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Project Winter: Explaining the Polar Vortex

First Alert Chief Meteorologist Brian Walder explains what the Polar Vortex is and how it can be disrupted to bring cold air to the Heart of Illinois.
Published: Nov. 15, 2021 at 9:42 PM CST
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PEORIA (Heart of Illinois ABC) - Unless you’ve ever read a meteorology textbook, you probably hadn’t heard of the Polar Vortex until a few years ago.

The term became popular during the winter of 2014, and many equate the Polar Vortex to a surge of arctic air. While the two are related, that’s not what the Polar Vortex actually is.

“The Polar Vortex is actually in the stratospheric level above the poles. It’s the swirl. It’s actually a very, very cold air mass and the jet stream around it is usually very concise.”

Normally the Polar Vortex remains over the poles, but disruptions allow for that colder air to spill south into the mid-latitudes. One way this happens is when the stratosphere rapidly warms up. This is known as a sudden stratospheric warming.

“Stratospheric warming will cause the temperature difference to weaken, and as a result the Polar Vortex cold circle will become wavy. And this will also cause the jet stream in the troposphere to weaken.”

A weaker jet stream loses the ability to contain cold air at the poles. The southern United States saw this first-hand last winter.

“What happened last winter with Texas getting so cold, that was related heavily to a stratospheric warming.”

Stratospheric warmings aren’t the only thing that can cause Polar Vortex disruptions. Climate change is warming our planet, but the arctic is warming three times faster than the rest of the world. Scientists believe that this could also be affecting the polar vortex.

“The latest is that it is probably more related to the overall warming of the arctic and the melting of ice throughout the arctic. It’s a complicated picture so it’s really hard to pick that apart exactly what is causing it.”

Professor Emeritus of Atmosphere Science at the University of Illinois Dr. Don Wuebbles says that scientists are still trying to find the root cause, but a new trend has become clear.

“We’ve seen deviations in the past in the jet stream which brings cold air from the arctic, from the polar region down to the Midwest. You know, we’ve seen that many times in the past, but we’re seeing it more now because of the strong waviness that is happening yearly now in the jet stream as in relationship to the changing climate. So it’s become a more regular phenomenon than we’ve had before. What was pretty unusual has now become much more common.”

Earth’s climate system is very complex. But even in a warming planet we can still see extreme surges of cold air, some of which are directly related to disruptions to the Polar Vortex.

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