...they've been cold.
5:30 PM EST 2/27/12 Though Blizzard Watches and Winter Storm Warnings are posted for the Northern Plains today, the overall pattern for much of North America has been a milder, drier winter with above-normal temperatures. This week, places along the East coast may once again aim for 60 F or higher ahead of a cold front. Contrast with record-breaking frigid temperatures in much of Europe recently, (as low as -22 F) with snow to Rome and Northern Africa. It's no surprise that inquiring minds are repeating a line from Jake Gyllenhall in Day After Tomorrow "What is going on out there, Dad?!?"
This excellent report from the Physics website physorg.com details the background behind why we've been warm, while they've been cold. A few talking points we'd like to offer in support of the article.
- Oh, the NAO: Winter 2011-12 in North America has been strongly influenced by a moderate La Nina, in combination with a resoundingly positive "North Atlantic Oscillation" (NAO). This climate teleconnection, as shown in the screen cap above, has shown generally up values since well before winter. When this index is positive, intrusions of Arctic air into the Eastern U.S. are short-lived and infrequent. Where did all the cold air go? (insert big, devious smile here...)
- Argh, that AO: Now compare the positive trend in the NAO this winter to the wild swings recent negative trends in the Arctic Oscillation. As noted in the physorg.com article, one factor may have been that "The tight polar vortex that had bottled up the cold arctic air in the beginning of winter suddenly weakened. Cold air swept out of Siberia and invaded Europe and the Far East. Now the vortex is weakening. With 'the AO Index going negative,' as an expert or weather-nerd* might put it, cold air escapes from that whirlpool and heads southward, resulting in the killing extremes now plaguing the other half of the planet." (phys.org.com)
THE ELEVATOR VERSION, PLEASE... If it's much colder (or warmer) than normal where you are, chances are high someone else is also getting scammed out of their normal pattern in the opposite direction. Why? With at least three major climate indices on a rollercoaster ride this winter (La Nina, NAO and AO)...it's safe to say that "Momma" (Mother Nature) isn't very happy.
And if Momma's not happy...
(Forecasters Foot; Contributors Mike N., Jason M. and Advisor Dr. Pete Winstead)