Hi all, I will try to make this post much shorter than the past several ones and I do want to dedicate this one to some of my early thoughts on winter. In the future, I do plan on making a post dedicated to a review of the hurricane season & some of the MJO research that I’m still compiling together & analyzing. I will make this note that due to the government shut-down, many of my favorite sites to retrieve temperature & pattern composites aren’t available, so my posts will be somewhat limited by this until the government shut-down ends.
First of all, though before I get into my winter thoughts I do want to make mention of the absolutely incredible winter storm that has blasted the Rockies & the western Dakotas. This incredible storm was originally spawned as a spin-off from the abnormally strong negatively tilted Gulf of Alaska trough which eventually was forced east thanks to a trough that originated over eastern Russia that helped break down the seemingly stagnant north Pacific height pattern to progress, in which, featured a formidable Alaskan-Siberian Vortex sitting over top a powerful north Pacific ridge. You can see here in this side-by-side map of the 500 mb height anomalies & MSLP (Mean Sea Level Pressure) with overlaid cloud cover that trough in the Sea of Okhotsk, helping to amplify the relatively flat, zonal jet stream flow by pumping a Bearing Sea ridge which in turn amplifies the prominent Gulf of Alaska low pressure gyre that has been one of the reasons as to why the pattern has been so blowtorch warm in the eastern US.
Now look what happens a few days later, the trough that was coming off the east coast of Russia has now moved to the Aleutian Islands and the once strong Gulf of Alaska vortex decayed & most of it’s energy was force to diffuse eastward into North America under an increasingly strong northern hemisphere jet stream. It’s interesting to note in spite of this general pattern change how the southeast US ridge stays relatively in tact & keeps going strong in the eastern US.
As time progressed, this trough over the Bering Sea moved further east into Alaska, thus continuing to press a piece of the north Pacific ridge further east, & with the US east coast ridge still well intact & showing no signs of giving in, this trough over the Rockies was allowed to slow down & acquire a negative tilt & with the strong northwest to southeast temperature gradient over the US that is commonplace in the -PDO, whatever storm system was to be spawned from this trough had a lot of instability to work with and when you combine a strong moving storm with slow forward progression as it’s a cut-off low pressure center still well to the south of the main jet stream, this can lead to amazing results.
Here is the latest storm report courtesy of the National Weather Service in Rapid City, South Dakota as of 1103 AM Mountain Standard time, Check out some of these snowfall totals in this report, many areas seeing at least 1 foot if not 2-3 feet of snow, with the highest report I’m seeing from Lead, South Dakota of 37 inches of snow with many wind gusts coming in anywhere from 55 to over 70 MPH, what an absolutely unbelievable snowstorm. Also much of the very heavy, blinding snow was accompanied by frequent thunder & lightning, ie. “thundersnow.”
PRELIMINARY LOCAL STORM REPORT...SUMMARY NATIONAL WEATHER SERVICE RAPID CITY SD 903 AM MDT SAT OCT 05 2013 ..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON... ..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE.... ..REMARKS.. 0400 AM SNOW DOWNTOWN GILLETTE 44.29N 105.50W 10/04/2013 M5.0 INCH CAMPBELL WY EMERGENCY MNGR SOME TREE BRANCHES DOWN 0513 AM SNOW 1 ENE DOWNTOWN CUSTER 43.77N 103.57W 10/04/2013 E4.0 INCH CUSTER SD TRAINED SPOTTER SPOTTER REPORTED THUNDER WITH THE SNOW 0540 AM SNOW 4 NE ROCKERVILLE 44.00N 103.31W 10/04/2013 M2.0 INCH PENNINGTON SD TRAINED SPOTTER HAVING POWER INTERUPTIONS...THUNDER ALSO REPORTED 0632 AM SNOW 9 SSE DOWNTOWN GILLETTE 44.16N 105.45W 10/04/2013 M4.0 INCH CAMPBELL WY TRAINED SPOTTER TOTAL SO FAR 0700 AM HEAVY SNOW 5 SSW LEAD 44.29N 103.81W 10/04/2013 M19.5 INCH LAWRENCE SD COCORAHS 0700 AM SNOW 4 NNW WHITEWOOD 44.52N 103.67W 10/04/2013 M5.4 INCH LAWRENCE SD COCORAHS 0700 AM SNOW 5 SW DOWNTOWN RAPID CIT 44.03N 103.30W 10/04/2013 M4.8 INCH PENNINGTON SD COCORAHS 0700 AM HEAVY SNOW HILL CITY 43.93N 103.57W 10/04/2013 M8.0 INCH PENNINGTON SD CO-OP OBSERVER 0700 AM SNOW 5 NE DOWNTOWN BELLE FOU 44.72N 103.77W 10/04/2013 M2.5 INCH BUTTE SD COCORAHS 0700 AM SNOW 6 SW DOWNTOWN CUSTER 43.71N 103.68W 10/04/2013 M3.6 INCH CUSTER SD COCORAHS 0750 AM HEAVY SNOW 4 N HULETT 44.74N 104.60W 10/04/2013 M11.0 INCH CROOK WY TRAINED SPOTTER POWER OUT TREE BRANCHES DOWN 0755 AM HEAVY SNOW 8 W DOWNTOWN SPEARFISH 44.50N 104.02W 10/04/2013 E11.0 INCH LAWRENCE SD TRAINED SPOTTER POWER OUT 0800 AM HEAVY SNOW PACTOLA RESERVOIR 44.07N 103.50W 10/04/2013 M9.6 INCH PENNINGTON SD CO-OP OBSERVER 0800 AM HEAVY SNOW 7 W DOWNTOWN RAPID CITY 44.08N 103.37W 10/04/2013 M8.1 INCH PENNINGTON SD COCORAHS 0814 AM HEAVY SNOW 4 WNW NEMO 44.21N 103.58W 10/04/2013 M14.0 INCH LAWRENCE SD TRAINED SPOTTER POWER OUT TRESS BENT OVER 0900 AM HEAVY SNOW 2 SSE DEERFIELD 44.00N 103.82W 10/04/2013 E12.0 INCH PENNINGTON SD TRAINED SPOTTER AT LEAST 12 INCHES 0905 AM SNOW 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/04/2013 