relatively high for a storm to recurve out to sea. In the case of category 5 Cape verde hurricanes, the majority of them track west-northwestward to near & just to the northeast of the NE Caribbean & Puerto Rico, from there many go on to hit the eastern seaboard & even the Gulf. A few southerly tracking systems like hurricane Allen, Dean, & Ivan make for some of the most infamous “caribbean cruiser” hurricanes.
Now, given that we have observed above normal Sahel rainfall this year & are in an overall upward trend in precipitation, this suggests that the formation of a category 5 Cape Verde hurricane within the next several years is relatively high to begin with. However, we haven’t observed a category 5 Cape verde hurricane since Hurricane Dean in 2007, a 6-year period without a category 5 Cape Verde hurricane in an overall wet Sahel & increasing precipitation is uncommon.Yet, with the already observed favorable conditions in the eastern Atlantic as evidenced by the formation of tropical storms Chantal & Dorian before August 1, & in looking at those hurricane seasons which had 2 tropical cyclones in the east Atlantic before August, half of which had category 5 Cape Verde hurricanes, the odds of this year seeing a category 5 Cape Verde hurricane are relatively high. Also given that 12 out of the 14 category 5 Cape Verde hurricanes have hit landmasses further west, there’s certainly concern, if such a storm were to form, that landmasses, including the US coastline could be threatened. If you also take into account that of we are in an active hurricane “series” as described earlier in this post & we’re currently in a similar cycle of PDO/AMO as the 1950s, when the category 5 Cape Verde hurricane Donna hit the US eastern seaboard as a major hurricane & a period when 8 major hurricanes hit the US east coast…..
Given the conditions at hand, things certainly are pointing towards the east coast for a potential hit from a category 5 Cape Verde hurricane this year (no one is saying or should be saying with any certainty that we’ll see a category 5 landfall), & this is also supported by climatology of such storms, in that of the 14 category 5 Cape Verde hurricanes, 8 of them hit the east coast of the US (57% of all category 5 Cape Verde hurricanes), thus if any region of the US coast should be wary this year of impending hurricane threats, its the US east coast.
Thus, with all things considered, my hurricane season forecast from all the way back in March hasn’t changed for 13-18 named storms, 7-11 hurricanes, 3-5 major hurricanes.
If anything, I’m even more confident in my forecast & in fact I am going out on a limb & saying that the odds are quite high this season (70%) for a category 5 Cape Verde hurricane this year, regardless, it will still be an active Cape verde hurricane season.
As discussed earlier in this post, relatively weak tropical developments in the deep tropics early in the hurricane season are usually followed later by very powerful hurricanes, 2009 is another great example of this & it was the first year I really started to track hurricanes & try to understand the concepts that go into them, so I thought it was necessary to add this little bit of information in. Although 2009 was an el nino year, if you recall back in my previous post, despite the ENSO conditions being overall unfavorable for deep tropical activity in the Atlantic, we still observed two major hurricanes (Bill & Fred) in the “Deep tropical Atlantic” that season. Of course people may seem to remember storms like that, but they tend to forget that there are many systems which leave Africa that although may look fairly good on satellite presentation, have an appreciable amount of vorticity in the lower & mid levels and are fairly persistent, still don’t develop for various reasons, like wind shear trade winds, etc..
In mid July 2009 there was a fairly potent tropical wave which looked fairly promising in the eastern Atlantic for development, however due in part to the el nino in place over the eastern Pacific inflicting higher than normal wind shear in the tropical Atlantic,& along with naturally strong trade winds in July, this system was completely ripped apart.
Only a few weeks later, look what happened, a series of rather healthy tropical waves moved off the African coast & led to formidable tropical development.
TWC coverage of Tropical Storm Ana, the storm mentioned towards the end of the video to potentially develop would become the monstrous hurricane Bill.
Hurricane Bill coverage August 18th, 2009
Now, if you’re still thinking about next winter & i know many of you snow lovers already are, well my ideas still have not changed since April that years that feature significant hurricane landfalls on the US coast seem to have winters that get off to a fast start at the very least & many of those winters also stay cold through at least February. Just check out my hurricane season analogs for the month of December, a generally cold look from the northern Plains, Great Lakes, & the northeast, southeastward into the southeast US with warmer than normal conditions prevailing towards the Great Basin, Rockies, & the Pacific Northwest.
Extrapolating my hurricane season analogs out into their following winter gives you a look this for temperatures, cold generally from the plains & points eastward, warmer than normal towards the Great Basin & Pacific northwest.
