UNITED STATES PRE-WINTER FORECAST BRIEFING

Written by on October 20, 2013 in United States of America with 0 Comments

My Official USA Winter Forecast is due for release at the end of the month but I thought now would be a good time to show you generally how I think this winter across the US and indeed North America will play out.

We’ve seen some very warm weather in the east through the first half of the month but we have a major turnaround now setting in and a lot of that is simply down to the PNA flipping positive. Often we look at a -NAO/AO for cold in the central and eastern US but due to a -PNA, it was quite the opposite. Now, it’s going positive just as the NAO takes a second tanking at the same time the AO is negative.

The next 2 weeks have some tremendous cold driving deep into the Lower 48 with snow whitening the Northern Tier and particularly the Upper Midwest and around the Great Lakes over the next 7-10 days.

Check out the snow forecast off the GFS through Friday.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s a closer look at the Northeast. Wild stuff given this early on still.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s the 168 hour.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

We’re seeing the current shot of cold with lows dipping to 27 yesterday morning at Amarillo. The second shot comes down in the coming days on the backside of a clipper system which brought snow to parts of Minnesota, Wisconsin and Michigan today.

As the cold penetrates further and further south and east through this week, we should see snow flakes fly over the Appalachians, perhaps as far south as the North Georgia Mountains. Atlanta may even hit freezing with 20s are widespread across the Ohio and Tennessee Valleys.

Check out these lows by Wednesday and Thursday mornings.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Here’s the front running 7 day temperature departures off the GFS, helped by the recurve of Typhoon Wipha

350x279_10201215_20gfsdepart23

A second shot follows this upcoming week’s cold which drops into the Midwest and East day 7-14 day and is reinforced by aided Typhoon Francisco which is set to impact Japan in the coming days before recurving.

Check out the even colder departures

350x279_10201217_20gfsdep31

Here’s the ECMWF 500mb/850mb temps over the next 10 days and you can see just how deep and cold that trough is coming down.

Sun 20

Geopotential3250032hPa32and32Temperature32at3285032hPa_North32America_0

Wed 23

Geopotential3250032hPa32and32Temperature32at3285032hPa_North32America_72

Fri 25

Geopotential3250032hPa32and32Temperature32at3285032hPa_North32America_120

Sun 27

Geopotential3250032hPa32and32Temperature32at3285032hPa_North32America_168

Wed 30

Geopotential3250032hPa32and32Temperature32at3285032hPa_North32America_240

Here’s the CFSv2 weeklies and note the next two weeks are very cold compared to normal from north-central Canada down to the Southeast US.

wk1_wk2_20131019_NAsfcT

By week 3 and 4 you notice the turnaround begins and we start seeing warming which I expect to see given my long term idea of a strongly positive NAO/AO for a couple of weeks during November. The CFSv2 agrees with my idea stemming back to August of a cold end to October, potentially start to November, then it warms up but could turn colder over western part of the continent.

Nov 3-9

wk3_wk4_20131019_NAsfcT

As you can see the AO is projected to not only go positive but wildly so! That is crucial for rebuilding arctic in it’s source region. You need a period of ‘building’ in order for there to be ‘intense’ cold, afterall the cold must be made so to speak and there’s no better place for that to occur other than the arctic right?

ao_fcst

The NAO is currently in the tank but it too goes positive during November.

nao_fcst

As for the PNA, it of course has turned positive just in time for the coldest air yet to drive not only south in the US but into the east. The last episode of -NAO/AO had a -PNA which held the cold in the west.

pna_fcst

Here’s the CFSv2 forecast for November and I agree with it, although the warm departures in the South and East will depend upon how quickly it warms back up. The first 7-10 days of November look cold and so it would have to significantly warm in order to get these departures of the month overall.

usT2mMonInd1

So, just because it’s cold now, why do I think the winter is likely to be cold?

Check out the difference in both arctic sea ice and Asia snow cover now compared to this time last year.

Quite a big difference. The greater coverage is sea ice should help build cold faster and stronger than in recent years and as well as that, there is still a a low enough amount of sea ice and warmer than normal water up there, for blocking over the pole this winter!

RecentSnowCoverNHhemisphere

As for solar activity, well it peaked in the current ‘weak’ cycle 24 and is now heading for the minimal. While not as low as back around 2009-10, it far less than in 2011-12 when the winter was warm. Oh wait, when the sun was at it’s quietest in some 100 years was that winter (2009-10) not very cold winter over the US, Europe and East Asia? Hummm. The trend is downward and heading for those levels and I believe that is something worth considering for this winter as low solar activity along with warm SST’s support more high latitude blocking.

Solar_Cycle_Prediction

Let’s not forget the recent volcanic activity up in Alaska which can also support increased blocking too.

Here’s the current global SST’s.

anomnight_10_14_2013

Let’s take a look at the forecasted SST’s this winter off the CFSv2 and Jamstec models.

CFSv2

glbSSTSeaInd2

Jamstec

ssta_glob_DJF2014_1sep2013

SST’s are important when it comes to atmospheric feedback as you know and it’s interesting when looking at the forecasted Dec-Feb global SST’s. While they both agree on the North Atlantic tripole of warm-cold-warm which supports a Greenland block, they disagree on SST’s over the equatorial Pacific. The CFSv2 shows a centrally positioned El Nino signal which supports a cold signal for the US while Jamstec has a weak La Nina signal.

This disagreement is very clear in it’s forecasted temperatures over the continent. While modelling bounces from warm to cold almost daily, the Jamstec shows a warm winter for NA.

To conclude and based on current as well as forecasted SST’s, the low solar activity, the trend towards a -NAO/AO and the larger arctic sea ice coverage as well as the greater coverage of Asian snow cover. I believe a cold winter is on the way to the US and the pattern now shaping up over the Midwest and East, well that’s what I think the upper air pattern will look like through the heart of winter.

My official winter forecast will have details on when I think cold outbreaks will occur and where the biggest snows will be.

Here’s the CFS temperature anomalies for this winter off the CFS. I’m in agreement and yes, December is warm and it may well be. I believe it will be a cold winter and colder than last year, especially in the heart of the season rather than at the end. The timing of the cold is key though.

Dec

cfsnh-8-12-2013

Jan

cfsnh-8-1-2014

Feb

cfsnh-8-2-2014

Stay tuned. My official US Winter Forecast will be released at the end of this month.

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