Hi all, as many of you know, the mid-atlantic next week will be under the threat for a significant winter storm and I’ve been discussing in the comments section how similar this pattern looks to the Ash Wednesday Storm of 1962, which also came around about the exact same time of the year and many of the parameters going into that pattern were quite similar and I’ll discuss that below. Also, now as we are into March and the late winter pattern over the US and in the northern hemisphere is beginning to reveal itself, we can begin to look and get an idea of what this upcoming tornado season will be like.
Of course, in the mean time, with some of the significant severe weather, here is the official NESIS snow map showing the February 8-9 blizzard that struck the northeast with a very large widespread area of 1-2 feet of snow, with isolated areas from the coast of Maine through Connecticut picking up over 30 inches of snow, with up to 40 inches of snow reported in southern Connecticut.
From the Plymouth State website, a graphic I created here where you can see the pressure pattern at the surface, where you note the significant area of blocking located over Quebec and Ontario, extending into the central plains and out into the north Atlantic, with the main feature, being the area of low pressure off of the mid-atlantic coast in somewhat of a similar position, with a very similar set-up to the upcoming pattern and 1962, although the shortwave disturbance that was south of the Hudson Bay had enough influence to act as an “anchor” to the developing system, thus pulling it farther to the north closer to the southern New England and northeastern US coastline. Also noted is the +PNA signature with the trough over the Bearing Sea and ridging over the NE Pacific extending into western North America, and the trough into the four-corners region of the US. This pattern is actually not too terribly different from what will be coming next week, although this pattern was much more progressive, and the upward MJO is also evident with relatively low pressures throughout the Caribbean at the bottom of this picture.
Also, here’s a few satellite animations of the storm system, where you can witness its evolution from two distinct shortwaves in the subtropical and the polar jet, to the phasing that began to occur in the mid-atlantic, to one very powerful mid-latitude cyclone off of the New England coast.
Also, here’s the Contiguous US 500-1000 mb thickness at the time of this storm, and this map I also made from the Plymouth State website, where you can see the main low pressure feature just sitting to the south of the New England coastline, with a notable extension of the trough axis to the northwest which is due to the fact that a shortwave disturbance was in the vicinity over the northern Great Lakes, and was a good reason as to why this storm system cam north as opposed to moving out to sea.
When stacked against the highly referenced analog of the “Lindsay Storm” of 1969, you can see how very similar both storms were to each other.
Although it would appear as if the positioning of the central US high farther to the west with even some influence into the four corners region in 1969 may have made all of the difference as to why the axis of snow was farther to the west in the Lindsay storm, closer to NYC, west-central massachusetts, and into New Hampshire and more into west central Maine as opposed to the New England coastline where the heaviest axis of snow was centered.
Going back to tornadoes, here are so amazing videos of the Hattiesburg Tornado, the strongest tornado thus far this season, as it happened.
Here’s a really interesting 3D radar image of the Hattiesburg storm showing how tall the thunderstorm was at over 50,000 feet, with the areas in green and red showing objects coming to an and away from the radar. You can see how this division area between these two areas where the greatest rotation is located tilts towards the surface and is tilted towards the east with height due to the wind shear above the surface helping to create the tornado in the first place with the strong difference in wind speed and direction with height.
For a perspective on the tornado season thus far, here is the latest graph from the SPC showing the tornado count for the year with 102 tornadoes as of February 13th, making this the 2nd most active tornado season since 2005, only trailing 2008.
Here are the severe weather reports thus far this year for the US showing not only tornadoes but hail and wind damage as well showing the expansive coverage of the severe weather thus far this year.
The average number of tornadoes per 1,000 square miles in the map below shows that “tornado alley” although usually seeing many tornadoes, is not as prevalent as some consider it to be with other areas, like “Dixie Alley”, “Hoosier Alley” and “Carolina Alley” with significant amounts of tornadoes.
Also, you should take notice that in recent years, with the flip to the cold PDO, the # of tornadoes has been on the increase overall with warm ENSO years like 2002, 2006 and 2009-10 seeing less tornadoes.
For comparison, you can clearly see what the influence of the ENSO on the overall state of the PDO does to the tornado count.
2008, a la nina year, notice how not only is their a higher concentration of tornadoes, but also, they are more focused over certain areas.
Notice unlike 2008, 2010, a warm ENSO year featured significantly less tornadoes, also more spread out in nature over the US, but interestingly, many more tornadoes noted over the western and southwestern US.
You can also see this notable correlation of ENSO to tornadoes in the summaries of tornado seasons over the US from 2008-2011
A few interesting graphics here, the first one showing the average # of tornado watches issued by county over the US in a given year, shows that Dixie Alley and the southern Plains are typically hardest hit, with lesser amounts elsewhere.
Of course, the average # of severe thunderstorm watches per year over the US reveals more of a classic pattern with the worst of the action towards traditional tornado alley areas, with lesser amounts towards the mountains of the Rockies and Appalachians, and notable increases near the US east coast.
Ever wondered when you see damage photos from a tornado why some areas in its direct path are completely destroyed, while some areas seem relatively “untouched”? Well, if you never knew it before, but a tornado itself actually is not just one rotating vorticy, but is in fact, comprised of multiple vortices that rotate around each other in somewhat of a “Fujiwhara-like” motion around a common center, its just that many times, the dust and debris surrounding the tornado can obscure this structure and give you the false impression that the tornado itself is one spinning center.
