Ag Weather Forum
Duration Of Cold May Be Impressive
To start out this blog entry, I call your attention to the final paragraph of a post that my colleague Doug Webster authored just two weeks ago on Thursday, October 30. In writing an update on the weather pattern for the Canadian Prairies, Doug concluded with this comment:
"The key to the upcoming winter pattern will be if and when any high latitude blocking high pressure develops and where the polar vortex decides to be. If the polar vortex stays more on the Asian side and blocking is minimal then the milder El Nino aspect of the pattern is likely to be a more important player. If blocking returns along with a stronger polar vortex across North America then the El Nino pattern will be disrupted."
Jump ahead two weeks, and what are we experiencing? We have high latitude blocking high pressure over northwestern Canada and portions of Greenland. We have also had the polar vortex migrating across the North Pole and onto the North America side of the polar region, with the result being the bitter cold wave that has covered the entire central U.S. and is heading toward the eastern and southeastern sectors of the country. Only the far western and southern portions are truly escaping the incursion of this cold wave.
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This very cold pattern is of course far out of season. It's one thing to have this type of cold move in during late December and into January--after all, that's the period with the shortest days of the year in the northern hemisphere, so we expect that. But mid-November is still a time period when Indian Summer conditions are possible. I don't associate air temperatures in the single digits Fahrenheit and wind chill index values of well below zero F with Veterans' Day--but that's what we have.
Have we had cold snaps of similar magnitude in the past--yes, of course we have. One such event was the Armistice Day Freeze in November 1940, when a quick and brutal cold wave swooped into the Midwest following a very mild October-early November period--one of the Indian Summer occasions. That cold wave killed many acres of apple trees, and likely wiped out true commercial fruit production in the western Midwest.
But--a big difference between that event and the Big Chill we have in effect now is that, back in 1940, the cold snap came in, did its (significant) damage, and then modified in just a few days. That's not the case with this Arctic package. Forecast charts have this very cold pattern staying around for the better part of two weeks at least.
That hanging around--the duration--of this cold wave is where the real records may come into play. It will be noteworthy to see how many days are tabulated with temperatures in the range of ten to twenty degrees Fahrenheit below normal. That is an outrageous--extreme--departure from normal and may be the real legacy of the November 2014 cold wave.
Bryce
Twitter @BAndersonDTN
(ES)
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