M3.0 INCH PENNINGTON SD NWS EMPLOYEE 0911 AM HEAVY SNOW 1 NNW PIEDMONT 44.24N 103.40W 10/04/2013 M6.0 INCH MEADE SD NWS EMPLOYEE 0919 AM NON-TSTM WND GST 1 W WIND CAVE VISITORS 43.56N 103.49W 10/04/2013 M59 MPH CUSTER SD MESONET 0945 AM HEAVY SNOW LEAD 44.35N 103.77W 10/04/2013 M22.0 INCH LAWRENCE SD PUBLIC 1020 AM SNOW NISLAND 44.67N 103.55W 10/04/2013 M3.5 INCH BUTTE SD TRAINED SPOTTER SNOWFALL RATE .5 TO 1 INCH AN HOUR 1129 AM HEAVY SNOW 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/04/2013 M6.0 INCH PENNINGTON SD NWS EMPLOYEE 1200 PM HEAVY SNOW DOWNTOWN GILLETTE 44.29N 105.50W 10/04/2013 M12.5 INCH CAMPBELL WY EMERGENCY MNGR 1230 PM SNOW 12 SW HEREFORD 44.26N 103.05W 10/04/2013 M4.0 INCH MEADE SD CO-OP OBSERVER 1249 PM HEAVY SNOW DOWNTOWN BELLE FOURCHE 44.67N 103.85W 10/04/2013 E13.0 INCH BUTTE SD TRAINED SPOTTER 0120 PM NON-TSTM WND GST 8 S WALL 43.88N 102.24W 10/04/2013 M59 MPH PENNINGTON SD MESONET 0136 PM NON-TSTM WND GST 1 E DOWNTOWN RAPID CITY 44.07N 103.21W 10/04/2013 M68 MPH PENNINGTON SD NWS OFFICE 0137 PM HEAVY SNOW 11 NW DOWNTOWN RAPID CI 44.19N 103.38W 10/04/2013 E12.0 INCH MEADE SD TRAINED SPOTTER 2.4 INCHES PRECIPITATION 0140 PM NON-TSTM WND GST 2 SW BRIDGER 44.53N 101.93W 10/04/2013 M64 MPH ZIEBACH SD DEPT OF HIGHWAYS 0142 PM HEAVY SNOW 1 SE DOWNTOWN RAPID CIT 44.07N 103.21W 10/04/2013 E8.0 INCH PENNINGTON SD NWS OFFICE 0155 PM HEAVY SNOW 8 WNW USTA 45.26N 102.31W 10/04/2013 E6.0 INCH PERKINS SD TRAINED SPOTTER 0200 PM HEAVY SNOW 1 NNW PIEDMONT 44.24N 103.40W 10/04/2013 M10.0 INCH MEADE SD NWS EMPLOYEE 0208 PM HEAVY SNOW 1 NNW ARDMORE 43.04N 103.67W 10/04/2013 M6.0 INCH FALL RIVER SD TRAINED SPOTTER 6-8 INCH DIAMETER TREE BRANCHES BROKE POWER OUTAGES 0212 PM HEAVY SNOW 5 SSW LEAD 44.29N 103.81W 10/04/2013 E33.0 INCH LAWRENCE SD COCORAHS TOTAL SO FAR STILL SNOWING 0213 PM SNOW 13 W LODGEPOLE 45.81N 102.93W 10/04/2013 M4.0 INCH PERKINS SD TRAINED SPOTTER POWER OUTAGES .93 INCHES PRECIPITATION 0224 PM HEAVY SNOW 5 N UPTON 44.17N 104.63W 10/04/2013 M10.0 INCH WESTON WY PUBLIC 0239 PM HEAVY SNOW 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/04/2013 M12.0 INCH PENNINGTON SD NWS EMPLOYEE 0257 PM NON-TSTM WND GST RAPID CITY AIRPORT 44.05N 103.06W 10/04/2013 M54 MPH PENNINGTON SD ASOS 0305 PM HEAVY SNOW 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/04/2013 M12.0 INCH PENNINGTON SD NWS EMPLOYEE 0305 PM NON-TSTM WND GST 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/04/2013 E55 MPH PENNINGTON SD NWS EMPLOYEE 0409 PM HEAVY SNOW 2 SSE DOWNTOWN RAPID CI 44.05N 103.22W 10/04/2013 E9.0 INCH PENNINGTON SD NWS EMPLOYEE MANY TREE BRANCHES BROKEN 0415 PM HEAVY SNOW RAPID VALLEY 44.07N 103.13W 10/04/2013 E7.0 INCH PENNINGTON SD PUBLIC 0420 PM HEAVY SNOW LEAD 44.35N 103.77W 10/04/2013 E37.0 INCH LAWRENCE SD CO-OP OBSERVER 0547 PM HEAVY SNOW 1 E DOWNTOWN RAPID CITY 44.07N 103.21W 10/04/2013 M13.3 INCH PENNINGTON SD NWS OFFICE 0605 PM NON-TSTM WND GST 8 WNW USTA 45.26N 102.31W 10/04/2013 E70 MPH PERKINS SD TRAINED SPOTTER 0620 PM HEAVY SNOW 5 W DOWNTOWN SPEARFISH 44.50N 103.96W 10/04/2013 M22.0 INCH LAWRENCE SD TRAINED SPOTTER 0639 PM NON-TSTM WND GST ELLSWORTH AFB 44.16N 103.10W 10/04/2013 M71 MPH MEADE SD ASOS 0652 PM HEAVY SNOW 1 NNW PIEDMONT 44.24N 103.40W 10/04/2013 M20.0 INCH MEADE SD NWS EMPLOYEE 0736 PM HEAVY SNOW 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/04/2013 M20.0 INCH PENNINGTON SD NWS EMPLOYEE 0800 PM NON-TSTM WND GST 3 WNW WASTA 44.09N 102.50W 10/04/2013 M59 MPH PENNINGTON SD DEPT OF HIGHWAYS 0815 PM HEAVY SNOW DOWNTOWN SPEARFISH 44.50N 103.86W 10/04/2013 E26.0 INCH LAWRENCE SD PUBLIC 0855 PM HEAVY SNOW 7 SSE BISON 45.43N 102.43W 10/04/2013 E12.0 INCH PERKINS SD TRAINED SPOTTER LIGHTNING AND THUNDER WITH HEAVY SNOW CONTINUING. 0855 PM HEAVY SNOW SUNDANCE 44.40N 104.37W 10/04/2013 E24.0 INCH CROOK WY PUBLIC STILL SNOWING. MUCH TREE AND LIMB DAMAGE. 0230 AM NON-TSTM WND GST 8 SE BISON 45.44N 102.35W 10/05/2013 E70 MPH PERKINS SD TRAINED SPOTTER 0308 AM HEAVY SNOW 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/05/2013 M29.0 INCH PENNINGTON SD NWS EMPLOYEE 0643 AM HEAVY SNOW 8 SE BISON 45.44N 102.35W 10/05/2013 E24.0 INCH PERKINS SD TRAINED SPOTTER 0649 AM HEAVY SNOW WRIGHT 43.75N 105.50W 10/05/2013 E15.0 INCH CAMPBELL WY TRAINED SPOTTER 0653 AM HEAVY SNOW BUFFALO 45.58N 103.55W 10/05/2013 E10.0 INCH HARDING SD TRAINED SPOTTER 0659 AM HEAVY SNOW 1 SW DOWNTOWN RAPID CIT 44.06N 103.26W 10/05/2013 M31.0 INCH PENNINGTON SD NWS EMPLOYEE 0750 AM NON-TSTM WND GST 8 S WALL 43.88N 102.24W 10/05/2013 M54 MPH PENNINGTON SD MESONET 0808 AM HEAVY SNOW DOWNTOWN HOT SPRINGS 43.43N 103.48W 10/05/2013 E6.0 INCH FALL RIVER SD CO-OP OBSERVER 0825 AM HEAVY SNOW 4 N HULETT 44.74N 104.60W 10/05/2013 M20.0 INCH CROOK WY TRAINED SPOTTER DRIFTS 3-4 FEET 0825 AM NON-TSTM WND GST 4 N HULETT 44.74N 104.60W 10/05/2013 E60 MPH CROOK WY TRAINED SPOTTER DRIFTS 3-4 FEET 0855 AM HEAVY SNOW 4 SE KEYSTONE 43.85N 103.37W 10/05/2013 E20.0 INCH CUSTER SD TRAINED SPOTTER
0730 PM HEAVY SNOW LEAD 44.35N 103.77W 10/04/2013 M43.5 INCH LAWRENCE SD PUBLIC
0834 AM HEAVY SNOW 2 WSW DEADWOOD 44.37N 103.77W 10/05/2013 E48.0 INCH LAWRENCE SD TRAINED SPOTTER
Here’s a statement from the National Weather Service in their Blizzard Warning that’s still in effect as I’m writing this for portions of west-central North & South Dakota.
