SIGNS POINT TO A STRONG POLAR VORTEX TO START WINTER. HERE’S WHAT THAT MAY MEAN ~ THE WASHINGTON POST

It should bottle up frigid air in the Arctic, favoring mild conditions in much of the Lower 48

A simulation of air temperatures in the stratospheric polar vortex during late November. (Hannah Attard/University of Albany)
A simulation of air temperatures in the stratospheric polar vortex during late November. (Hannah Attard/University of Albany) 

By Matthew CappucciNovember 19, 2020 at 1:08 p.m. MSTAdd to list

It’s almost the time of year when the term “polar vortex” will become inescapable. It will blast across television tickers, blare from afternoon drive radio shows and crowd any headline related to snow. Though it has become a pop culture buzzword, the polar vortex is a real scientific phenomenon — and atmospheric scientists are anticipating a strong one to kick off winter.

Contrary to popular belief, that doesn’t mean widespread snow or cold for the Lower 48. In fact, the opposite may be true, with unseasonable warmth and mild temperatures more likely for most of the southern, central and eastern United States.

A positive Arctic oscillation, left, is associated with a strong, stable polar vortex, whereas a negative Arctic oscillation, right, is associated with a weak, unstable vortex. (NOAA)
A positive Arctic oscillation, left, is associated with a strong, stable polar vortex, whereas a negative Arctic oscillation, right, is associated with a weak, unstable vortex. (NOAA) 

The polar vortex is a staple of the atmosphere; the southern hemisphere has one, too. Each polar vortex has two parts — the tropospheric polar vortex, which occupies the lowest level of the atmosphere in which we reside, and the stratospheric polar vortex up above. The tropospheric polar vortex is usually wavier and more erratic, while its counterpart in the stratosphere tends to be smoother and more self-contained.

Both are “coupled,” meaning changes in one can influence the other. That’s why meteorologists look at the health of the stratospheric polar vortex for longer-range indicators of how the weather people actually experience evolves. A stronger stratospheric polar vortex tends to fence in the cold, while a weaker one allows Arctic outbursts to visit the mid-latitudes.

How does the polar vortex affect us?

A simulation of the strength of the polar vortex over the next several weeks indicates it could become atypically strong. (Hannah Attard/University of Albany)
A simulation of the strength of the polar vortex over the next several weeks indicates it could become atypically strong. (Hannah Attard/University of Albany) 

“The weather during a strong polar vortex is usually not as exciting as we get when we have a weak polar vortex,” explained Hannah Attard, an associate professor of atmospheric sciences at Embry-Riddle Aeronautical University in Daytona Beach, Fla.

“When you have a strong polar vortex, it’s really acting to bottle up all that cold air at the poles, so you won’t get those undulations at the mid-latitudes letting that cold air spill out,” said Attard.

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