Such a temperature distribution pattern like the one shown above has the look of a -NAO set-up with higher than normal pressures towards Greenland & northeastern Canada keeping temperatures above normal towards the Hudson Bay, northern Quebec & Ontario, and into Labrador. With high pressure in this area, this forces cold air masses originating from northwestern North America & Alaska to generally ride on the southwestern periphery of the high into the northern plains & eastern US. With cold air being directed into the eastern half of the US, this subsequently means warmer than normal temperatures will dominate the western US. Looking at the 500 millibar mean height pattern in those winters, you can see suspicions are indeed correct, as the classic -NAO sets itself up with blocking near & to the south of Greenland. This region of high pressure in this position forces air to pile up & pressures to significantly lower underneath the high & that region is generally the US eastern seaboard, thus this type of set-up is generally favorable for east coast winter storms. However, there are a few complications with this pattern that stick out at me that have me aware that such a set-up can still possess some volatility at times with the overall winter pattern. The one big factor that leads me to this conclusion is the anomalous region of high pressure over the Bering Sea & near and just to the north of the Aleutian Islands. A region of high pressure in this area usually is not a favorable indicator for winter for the eastern US, as a region of high pressure over the Bering Sea naturally forces pressures to fall over towards the Pacific northwest & western Canada, & in this usually in turn causes pressure rises to occur over the eastern US, which leads to unfavorable ridging that tends to severely lower the chances for winter weather. Thus, when you are looking at pressure patterns near the Pacific side of the arctic, you usually like to see a significant trough of low pressure near the Aleutian Islands, as this forces a ridge over Alaska & generally towards northwestern North America, & such a set-up usually precludes major arctic intrusions into the US, especially for areas east of the Rockies, and accompanying these arctic air masses is usually some sort of significant winter storm system that rides along the boundary of the residual warm air and the incoming arctic air mass. However, what makes this pattern interesting is that the ridge over the Bering Sea doesn’t seem to hinder a major trough over the eastern US, & a lot of this has to do with the PDO. For getting an overall indication of the pattern of the PDO you need to look towards the north Pacific, & in the current state of cold PDO (negative phase) that’s been in place since the mid-late 2000s, there is usually a formidable ridge over the North Pacific sitting over a ring of warm water near & just to the east of the dateline in the mid-latitudes with a signature of colder than normal water going down the west coast of North America & extending towards the east-central equatorial Pacific.
However, the PDO pressure pattern in the composite of the winters following my analog hurricane seasons reveals that the PDO is into its warm cycle, with lower than normal pressures dominating the North Pacific. Now, when you also have the aforementioned Bering Sea ridge in place that would tend to force lower than normal pressures in western Canada & the Northwestern US, & thus an unfavorable pattern for the eastern US for winter weather, with lower than normal pressures already in place over the North Pacific as a result of the warm PDO, it seems like if the warm PDO signature is strong enough, it can be enough to offset the Bering Sea ridge & actually force pressures to rise over the western US & western Canada. That in turn along with the warm AMO in place that favors -NAOs means a trough is established over the eastern US, a generally favorable winter weather pattern with plenty of snow & cold. You can attribute this warm PDO pattern being favorable to how the region of low pressure over the North Pacific forces the Pacific jet stream to speed up while over the Pacific, but with a trough of low pressure centered in the general region of the north Pacific, it forces air flow around the trough to change direction as it approaches western North America, thus, in doing so, this causes the air to slow down & in turn leads to jet stream buckling & ridging over western North America. Here is the 500 mb mean height pattern of my hurricane season analogs’ following winters, where you can see how the warm PDO with low pressure over the north Pacific (shown in blue & purple) affects the Bering Sea ridge.
Now, look at the global sea surface temperature anomaly, you can see looking at the north Pacific, how the cold PDO signature appears at the very least severely disrupted with warmer than normal water now extending towards the west coast of North America, however, you should note that despite the cold PDO seeming to disappear for the moment, that there is a region of 3-5 degree celsius warmer than normal water right where the the cold PDO signature usually is, in the mid-latitude regions of the north Pacific, near the dateline, which indicates to me that although the cold PDO may appear to be gone for the moment, it is clearly still there & hanging tough and is more than likely to come back once again as we approach winter. In fact, it is not too uncommon for the PDO to suddenly switch phases in the middle of the summer, it’s happened numerous times before even at the very height of the cold PDO in the 1950s, 60s & even the 1970s.