.A STRONG WINTER STORM SYSTEM HAS MOSTLY MOVED OUT OF NORTHEAST WYOMING AND IS WORKING ITS WAY ACROSS WESTERN SOUTH DAKOTA THIS MORNING. IT WILL CONTINUE TO PRODUCE WIDESPREAD HEAVY SNOW AND STRONG WINDS THROUGH EARLY SATURDAY IN WESTERN SOUTH DAKOTA AND THROUGH LATE SATURDAY IN CENTRAL SOUTH DAKOTA. NEAR RECORD SNOWFALL ACCUMULATIONS HAVE OCCURED IN THE BLACK HILLS AREA...AND MUCH OF WESTERN SOUTH DAKOTA. ALONG WITH THE SNOW...BLIZZARD CONDITIONS WITH VERY STRONG NORTHEWEST WINDS ARE IMPACTING THE WESTERN SOUTH DAKOTA PLAINS AND THE NORTHERN AND EASTERN SLOPES OF THE BLACK HILLS. THE COMBINATION OF STRONG WINDS WITH THE WET HEAVY SNOW HAS CAUSED WIDESPREAD ROAD CLOSURES IN WESTERN SOUTH DAKOTA. MANY POWER LINES AND LARGE TREES ARE DOWN ACROSS WESTERN SOUTH DAKOTA DUE TO THE HEAVY WET SNOW AND STRONG WINDS.
SNOWFALL ACCUMULATIONS OF 18 INCHES OR MORE ARE COMMON ACROSS WESTERN SOUTH DAKOTA THIS MORNING WITH ACCUMULATIONS OF SEVERAL FEET IN THE BLACK HILLS. THIS HEAVY WET SNOW AND POOR VISIBILITIES IN BLOWING SNOW HAS SHUT DOWN ALL BUT EMERGENCY VEHICLE TRAFFIC ACROSS MOST OF THE REGION.
BULLETIN - EAS ACTIVATION REQUESTED CIVIL EMERGENCY MESSAGE LAWRENCE COUNTY EMERGENCY MANAGEMENT IN LAWRENCE COUNTY SD ISSUED BY NATIONAL WEATHER SERVICE RAPID CITY SD 145 PM MDT FRI OCT 4 2013 THE FOLLOWING MESSAGE IS BEING TRANSMITTED AT THE REQUEST OF THE LAWRENCE COUNTY EMERGENCY MANAGEMENT AGENCY. A BLIZZARD IS ONGOING ACROSS LAWRENCE COUNTY. NO TRAVEL IS ADVISED ANYWHERE IN THE COUNTY. TREES AND POWER LINES ARE DOWN...MAKING IT DIFFICULT FOR SNOW PLOWS TO CLEAN THE DEEP SNOW OFF THE ROADS. ALL OTHERS SHOULD AVOID THIS AREA. FOLLOW THE INSTRUCTIONS OF YOUR LOCAL EMERGENCY MANAGEMENT OR LAW ENFORCEMENT OFFICIALS.
Snowfall depth map for South Dakota reveals just how extreme this even was with some areas in the Black Hills of South Dakota just to the west of Rapid City picking up in the dark blues & purple shades, anywhere from 2 to as much as three feet of snow or more in isolated areas. Officially, 23.1 inches of snow fell at Rapid City, SD, making it their 2nd biggest snowstorm on record, & to get that recognition in October is incredible. Also, in looking at this snowfall depth map, you can kind of get an idea where the mountains are located as you should note there is a slightly lighter band of snow from Newcastle to Hot Springs, & with the persistent & very stiff northwest winds on the northwest side of this low pressure area, this has actually lead to descending air flow on the backside (leeward side) of the mountains, where in air pressure tends to rise in response to a decrease in volume as the air loses altitude, thus leading to subsidence warming that can significantly lower snowfall totals in areas on the backside of a mountain range.
You can see into this morning, the low pressure system was still cranking with a minimum central pressure near 998mb, and a nice 1030 mb high is noted to the north near the Ontario-Manitoba border helping to funnel some cold air into the system, thus this is still a fairly decent mid-latitude cyclone. However, as you should note by the occluded front, shown in purple where in the cold front outruns the preceding warm front associated with a storm system, this cyclone has likely already peaked in intensity, but it should still remain a formidable entity, bringing unsettled weather into the Great Lakes & Ontario over the next few days while the ridge in the eastern US tries to hang tough & will likely help to keep the worst of the weather off to the north & west away from the eastern seaboard, but weather still will be relatively unsettled near the eastern US.
A few other things to note here in the current pattern is that there will be yet another storm system for the northern Rockies & extreme northern plains worth watching next week as a piece of energy from the gyre of low pressure currently over the Bearing Sea merges with a trough currently well over a thousands miles away from the Pacific northwest, which could lead to potentially yet another interesting system that does have some potential to put down some early wintry weather again. Of course, also on the front side of the storm system like what was observed in the midwest with this latest storm system, severe weather will be commonplace & this is certainly something worth watching as we head towards the middle of next week. Still a lot of time to watch this as most of the associated energy is still over the Pacific under limited data observation & it may be at least a few days until the models get an “accurate” handle on this situation. Regardless, it looks like the very active storm track into the Rockies will continue to lay down a fairly decent early season snowpack & considering that we are now into the “2nd severe weather season” that usually comes around in the fall, although nowhere near as prolific as the spring severe weather season, now will be the time where we have to start monitoring each system that comes into North America as the jet stream naturally begins to strengthen throughout the month of October & thus forcing the US start to getting more involved into the northern hemisphere pattern & shift away from the relative tranquility found in summer.
CMC along with other model guidance are in pretty good agreement with some sort of storm system coming out of the Rockies again & into the plains, exactly where this system goes who exactly will be affected & what precipitation type will fall in which areas still remains to be seen.
GFS for about the same time frame for next Saturday, fairly similar look to the CMC cut-off low pressure system diving into the Rockies begins to gain latitude & poleward momentum as it begins to feel resistance from the formidable ridge near the US east coast & SE US, could be interesting once again for some of the same areas that were just affected by the recent historic winter storm.
