Everyone should be wary when weather geeks start getting excited about an upchartph.coming shift in the jet stream because it usually means inclement weather is ahead.?
After all, weather enthusiasts — whether they be armchair forecasters or professionals — tend to abhor boring stretches of "nice" weather.
Forecasters have reason to be psyched right now, given strong hints for what could be a major weather pattern realignment during the next two weeks.?
Computer models are increasingly showing the potential for a cold and possibly snowy weather pattern to develop along the East Coast of the U.S. during the second week of December. While there are many uncertainties associated with the forecast so far in advance, the general contours of what is likely to happen are bechartph.coming clearer.
Some of the building blocks for the cold weather are already in place, including a predominantly negative Arctic Oscillation, which favors — but does not guarantee — colder-than-average conditions in the eastern U.S.?
"Where have you gone (negative) #Arctic Oscillation our nation (of weather geeks) turns its lonely eyes to you." Nearly classical AO- predicted by the models early Dec with three poles of #cold, Europe, East Asia and East US (Euro not quite there yet). It's been at least 5 years! pic.twitter.chartph.com/EwnJja2Wmv
— Judah Cohen (@judah47) November 22, 2017
The Arctic Oscillation, or AO, is climate pattern that describes the atmospheric circulation over the Arctic and North Atlantic Ocean. During a negative phase of the AO, the polar vortex over the Arctic is weaker, resulting in a slackening of the upper level winds ringing the Arctic from west-to-east.?
This can allow frigid, Arctic air to spill into the midlatitudes, including Europe and the U.S.
For much of late November, we've had a strongly negative Arctic Oscillation with milder-than-average conditions in much of the U.S., which goes to show that other factors, including weather patterns across the North Pacific Ocean, also have an influence on winter weather in the lower 48 states.?
Computer model projections for 11 to 15 days from now show a strikingly favorable weather pattern for cold air to invade the eastern U.S., as well as parts of Europe and East Asia. Strong areas of high pressure at high latitudes, including one in the Gulf of Alaska and another monster high over Greenland, plus another across the Ural Mountains, will each act to help steer air masses around the world.?
A blocking high over Greenland is typically associated with some of the East Coast's most memorable snowstorms, because it helps direct cold air into the Northeast and Mid-Atlantic states while also preventing storm systems from quickly escaping out to sea.?