Polar vortex 2021: Arctic blast to send much of U.S. into deep freeze


ROCHESTER, N.Y. (WROC) — The buzzword made famous from an arctic blast in 2015 is making a comeback.

The polar vortex, a rotating bubble of cold air around the North Pole, is about to break off and head into much of the United States for the second half of January.

The polar vortex gets its name from a counter-clockwise spin around the North Pole. The constant air mass is protected by the polar jet stream. It weakens in the summer and strengthens in the winter.

Occasionally, the air mass splits and sends cold air southward into the middle latitudes.

In recent years, the polar vortex caught on as a buzzword and became one of the most recognizable “new” terms in meteorology, even though the polar vortex itself has been known about and studied within the weather community for decades.

When the polar vortex is strong, it remains solidly in place over the poles. When it starts to weaken as warmer air “injects” into the poles, the stronghold can erode away and cooler air can be forced southward, where more people live and will be impacted by an arctic blast. While the polar vortex is always around, we only feel its cold a few times a year, if at all.


Note the United States at the bottom of this image. See the blue colors are over the Alaska and Midwest U.S., and where the purple colors are over Russia and northern Canada. Those are chunks of the polar vortex. Image as of Friday, January 15th.

Long range models are forecasting for a chunk of the polar vortex to break off and invade the central United States across the Dakotas, eastern Great Lakes, central United States and a section of the Northeast. While this specific intrusion of polar air is not the most overwhelming we’ve seen, it does look like we’ll see a decent return to colder air by month’s end.

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