Now, if you look at those winter in which the PDO was cold but briefly flipped to warm during the previous summer, like what was observed this year in fact, here are the PDO values for the first 6 months of this year (January on the right June towards the left) courtesy of JISAO. You can clearly see that in the month of May, the PDO briefly spiked to its warm phase,
-0.13 -0.43 -0.63 -0.16 0.08 -0.78
Years in which the PDO was cold in the winter & then flipped briefly to its warm phase in the summer, gives us 1953, 1954, 1957, 1958, 1959, 1965, 1966, 1968, and 1969. Look at the temperature anomalies for the following winters in those years, looks like a very classic look of northwest to southeast cold under a -NAO with warmth towards Atlantic Canada & the Rockies.
This looks a lot like my extrapolated hurricane season analogs into their following winters, with a -NAO look, a cold tongue extending southeastward from the upper midwest & Great Lakes into the southeastern US.
I also came across this post from Mark Oleg’s website USWeatherPlus from Karl, in which he also had noted a very similar look for this winter with northwest-southeast cold from the upper midwest & Great Lakes into the southeastern US when he looked at all of the ENSO analogs to this year since 1950, which really isn’t a bad idea.
However, there is one problem with this & I have a small shadow of doubt still at the moment at just throwing myself into forecasting this winter to be colder than normal, at least over the southern US, regardless, looks like based on the hurricane hit pattern & -Indian Ocean Dipole summer connection to the following start of winter, this winter should at the very least start off cold. However, let’s just remember, with the ENSO in neutral, this means that it will be a relatively non-factor to some degree this winter & will allow other factors & oscillations to control the pattern like the PDO. In fact, if you look at the temperature anomalies for all similar ENSO neutral years in the cold PDO like we’ve been in since about 2007, it actually ends up looking warmer than normal for the southern US, which contradicts all of the ENSO neutral years since 1950 & extrapolated hurricane season analog winter temperature patterns.
US mean temperature pattern for ENSO neutral years under the cold PDO.
The 500mb pattern shows the issue, with the ENSO a relative non-factor, this allows for the PDO to take more control of the pattern, & with the cold PDO in place, this enhances a ridge of high pressure over the Bering Sea & forces pressures to fall near western North America. However, with ENSO neutral, the pressures near Hawaii are slightly below normal & in the instances in the winter in which a trough of low pressure can intensify & sit near Hawaii, much like a rock in a stream, it forces the flow of air around the low to slow down & pile up to its northeast, & thus in doing so, when the Hawaiian low is strong, which is usually a result of the el nino, (most favorably a central-west based el nino, this forces the placement of the Bering Sea Ridge to move eastward towards western North America, that in turn would then lead to the PNA to go more towards its positive state, that is usually associated with troughiness, snow & cold in the eastern US. This is exactly why an el nino can be so helpful to offset the cold PDO. However, not all el ninos are created equal, when the el nino is east-based, where pressure anomalies are lowest towards South America, this then forces the air to sink near the central Pacific in & around the Hawaiian low, which then would allow for the Bering Sea ridge to stay further east & force troughiness into the western US. This is exactly why you shouldn’t automatically assume based on the ENSO what a winter weather pattern is going to shape up like, because even a seemingly favorable el nino, which goes east-based can turn out to be a relatively boring winter for the US.
Also considering that we are in a warm AMO, allows for the Atlantic tripole to be favored (cold mid-latitudes, warm water in the deep tropics & arctic), which helps to then enhance -NAOs that can to some extent offset the effects of a cold PDO, even at times in extreme cases like the winter of 2010-11.
In fact, although there are many out there who say that you can’t really accurately predict the NAO & AO this far in advance, well, there is some predictability to it in the longer ranges, in particular, looking at solar cycles.
In this graphic below, you can see evidenced by the areas in yellow & even orange that during periods of lower solar flux, high-latitude blocking is favored near Greenland & especially over western Russia, which is more than likely good reason as to why the winters have been so cold recently in Europe as solar activity has been overall abnormally low, at least since 2008, which is coincidentally when the PDO flipped into its cold cycle. You can also see under lower solar activity, there is a region of overall troughiness over the US, which is consistent with temperature correlations that show generally cooler than normal conditions over the US in the winter thanks to declining solar activity.
US winter temperatures & low solar cycles
These winter temperatures above are fairly consistent with the winters of 2009-10 & 2010-11 which both featured relatively low solar cycles throughout much of the winter, however you do notice a major jump in sunspots just after the start of 2011, which correlates to how winter shut-down relatively early that year. You should also notice though how last year, sunspot numbers were relatively high going into 2012, which would have overall implied for a very warm winter, that did transpire, there was a minor dip towards February, signaling that winter was going to at least attempt to comeback.