The ECMWF like the CMC & GFS shows a decent storm system as well diving down the west coast of the US into the Rockies, likely dumping some needed rains & some nice mountain snows over the area, but considering that due to the lack of data input the ECMWF usually has over the southwestern US & the region of the Pacific off the southwest US coast, it tends to force systems to “drag their feet” over this area of the country, thus the ECMWF likely may be a bit too far west at the present time & is witholding too much energy too far the west. However, once we can physically get this system to reach the US west coast where data observation is stronger, then a better handling on this system should be in order.
It’s also interesting to note in this pattern with the historic snowstorm over the western Dakotas with blowtorch warmth prominent on the eastern seaboard, that there was a typhoon over the western Pacific, Wutip, which went into Vietnam at the end of September.
Radar of Wutip as it neared Vietnam, interesting to note the double eye wall structure, indicative that the storm was likely about to experience an eye wall replacement cycle where in the upward motion & associated convective activity from the outer eye wall steals energy & upward motion from the tighter, generally more well defined inner eye wall, thus leading to a collapse of the inner eye wall. This was definitely good for Vietnam because the ongoing eye wall replacement cycle near the time of landfall limited the intensity of Wutip. Also, in such eye wall replacement cycles, especially with rather large tropical cyclones, they often ingest dry air into their cores from the surrounding environment, thus this usually halts intensification if not even leads to weakening. If however the eye wall replacement cycle is successful, the outer eye wall can proceed to contract, leading to intensification once again. These eye wall replacement cycles are just one reason why it’s hard for very intense major hurricanes to maintain their intensities for so long even under seemingly favorable conditions, & why many storms are never able to regain their “former glory” per say & never are really able to recover from an EWRC.
Satellite of Wutip as it was near its peak intensity of 90 knots, although one could certainly make the case that this storm was stronger than that.
Since the JTWC (Joint Typhoon Warning Center) does not have invaluable recon data going into tropical cyclones anymore, typhoon intensities are usually estimated based off of satellites & somewhat reminiscent of our own National Hurricane Center, the JTWC does have a tendency to be somewhat conservative in their forecasts. This isn’t necessarily a bad thing, unless of course you have a typhoon that has estimated wind speeds of 100 knots when in reality, the storm actually is has maximum sustained winds of 120-125 knots. Now, 20-25 knots (which equates to about 25-30 MPH) may not seem like much, but when it comes to actual damage, at least according to (link) http://www.srh.noaa.gov/jetstream/tropics/images/saff_wheel.pdf
Wind damage with increase in wind speed is not linear or even squared to the wind speed as one may think. Rather, wind damage with increasing wind speed is logarithmic in nature, where the damage induced by a specific maximum winds are raised to an exponent of 8 (the eighth power, 10^8, or 100,000,000) & in this case the seemingly small difference in potential wind damage from a 100 knot to 125 knot storm is actually very extreme, where in the 125 knot winds actually lead to nearly 6x the amount of damage as 100 knot winds, simply amazing. It’s more startling when you compare the potential damage from a minimal hurricane with 65 knot winds to a 160 MPH (145 knot) category 5 storm, the difference is on the order of over 600x the amount of potential damage with a category 5 storm to a minimal category 1 storm.
A logarithmic function looks somewhat like this (although you’ll see most veer sharply to the right with increasing x values, this one does appear to be more reminiscent of an exponential function), where you have a given number that ‘s raised to a specific value (x) & results in a graph like this. You can actually see by the graph in a logarithmic function how the difference in values as you go along the x axis increases between associative number, this type of function can be applied not only to hurricane potential wind damage but to the energy differential between each degree increment increase in temperature, where the amount of energy in one degree change in a temperature of 80 degrees is equivalent to 20-25 degree change in temperature at -30 degrees F.
Now, getting to my point here about typhoon Wutip which is a bigger part of a pattern that’s driving this unusually warm weather in the eastern United States. I’m sure if you have followed me since last fall, you have probably heard at one point or another about the western Pacific typhoon recurve teleconnection to an eastern US trough several days later. Well, there is also another teleconnection where in a typhoon that crashes into Asia rather than recurving out towards or just east of Japan actually results in the opposite pattern, where the eastern US actually is quite warm and sees predominant ridging, but why is this the case? Think about why looking to the western Pacific is important in the first place, it has the largest heat energy budget of anywhere on the globe going into the northern hemisphere fall, because with it being in the tropics it receives more energy than it gives off back into space, thus leading to a general warming of temperatures in response, & as you increase in temperature, the amount of energy differential between each degree increment increases, thus you have a relationship between the amount of energy & temperature that is at least quasi-expoenential. Not only that, but the energy capacity of the oceans compared to the atmosphere aloft is 1100x greater.
This amplifies the effect of energy differential when dealing with the ocean, thus you can probably see now why the equatorial Pacific is given quite a bit of attention in regards to ENSO index because the Pacific covering the encompassing the largest distance of tropical ocean has the largest heat energy budget & will in turn have the largest impact on the global weather pattern. Now, the real difference between the typhoons that recurve out near Japan & the ones that crash into Asia is the pressure anomalies to their north over northern Asia. As opposed to a recurving typhoon which amplifies an east Asia trough that is able to get caught up in the strong North Pacific jet & especially under cold PDOs has the capability to break the relatively stagnant pattern with strong northeast Pacific ridging & force it to progress east, the crashing typhoon into Asia does the exact opposite, Instead of enhancing a trough over east Asia, the typhoon helps to give rise to a formidable ridge of high pressure over NE Asia that extends it’s influence into the North Pacific, this in turn, at least in this time of the year, will help to force pressures to fall near Alaska & Siberia, thus enhancing the polar vortex anomaly there, which combined with our current state of cold PDO means that a tight pressure gradient will exist between that low pressure system & the North Pacific high. This strengthens the jet stream here & in doing so, once the jet reaches the North American landmass it encounters increased friction from the terrain underneath it, thus causing the jet to slow down. This slowing of the jet stream, reminiscent to the slowing of a car to lower its inertia to round relatively sharp corners & turns, has same concept in that, the resistance the jet meets when it encounters North America allows it to turn more sharply, thus allowing it to round the edge of a trough base that leads to a considerable trough of low pressure to sit over the western US & the Rockies.
With Typhoon Fitow getting ready to plow westward into China
And Typhoon Danas about to recurve near Japan, we are left in quite a quandary to exactly what the pattern will be like, although it would seem in this situation that both storm systems would try to cancel each other out & more likely that pattern over the US, although not quite as warm as what’s being currently observed, the pattern would appear to be rather transient in the long range, & thus it does make some sense as to why the ECMWF has since backed off on its long range forecast somewhat that called for a huge ridge to go up & down the east coast. However, the pattern that it’s depicting is certainly no walk in the park and will likely still be a warm one, but it does show a more sympathetic trough with relatively zonal flow to overtake the United States in the 8-10 day timeframe, & the GFS is in fairly good agreement with this solution.
