Remember in the mid-1990s when we couldn't stop talking about El Niño? Well, we're doing the same thing now with the polar vortex.
Yes, the polar vortex is back, and according to The Washington Post, it could make for a wild winter for much of the Northern Hemisphere in January, particularly for the Eastern United States.
This extra brisk winter forecast comes courtesy of Judah Cohen, a climate researcher at Atmospheric and Environmental Research, a private meteorological research and risk analysis firm that provides data to government agencies like NASA and the Department of Defense. Cohen studies polar vortex conditions and prediction models every day, looking for potential disturbances that could turn a normal winter into a harsh one.
The vortex, in case you need a reminder, is a large area of low pressure located about 60,000 feet up on the atmosphere over both the poles. That's the polar part. The vortex part describes the counter-clockwise flow of air that keeps the cold polar air up at the poles. Sometimes, however, that flow of air is disrupted, either by the winds changing direction or stopping entirely. Either of these events allows the vortex area to warm and the cold polar air goes south, causing frigid conditions in much of North America, Europe and Asia.
Sometimes this cold air is trapped by the jet stream and hangs around. Think back to March 2018 when the U.S. experienced a four-punch combo of nor'easters, or Europe getting pummeled in March, and you'll have an idea of how that cold air can linger.
This wasn't Boston in December. It was Boston in March 2018. (Photo: Kaleb Kloppe/Flickr)
The factors at play
Cohen says a disturbance is likely to occur given two factors he uses in his modeling. The first is the behavior of snow cover in Siberia and the second is the amount of Arctic sea ice. When the snow cover advances quickly in the fall and the extent of the sea ice in the Arctic is below normal, Cohen says historical data leads him to predict that a disturbance in the vortex is a good bet.
And guess what happened during the fall? Both of those things.
Cohen's model is predicting colder than usual temperatures for the Central and Eastern U.S. and around 21 inches of snowfall in Washington, D.C., between late December and into February.
A 3-way split?
Cohen also says the vortex could split into three pieces, which could cause severe winter weather. "Arctic change has increased the frequency of these polar vortex disruption events and following these polar vortex disruption events you get more severe winter weather,” Cohen told Axios.
Axios points out that in the past, polar vortex splits have been linked with major snowstorms, including one in 2010 when the Mid-Atlantic was engulfed in blizzards.
"Double, double toil and trouble." GFS predicts that the #PolarVortex splits into three separate daughter vortices. Now like Macbeth's witches let's see what mischief these three "weird sisters" can brew. pic.twitter.com/FPBU2mADVc— Judah Cohen (@judah47) January 2, 2019
Of course, weather forecasting, while a science, isn't always an exact science. The variables meteorologists use in their models differ, and that can influence the results. For instance, the American modeling system says a disruption could happen this month while the European model pushes the disruption to early January 2019 for Europe and a little later for America. (This is to say nothing of forecasts from the like of the Farmers' Almanac (very cold) or the Old Farmer's Almanac (wet and warm).)
Keep your fingers crossed that the European model is more on the nose, and that the disturbance gets delayed further.
"The longer it takes to happen, the bigger chance we have of a warmer winter," Cohen told The Post.
Editor's note: This story was originally published in December 2018 and has been updated with new information.