The polar vortex

By Meteorologist Mike Skurko

The record cold that gripped the nation this past week spawned the headline “polar vortex” among mainstream media.  What exactly is this catchy-sounding polar vortex?  While it got a lot of buzz this week, it’s not a new concept at all, at least not to meteorologists.

First of all, the polar vortex is not an individual storm like a hurricane or tornado.  Social media pictures and videos “capturing” the polar vortex moving through are completely incorrect.

The polar vortex is a permanent area of low pressure spinning in the upper-levels of the atmosphere in the Arctic, thus the term “polar.”  This area of low pressure has two centers, one near Baffin Island, Canada and another in Northeast Siberia.  The “vortex” refers to the strong winds swirling around this low, which contains the pocket of the brutally-coldest temperatures within the Arctic.

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Occasionally these winds weaken, which disrupts the shape of the vortex.  If other atmospheric conditions are favorable, such as the position of the jet stream, it can allow a part of those coldest temperatures to drain south into the U.S. instead of staying confined to the polar regions.

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Therefore, only a piece of the cold air associated with the polar vortex makes it into the U.S.  The polar vortex can be deemed responsible for a cold outbreak.  However, the polar vortex will not suddenly find itself entirely centered over the U.S.  It’s also a very broad area, and will not enter the U.S. at a specific time and specific place like the eye of a hurricane making landfall.

In November, our CBS3 Pinpoint Weather Winter Outlook briefly talked about the Arctic Oscillation.  The distortion of the polar vortex … how the winds weaken or strengthen around this Arctic low … essentially is the Arctic Oscillation.  When the winds around the polar vortex weaken and allow the coldest air to drain a little southward, that is known as a negative phase of the Arctic Oscillation.

To further demonstrate the polar vortex, check out the low temperatures on Monday across North America (top image) and Friday (bottom image):

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Notice how the Arctic air spilled south into the U.S. on Monday, and then retreated back to the north by Friday.  Meanwhile, check out the temperatures across the far northern Canadian territories.  Their temperatures didn’t change much at all (staying with the purple numbers of about 20 to 30 below zero).  This is the permanent area of Arctic air that typically stays up to the north.  When those upper-level winds weakened, we got a taste of those same numbers in the U.S. on Monday as part of the “polar vortex” draining to the south.

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