However, what does appear to be more significant about this pattern is the large sprawling region of high pressure that will park itself near Atlantic Canada. Such pattern set-ups are concerning, because they invite tropical trouble into the US as the high pressure directly to the north of the Caribbean & the southwestern Atlantic force convergence into this area & lead to a piling up of air that induces enhanced upward motion that’s generally favorable to tropical cyclone genesis. Also, the strong high pressure to the north of the tropics over Atlantic Canada forces an anomaly of low pressure underneath to the north of the Greater Antilles, this reduces the pressure gradient between the Panama-Columbian monsoon heat low & the Bermuda high that leads to a break in the fast northeasterly trade wind flow commonly found in the tropical Atlantic, & the slowing of the winds at the surface & aloft with the decreased trade wind flow generally more conducive to the bundling up of tropical energy & formation of a surface circulations as it generally allows the atmospheric column to become more vertically stacked which is also favorable to tropical cyclone development. In addition, given the lack of activity this year in the Atlantic, hasn’t stirred up & cooled the surface waters leaving much of the tropical Atlantic still quite warm for something to its act together. Picture courtesy of tropicaltidbits.com.
It’s very interesting to note how the experimental analog height potential forecasts from tropicaltdbits.com have been able to “see” this abnormally strong ridge of high pressure near Atlantic Canada in October.
8-10 day 500mb ECMWF & GFS
Tropicaltidbits.com 500mb analog based forecast for October
Very good forecast if I could say so myself, thus with this type of pattern set-up, it does appear that the hurricane season isn’t quite over just yet. In response to this ridge of high pressure setting itself up over Atlantic Canada & New England, the models are trying to hint at the potential for tropical trouble to brew in the SW Atlantic.
CMC 0Z October 5 develops African wave & shows mischief brewing of the US east coast in the wake of the trough that will affect the eastern US early next week.
12Z CMC October 5 develops African wave and develops the system in SW Atlantic much sooner in response to the model progressing the mid-latitude trough much faster to the east, allows pressures to balloon much faster in time over Atlantic Canada. Although it is the CMC, one should take note that this model does not tend to overdevelop systems in the eastern Atlantic, thus it’s fairly significant to see this model latching onto development here in this instance.
GFS tries to keep things interesting to say the least near the SE US coast by next week with a low pressure area that gets blocked underneath a nice region of high pressure over east-central Canada, newest run is more aggressive towards potential SW Atlantic development
12Z October 5
0z October 5
GFS ensembles are hinting at some sort of mischief as well in the SW Atlantic underneath the strong ridge of high pressure over Atlantic & eastern Canada, with a sympathetic depression in the pressure field noted off the SE US coast. Graphics courtesy of tropicaltidbits.com
12Z GFS ensembles Oct 5
0Z GFS ensembles Oct 5
CMC ensembles don’t appear to be as aggressive as GFS with just a minor break in the subtropical ridge noted near the SE US coast, although the more recent run of 500mb height anomalies looks a bit more favorable towards tropical development in the SW Atlantic
0z CMC ensembles
Even the NAVGEM shows some interesting feature near the eastern seaboard, although nowhere near to the extent of the CMC & GFS. Interestingly, the NAVGEM also develops the new African wave
The ECMWF like other model guidance shows some trouble trying to brew off the SE US coast by next week, & for this model’s standards, it also develops the new oncoming tropical wave into a tropical storm as it passes to the northeast of the Lesser Antilles
Given the pattern set-up going into next week, the MJO which contrary to those who are familiar with the oscillation, is actually generally favorable in phases 5 & 6 where we’re at now, and even phase 7, that usually is very detrimental to Atlantic activity is somewhat supportive for Atlantic development in October, I’ll explain why this is the case in a future upcoming post as I finalize my MJO research. Also, with model support to back this up, it does appear some sort of tropical mischief will at least attempt to get going off the SE US coast & we will probably have a decent chance at seeing development from the new wave emerging off Africa, regardless, there should be no threat from the tropics over the next 5 days, despite the remnants of Karen that will move into the southeastern US & dump some needed rains.
My general tropical ideas based on MJO in October, physical mechanisms in the pattern & significant model support. I do remain relatively on the conservative side of things for now, especially given the unexpected behavior of this hurricane season.
This type of pattern set-up described earlier in this post with a crashing typhoon into Asia leads to the unfavorable negative PNA where a west coast trough forces the jet stream to buckle poleward as it comes to the eastern US, thus leading to a stormy pattern for the west, Rockies, & even to some extent the midwest, while the eastern US remains relatively warmer & drier than normal.
In looking at all of the typhoons that have crashed into Asia this year, & although it’s commonplace for this area to see numerous storms, the ratio of storms going into southeast Asia as opposed to going out to sea does appear to be rather high.
These storms include
Super-typhoon Usagi, which gave quite a scare to Hong Kong, thankfully this storm weakened significantly prior to landfall as an EWRC & dry air help keep Usagi in check
Of course there was the already aforementioned Wutip that went into Vietnam
And Fitow which is expected to crash into China within the next few days
Would be interesting to see if any further research on my behalf could potentially draw a further link between crashing typhoons into Asia & PDO and PNA. Speaking of the PNA, here is a PNA correlation to 500mb height for various points in the year, clearly see how in October, big trough near Aleutians generally favors a nice trough over the eastern US, especially the southeast. However, this is not the case this year as the north Pacific ridge from just south of Alaska to eastern Asia has been quite strong indicative of a generally -PNA.
The PNA is strongly related to the PDO, & in this case, with the -PDO, that favors a nice ridge over the north Pacific & near the Aleutians with considerable troughiness along the US west coast, i.e. a negative PNA.
Here’s the December-February averaged PDO 500mb height pattern from 1948-2010, easily can see how the Aleutian/strong NE Pacific helps to promote a stronger than normal polar vortex & associated trough over Alaska & northwestern North America that helps force the jet to buckle near the southeastern US, leading to generally warmer & drier than normal conditions with generally less of the classic east coast snowstorms, & more systems which tend to go towards the area of not only least resistance, but a temperature gradient, & that gradient is usually strongest from the central Rockies into the Great Lakes.
The cold PDO and strongly related negative PNA are not only detrimental for the fact that they lead to southeastern US ridging, but these oscillations in tandem with each other often lead to a +NAO signature.
Take for example this comparison of 500mb height patterns when the PNA was negative (on the right) compared to the +PNA & it’s somewhat easy to tell that during the period of -PNA, the strong north Pacific blocking & Alaskan vortex which are associated also with -PDO that it’s much harder to get considerable blocking near Greenland because the forced stronger than normal high pressure over the southeastern US & on the US east coast will tend to force pressures to fall off northeastern North America in the vicinity of Greenland.
