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Why Is It So *&%# Cold? Come Warm Up In The Answer Vortex

January 30, 2019 4:24 PM ET


Frigid temperatures arrived in the Upper Midwest with a polar vortex. In Chicago on Wednesday, Marius Radoi walked along a freezing Lake Michigan.
Joshua Lott/AFP/Getty Images

Updated at 5:43 p.m. ET

How cold is it in the Upper Midwest today? It's so cold that if you toss boiling hot water in the air, it may immediately evaporate... https://twitter.com/ARobertsjourno/status/1090601793086803968 (Be careful out there and always check which way the wind is blowing, folks.
People tend to scald themselves doing this.) http://articles.latimes.com/print/2014/jan/07/nation/la-na-nn-boiling-snow-20140107

A polar vortex, as NOAA explains here, ... https://www.weather.gov/safety/cold-polar-vortex ... is a large area of low pressure and cold air surrounding the Earth's poles. The "vortex" is the counter-clockwise flow of air that helps keep the colder air close to the poles. On occasion throughout winter, the vortex will expand, and send cold air southward with the jet stream.





The polar vortex is a large area of low pressure and cold air surrounding the Earth's North and South poles. "Vortex" refers to the counterclockwise flow of air that helps keep the colder air close to the poles (left). During winter in the Northern Hemisphere, the polar vortex can shift, sending cold arctic air southward over the United States (right).
NOAA

While we're cooped up inside, we called Greg Carbin, who is in charge of NOAA's Weather Prediction Center Forecast Operations Branch, to answer our questions about this blasted polar vortex sweeping the Northern parts of the U.S.

He shared one fact that blew our minds: The difference in temperatures across the contiguous U.S. on Wednesday is nearly 120 degrees. A temperature of minus 44 was measured in Bottineau, N.D., while temperatures in Imperial Valley, Calif., hit 74 degrees and rising.

[...]

How common is a polar vortex?

It happens every winter. Actually it's not uncommon at all across the Northern Hemisphere in the winter.

Is it weird that the vortex is over the U.S.?

It shifts. This core of very cold air associated with the Arctic regions of the globe basically wobbles and shifts around. As you go through the winter months, the jet stream becomes unstable — and occasionally the system can wobble across parts of the North American continent where it's not normally centered. That's when we have what we call "Arctic air outbreaks."

The farther north you are in the Northern Hemisphere winter, the more likely you are to experience this type of cold air. But it's not uncommon at least once or twice a winter for that air to spread south out of the Arctic regions and into other parts of the Northern Hemisphere.

This is unusually cold, no doubt about it. We'll establish some new records.

But events of similar magnitude have occurred in the past. The last one was back in 2004, and another one in the mid-'90s, and another one in the mid-'80s. Every few decades we see these events occur, where that arctic air that normally resides at the pole starts to make its way south into parts of the U.S.

Any reason why this is happening now?

It's basically the most likely time for it to happen. You have snow and ice cover over a large part of the Northern Hemisphere. And so these cold air masses that have been generated over the past several weeks over the Northern climes can more easily translate south into the more Southern latitudes. This is the most likely time of the year that we would experience this type of outbreak: the middle of winter

What happens next?

It's not much consolation for those that are experiencing 50-below wind chills today across the Midwest, but [the freezing temperatures will be] relatively short-lived. We'll see a change back to above-normal temperatures across much of the region by the beginning of next week.

Then another wobble in the jet stream will bring another mass of cold air south across the border with Canada and into parts of the Midwest and Great Lakes. That's kind of an extended-range forecast, but it does look like we're in a very changeable pattern right now, and so another outbreak is possible across some of these areas. Hopefully not quite as severe, but it'll bring below-zero temperatures to Northern states in about two weeks.

[...]

https://www.npr.org/2019/01/30/690034103/why-is-it-so-cold-come-warm-up-in-the-answer-vortex