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Originally posted by wxrisk1 wrote:http://www5.wright-weather.com/bb/showt ... adid=36735
OCT GSM SEASOIAL MODELS-- looked very cold and this model was important to some in arguing for a very cold winter in the eastern US
NOV NEW GSM SEASONAL MODELS -- total Model flip flop.
why the MASSIVE change and is it time fo eastern and central US winter wx lovers to start worrying ?
I dont know this for sure YET but I suspect The GSM climate flipped flopped b/c the model is seeing the current pattern which in late OCT and early NOV has been quite mild and well Non stormy and very non threatening at 500 MB.
Current 500 MB NOV 9 pattern
[img] http://www.wxrisk.com/MODELFOLDERS/t0.gif [/img]
NOV 9 00Z ECMWF 3 DAY 500 MB MEAN PATTERN FOR NOV 18
[img]http://www.wxrisk.com/MODELFOLDERS/ecD101109.gif [/img]
By D10 the day 8-10 500 MB mean pattern shows a number of important features... FIRST please note that the PV is on the WRONG side of the hemisphere -- North Central Russia-- which means the heart of the cold air is on the wrong side of the globe for winter lovers of eastern and central US.
(I have highlighted these features on the map and as you can see once again the PV (polar vortex) is located.)
It also means that as a general rule 500 MB heights will run Above normal and there will NOT be any deep troughs over the central / eastern US thru NOV 20. That is not a good sign for early winter forecasters and if the current pattern holds... and for those forecasting a colder than normal 2nd half of November over the Central eastern US are in deep doo doo.
BUT the appearance of the HIGH at 500 MB over the far northern portion of Baffin Island becomes more important. This feature serves to split the PJ (polar jet) from the Arctic Jet and cuts off the supply of cold air into Central Lower Canada.
Also note we have a strong Jet streak of Pacific energy coming around from Japan into the Central Pacific which then splits into three distinct streams as I have highlighted -- the Arctic jet which is North of Greenland around the vortex in Central North Russia... the PJ or Polar Jet which is running W to E across the Central Canada.... And the STJ or subtropical jet which comes into Southern California and northern Mexico and that emerges into the ocean Low pressure off the SE Canada coast.
The splitting on the Jets into three distinct phases is GOOD thing and one of the best ways to get out of the rather bland and current mild pattern over most of North America. A clear 3 stream split increases the odds that the pattern at D10 is NOT going to last for long. .
NEW NOV 10 12Z RUN ECMWF VALID -- NOV 20
There are some major shifts developing -- iof this mean day 8-10 500 MB model is correct. FIRST I have highlighted the OLD position of the PV to show how the ECMWF is sliding the PV into eastern Europe ... and of course as the PV doies so the +Scandinvia pattern will end.
SECOND th 500 MB Block over far northwewt Greenland has retrograded sothwest into NW canada... which now SHIFTS the ARCTIC JET back into north central and eastern Canada for the 1st time in 2-3 weeks!
THIRD -- the Retrogresion of the PV into a position halfway between NE greeland and Narvik Norway.... and the RETROGRESSION of the 5H MB HIGH into NW canada TELECONNECT to a 2nd PV forming over Hudson Bay Canada...
The development of this feature is CRITICAL to establishing normal winter time pattern for North America.
FOURTH [B]*** IF -- and ONLY IF -- a 2ndary PV does form over Hudson bay ... and IF and ONLY IF the PV does moves into far N Scandinavia.... the GAP or wavelenght beween these features would allow the 500 MB high in the NE Atlantic to build into Greenland and set up a VERY strong
-NAO. *** [/B]
This would be very cool if it were to verify
