What is the polar vortex, this meteorological phenomenon that threatens to paralyze the United States?

“Unheard of for generations”. The various messages from the meteorological services of the United States and Canada, describing the polar vortex which is currently beating down on the northeast of the two countries are more than alarming. Indeed, it will be very cold. The northern state of Maine in particular could see in the evening of Friday and Saturday the temperature drop to -51 degrees Celsius felt, according to a bulletin of the National Weather Service for the region of Caribou, not far from the border with Canada. Also according to the NWS, this is a phenomenon that in the Maine region has not been experienced since 1982 and 1988.

A modified North Pole wind circulation

But what is it exactly? The polar vortex is a natural meteorological phenomenon that forms during the winter season. Confined to the poles, it is normally kept above the Arctic region at an altitude of around 30 kilometers by circular winds, called the “stratospheric jet of the polar night”. But it happens that this prison of winds breaks.

According to the explanations of Sébastien Léas, forecasting engineer at Météo France, it sometimes happens that in the heart of winter the temperature rises very quickly, from -80 to -20 degrees. In just a few days, therefore, we recorded a rise of 60 degrees in this zone of the stratosphere. And it is this warming that changes the wind patterns, allowing the polar vortex to shift, sometimes into an unusually cold region.

-15 degrees expected in Boston and New York

The polar vortex will place the American northeast under an icy wind, with temperatures that “could reach their lowest level in decades, or even a level never before recorded”, according to the NWS. The worst of the cold and wind in the United States was expected to hit Friday night into Saturday, especially in Boston and New York, further south, where it could be -15 degrees.

INSANE conditions on Mt Washington, NH. 120mph+ winds and -95°F wind chill. It is above the tropopause, meaning that these are stratospheric winds.

Footage from the summit live stream 2:30-2:40pm. #nhwxpic.twitter.com/OgDakbNn97

— Peter Forister ❄️ ❄️ (@forecaster25) February 3, 2023

On the other side of the border, polar cold alerts have been issued for eastern Canada, according to the Ministry of the Environment, which warned of the risk of frostbite within minutes. The temperature felt like -41° in Montreal on Friday afternoon. White smoke, called “Arctic Sea Smoke”, was billowing over the St. Lawrence River due to the extreme cold passing over the unfrozen water.

This region of the globe has been subject throughout the year to extreme weather phenomena which are accompanied by loss of human life and material damage. Latest: During the Christmas weekend of 2022, a blizzard and a snowstorm hit the city of Buffalo, in upstate New York, killing dozens.