Here is a tornado diagram to help you to better understand what I’m talking about, and this was developed by Dr. Fujita (Also founder along with the Weather Channel’s Dr. Greg Forbes of the Enhanced-Fujitia scale for tornadoes) developed in 1971.
These videos may help you to visually understand how this process works, so interesting!!
Of course, you can see this process going in on also in the Joplin tornado case you haven’t seen it, and if you have never seen explosive tornado development before, you will be absolutely amazed at how fast this tornado goes from a simple rope tornado to a giant wedge within just a few minutes!!
Now, when you think about what ingredients it takes to get tornadoes, I think many of you already know the basics, we need a strong gradient, or difference in temperature over a relatively short distance, which helps to create differences in pressure, and differences in pressure and temperature create wind, and since there is naturally less friction of air molecules higher up in the atmosphere, winds tend to be generally higher, also large temperature gradients also found higher up in the atmosphere above the surface and add to the temperature and pressure gradient, which amplifies the available wind energy, thus you tend to get differences in wind with height. Differences in wind with height creates the column of air to “roll-over” near the surface, which causes a rolling motion in the atmosphere. Also necessary for adequate tornado formation is changes in wind direction with height, which is typically found in intensifying mid-latitude cyclones, especially upon encountering the Gulf of Mexico. As this rolling column of air near the surface is tilted up into the vertical by thunderstorm updrafts, and more easily kept in tact by changes in wind direction with height, this also forces the rolling column of air to become vertically titled, and as this process continues, eventually, the rotating column of air is able to reach the ground and form a tornado. When dealing with differences in temperature, this is usually dealing with colder air over the northern US and Canada to the relatively warmer air over the Gulf of Mexico and Atlantic, and these differences are usually enhanced, cold air to the north in particular by above normal snow pack or even late season snows. Although the amount of energy received to earth’s surface in the northern hemisphere is increasing and the solar wavelengths are increasing as the axis of direct sunlight crosses the equator and works its way towards the Tropic of Cancer at the start of the summer solstice, 23 degrees, 26 minutes, 16 seconds north or (23 + 26/60+16/3600)=23.44 degrees north latitude, there still will be lingering cold air masses in place and due to the natural weakening of the jet at this time, this causes significant perturbations within the jet stream, where areas of low pressure have characteristically more random development, thus snowstorms are still bound to occur, especially the farther north in the US you get. Despite the increasing solar radiation, with snow on the ground, this reflects 85-90% of solar radiation, and thus with water having 1000x the energy capacity of the warmer air around it, it takes significant amounts of energy out of the atmosphere to melt the surface snow, and thus with energy over the snow pack being lowered in comparison to areas farther to the south where it is significantly warmer, this can create great discrepancies in temperature and pressure, which in many cases can only be balanced out by severe weather or tornadoes. (As it would only make sense this would occur as weather itself is here because of the natural variances such as earth’s tilt, precession, elevation, uneven distribution of sunlight, ratio of land to ocean in northern & southern hemisphere, etc.., and as long as those differences stay in place, we’ll always have weather to admire and enjoy)
Many of you probably already know and understand the ingredients and the dynamics that go into tornadoes and severe weather, here are a few diagrams to help you either refresh you memory or even assure of some of the processes involved.
A great example of why I get concerned when I see heavy snows over the northern US late in the season and even into spring, one only has to look back to 2011 to see how this is the case.
Look at the temperature map for the start of April 2011, and notice how predominantly warm it was over much of the US, in exception for the Pacific northwest and areas west of the Rockies.
However, as I mentioned above, as the jet stream is naturally weakening in the spring overall and retreating north, random perturbations can occur, and this certainly did happen as a low pressure area ejected out of the Rockies and dropped large amounts of snow over the upper midwest in mid April.
As you know, snow reflects solar radiation, thus only further cooling the surrounding air and enhancing the differences in temperature and pressure over the US, thus a severe weather outbreak unfolded over the southern US, eventually leading to the one of the greatest tornado outbreaks in NC history on April 16, 2011.
The deadly outbreak of tornadoes began in Oklahoma and other areas of the southern plains, which originated from a cut-off region of low pressure which moved out of the central Rockies containing cold air aloft, among many other necessary ingredients for significant tornado formation.
The next day, severe weather shifted farther to the south and east towards “Dixie Alley”, of course being the first of many tornado outbreaks to occur that month, with the storm system itself having split up, with the mid-upper level low pressure system, carrying cold air aloft supportive of large damaging hail near the low pressure center towards the central Mississippi River Valley, and a new area of severe weather as mentioned earlier developing over the south in association with a new area of low pressure that would move northeastward towards the Carolinas on the 16th.
Of course by the 16th of April the area of low pressure moved northeastward to the Carolinas, leading to a very impressive and deadly tornado outbreak, one that holds personal experience for me, as I came extremely up close and personal with the Raleigh-Sanford tornado, and it was an experience like no other, something storm chasers dream of, of course I was just proud to make it out alive through that storm.