2009-10 winter temps
2010-11 winter temps through mid February, very cold
However, people tend to forget the bad times in an overall good winter, look how things quickly warmed up after mid February, (pretty much just 2 months of very good winter, 1 month of non-winter, at least in the south & the eastern US, same can’t be said further northwest.) in response to the increasing sunspot numbers that were observed shortly after the start of the new year.
Now, here are the US winter temperature correlations for moderate solar flux, & you can see overall temperatures warm-up dramatically.
his was certainly the case in the 2011-12 winter, which was blowtorch warm, with a few exceptions of course in the Pacific northwest & near El Paso & Midland-Odessa, Texas which were given quite a helping of winter snow, which at one point in January of that winter gave Midland, TX more snow than Minneapolis-St.Paul, Chicago, & NYC combined!
Of course, I did mention that solar cycles took a brief tumble in February before increasing again, & of course this did allow for at least a very brief window of hope in mid-February for those wanting a big winter that year.
Sadly, their dreams were crushed as the following month of March was among the warmest on record in the US.
You can see the monthly sunspot cycles for yourself here & compare against US temperatures.
You can see in this graph below the mean US DJF temperatures, & their associative ENSO index & AO/NAO states, if we do indeed experience “la nada” conditions with a -AO & -NAO, then our temperature pattern is bound to look a lot like the picture in the center of the bottom row.
Now, also knowing that we have to factor in other conditions such as stratospheric warming events that can lead to major arctic outbreaks into the mid-latitudes during the winter & knowing their unpredictability, there are still some question marks as to how exactly this winter may play out, but given what is at hand in front of me, as I’ve been saying for several months, the winter should definitely start out cold, but also as we are now approaching the peak of the solar cycle, it’s at the extremities of the solar cycles where we’re currently located now where stratospheric warming events are heavily favored, thus I am suspicious that given the weak solar cycles & that we’ve seen many stratospheric warming events recently as the sun’s activity quiets down, I’m definitely beginning to be under the impression that we may indeed see a major stratospheric warming event this winter.
Major changes in QBO & the solar cycles, with this graph below showing definitive correlation between the solar cycles, QBO, & mid-winter stratospheric warming events. The QBO is known to have a significant effect on the transport of stratospheric ozone between the tropics & the arctic in the Brewer-Dobson Circulation, thus large changes in QBO, as what is usually observed near solar maximums & minimums can lead to increased risk of stratospheric warming events.
Of course the “final nail in the coffin” per say will be to see what the northern hemisphere snowfall anomaly looks like when we come out of October, I’m sure by then, other factors like the ENSO index, PDO, NAO, & AO will have sorted themselves out to a point where we can more accurately predict what will occur this winter.
Here are my overall thoughts given the conditions at hand. Weighing my hurricane season analogs’ extrapolated winters, the La nada, -NAO temperature distribution pattern, the low solar flux to US winter temperatures, the years like this one under the cold PDO that featured a brief flip into the warm cycle during the summer & with support also coming from the CFS, here are my initial thoughts on the winter, at least as far as temperatures go, trying to predict how much snow at this time is virtually pointless as there are numerous other factors & conditions that must be considered, & just because temperatures are colder than normal, doesn’t necessarily mean (although it usually does in the winter because of snow’s reflective properties in cooling the surrounding air temperatures & colder air usually begetting more snow in the US) you’ll see above normal snow this winter.
My current temperature outlook for this winter, these ideas may be prone to change, however, I like my ideas & have put a lot of research & effort into them, you can obviously see I’m a little less certain about this winter, in particular across the southern half of the US, mainly south of I-64.
I’ll leave you with this,
Considering 95L became Tropical Storm Chantal just east of the Lesser Antilles, ironic given that Chantal in 2001 was in a similar situation & was facing similar issues as 95L in that it was suffering from some easterly wind shear simply because of the fact that it was moving quite rapidly to the east at 25 MPH, & this makes it naturally more difficult for westerly winds to wrap around on the southern side of thee circulation, however, the main difference between this storm & 95L is the fact that it formed later in the hurricane season, which is likely the reason why it was able to intensify once again over the eastern Caribbean. In fact, it’s rather rare considering that surface divergence is naturally promoted in this area because of increasing trade winds squeezing in between the Greater Antilles & South America, thus significant intensification of a weak tropical cyclone in this area of the tropical Atlantic is somewhat unexpected.
