The Polar Vortex Explained

The Polar Vortex Explained

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The Arctic outbreak of early January 2014 added a new weather phrase to the vocabulary of many folks, "polar vortex". The polar vortex is a mass of frigid air that forms in the Arctic, in the winter, due to no or low sunlight for several months, and is bounded by a strong polar jet stream. This happens every year.

The polar jet stream may have winds over 200mph and it often locks the coldest air in place. The polar vortex is named simply because the wind flow of the jet stream encircles it, but it's not a giant storm! Vortex is a word often applied to tornadoes so it may paint a different picture in your mind of the polar vortex- what is really an immense regional event. The jet stream is driven by the difference in temperature between the tropics and the Arctic so in winter, when the pole gets colder, the jet stream gets stronger.

Polar vortex is like other weather phrases that have come into the public view in recent decades like loop current, subtropical, derecho, and El Nino. Each phenomena is as old as the Earth, and each phrase or word has been used by meteorologists for a very long time. Social media and some online and broadcast media have made polar vortex sound like something that has never happened before. It's also been improperly used. For example, the Arctic air that made it to the Gulf Coast broke off from the polar vortex and was pushed by the jet stream. It wasn't the actual polar vortex that moved that far south!

These Arctic outbreaks happen in all mid latitude regions and countries of the northern hemisphere from time to time. The record cold outbreaks may occur once every 5 or 10 years, with the most extreme ones happening every couple of decades. On a side note, a warming Earth (land, air, water) does not mean Arctic outbreaks or extreme cold will stop. In fact, a warming Arctic can result in a slower winter jet stream, which would be more likely to take the large north and south deviations to produce temperature extremes in both directions.

If you'd like to learn more weather phrases or the original meaning of some that you hear, look at the Glossary of Meteorology by the American Meteorological Society. There are thousands and thousands to choose from.

Alan Sealls, WKRG-TV Chief Meteorologist
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