Here’s a satellite loop from Plymouth State of the event showing the progression of this system from the southern plains to the Carolinas from April 14-16 2011
The 500 millibar pattern at the time of this storm over the US shows what the pattern was like during this event, with the classic negatively titled trough orientated from NW to SE, and of course a few other notable features that could be of future reference for any potential outbreaks in the future is the vortex of low pressure near the Baffin Bay and the trough of low pressure digging into the northwestern US with a relatively flat west to east flow in the wake of the trough in mid-April.
Here is the evolution of radar during this time, courtesy of analysis done by the National Weather Service, and you can see how this starts out as a simple line of thunderstorms, however with increased instability lapse rates, plenty of moisture in front of the thunderstorms, and wind shear, you can clearly note the evolution of the severe thunderstorms to discrete supercells producing numerous tornadoes.
A total of 30 tornadoes were produced over NC during this outbreak, and the one that will haunt me for the rest of my life remains the EF-3 Sanford-Raleigh tornado, and most of the fatalities you see in Wake County NC occurred in the mobile home park less than a half a mile from my location, I consider myself very lucky.
Courtesy of the NWS, radar from the Raleigh-Sanford tornado shows a very classic hook signature, with a “debris ball” located at the southwestern flank of the supercell, classic for tornado-producing thunderstorms in the northern hemisphere, especially the US, interestingly, most tornadoes also usually move in a SW to NE direction.
Interestingly, the other very large and comparable tornado outbreak to April 16, 2011 was in late March of 1984, and of course if you don’t think enhanced snow cover does not have very significant influence on tornadoes, it is not more than just mere coincidence that the northern hemisphere snowfall during this time, especially over the US was above normal, with lingering snow evident over the northern US towards the Canadian border.
Infrared satellite loop of the storm system that produced the significant tornado outbreak in North Carolina in 1984.
Here is Rutgers snow Lab official northern hemisphere snowfall coverage for March 20-26 1984, showing lingering snow cover over the northern US, which may have played a role in the intense tornado outbreak that occurred in the same time period, only significantly surpassed by the April 16 2011 outbreak.
Here are the total number of tornado reports during April 2011, a total of 874.
Here is the overall evolution of the jet stream during this time period, including all of the severe weather events of April 2011
Then, later in the month, one of the greatest tornado outbreaks in history occurred, of course the severe weather never really let up in the days preceding the outbreak, with significant severe weather each day.
April 24 NWS storm reports
NWS April 25 storm reports
NWS April 26 storm reports
NWS storm reports April 27th, the day of the remarkable tornado outbreak
NWS storm reports April 28th
A satellite animation of the event also helps one to understand the scope of this outbreak
When you look at the conditions at hand leading up to this deadly month of tornadoes, one of the most important things of note is the significantly above normal snow pack in the northern hemisphere during that spring, and as explained earlier in this post, increased snow coverage during the late winter and into spring plays a role in increasing the potential for tornadoes.
The northern hemisphere snow cover anomaly on April 25, 2011 in the days before the major tornado outbreak in late April reveals, once again, that above normal late season and spring snow plays a role in increased tornado production.
Also of note is the very sudden SOI crash at the beginning of April 2011, due to a very large Kelvin Wave over the equatorial Pacific, and with such a crash in the SOI (Southern Oscillation Index), this forces a sudden crash in pressure anomalies over the tropics and subtropics over the eastern Pacific and into the Atlantic, which enhanced the subtropical jet stream, and along with the difference in temperature and pressure enhanced by the above normal snow pack over the US and the northern hemisphere, this favored intensification of mid-latittude cyclones, which in the spring, can lead to increased severe weather and tornado outbreaks.
Of course, the oscillation that plays a large role in the SOI, the MJO, being the only other thing besides Kelvin Waves that moves against the natural east-west movement of weather in the tropics put in place by the Coriolis Effect, obviously would have large influence on the SOI, and when one looks at the MJO, there is something a little concerning. For one thing, the MJO has been relatively free to move about in the global tropics, and is moving about through the entire global tropics in a much more predictable manner, due in part to the neutral ENSO, allowing the MJO to be more predictable on its natural 30-60 day variation through the global tropics. When you look at the MJO and where it may be headed in the future, there’s obviously some reason to be concerned in relation to the tornado season, because in a few weeks, we should begin to see the MJO propagate eastward through the tropical Pacific, in doing so, will leave behind in its downward phase, a trail of relatively higher than normal pressures, which will help to trigger a kelvin wave, and with a kelvin wave in place this forces the SOI to crash negative, where the pressures are lower than normal at Tahiti in relation to the above normal pressures at Darwin, Australia. Such a crash in the SOI as shown above, also occurred before the historic tornado month of April 2011, and if it were to happen again, combined with the above normal snowfall in the northern hemisphere thus far, being easily in the top 5 for the Dec-Jan period, there’s reason to believe that this tornado season could follow suit if the MJO were to propagate towards the Atlantic as April approaches, as indicated by the ECMWF.
Although, I will say that one positive aspect about the pattern is that according to AMSU
(link) http://discover.itsc.uah.edu/amsutemps/ , the 400 millibar temperatures are warmer than 2011 and 2008, but below that of 2010, hopefully considering all of the other factors and conditions at hand, this may be enough to outweigh them and put a limit on the tornado activity.