Chantal 2001’s track
Video of tropical storm Chantal
In spite of Chantal & Tropical Storm Dorian that followed being relatively weak systems in general, the fact that we have 2 tropical developments in the deep tropics before the start of August says a lot about how conditions are very favorable this year for tropical cyclone genesis in the eastern Atlantic as compared to the last 2 years. That can be thanked a lot by the -Indian Ocean Dipole that has enhanced the east African monsoon & for areas in & around the Arabian Sea, & thus with a stronger monsoon, this warms the atmospheric column in this area allowing for more latent heat release that is favorable to tropical cyclone genesis & the increased precipitation can also help to limit the Saharan Air Layer & of course with a stronger gradient in precipitation across Africa, especially in the Sahel, this forces the gradient in temperature to increase as a result, which then leads to differences in wind that can lead to a stronger African easterly jet that’s able to power much stronger African easterly waves that account for around 90-95% of all significant tropical cyclones in the Atlantic & also a large amount in the eastern Pacific basin.
Also, I have noticed the MJO
For those who aren’t yet familiar with the MJO, I made a nice comment to Mark Oleg on USWeatherPlus that helps to explain it.
“Ok, in case you don’t what the MJO (Madden Julian Oscillation) is, it is certainly not a model, but simple terms a combination the atmospheric & oceanic circulations which result in variances in how the air behaves over the global tropics. Essentially it is an oscillation that is used to measure upward motion in the tropics, literally upward motion where air is rising & where it’s sinking, thus inducing thunderstorms & convection where the air rises (generally lower pressures), & generally dry & sunnier conditions where the air sinks, forcing regions of high pressure where this region of high pressure allows for the surface waters to warm, whereas where thunderstorms & convection are occurring, their natural turbulence created by their intense updrafts & downdrafts stir up the surface ocean waters, much like stirring a bowl of hot soup for example, it forces the surface waters to cool overtime, thus generally over an extended period of time this oscillation also helps to regulate & determine surface water temperatures of the oceans which can also affect ocean currents & the even the behavior of the ENSO (el nino & la nina). Also, the effects of MJO can alter the PDO (Pacific Decadal Oscillation) & AMO (Atlantic Meridional (Meridional refers to something that’s north-south in nature) Oscillation) both which have their respective warm & cool cycles that have large implications on the winter, hurricane season, tornado season, precipitation & temperature patterns over the globe. You’ll often hear how the MJO is in this phase or this phase, etc.. and what they are talking about are the 8 phases of the MJO, which make up the entire global tropics. However, these 8 phases are not divided up equally by distance as one may tend to think, rather they are divided up by how certain areas of the world behave convective wise, thus some “phases” of the MJO will be shorter or longer in distance than others. Now, why aren’t the phases equal distance? Think about it, remember what I mentioned earlier that the Madden-Julian Oscillation, that is a measure of upward & downward motion of the air in the deep tropics, & also realize that there are certain parts of the globe that for various reasons, such as significantly warmer waters, topography, etc usually have more convection (thunderstorm activity) than others, like Indonesia & it’s surrounding areas (often referred to as the “Maritime Continent” thus they only need a smaller region of the globe to account for the same amount of thunderstorm activity, let’s say like the Atacama Desert where it’s usually bone dry & has very little thunderstorms, so it needs a larger region to account for. This is the reason why the MJO’s 8 phases don’t equally divide up into 8 equal regions on the globe.
