Monday, March 25, 2013

Long Range Chatter; Will The Cold Ever End?

It’s looking more and more like the unusually cold weather we have been experiencing may very well continue through the remainder of March and at least a week into April.

Much of the country has been in the grip of a serious chilly start to winter, with temperature anomalies well below normal in many parts of the country. We have seen lower than 6 degrees (K) below normal in the heart of the Plains, with only a fraction of the Southwest and much of New England getting into above normal temperature anomalies from the start of March to March 23rd. While this may seem like a brutal start to spring, there's only slight indication it could end by mid April.

Shown above is a forecasted image from the European ensemble system, projecting 850 millibar temperature anomalies for 12 days from today. While a brief relaxation of the current cold snap is incoming, the chances of a follow-up Arctic cold shot are high. The European ensembles have anomalies just above 10 degrees (C) below normal across much of the northern Plains and Upper Midwest, with less-intense below normal anomalies across the Midwest and the rest of the Plains. Cool weather could reach as far as New England. This would more than likely continue the streak of cold weather across the nation, and the European ensembles bring another cold blast into the same regions just under 2 weeks out.

In the longer range, the American ensemble mean pushes the below normal temperature anomalies out of the Contiguous United States on March 31st. However, just a day later, we see a progressive cold shot in the Upper Midwest, and these progressive cold shots continue throughout the 16 day forecast period. In the longer range, the American ensembles seem to be hinting at below normal temperatures, mainly centered in the Eastern Seaboard and parts of the Northeast.

The general idea of the longer range is high pressure will continue to hold its ground over Greenland. When you see the placement of high pressure over Greenland, it is common to see an increased risk of cold weather across the northern Plains and New England. It also looks like we will be seeing a more active Pacific Jet Stream in the longer range, something that could add energy to the storm potential (winter weather and severe weather), especially in the Northeast. There are a few more indices I am observing that seem to support some stormy times for the Northeast. Whether that ends up as winter weather or severe weather remains yet to be seen.

So what is driving all of this cold weather??

This past winter, I continued to press the issue of how snow cover over Siberia in October could affect temperature anomalies in the following winter. In October 2012, we saw below normal snow cover for the first half of the month. This reflected nicely with December 2012 temperature anomalies, as shown below:

December 2012 brought above normal temperatures to the Plains, Midwest and Great Lakes, among other regions. New England ended up with below normal temperatures, as did the southern half of the Eastern Seaboard. California and portions of Nevada also got in on these below normal temperatures. I feel very strongly that this was indeed the Siberian snow cover correlation at work.

Looking towards mid October, we see a moderation in snow cover anomalies over the northern Hemisphere. Let's take a look at what January 2013 brought, temperature anomaly-wise.

As unequal as this may look, you can kind of see how the Plains cold and Northeast warmth can cancel out. Now, this could very well go towards the side of below normal temperature anomalies across the month of January, but I still can see how the relatively normal snow cover anomalies during mid October 2012 can reflect onto the observed temperatures in January.

Now, the end of October 2012 held very above normal snow cover. This correlates to a weaker than normal polar vortex, which can easily translate into below normal temperatures across the nation. Considering the snow cover anomalies came in late October, and we are seeing the extreme cold now in March, there is little reason to not believe that the Siberian snow cover/temperature correlation isn't an actual index.

Beyond the beginning of April, I expect a rather moderated temperature pattern, but with cold shots moving throughout the nation every once and a while. The frequency of these cold shots will decrease as spring progresses on and winter inevitably releases its grip on the nation that should be enjoying a beautiful spring.



Logan said...

Too bad all these storms/ the cold wasn't in January/February!!!

I want a big snow storm still :(

Elizabeth said...

Logan ---me too...i am still hoping for snow......thx to Andrew for all of the info-