Also, the stronger than normal North Pacific high pressure commonplace in the -PDO mitigates the phasing of the subtropical & polar jet, & thus keeps much of the associated upward motion in the tropics at bay, while the +PDO & +PNA signal encourages upward motion over the tropical Pacific by crashing a trough near the international dateline, this helps to give rise to troughiness & an active subtropical jet in the eastern/central Pacific. This low pressure anomaly that develops there as result of the +PDO/+PNA pattern acts much like a rock in a stream, forcing air to slow down & pile up to the northeast of the region of low pressure in the subtropics, thus helping to force the pressures to rise over western North America that in turn causes a trough to crash over the eastern US. This forces the polar jet to dive southward & leads to increased threats for phasing with the subtropical jet, that in turn leads to upstream blocking over Greenland/Iceland. This is a good reason as to why MJO phases 6-8 in the winter tend to be associated with -NAO while MJO phases 3-5 promote a +NAO.
Just look & compare the MJO to the observed NAO values in the 2009-10 winter for yourself to see this connection.
This picture below shows the observed MJO for the October-December period in 2009,( red is October, green is November, & blue is December and the small numbers you see located near the MJO line denotes specific days in a month where the MJO was.) look how the MJO which started to enter phase 6 in December the NAO begins to tank negative, then the MJO comes out strongly into phases 7 & 8 and the -NAO sticks around. However, look at how the MJO heads towards phases 3-5 towards the end of December & beginning of January & the NAO later responds by starting to retreat back towards neutral territory.
This picture shows the January to March 2010 period & although the NAO briefly went positive in mid January, the MJO which came out strongly once again into phases 6-8 like it did in December forces the NAO to crash & it continued to tank until mid February, at the exact same time the MJO went into the “null” phase of Circle of Death (COD). NAO stays negative until about mid March when the MJO begins to head towards phases 3-5 which favor a +NAO in winter.
Or how about the 2010-11 winter’s NAO to the MJO?
The MJO in the January to March period shows how the oscillation goes briefly into phase 5 in early January helping to lead to the rise in the NAO towards its positive state, however, the huge crash in the MJO into phases 6-8 through late January helps keep the NAO generally negative, however, once the MJO left in February & especially in March when it started to enter the dreaded phase 3-5, is it any surprise that the NAO went positive? Nope.
Now look at the 2011-12 blowtorch warm winter, look how well the +NAO correlates with how the MJO was in phases 3 through 5 in December, you should also notice how we observed a very deep pulse in October into octants 1 & 2 which correlates with the historic late October snowstorm that gave unusually large snows to areas of the northeast, even down to areas of the i-95 corridor.
MJO October-December 2011.
Now, look at how the NAO slowly begins to fade towards a more neutral look as February came around, makes sense given that the MJO had a large pulse into phases 6-8 around that same timeframe.
Now, exactly how the MJO will play out this winter to influence the NAO remains to be seen, but the MJO has a tendency to go the area of the tropics with the warmest water temperature anomalies compared to average, & right now although it’s still fairly early in the game as far as determining exactly what the NAO will do based on global SST anomalies, I’m definitely seeing some hints as to exactly where the pattern wants to go this winter towards the NAO. I obviously understand the looking at the Atlantic Ocean Tripole is important, but I do think there’s a little bit more to it than that & understanding how the MJO operates in going towards the area of warmest SST anomalies when compared against its tendencies in phases 3-5 to force the NAO positive, while 6-8 gives a negative look. Thus, if you compare the Atlantic & eastern Pacific SST that generally are associated towards phases 8 & 1 of the MJO against the Indian Ocean SST that are associated with phases 2-3 (& is in relative proximity to the Maritime Continent MJO phases 4 & 5) it would make sense to see certain trends in the NAO by looking at differences between them. If you also take into account how the MJO likes going towards the area of warmest SST against average, you can conclude then that warmer SST in the Indian Ocean compared against the equatorial Pacific & tropical Atlantic will tend to yield a +NAO the following winter while the opposite is true when the E Pac & Atlantic basins are warmer than the Indian Ocean.
Let’s see if this is indeed the case by looking at the early October SST the past several years, & then looking at this year to see if there is indeed a trend.
Early October 2009, clearly the eastern Pacific & Atlantic are warmer than the Indian Ocean, thus implying for enhanced upward motion & MJO festering in phases 6-8 that would tend to promote the more favorable -NAO pattern.
In early October 2010, although a la nina is in place making the eastern Pacific warmer, look how warm the tropical Atlantic was vs the northern Indian Ocean, thus not a huge surprise here that the -NAO also won out in that following winter.
The temperature anomalies in the eastern Pacific were cooler than normal, thus the tropical Atlantic would have to pick up the slack, but that wasn’t the case as the tropical Atlantic was relatively similar temperature wise, if not slightly cooler than the Indian Ocean, which favors a +NAO, which did indeed occur during that blow-torch warm winter.
Last winter, the eastern Pacific which neared borderline el nino that winter along with the warm deep tropical Atlantic that was left untouched by the tropics that season helped give this region even warmer than normal water temperatures relative to the North Indian Ocean, thus leading to a generally -NAO that winter, & this was especially true late in the winter & even into spring.
Looking at this year, it looks pretty clear that the tropical Atlantic & eastern Pacific are winning the battle over the north Indian Ocean for warmth, thus one could possibly conclude that the NAO will tend to trend negative for this upcoming winter due to the MJO generally being more favored towards the Atlantic & eastern Pacific, leading to enhanced MJO action in phases 6-8 as opposed to 3-5.
This is further supported by the MDR SST weighed against the rest of the global tropics (graphics courtesy once again of tropicaltidbits.com & Levi Cowan) which have been in a general upward trend over the last several months & if this were to continue, one could see that the NAO would tend to trend negative for this upcoming winter.
The -NAO regime is given even more support by the general decadal trend in NAO, in which as the AMO turns cold as it did around 1965, during the course of the cold cycle, the NAO tends to trend more positive with time, but look how once the Atlantic entered its positive phase in 1995…
The NAO has since tanked & with still likely at least a few more years of warm AMO left to go, makes sense that overall trend of negative NAO should continue for the next several winters.
Although conditions do appear to favor the -NAO, many weather enthusiasts will tend to think that it may be a “sealed deal” relatively speaking when it comes to winter because -NAO=more cold & snow right? Well, I am certainly seeing quite a few forecasts already and many in the blogosphere are already attempting to jump the gun on this being a cold winter, however, I have a much different opinion on this at the moment. A few things do stick out at me & I want to address them, the biggest concern I have regarding the cold PDO which I’ve already mentioned a few times in this post. The PDO is generally a 25-30 year oscillation or so that is a resultant of the overall state of the Pacific & is at the mercy of the ENSO index, generally in the cold PDO la ninas are favored (that does not necessarily mean that cold PDOs cause la ninas) over el ninos in over a 2:1 ratio.