Why is the MJO so important? Remember, it measures upward & downward motion over the tropics, & if you recall to one of my previous posts where I talked about the “ultimate driver” of the weather patterns, & why I said that people tend to focus so much on ENSO (El Nino Southern Oscillation) (ENSO generally means I pertaining to el nino & la nina) index, & that’s because the oceans have 1100x the energy capacity of the atmosphere (higher heat content, which means that water naturally doesn’t change temperature easily, which makes the water vapor that evaporates from the ocean a natural greenhouse gas) & that as you increase in temperature (temperature itself is a general measure of the amount of energy that a substance, such as air or water has) the amount of energy difference between each degree of temperature grows, meaning that a change in temperature of 1 degree in air that’s 80 degrees to like like 79 or 81 degrees has the same amount of energy as a change in temperature of 15-20 degrees with the temperature at -40 (this is the reason why I scold at AGWers for focusing so much on the arctic, it is merely a resultant of the effects of the tropical oceans which along with the sun ultimately push around the weather & climate). Thus, with this considered, I think you can see why I focus so much on the tropics & I think it’s very important for you to understand the MJO because unlike the PNA, NAO, & AO which have their most dominant effects on our pattern at certain times of the year, the MJO is ALWAYS a big factor & should always be considered especially when making long range forecasts”
Now, the MJO is divided up into 8 phases (also known as “octants”) With phases 8 & 1 being in the “western hemisphere & Africa, generally referring to the very eastern Pacific, North & South America, the US included, & the Atlantic Ocean as well as Africa that was mentioned earlier) (notice these 2 phases alone cover much more area than all other phases of the MJO because as I mentioned earlier, convective activity (thunderstorms) are generally less in comparison to the Indian Ocean, southeast Asia & the western Pacific). Phases 2 & 3 are when the MJO is over the Indian Ocean, phases 4 & 5 account for just the relatively small but very convectively active “Maritime Continent” generally in the vicinity of Indonesia & the landmasses in between the Pacific & Indian Oceans) Octants 6 & 7 are the Western Pacific ocean. The MJO is very useful in the hurricane season, especially early & late in the season when conditions aren’t as favorable and when the Atlantic may need an extra “boost” to get tropical cyclones going outside the “meat” of the hurricane season that runs from mid August to mid October. The most favorable octants where the MJO is over the Atlantic is phases 1 & 2, the most unfavorable are 6 & 7 (West Pacific) and I think by now once you understand that having the MJo over phases 6 & 7 are most unfavorable while octants or phases 8,1, 2, & 3 are generally conducive while 4 & 5 are ok.
The MJO over the last several months has hung around phases 1-3 a lot. This is likely an indication that upward motion is favored in our part of the world, thus regardless of conditions which may limit activity, the favorable enhanced upward motion the Atlantic is seeing may be able to override some of the adverse conditions at hand such as dry air & actually turn what may have been a relatively inactive hurricane season otherwise into one that, although not up to the standards set by 2005, is still fairly active nonetheless, even when weighed against all other hurricane seasons since the start of the warm AMO cycle in 1995.
Notice how from late March to late June, the MJO spends a considerable amount of time near the Atlantic basin, a hint that upward motion in our part of the world is favored.
MJO recently has become more “well behaved” over the last 90 days….
This is thanks to ENSO neutral conditions which aren’t helping to focus upward motion over one particular area of the globe, the MJO in this instance is usually much more predictable & is closer to its natural progression of 30-60 days around the global tropics…
If the Atlantic continues to have its mojo the MJO over the next few months as we get into the peak of the hurricane season, we could certainly be in for it
Although the MJO isn’t as important during the peak time of the season because conditions are favorable anyway, any little bit of enhanced upward motion certainly can’t hurt & in a season that has the markings of an active Cape Verde hurricane season as well as one which lies within the overall cycles of cold PDO/warm AMO that favor east coast activity along with other evidence to suggest we are in an active “series” for hurricanes on the east coast, which if history is correct, would almost guarantee a storm & knowing that we are 8 major hurricanes behind the 1950s when we were last in this position, there’s certainly reason to be concerned this season.
For good measure this upcoming season and because of the fact that I personally get sick & tired of staring at the same old hurricane climatology map every season, I took all of my hurricane season analogs, & other analog years I saw in other seasonal forecasts as well as incorporating some years which fell in line with the overall PDO/AMO cycles & the specific years within those cycles. Thus, I was able to compile a hurricane season climatology chart, which I made specific for this particular hurricane season. From there, I took the maximum intensities for each storm in each year by day & this gave them a category from tropical depression in light blue, to category 5 hurricane in black, & from there I could overlay other storms on top of that which eventually gave me this. This took about a week in all to make, to gather all the data, number on it on graph paper, color that, then go & do that onto a computer program, quite a lot of work, but when it’s all set & done it was definitely worth it. In fact, this chart’s mini-peaks in July actually were able to catch the development of tropical storms Chantal & Dorian and the chart accurately depicted the relative lull in tropical activity as we left July and entered the first days of August. If this chart to continues to be as accurate as it has been the last several weeks, it says that activity will start to pick up in earnest starting on August 10th.
Interestingly, the CMC ensembles, which actually caught the development of Dorian completely agree with this idea that around August 10th, things will pick-up big time as they’re hinting at potential tropical development in the eastern Atlantic around this timeframe. The red numbers on this picture below denote low pressure centers indicated by each ensemble member, with the brighter colors of yellow & orange showing large differences in the pressure forecast by the model, which is a signal that some of the CMC ensemble members are beginning to show development in the eastern Atlantic starting around August 10th. Image courtesy of tropical tidbits.com & Levi Cowan. Below, I’ll post a series of these models & the associative times they were run. A few things to note here are that although the model has been fairly consistent regarding potential development in the east Atlantic, the one trend that is becoming evident is that the CMC ensembles are getting more aggressive & are hinting that there could be a disturbance by this time nearing the NE Caribbean islands that might be worth watching, & the system this model may be picking up on is a strong tropical wave located near Nigeria & nearing Togo, the wave disturbance in the African easterly jet they are picking up would be close to the western edge of the convective mass that extends now all the way eastward to the Ethiopian highlands.