Of course, should we really be surprised by the increase in tornado activity, because even though AGWers claim that warmer=more tornadoes, actual data contradicts this, especially that of strong tornadoes (which is a better comparison to that of all tornadoes, because weaker tornadoes without the advent of satellite technology, more trained weather spotters and enthusiasts, among other things, the modern total tornado count is somewhat inflated.) which more prominent back in the 1970s, when the climate was COLDER, not warmer, with strong correlation to the PDO.
For those of you that think this winter is still a bust take a look at the entire picture and see that the northern hemisphere snowfall extent was once again very high for January being 6th highest since 1967 and way ahead of last year.
Here’s what it looks like over the northern hemisphere as far as actual snow cover goes.
Let’s compare this upcoming storm system to some famous mid-atlantic storms.
“Snowmageddon” of 2010
Snowmaggedon in 2010 was actually comprised of 2 significant winter storms that struck the northeast within only a few days of each other.
February 6-8 snowfall accumulation
February 9-11 snowfall accumulation, notably slightly farther to the north than on the 6-8th, but some of the exact same areas of Washington, Baltimore, Philadelphia and other areas of the mid-atlantic were hit yet again with more snowfall after a major winter storm only a few days earlier.
From Plymouth State University, here is a few satellite presentations and patterns of the event so you can see the evolution of the storm and the pattern involved.
The 1000-500mb thickness with overlaid pressures over North America at the time of the first system that struck the mid-atlantic reveals that this pattern is significantly different than that of the upcoming pattern, especially in the fact that instead of a region of blocking high pressure over Quebec and Ontario, there’s a gyre of low pressure, and the placement and shape of the ridge over the western US is farther east and much more sharp north-south in nature. However, the things this pattern has in common is the slightly +PNA signature with troughing centered just west of the Gulf of Alaska with ridging over western North America, although the placement, strength and shape of the ridge is certainly far from ideal, as there were other factors that helped to play a part in making this winter storm so significant for the mid-atlantic.
However, the 2nd winter storm that struck the mid-atlantic towards February 9-11th is much closer to the current pattern, although still not the precise set-up or ideal analog. What is similar in this case is that instead of the large gyre of low pressure over eastern Canada, this is significantly weaker, with actually some ridging evident just to the east of the Hudson Bay. Also, the trough is somewhat similar in nature west of the Appalachians, where this storm dives southeastward initially as a clipper system from southern Canada with some support in the subtropical branch of the jet, and as I will talk about later in my post, there’s a a shortwave trough orientated to the northwest of the main region of low pressure that is trying to capture or at least act as an “anchor” to the low pressure that is beginning to exchange energy from the initial center of low pressure over the Ohio Valley to the mid-atlantic coast, which allows the low pressure area to be somewhat farther to the north and west, and slower in its movement eastward and out to sea. Also of note is the trough over the Bearing Sea and the ridge over the western US and Canada is much more in line with the current pattern, although not exactly the same, and even this set-up is able to capture the developing trough over the four corners region, which is also being noted in the medium to longer range model guidance and overall pattern.
In that following March and April, a more classic el nino signature pattern took over with a dominant subtropical jet with stormy and wet conditions over the south, to comparably warmer conditions over the northern US, however, considering this year has been relatively neutral as far as ENSO goes, and the fact that the northern US, not just to the south, but also the northern US should be cooler this year based off of more profound analogs like 1960, 1956, and 1996, among others, this spring probably will not follow this pattern for March and April, which was also below resulted in a below average tornado season, which is probably not where this upcoming season is going.
And at 500 millibars this is what the pattern looked like from Feb-May 2010
Compare this to the recent 500 millibar pattern and you will note there are probably a few interesting similarities, especially towards the end of this loop, where you can see just how similar this pattern gets to the Feb-May pattern in 2010, where the ridging towards Greenland expands and intensifies, with the very persistent trough over the north Atlantic getting enhanced due to the intensifying ridge from Scandinavia to eastern Canada. However, the significant trough over north-central Asia is exactly the opposite of the Feb-May pattern, and considering in a general sense that this pattern was not very productive in severe weather, it shouldn’t be surprising that we have seen a recent lull in the amount of severe weather.
Also of note is the trough over the Gulf of Alaska becoming enhanced due to the +PNA signature that begins to intensify thanks to the declining 30 day sunspot cycles, and is just another reason why I am scratching my head at the long range PNA forecasts for it to tank negative, when the 30 day sunspot cycles, which shows a very clear inverse correlation to the PNA, remain predominantly low, as they have been for quite some time, and this fits quite nicely with the PNA beginning to become significantly more positive as the month of February progressed.
ECMWF observed PNA & forecast
ECMWF ensembles PNA forecast, although a little more sensible than the operational ECMWF, still strange given that the 30 day sunspot cycles remain low.
The 30 day sunspot cycles, as mentioned in previous posts and above, has a very interesting inverse correlation to the PNA, and why should anyone be surprised by the PNA’s positive spike with the 30 day sunspot cycles in the tank since late January?
Of course the decline of the 30 day sunspot cycles also correlates nicely with the flip of winter from generally warm and a lack of snow over many areas to a much colder and stormier pattern that began around the 20th of January and continued right on into February.