Now you might be asking why do I insist despite signals which suggest a -NAO that the PDO would overrule it? I think I best explain why in response to Armando on Scott Reinhardt’s blog
Because the PDO has a stronger effect on the long-wave jet stream pattern & since the geographic locations of the North Pacific & northwestern North America where the PDO’s effects at the 500mb level are greatest against the NAO which encompasses Iceland, Greenland & the North Atlantic are so close together, usually one or the other is negative, it’s next to impossible to get both to be strongly negative because these oscillations truly are so close to each other. It’s usually a tug of war & a power-struggle between the NAO & PDO for dominance in terms of northern hemisphere blocking each winter, usually, the PDO wins these battles, of course unless it is generally weaker in nature. Which in that case, does allow for other things like the ENSO & NAO to gain a stronger voice in the northern hemisphere pattern. Getting to my point though, it’s very hard to just throw caution to the wind when it comes to the PDO, & in it’s current negative state, where in fact I am beginning to see over the last several weeks, intensification of the -PDO regime, suggests to me that this factor really won’t be going much of anywhere come winter & is likely going to be enough to hold the ENSO in check & prevent a sudden wild swing this winter to el nino, which even in that case still may not be enough to overcome the PDO. Many other factors have to line up to make conditions even somewhat favorable in that case, as was observed last year when we saw a borderline el nino that may have suggested a cold winter in the eastern US, but the PDO was able to fight against that, the stratospheric warming event & the -NAO to keep temperatures relatively near normal in the eastern US.
In general, with the -PDO that we’re in now, this tends to favor a strong Alaskan Vortex, formidable north Pacific ridge, west US trough & because the jet stream literally gets “squeezed” as the pressure gradient between the Alaskan Vortex & North Pacific ridge tightens, this forces the mid-latitude westerlies to strengthen & thus establishing a strong NW-SE temperature gradient across the United States.
Cold PDO US temperature composite
North America la nina temperature composite
Occasionally though, under this type of set-up, temporary ridging will try & fire up over the Bering Sea & Alaska which many usually cheer for, but this type of set-up is relatively temporary as the North Pacific jet tends to undercut these ridges & force them to retrograde towards Siberia & in their wake pressures tend to fall, thus reinvigorating the Alaskan Vortex. Levi Cowan back in January 2012 when many (including myself) thought that the cold trends of the past two blockbuster winters of 2009-10 & 2010-11 was going to continue, yet Levi was the one voice who “went against the gradient” per say & thought that the winter of 2011-12 would be warm. His explanation in this video (link) http://www.tropicaltidbits.com/blog/2012/01/ helps to better explain this phenomena of the transient Alaska ridge in the cold PDO much better than I ever could. I definitely would suggest looking into the models his site provides & following him on twitter @tropicaltidbits if you haven’t done so already, definitely worth it, IMHO. Amazing how some of the concepts he mentioned years ago in videos like this still can be applied to today.
Now, what’s really significant about the height patterns near the Bering Sea & Alaska is the strong Alaskan-Siberian Vortex. This abnormality in the pattern has definitely been enhanced by the -PDO & of course the strong snowpack over this area which, contrary to what happens later in the winter, this snowpack early or very late in winter when climatology dictates it to be low anyway, this tightens the pressure gradient between this area & the mid-latiudes, thus leading to an enhanced polar vortex anomaly. This type of pattern of course in the winter, one would think would not be all that detrimental to the overall winter pattern, after all it’s only October right? Well, actually looking at the data reveals this kind of height pattern with a strong Alaskan-Siberia vortex in October is associated with a strong -PDO signal.
Just compare this earlier forecast for 8-10 day 500mb height (which did verify somewhat) to the -PDO signal, look very alike to say the least.
Mean North American temperature pattern in those years with the strong Alaskan-Siberia vortex in October reveals a squished la nina/-PDO look with residual warmth still trying to hang around in association with the SE US ridge, over the southern US, thus adding further credence to idea of warmth there. In addition, plenty of cold at the same time being infiltrated into North America & spilling into the United States, partially thanks to strong snowpack build-up that results from strong vortex in October.
Another thing worth monitoring this winter, especially in times of low & maximum solar activity in the overall solar cycle where stratospheric warming events are more common…
I should note that this chart you’re looking at below shows a vertical representation of the troposphere & the stratosphere with letters on the bottom representing different months of the year & the numbers on the side representing atmospheric height in (mb). The blue colors & white represent generally lower than normal pressure, while yellows, oranges, & red etc show higher than normal pressures. You should notice right away that looking at this chart, there seems to be a somewhat regular pattern in the stratospheric temperatures in the top half of the picture & you should note that with increasing time on your x-axis how these temperature anomalies in the stratosphere eventually tend to propagate themselves downward into the troposphere in a diagonal fashion. You can even see last year’s stratospheric warming event at the far left end of the picture & how with time that propagated down to the lower levels of the troposphere & kept the NAO & AO negative right on into March & April leading to some unusually cold late season weather & even snowfall in May over the midwest. This was followed by a substantial cooling event in the stratosphere that eventually worked its way down to the surface & helped to enforce the +NAO & AO I talked about in some of my posts over the late spring & summer, which I thought was going to lead to an active hurricane season (I’m going to talk a little more about why the hurricane season was less active than expect later down the road, really need this government shut-down to go away so I can go back to posting, I would make a brief post on my winter thoughts but since my main site, NOAA ESRL is down, I can’t do any of that.). Now, that same cooling event over the pole helped to bust Joe Bastardi’s ideas for a huge -NAO in May that would lead to the active hurricane season, why was the +NAO so detrimental? The strong pressure gradient between the poleward advancing monsoon trough & ITCZ along with the Azores-Bermida high strengthens the northeasterly trade winds, which much like blowing on a spoonful of hot soup, forces a cooling of the water & that’s exactly what we saw. Then we saw another warming event start to develop late in summer & has still lingering effects on the arctic & has likely helped to lead to the generally -AO that has tried to develop since September. However, you should notice that there is yet another pool of cold air in the stratosphere which looks poised to propagate downwards in the atmosphere, thus suggesting that any residual warm air & blocking that tries to develop as we head through the rest of October, into November & even December will be at the very least mitigated if not reversed completely towards a +AO/+NAO.
This also is in strong agreement with where the QBO is going. In case, you don’t know what the QBO (Quasi-Biennial Oscillation) is, it’s a general oscillation measuring the vertical propagation downwards of the stratospheric winds in the global tropics at around 30mb, which generally oscillates on the order of 28-29 months or so. Easterly or westerly winds usually begin near the top of the stratosphere & move downward where they dissipate at the tropopause (layer dividing the stratosphere from the troposphere underneath) because of the inverted temperature gradient relative to the stratosphere that begins in this area as you descend towards the surface, which is opposite of the stratosphere where temperature increases with increasing height, in the troposphere, it decreases. Now, this QBO chart I have attained courtesy of Mike Ventrice’s website & much like the MJO, the QBO was broken down into 8 phases using the EOF (Empirical Orthogonal Function), among other things, & like the MJO, each phase of the QBO has different characteristics, behavior & relative frequencies over time & the QBO chart also has a “null” phase or Circle of Death (COD). You can also see how the QBO propagates around the chart much like the MJO going on natural progression, with phases 7-2 favoring an “east” QBO, while a “westerly” QBO is favored in phases 3-6.
Going into phase 6 as we head into October, November & into December, favors a strong polar vortex, (+AO/+NAO) & -PDO.
Phase 6 QBO mean 500mb pattern
However, look what happens when the QBO goes into the very next phase, phase 7, complete pattern reversal in the northern hemisphere, big time blocking fires up over the pole huge mid-latitude trough all the way from Europe to eastern North America, a classic -NAO, snowlovers pattern.
