Long Range Discussion 22.0

Today's U.S. subseasonal report was an interesting exercise: big model changes, plus a striking analog related to the weak stratospheric vortex. Subseasonal reports go out Tue and Fri a.m. as part of our trading markets application #powermarkets https://t.co/WEt2tbgABA pic.twitter.com/CeNxg5gCHu

— World Climate Service (@WorldClimateSvc) October 26, 2021

amugs wrote:Dr Cohen says colder weather ahead from these charts - Stratospheric warming in teh orangy colors coupled down to the Polar Vortex Arctic Region to help release the colder air

Boy the GEFS is just going bonkers for November into December. Western ridge, Alaskan ridge, blocked up arctic.

This is NOT a forecast, but all signs point towards a front loaded winter pic.twitter.com/3RrYT6IEPO

— Joey Scherkenbach (@jscherkenbach1) October 29, 2021

sroc4 wrote:Good morning everyone.  Its about this time that we begin to look at the Siberian/Eurasian snow cover.  Between about now through the end of Oct/November, the snow growth rate and persistent snow cover in this area has been shown to have a relationship in determining the state of the Arctic Oscillation(AO) during the winter months.  The more rapid the snow growth rate and the expansiveness of the snow cover over Siberia/northern Eurasia during this time frame, the stronger the correlation with a negative AO during winter months seems to be.  As far as my understanding, the idea behind this is that a rapid expanse of snow cover over this extremely large region acts as a giant mirror if you will.  A white blanket of snow acts to reflect a large amount of sunlight back up into the atmosphere over the arctic.  On a smaller scale this reflective light is why its easy to get a sun burn on the ski slopes on a sunny day in the dead of winter.  This reflected sunlight back up into the atmosphere on such a large scale can influence the temperature and pressure patterns over the Arctic regions at various levels of the atmosphere.  A negative AO means the tendency is to form "blocking" domes of high pressure in the northern latitudes, particularly over the arctic circle, which tends to favor the discharge of cold arctic air masses into the southern latitudes.  

Keep in mind Siberian/Eurasian snow cover during the fall is only one piece to the complex puzzle that comes together to determine the winter pattern over the short and longer term.  In addition the exact relationship of the snow cover and the AO state is still not fully understood.  Other oscillations(QBO, NAO, EPO, PNA to name a few), large scale sea surface temp patterns, and stratospheric temps, etc all come together to determine the final outcome of the pattern.  Within any given year these varying factors all may play larger or smaller roles in determining the outcome.  

Anyway here is the current snow cover anomalies for the northern hemisphere with purple colors above normal snow fall for this time of year, red below and white normal.  

Frank_Wx wrote:Pattern in the first 7 days of November is setting up for the first significant snow of the season central to upstate NY. There’s a chance those N&W of NYC in our region see their first snow as well. I’m not yet confident in anything for the coast but obviously very early for that to change. Regardless, the pressure put on the SPV only means good things down the line for us. Just don’t want to see La Niña takeover completely

Latest QBO plot & E'ly phase continues above 40hPa, weak W'lies below - Of importance: We have the rare combo of a La Nina & eQBO moving into winter, which has been highlighted for some time. I, therefore, suggest a SSW is a higher risk this winter, between mid-Dec to mid-Jan... pic.twitter.com/EdTPxcQrXi

— Matt Hugo (@MattHugo81) November 3, 2021

Looking at the pattern ahead, chilly to end this week, rather mild next week, then perhaps a legitimate pattern flip the following week. Strong signs of a +PNA/-EPO couplet, which pumps western ridging/eastern troughing. This *could have staying power, too far to know for sure. pic.twitter.com/DX7qF0Ns9T

— Joey Scherkenbach (@jscherkenbach1) November 3, 2021

Updated run of the ECMWF weeklies are complete.

They strongly indicate that weeks 3 & 4 of November will kickoff winter across the Eastern US and Canada. Classic signal for significant cold and snow potential. pic.twitter.com/wlrvhuPNOs

— Ethan Sacoransky (@blizzardof96) November 4, 2021

What's the significance of this event? The east-asian cutoff low allows the north pacific jet to amplify in a wavelike/stepwise pattern. Notice how this eventually results in a great lakes trough ~Nov 13th. pic.twitter.com/dkr7YeAuFT

— Ethan Sacoransky (@blizzardof96) November 5, 2021