Monday, March 18, 2013

Colder Weather On The Way - And It's Here to Stay

"He said I wanna see you again
But I'm stuck in colder weather
Maybe tomorrow will be better
Can I call you then"
(From Zac Brown Band song, Colder Weather)

As the Zac Brown Band tells in Colder Weather, it looks like the majority of the nation is going to be stuck in colder weather. Unfortunately, tomorrow will not be better- if anything, it will be even colder.

Shown above is the European model's projected 850 millibar temperature anomaly forecast for 6 to 10 days away from today. The 850 millibar level is commonly referred to as one of the lower levels of the atmosphere. The European model is very clear with its intentions over the next 10 days. The projection is for harsh cold to start out in the North Plains and Upper Midwest, where anomalies of 10 degrees (C) below normal will be commonplace. As time progresses towards that 10 day forecast mark, we start to see the cold slide south, into the midsection of the nation by the time the weekend is around, and penetrating the South US 10 days from today.

The long range American temperature anomaly forecast is no more comforting. This forecast is from the American ensembles and is forecasting surface temperature anomalies in Celsius. From the next 8-16 days, the ensembles are pretty firm in saying that all areas east of the Front Range in Colorado should be able to achieve below normal temperature anomalies. The atmospheric set-up favors frequent cold shots into the Mid-Atlantic and Southeast as a result of the suppressed jet stream, and the American Ensembles latch onto that idea quite well. The Northern Plains also experience a solid degree of below normal temperatures.

So what's causing all of this cold to suddenly evacuate the Arctic and ruin the onset of spring? As you see in the 2-6 day forecast of 500 millibar height anomalies from the European model above, record-breaking high pressure in the Arctic Circle is causing the Arctic Oscillation to go negative. For those unfamiliar with the term, the Arctic Oscillation involves a positive and negative phase. The positive phase has strong low pressure over the Arctic that locks cold up in the higher latitudes and allows warmth to prevail in the US. The negative Arctic Oscillation (AO) permits strong high pressure to take over the Arctic, which in turn allows cold air to flow freely into the United States. The Arctic Oscillation is forecast to reach a negative level that is so low it has not been seen since 2010. If the AO goes as low as the most extreme forecasts are calling for, we could see a negative level not experienced since 1985. Regardless of how low the Arctic Oscillation will go, the big picture is that cold weather will dominate the nation for the rest of March, likely into at least the first week or two of April. This event is not just a few days of chilly weather- we're talking multiple weeks of below normal temperatures. There is no end in sight to this colder weather at this time. I suppose this winter cold just got backordered.

For those of you who follow the idea that above normal snow cover in Siberia during October can make the Arctic Oscillation go negative in the following winter, this is a direct byproduct of that idea. The last third of October 2012 had way above normal snow cover, meaning we could be in for a month or more of below normal temperatures. Happy Spring!



Anonymous said...

Hmmm..well, this bits! & yes it’s very cold!
What a sense of humor Mother Nature has indeed!
I think she hates me! Well be that what it is… Thank you Andrew
for your updates! I look forward to them & enjoy them very much!
Happy spring? I don’t think so…no… but there is always summer!!

Anonymous said...

I certainly like what I am seeing in our forecasts, because despite what forecasters are saying about huge, blocking lows developing over the Colorado Rockies, the changing pattern is showing almost stark opposite of that, with the pattern flipping to cold and wet/snowy for at least a 4-5 day stretch, and no end to the cooler weather after that, and still more chances for precipitation beyond that, hopefully we can keep this up, because the absolute last thing this area needs, is any more patterns that are anything similar to last year's never-ending nightmare, but one thing is for certain, right now, things have been in the last few weeks and definitely continue to look a little better in terms of at least some alleviation from what has already been deemed the worst drought in Colorado history, and once this thing is squelched, I hope I never see another one like it again in my lifetime.