During the first half of winter, with the 30 day sunspot cycles relatively high in comparison to what is being observed lately, it really is not too surprising that the 1st half of winter featured much warmer than normal conditions across the US, especially across the eastern US, but towards the west, where higher levels of sunspots usually induce a -PNA, it is no wonder as to why the overall pattern supported cold & stormy conditions over the western US, at least for the first half of winter.
Of course, within the 1st half of winter, there was relatively a two week period spanning from just before Christmas and into the first week of January where conditions were colder than normal over the US, and this can be attributed to the -SOI crash from the Kelvin Wave that occurred in the 2nd week of December, which forced troughiness east of Hawaii, not to mention, the MJO actually became slightly favorable for once during the winter, and the PNA went positive, with ridging towards western North America, which was in response to the troughiness underneath over the eastern Pacific created by the Kelvin Wave. Also, there was a significant lull in the 30 day sunspot cycle, and it should come as no surprise that temperatures as a whole over the US fell in response.
Then, after this period of cold, of course many began to scream that winter was over and spring was coming, lol, of course the period of warmth over the US in the heart of winter also correlated nicely with the uptick in the 30 day sunspot cycles, then the as the sunspot cycles began to drop again, the cold, not surprisingly returned as well.
US temperature anomaly for January 20-27th, although with the very impressive stratospheric warming event, notice that temperatures were not overwhelmingly cold, and that’s due to the MJO being over the western Pacific and octants 6 & 7, which favor a stronger southeastern US ridge, which in this case, was able to fight off some of the cold from the stratospheric warming event, but still a cold pattern, especially across the northern US.
Now, look at February, much colder as a whole over the US, with some warmer than average temps towards the Gulf coast, where the warm AMO induced Gulf of Mexico exerted its influence and over the northern Rockies, where down sloping winds may have played a part in the slightly warmer temperatures there. Overall, below average temperatures for most, correlates nicely with the low 30 day sunspot cycle, which was indeed low for the entire month of February
Also, especially across the southern US and the lower Mississippi Valley, and virtually for about 2/3rds of the US, March has gotten off to a cold start, which is still consistent with the low sunspot cycles.
Of course the colder than normal February temperatures and a cold start to March is a nice reprieve from the observed warm start to winter in December and January for much of the eastern US, with below normal temperatures, especially over the inter-mountain west and the south-central Rockies, where it is actually warmer than normal for the moment.
To go along with the cold, snowfall increased as well, with the Chicago snow-hole filling in and significantly more snow in cities like Boston and New York, which is somewhat comparable to 1969, which also featured a relatively warm and slow start to the snow season that turned around into a snowy February for many in the northeast, although the same could not be said for areas farther to the south towards Philadelphia, Baltimore, and Washington DC, but their turn at the snow is coming.
Looks a lot like 1969, (in exception for November which featured the “Sandy Sequel” snowstorm) which was of course, the same year referenced in accordance to the “Lindsay Storm” with a close analog to the winter storm that occurred in early February, and 1969 also was very snowy in February after a relatively slow start to the winter.
Like what is anticipated this March, and somewhat similar to what occurred this February with colder than normal temperatures over much of the US, 1969 was also cold from mid February to mid March
Already thinking about next winter and snow? For our amusement and interest, look at the temperature anomalies for the winter of 1969-70 after the comparable analog winter of 1968-69, plenty of cold across the eastern US, warmer to the west and the Rockies
Now, compare this upcoming system to another notable winter storm, the Blizzard of 96.
Of course, when one looks at the pattern going into the Blizzard of 1996, you can see there are some overall similarities in respect to the upcoming storm, although the ridging in on the west coast of the US and North America is significantly different, and will not be there with this upcoming storm, and of course the trough over the Gulf of Alaska is also different, and these differences equate to the fact that our current pattern is more progressive in nature than in January of 1996, of course one would anticipate this as we get into March and the jet stream begins to weaken and solar wavelengths strengthen, thus more random disturbances can form within the overall pattern, which would tend to make a pattern more progressive in nature.
Interestingly, when one looks at the temperature anomalies over the US for March of 1996, it offers just more support for a cold March over the US and a slow end to winter, with the potential for this March to rival the cold experienced in 1996.
Also, more comparisons can be made to the winter of 1996, of course it was also a year that was compared with this year as far as the greatest US snow cover on Christmas, which was the greatest since 1996.
None of these systems is nearly as good of an analog as the 1962 “Ash Wednesday” snowstorm, which not only had similarities in the precise time of the year, but also the pattern going into the storm and the areas to be effected by the upcoming storm are also notably similar.
First of all, since we are dealing with a storm system that looks to focus its greatest impacts towards the mid-atlantic, here’s a map from 1962 showing the track and the general area of some of the heaviest snow associated with the storm.
Now look into the pattern of this storm and compare it to what is coming down the road with this storm next week.
Starting with the initialization of the ECMWF, (by no means I am staring at a model here, just describing the pattern and using it as a guide.), this reveals that the trough of low pressure that produced snowfall over much of the Tennessee Valley and into the Atlanta metro area with widespread frosts and freezes deep into Florida.
