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Weather Blog: The Truth About The Polar Vortex

Ahhh, the polar vortex -- a term that garnered much more than its 15 minutes of fame last winter. I mean it sounds pretty awesome, like a mutant tornado composed of icicles and doom, and though that'd be something to see, the polar vortex is no polar-bear-nado, but a large scale weather system that has been in existence long before any of us.

The term was first used in 1853.

Polar Vortex Blog
(credit: NOAA)

The polar vortex is a persistent, semi-permanent area of low pressure in the upper atmosphere. It typically has two centers -- one located over Baffin Island in Canada and one near northeastern Siberia, and, as its location near Siberia would hint, the polar vortex contains a large mass of very, very cold air.

In atmospheric dynamics, vorticity essentially describes spin or rotation, and a "vortex" refers to a closed area of vorticity. Upper air vorticity is analyzed by us meteorologists on 500 millibar charts -- 500 millibars is about 18,000 feet up into the atmosphere.

Polar Vortex Blog
(credit: NOAA)

The polar vortex is "semi-permanent" in that sometimes, usually motivated by the jet stream, it takes a stroll south. This allows all of that bitterly cold, arctic air to plunge south as well.

You can also consider vorticity in terms of energy. What you could think of as a little piece of vorticity or energy can break off from the parent vortex bringing with a blast of arctic air, but typically not as prolonged an episode as experienced with a positional shift in the polar vortex itself.

Thus the polar vortex is not an atypical outbreak of arctic air, but an ever-present large-scale system which influences our sensible weather, and though it sounds catchy and made-up, it is meteorologically viable when referred to in its proper framework. And not all cold spells are attributable to the polar vortex.

Polar Vortex Blog
(credit: National Weather Service Chanhassen)
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