Monday, October 24, 2016

Monday Morning Weather Discussion: Winter Knocking on Our Door

Good morning, I hope everyone enjoyed my winter outlook. We are going to stay on a similar theme today as the weather pattern has really come alive in recent days and shows more signs of life in the coming weeks. The mountains of New England got their first snowfall of the season over the weekend with areas like Jay Peak, VT receiving a foot plus of snow! Believe it or not, more snow is on the way to the mountain areas later this week as a potent clipper system move through the area. 

Here is a summary:


  • Cold air enters region today through Wednesday. High temps will struggle to get into the high 50's for many spots with lows approaching freezing in northwest counties.
  • A potent clipper system enters on the heals of this cold air causing some snow to break out initially in north central PA and southern NY State. The mountains of New England get another moderate snowfall from this.
  • Moving to the long range, all signs point to a cooler than normal November
  • This is supported by a very early season warming of the stratosphere that is about to occur. 



To set the stage, cold air builds back into the region today through Wednesday with Wednesday being the coldest. Expect temperatures to be in the 50's in most spots and possibly not breach 50 in northwestern counties on Wednesday. The image below shows this injection of air from the north..


Notice the arrows coming down from the north showing a north to northwest flow of cold air into the whole area. On the heals of this cold air mass, we have a low pressure system (clipper) that is going to approach from the west on Wednesday night and Thursday. The initial burst of precipitation can be snow for areas of north central PA and southern NY State. Northwest NJ might squeeze out a flake or two but I am not sold on that idea yet. The mountains of New England receive another moderate snowfall from this.

You can see the initial projections of precip on the GFS model..


Model is showing how cold air tries to hang in there initially. As the cold air departs the southern zones, the focus then becomes the mountains..


We will have to keep a close eye on the dynamics between how long the cold air holds on vs the strength of this system. If this system ends up being modeled a little deeper than cold air can hold on longer.

In any event, here is an idea of snowfall. Just focus on the spotty areas as I do not expect much of any accumulation outside of the mountains. I do not think that the low level terrain sees accumulations at this point. The model is prob overdoing those areas. 


In any event, we can all see winter is around the corner. This brings me to my next point..the stratosphere.

We are currently about to witness a very rare event in the stratosphere for this time of year. Models are projecting a stratospheric warming event which will largely displace or even split the polar vortex over the next week or so. I can not emphasize how rare it is to see that happen so early and I believe it will have big impacts on our weather from mid November on (2 to 3 week lag in response in the troposphere).

To make a long story short, when the stratosphere or upper levels of the atmosphere warm, it puts stress on the polar vortex. This stress weakens the polar vortex which allows cold air to spill into lower latitudes. On the flip side, when the polar vortex is strong the cold air stays locked up north. Looking below we can see what the GFS model is showing way way up in the atmosphere (much higher than planes fly)..


This shows temperature/pressure patterns. Notice the area of warm invading the poll and causing the vortex to almost split into two separate lobes. We usually do not see this happen until January or Feb or sometimes does not happen at all depending on the winter. What does it mean? Well, if we in fact do get the vortex to come under this stress then attacks of arctic air will be frequent from mid November on. 

Really interesting stuff. 

The models are starting to hint at this as well as we enter November..


Remember it is not January of February so a cold outbreak is not as intense. However, I think this November will be much different than last year in terms of temps and storminess. 

Thanks for reading. 



7 comments:

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  2. Hi W.W, I like what your forecast is indicating about the SSW and the displacement of the Polar Vortex. I also visit this site for a more detailed look at the global atmospheric forecast and Polar Vortex predictions (https://www.aer.com/science-research/climate-weather/arctic-oscillation). I hope that the Elmira/ Corning/ Binghamton areas (aka Central Southern Tier) of NY gets an old-fashioned winter-big and frequent snowstorms this year, which we have not seen in ions.

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    1. Thanks, I will make sure I keep you guys in the loop in that neck of the woods this winter. You guys are due! And that is a very good site, one of the better ones out there.

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  3. I check aer.com too. AER is affiliated with Dr. Judah Cohen, the fellow who promotes the idea that snow extent in northern EurAsia during the autumn season strongly correlates with AO / polar vortex dynamics throughout the winter season. From what I've read, this idea is well respected in the meteorology field, but there are also some in the field who disagree as to just how strong and relevant the correlation is, or what its effects are south of the Arctic Circle. FYI, Jim G

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    1. Yeah, some dispute it but their track record is very decent and if you read the research papers Dr. Cohen has put out over the years there is some very compelling data in there. As with anything else, the weather is always the sum of many factors. If we have one dominating factor it can over power the influence of others. Last years killer Nino is an example of that. However, this year with a neutral to weak la nina that snow cover theory might hold more influence. The QBO is not helping BUT again that is only one of many other factors that look to make this season promising.

      Also Jim, not a bad idea to do a winter outlook update. Maybe when December rolls around we can see how the models and observations look. At least we will know if things are on track. If you havent seen, the new Euro Weeklies came out last night and all signs point to a very active and cooler November in the east. This could be great news for Ski Areas especially since the PV weakening is also happening which maybe the models are picking up on. We shall see!

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    2. I'm not a meteorologist but I just skimmed through some historical data and the link between the extent of Siberian snow cover and winter temperatures seems reasonably strong. The only years that it seems to not work is during strong El nino years (2016 and 1973). Of course, there haven't been too many years with snow cover as high as it has been this year and the past 3 years. I also haven't examined the rate of growth, only the monthly snow cover.

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    3. Took a look at one of Cohen's articles on the Noaa site. He makes the point that sudden strat warmings are part of the process thru which an expanded EurAsian snow field influences the AO. Last year had a rapid and extensive autumn expansion of the snowfield, but the Nino generally kept things mild here in the east. But OK, I'll give Cohen his due -- we did have a few big SSW event in January and February, and they were pretty significant if temporary -- I don't remember ever trying to start my 10 year old Corolla at minus 5 before! Not what I expected during a Nino winter. If there is a gangbusters expansion of the snowfield going on right now and Cohen is right, then we might expect to see some SSW stuff happening soon -- which you mentioned the other day. I'll be keeping an eye on those 30/10/5m polar temps (and just a few weeks ago, we were tracking hurricanes . . . ). Jim G

      oh, if your site allows -- here's a URL for the article for those interested:
      http://www.nws.noaa.gov/ost/climate/STIP/FY11CTBSeminars/jcohen_062211.pdf

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