Snowfall accumulation map courtesy of the NWS in Peachtree City, Georgia, showing mainly a trace to a dusting in and around the Atlanta metro area and up towards Budford, GA, to as much as 2-3 inches in the north Georgia mountains.
The NWS service office in Nashville, Tennessee with their snowfall accumulation map, helping to show the relatively sporadic and random nature of the snowfall, with some areas picking up next to nothing, while other areas in the vicinity received significantly higher amounts on the order of an inch or two, especially on the west side of the mountains.
As this moves onshore, much quieter weather builds into the eastern US with ridging taking over for the moment, however, the next trough that moved onshore of British Columbia on Saturday has now moved into the northern Rockies, bringing with it plenty of snow and wind to areas of the northern plains and the northern Rockies. Also of note is the next trough of low pressure still over the Pacific, which will play a large role in determining the strength, orientation, and position of the ridge in the wake of our storm system over the eastern US, and this ridge will help to feed air into the low pressure center from the snow covered plains, where pressures are significantly higher than over the eastern US, thus this will help to determine the precise location and strength of the low pressure area over the eastern US as we get into next week.
Below is the March 4 1962 500 millibar pattern for the US, and you can see right away the very interesting similarities already starting to show up in the pattern, with a trough positioned (although a bit farther east than where it is shown above) over the Pacific, with a region of troughiness extending into the northern plains, and of course the trough that moved offshore of the east coast helps to create a “rex-block” signature where a region of low pressure in the mid-latitiudes gets stuck directly underneath a blocking area of high pressure to the north, more in association with the polar jet stream, and this feature is evident in the 1962 map below with a “hump” to the north in the isobars over the great lakes and extending up into the Hudson Bay, indicative of the aforementioned high pressure block associated with the polar jet stream.
By tomorrow, the area of low pressure will begin to eject out southeastward in the northern plains, producing some significant snows on its northwestern flank generally from Bismarck and Fargo, ND, through Minneapolis-St.Paul into Waterloo, IA and areas predominantly northeast of Des Moines in Iowa to the Chicago area and areas along and northeast of the I-74 corridor from Illinois through Ohio. By this time, we will also have a very good idea on what this storm will be doing as the surface and weather balloon observational data is much more attainable in this area in comparison to the mountainous and rugged terrain of the Rockies, which can cause some issues in the model forecasts in the details of a particular system, thus it will not be until the storm gets into the plains by tomorrow, that we can begin to trust the models as they will have much more reliable and accurate data in them, and will have enough time to adjust their forecasts to the new data. Also, the region of troughiness and low pressure that moved off of the east coast has left behind an mid-upper level low pressure system to the south of the Canadian Maritimes, which is stuck underneath the powerful block of high pressure associated with the west-based -NAO over Labrador and east of the Hudson Bay, which has led to “Rex-Block signature. Also, the trough that was off of the northwestern US coastline is beginning to move onshore of the Pacific northwest and extreme southwestern Canada, and as mentioned earlier, this trough will help to determine the strength, placement and shape of the ridge of high pressure that will be left in the wake of the area of low pressure as it comes near the east coast, and this intricate detail will still be up in the air until at least Tuesday, and this along with the shortwave disturbance helping to connect the trough of low pressure over the midwest to the polar jet and the polar vortex over the northwest and Yukon Territories, could lead to a few last minute forecast adjustments that will have major implications in the forecast, even within 48 hours of the potential winter storm.
Here are what some of the local NWS service offices are saying over the midwest and into the Great Lakes, as it does not specifically pertain to the eastern US, the weather observation data received in these areas will be vital to model forecasts, and will help to determine the intricate details of this storm as it nears the mid-Atlantic.
NWS Bismarck, as much as 12-15 inches of snow possible towards Minot, with lesser amounts towards Bismarck and southwestern areas of North Dakota.
NWS in Fargo, ND with as much as 8-12 inches in some areas, especially just to the north of Fargo towards Devils Lake and Grand Forks.
NWS Duluth, with higher amounts farther to the south and west of Duluth and northeastern Minnesota.
NWS Minneapolis-St. Paul
NWS Aberdeen, SD
NWS La Crosse, Wisconsin
NWS Des Moines
NWS Chicago, IL, showing yet another snow event, which would continue to fill in the “snow-hole” that was at one point in and around the Chicago area.
By 72 hours, the area of low pressure that was over the plains has moved southeastward to over the eastern Ohio Valley, along the way producing significant snows across the plains and into the southern Great Lakes region. By this time, the trough that has moved off of the east coast is now to the south of Greenland, and the dragging mid-upper level low pressure system located underneath the block over eastern Canada is finally beginning to move away, however, the ECMWF suggests that there will be energy left behind into New England, and as I explained to a blogger and will do so here, this has major implications on the precise track of our storm system.
“the upper level low pressure system helping to create a “Rex-Block” signature has a region of vorticity and troughiness laying behind it extending back into New England and southern Canada, and with the area of interest being our low pressure system, enough of a distance away from this vorticity, some higher pressures are allowed to build in, especially considering there is still plentiful snow pack available generally from I-90 northward able to enhance this region of slightly higher pressures, this may be just enough to give the low pressure a nudge eastward, and plus a standard rule of thumb to use in this situation is considering the placement of the block of high pressure over Labrador and Quebec is that low pressures underneath such areas of high pressure can not begin to make significant poleward movement northward until at least aligning up in longitude with the area of high pressure, in which it may only then have the opportunity to make significant movements to the north. Considering the longitude of this high pressure block will be a few degrees or so east of the east coast, this suggests an eastward movement, possibly even slightly south of east movement is the most sensible solution, which would favor most of the snow for areas towards the I-70 and I-66 corridors of extreme southern PA, MD, and northern VA, although I think New Jersey should get in on the action as well.”