This image from Eumetsat shows what I’m talking about I highlighted this tropical waveof interest in pink as the potential culprit the CMC ensembles are picking up on to be near the NE Caribbean in about 10 days.
0z run July 30th
12z run July 30th
0z run July 31st
12z run July 31st
0z run August 1st
12Z run August 1st
0z run August 2nd
12z run August 2nd
Here’s my hurricane climatology chart, specific for this upcoming hurricane season. (black category 5 hurricanes, pink cat 4 canes, red-cat3, orange-cat2, yellow-cat 1, green-TS, blue-tropical depression). According to this chart as of August 3rd, we have still about 84% of the hurricane season left to go, & looking at the month of August, it’s definitely safe to say we’ve barely scratched the surface.
Now, if you’re still somewhat skeptical about this hurricane season being dangerous, let’s at a few more pieces of evidence, the first of which being SST over the Atlantic. I’ve been hearing some concerns recently & have also taken note of the band of cooler than normal water that has set itself up near the southeastern US coastline that extends just north of the Greater Antilles & into the central Atlantic.
Current NESDIS SST analysis showing the classic warm Atlantic tripole still in place with cooler than normal waters in the subtropics, or at least relative to the anomalies in the tropics & high-latitudes, which should help to force air to pile up & focus upward motion over the tropics.
Compare this to the SST in the top 10 highest hurricane impact years on the US coast, the look & distribution of the SST anomalies are almost identical.
Now, I’ve been looking for quite some time to find a year that matches up with our current pattern at 500mb over the Atlantic, it’s almost unbelievable how strong the ridge is this year near 45-50 north, which isn’t so far south as to suppress storm activity, yet isn’t too far north towards Greenland & the Canadian arctic, where mid-latitude troughs can slip in underneath, it’s in just the right or “wrong” spot if you like for storms to make hits on the US coast.
500mb May-July this year in the Atlantic, note the +NAO set-up with a trough near Greenland, very strong blocking across much of the north Atlantic, with another associative block of high pressure near & just to the west of the Hudson Bay. Also note the region of troughiness extending northwestward from Florida into the southern US & another weak cut-off low feature south of the sprawling high to the north.
I’ve searched endlessly for a pattern to compare this to & although 1999’s 500mb May-July pattern was as close as it can get since the start of the warm AMO, it’s doesn’t satisfy me & out of curiosity I looked at 1938 & lo and behold the pattern that season closely resembles that of this season.
1938 May-July 500mb pattern in the Atlantic is shown below, compare to our pattern posted above.
It gets worse, look at the US precipitation pattern this year & compare to 1938 for May-July
1938 for the same time period
1938 has been on my radar for quite some time, it’s only now that after seeing this precipitation anomalies I’m taking a closer look into it. For starters, I already was under the impression 1938 was a year that needed to be monitored more closely. The season before it, 1937, was characteristically much like last year where the strongest storms & most significant tropical development occurred outside the deep tropics.
1937 hurricane season
2012 hurricane season
Another thing that drew my attention was the fact that in April 1938, Chicago experienced record snowfall, denoted by areas of blue in the bottom two graphs of this picture below.
This seems reminiscent of the numerous late winter storms which hammered the midwest this past spring in March & April & a few other years which came up many times were 1893 & 1933.
This excerpt courtesy of the Minnesota Climatology Working Group, the State Climatology Office & the University of Minnesota back on April 18, 2013 helps describe the snowstorms of 1893 & 1933
“Heavy snows in April are fairly common in Minnesota’s past. The transition from winter to spring can spawn some rather strong storms and given the right conditions, can also tap into leftover cool air from the winter. Looking through historical anecdotes, the greatest chance of having a large snowstorm appears to be in the first half of the month. One of the greatest April snowstorms (besides theApril 5-7, 2008 event) was the storm that began on April 5, 1933. The old Pigeon River Bridge crossing in Cook County saw 28 inches in one day from that storm. This still stands as the 24 hour state record for snowfall in April. Two Harbors in Lake County saw 17 inches of snow from the 1933 storm.