QBO phase 7 500mb pattern
Compare the mean 500mb in QBO phase 7 to the top 10 warmest northern hemisphere stratosphere years & you can definitely see the resemblance
Now, why would a sudden switch in the QBO from phase 6 to phase 7 suddenly lead to a major stratospheric warming event? Think about it, go back & look again at the QBO chart, notice how the westerly phases go from 3-6 while easterly goes from 7 to 2. This means that when the QBO transitions from phase 6 to 7 what’s essentially happening is the stratospheric winds are reversing directions to easterly from at one point being westerly. What essentially happens here is that the westerly winds in the tropics, if extrapolated around the globe & looked upon as a stereographic model, you would see that they winds make a general counter-clockwise circulation that’s associated with low pressure in the northern hemisphere. However, since the polar vortex is somewhat reminiscent & has some characteristics of other more commonly known types of low pressure, if you slow down the easterly winds in the stratosphere or even reverse them, what happens is you cut-off the polar vortex’s “lifeline” even to the point where the sudden switch to easterly winds cause a sudden rise in pressures that can completely obliterate the polar vortex & even lead to total collapse. In such a situation the vortex becomes multiple low pressure eddies that propagate much further south than their normal position over the arctic, thus unleashing lots of cold air & havoc into the mid-latitudes. Also makes sense to see a stratospheric warming event when the QBO switches to phase 7 given that the switch to an east QBO is generally more favorable than a west QBO. Here is the temperature composites over the northern hemisphere for the east & west QBO pattern.
Worth noting as well with the cold PDO & “la nina like” conditions associated with it, a stratospheric warming event in such a pattern does not guarantee cold in the eastern US, actually according to Levi Cowan in one of his stellar videos a few years ago, such patterns can even tend to backfire on you.
Also, given this year currently going to be pushing 4 years without an el nino, there are only two winter analogs that come up in such a situation, 2001-02 & 1962-63, both of which were the last la nina winters in a pattern that went without an el nino for 4 years before the onset of an el nino the following winter season. I happened to break down the temperature pattern in those years, & not surprisingly, as I would expect given some of the conflicting factors in place at this time for this upcoming winter & potential stratospheric warming event, the pattern would appear to variate quite substantially, thus giving everyone a “piece of the action” per say. In general though, this factor really didn’t help all that much determine how this winter would play out given the small sample size of the analog years.
December North America ENSO analog temperature anomalies
January N. America ENSO analog temp anomaly composite
Feb N. America ENSO analog temp anomaly composite
In all, considering all these factors I’ve listed above in my post, this is my current preliminary thinking on the upcoming winter.
My temperature map reflects the -PDO, la nina & ENSO neutral blend and I also take into account the ENSO analogs I mentioned earlier in the post. I also understand that with the northern hemisphere snowfall anomaly well above normal in the early stages of October that a lot of cold air is going to be thrown at North America, the real question will be how strong will this cold air be & how far to the southeast can it penetrate in the face of the -PDO. The potential I discussed in this post for a potential stratospheric warming event which also throws a bit of a curveball into this pattern, but even so, stratospheric warming events which do tend to dump cold air into the mid-latitudes, when combined with la ninas & the -PDO, the cold air as a result of them tends to clash against the -PDO & “la nina-like” conditions which force a substantial ridge over the southeastern US & near the east coast, thus I have taken a compromise of all these factors, & the resulting preliminary 2013-14 winter US temperature forecast looks like this. Very cold in the northern Rockies, northern Plans, & into the upper Great lakes, pretty much anywhere north of i-90 west of the Mississippi looks quite frigid when compared against normal. It looks cold still further south you go, with generally the i-80 corridor west of the Mississippi being the dividing line between the very frigid conditions & somewhat chilly conditions found a bit further south. The dividing line between the colder than normal conditions & warmer air thanks to the SE US ridge will be near the i-70 corridor, at least that’s how it generally appears at this point in time, & it’s in this area of the country where I’m most uncertain regarding exactly how the winter will try to play out.
For comparison, this was the older “shot in the dark” ideas from back over the summer, my new map really isn’t too terribly different from this, the only significant change has been I’ve taken the -PDO into consideration more & the region of the southeastern US that appeared rather “uncertain” I now have warmer than normal.
Old US winter temperature forecast map (really just made this 1st map for fun)
New forecast map really not too terribly different from summer ideas, definitely I’d say not too bad considering how little I had to work with over the summer other than my hurricane season analogs which have busted (though the 500mb height patterns & US temperature composites from those years actually verified in spite of the lack of tropical activity)
My current preliminary US winter outlook based on all of the conditions at hand I’ve discussed in this post, this is likely to change with time & I likely will try to finish any adjustments to this forecast to release a final and official winter outlook late this fall as many of the winter forcing signals become clearer, this will be especially true after October.
In general, big snowstorm in the western Dakotas definitely was worth mentioning, had connections to the -PNA/-PDO pattern that has been dominating the northern hemisphere, partially thanks to the typhoons crashing into southeast Asia. Given the pattern, with a large ridge expected to build across eastern & Atlantic Canada, the western Atlantic will have to be watched very closely for development in the medium-long range along with a new wave emerging off the west African coast. Factors such as the potential stratospheric warming event, QBO, stratospheric temperature trends over the arctic, PDO, the strong Alaskan-Siberian Vortex showing up this month, NAO, & the difference in water temperature anomalies between the Indian Ocean and the east equatorial Pacific/Atlantic all help to give a general blend of winter that paints a generally favorable picture the further north & west you go in the US, while the opposite is true further to the south & east. Although the ENSO analogs didn’t help very much in my preliminary winter thoughts for this winter, the overall pattern of ENSO certainly does. As I mentioned earlier in a few comments on other blogs on this site & through my twitter account, we have not gone more than 4 years without an el nino, & if this is the case, then next year would look to be an el nino winter. If this is indeed true, then looking at the mean temperature composite of el nino winters that come off multi-yr la ninas, the pattern is usually brutally cold & snowy for the eastern US.
Definitely something to look forward to as well as my future posts which will of course cover any weather events that take shape, but also the MJO & hurricane research as well as the physical mechanism I’m coming up with to explain the relationship between US hurricane landfalls & strong global earthquakes above 8.5 magnitude or greater. Hope you enjoyed reading this post and if you have any comments, questions, or concerns regarding any of the topics & related information discussed in this post, or if you just feel like saying hi, feel free to drop me a comment, I’ll be more than happy to answer. Hope all of you weather nuts out there enjoy the rest of the fall & Halloween, which is almost around the corner. Hopefully we won’t get any “Halloween Scares” this year in the northeastern US like we’ve had the past few winters, but given the behavior of this year, anything is possible. After all, mother nature is naturally unpredictable as the weather is in a constant search for a balance it will never achieve & the forecasting of weather in general is still a major frontier in the scientific realm, it’s up to you, me, the professional meteorologists & all the other weather nuts out there to take it apart & discover its “secrets”, one small step at a time.