Now, in considering this, there will be a “wildcard” in this entire pattern that can throw my whole forecast ideas in the garbage, and that is this shortwave trough and associated vorticity you see located over western Ontario, being connected to the polar vortex, now over Nunavut. What this shortwave can do is with it in such a relative position in accordance to our developing low pressure farther to the south and east, knowing that in “Fujiwharas” in the northern hemisphere that areas of low pressure have a tendency to rotate towards one another in a counter-clockwise motion, with the more dominant of the two areas of low pressure usually absorbing the energy of the other region of vorticity and low pressure. In this case, a counter-clockwise motion of these two low pressures would mean that based off of the juxtaposition of the area of interest to the south and east, this would force it to move in a more northeasterly motion in comparison to the shortwave disturbance exerting its influence to its northwest. However, with the area of low pressure comparatively much stronger than than the shortwave to the south of the Hudson Bay, this means that it is the dominant feature, thus will absorb some of its energy and will have to do less “work” in order to achieve “equilibrium” in accordance to the fujiwhara effect. This is why it still may be a bit too early to make an exact call on this system, although the 1962 analog is still pretty close, like snowflakes, no two, three, four, or even more low pressure systems and patterns are exactly alike.
The GFS, however being a more northerly solution has some notable differences between it and the ECMWF, which is helping to create its more northerly track. Notice, like the ECMWF, the GFS has the mid-upper level disturbance over Atlantic Canada stuck underneath the block to the north, however, as I mentioned above about how low pressure areas stuck underneath blocks of high pressure can not gain significant polar motion until they have gained a similar longitude to the block to their north, and this instance with the axis of the high pressure block on the GFS only slightly farther to the west, this allows the low pressure system to come farther to the north and west.
Comparing to 1962 note that in 1962 the axis of the trough off of the west coast is in almost the exact same position, with the ECMWF notably much faster than the GFS, which is unusual given that the GFS is usually the progressive model. You can also see how far to the north the blocking is in 1962, which may of course be something to note and look out for, as the GFS shows the block farther to the south, yet tries to take the storm on a track near to just north of the 1962 storm. which does not make a whole lot of sense, of course, the shortwave disturbance to the northwest of the main area of low pressure may be a reason as to why the GFS has pulled to the north somewhat.
At 1000 millibars for March 5, 1962, this map hopefully gives you a better understanding of what is occurring in the lower levels of the atmosphere, and could be used as comparison along with the 500 millibar maps to check against the solutions and the validity of the model solutions.
Here’s a map showing the 500 millibar vorticity, helping you to get a better idea of what we’re dealing with here, with further comparison available against the models.
Snowfall accumulation map (in tenths of inches) from March 4 1962 reveals the snowfall across the upper midwest, Great Lakes, and Ohio Valley, with some beginning to approach the Appalachians.
By 96 hours, the ECMWF model has moved the system offshore, almost in a due east to east-southeasterly fashion off of the coast, and although this solution seems to far south and way out of touch, the solution being offered by the model itself makes sense given the placement of the block of high pressure to the south of Labrador, with its axis centered east of the east coast, in turn, forcing the system to move in an easterly fashion until it can achieve a similar longitude where it can viably turn in a more poleward direction. Also, unlike the GFS, the ECMWF keep the shortwave disturbance to the south of the Hudson Bay held back somewhat in nature, which lessens the amount of influence it can have on the developing area of low pressure, thus this ‘anchor’ is not in place to at least slow down the storm’s progression nor hold it back farther to the north and west. Also of note is by this time, the trough that was over the Pacific is deepening along the western coast of the US and has slowed down significantly due to the +PNA regime in place thanks to the low sunspot cycles, which is enhancing ridging over the Gulf of Alaska and into northwestern North America to the north of the trough. The next trough of interest behind this of course is waiting over the Bearing Sea.
The GFS, unlike the ECMWF has the axis of the region of blocking over eastern Canada centered farther to the west which allows the area of low pressure underneath to begin to make a more significant poleward movement sooner, thus forces the low pressure area farther to the north and west than that of the ECMWF. Also, another difference in the two models is the GFS’s handling of the polar vortex over northern Canada, with it having the center of the vortex laying back farther south and west than the ECMWF, and although this may not seem like much of a difference, what this does is it forces the axis at which the polar vortex will extend its influence into more towards the western US trough as opposed to the eastern US area of low pressure and the shortwave to the south of the Hudson Bay. This should mean that the system south of the Hudson Bay is weaker, thus there is a less of an influence from it on the low pressure area, which would logically mean this low pressure area does not have a formidable outlet farther to the north and west, thus I do somewhat question the current GFS solution, as it will probably change anyway from now until then as better data is input into the model once the disturbance gets east of the Rockies by late tomorrow.