Another historical snowstorm is the event that unfolded beginning on the morning of April 19th and ending on April 21, 1893. When it was all over 30 inches buried St. Cloud, with 24 inches in a single day. The 1893 Minnesota Weather Service bulletin describes this storm. “The (Low) caused the most disagreeable weather of the month, heavy snow fell varying in depth from six to thirty-six inches throughout the state: railroad lines were blocked, and traffic of all kinds was almost entirely suspended.” The Twin Cities saw 10 inches from this event and this is the third largest April snowstorm in the Twin Cities.”
To see full article (link)
Both 1893 & 1933 were devastating east coast hurricane years with storms failing to make the classic “c” curve on the east coast, rather the 1893 NY “midnight” hurricane & 1933 Chesapeake-Potomac hurricane both hit the coast in a relatively perpendicular fashion, indicative of an anomalous height pattern in this area at the times of these storms.
NOAA Reanalysis of 1893 NY hurricane 500mb & MSLP (Mean Sea Level Pressure) shows the storm approaching NYC on August 24, 1893, notice the ridging to the northeast of the storm near Atlantic Canada, a classic landfall pattern for the US east coast, especially New England. You can also see to the south of the 1893 NY hurricane is the Sea Islands hurricane, which would later go onto hit Georgia & South Carolina.
Once again, much like the 1893 NY hurricane & many others, looking at the reanalysis of 1933 Chesapeake-Potomac hurricane, it looks as if ridging over Atlantic Canada likely to blame for its anomalous track into the coast.
This gives me the idea that based on looking at the May-July 500mb pattern over the Atlantic Ocean (done research on this for all seasons, satellite-era & warm AMO, essentially since 1995) & given the set-up of the high this year is in such a way that implies for a system to hit from an abnormal direction, (south or southeast) this gives further credence to 1893 & 1933.
Now, going back to 1938, given that the central plains drought in recent years has waned, this naturally makes it much more compatible with 1938 that was towards the end of the Dust Bowl era of the mid 1930s. Also, knowing that our current cycles of AMO & PDO are much like the 1890s & 1950s when a barrage of hurricanes hit the east coast and that the 1938 Long Island Express is a great compromise in terms of track & timing between hurricanes Irene & Sandy, such a solution, although rare, would seem somewhat plausible this upcoming hurricane season.
Knowing what happened in 1938, when a storm system that was supposed to initially go out to sea, at least that was according to the weather Bureau in Washington DC & one that residents were very unprepared for as it traveled at 60-70 MPH due northward, giving it little time to weaken over the cooler waters. Also, the storm’s fast forward movement gave little warning to an already stunned southern New England & with the storm at one point being a category 5 hurricane to the south in the Bahamas, a weakening hurricane like this , as was observed with Sandy & Irene, would interact with a frontal system & mid-latitude trough in a way that would allow the storm to transition to relying upon extra-tropical & baroclinic processes, however at the same time the windfield & destruction felt by the storm would expand in coverage while decreasing somewhat in overall intensity. This storm was truly unprecedented & is referred to as one of the worst hurricanes in the history of New England & the northeast US, I mean when you have a 186 MPH wind gust at Blue Hill Observatory, MA & have Providence, RI that sits 15 feet above sea level put UNDER 12 feet of water, that should tell you something as to the magnitude & absolute power of this storm. Can’t even believe a storm could be so strong this far north, & looking at the pictures of the aftermath, this one truly tops the list as far as extreme hurricanes go.
A beach community in southern New England almost completely destroyed by the 1938 New England hurricane, there is evidence that there were other houses standing on this beach shown below, many of them though were completely washed away along with any people residing within them.
Thames Street, Newport, Rhode Island after the Great New England hurricane of 1938
Picture from NY times article in 1938 on the storm
This picture is from all the way up in Providence, Rhode Island, the storm surge from this hurricane completely over washing & covering up the New Haven Railroad tracks, waters in this picture below appear at least 5-6 feet deep, if not even more, which would somewhat validate the claim that the city was submerged under 12 feet of water thanks to the 1938 New England hurricane.
Those train cars in Providence, Rhode Island were tossed about like child’s toys sitting a considerable distance away from their railroad track.
Here are some good videos on the Long Island Express hurricane
What strikes me the most is just how close this year’s pattern in terms of precipitation & at the 500mb level seems to resemble that of 1938, kind of scary to see this, of all years, 1938 is definitely not a hurricane season you want to have close relation or correlation with. Given the other factors at hand which suggest that this season in particular could be a rather dangerous one for the US east coast, it’s certainly worth keeping an eye on this upcoming hurricane season which should begin to get cranking within a few short weeks.