I personally prefer the CMC solution which is a blend of the ECMWF and the GFS as far as track goes, and is a little bit more sensible in its placement of the polar vortex and the allows the shortwave disturbance to exert some influence on the low pressure area without being overly assertive or aggressive.
Now compare to the 1962 analog, and notice how the low pressure area is very close to the GFS and CMC, especially the CMC, however, a few notable differences in the forecasts to the actual observations during 1962 is the fact that the trough over the western US is deeper and located much farther to the south towards northern California as opposed to Oregon or Washington, and this forces the ridge farther to the east to be slightly stronger in nature, which in turn leads to more significant pressure falls towards the east coast, where our developing area of low pressure is. Also, a difference that could have major implications is the precise placement and orientation of the high to the north over eastern Canada, which is actually farther to the west than the model forecasts, and given the information above about how low pressures underneath areas of blocking can not make significant poleward motion until they have achieved a similar latitude suggests that the 1962 may actually end up farther to the west than our current situation, although the stronger ridge to the west of the storm from the deeper western US trough may offset some of that difference.
The slightly western displacement of the high pressure area is also evident on the 1000mb chart from 1962.
The snowfall accumulation map from March 5, 1962 (in tenths of inches) helps you to get perspective on the overall snowfall from this system and sets some boundaries as precedents for this upcoming storm’s snowfall accumulation.
By 120 hours, the storm has moved offshore of the east coast, with some still evident snowfall and high surf still occurring along the mid-atlantic and the northeast, but this worst of the storm should have passed by this point, and a quieter pattern should begin to take over. Also notable is the fact that on the ECMWF, the shortwave disturbance comes in closer contact with the area of low pressure finally, however, the block now located towards the Canadian Maritimes will aid in keeping the features separated, although, if the disturbance is closer to the area of low pressure, then this could alter the track depicted by the ECMWF farther to the north closer to the GFS. Also, by this time, a trough is beginning to dig into the western US, and thanks to the +PNA in place, this trough will begin to form a partial rex-block signature and the slowing down and deepening of the trough will pump the heights to the east over the plains and eventually the eastern US, bringing with it, likely a warmer period of weather, much more reminiscent of spring.
The GFS and the ECMWF differences grow as the GFS is much slower with the area of low pressure, and by this time it almost completely destroys and flattens out the block over eastern Canada and the Maritimes, which does not make too much sense, but is something to be anticipated when dealing with the usually flat and progressive long range GFS. Also, to no one’s surprise, the GFS is not as deep and is a little faster with the trough over the western US, in which the ECMWF is slower, although this can be attributed to the fact that it has a bias to be to slow with energy over parts of the eastern Pacific and into the southwestern US. Also, the GFS is much stronger with the trough towards the Gulf of Alaska, and to no one’s surprise is once again flatter with the ridge over northwestern North America, indicative feature of the +PNA.
Once again, for this time frame I prefer (the recently upgraded) CMC, as it is a nice compromise between the GFS and the ECMWF with notable features like the area of low pressure near the east coast, the trough over the west coast of the US, the ridge and trough near northwestern North America, and the blocking over eastern Canada.
For reference, the 1962 storm system by March 7th, and notice how this pattern seems to closely follow the compromised CMC solution, just another reason why I am currently siding with the CMC for this current storm and the pattern that follows in the longer ranges.
The snow map from March 6th, 1962 shows a drop off in snow intensity and gives a decent historical perspective of where snow could and may fall as well as when looking at the other snow maps posted, where the strongest axis of snow may end up with this next storm, although these should not be taken literally as two different storms can’t be exactly alike.
If you’re thinking about the overall pattern, well here’s just another example with more support for an upcoming cold March as 1962 was cold from coast to coast in the US, in exception for New England, but the orientation of this temperature map reveals to me that like this current pattern, there was a -NAO at this time as well, with warmer than normal conditions towards eastern Canada and Greenland, with cold hooking in underneath.
Overall, this is a very fun pattern, and of course I hope you enjoyed reading this, but as far as precise ideas on snowfall totals, this may not be able to be discerned until better model data comes in tomorrow once our storm system gets east of the Rockies, but even still this will be a challenge as there will be a shortwave disturbance to deal with, trough off of the west coast pumping a ridge to the east over the central plains which has to be accounted for, among other smaller-scale features such as the precise temperature in various layers of the atmospheric column as well as elevation, evaporative cooling on the storm’s leading edge, the melting process of some of the snow as it falls through warmer air layers aloft and near the surface. Certainly a lot to handle, and this is only the “tip of the iceberg” per say in regards to all of the variables, but I do think based off of the information given and the 1962 analog with a few other notable storms, I think the heaviest axis of snow with this storm will be north of the I-64 corridor in Virginia to south of the I-80 corridor in PA and NJ, with areas towards I-66 and I-70 like Hagerstown, Washington DC, Fredrick, Baltimore, Charlottesville, and even down towards Roanoke likely to be caught in the thick of things, but uncertainty remains with areas to the north and south including North Carolina and southern & coastal VA as well as NYC, PHI, Boston, and even southern New England where they should be keeping a close eye on the progress of this storm.
A little humor relief here at the end of this long post, as I’m sure every weather enthusiast and meteorologist strives to achieve this, lol.