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Will the Polar Vortex return?

By now, everyone has heard about the polar vortex. The frigid cold the United States has experienced is because the polar vortex moved south. Many cities saw the lowest temperatures in 20 years. But, what caused it to move in the first place? And can we expect it to happen again?

First off, what is the polar vortex? Mark Fischetti defined it, in Scientific American, as, “… a prevailing wind pattern that circles the Arctic, flowing from west to east all the way around the Earth.” Others gave very scientific geeky definitions.

Brad with S&S Storm Chasing & Forecasting Team (S&S Team) out of nearby Red Lion, explained that the polar vortex is just a jet stream which normally sits over the North Pole. This polar jet has wavy lines which, he explained, break free every once in awhile causing the cold arctic air to drop south.

Normally the polar vortex traps the sub zero air above the North Pole. However, when it becomes weakened then the frigid air drifts southward. This causes the historical sub zero temperatures and wind chills that the US has experienced this week.

Here in Lancaster, schools were cancelled Tuesday because of the record setting low temperatures. People stayed inside. Several were without heat on Tuesday after UGI had to shut off gas temporarily after the pressure in a gas main dropped too low. Shelters were at capacity.

And it is not over.

The “arctic air mass remains in place across the Eastern two thirds of the nation,” according to a storm summary statement from the National Weather Service (NWS) Tuesday afternoon. Wind gusts peaked at 53 mph in parts of Pennsylvania on Tuesday. In comparison, the wind gusts at Buffalo International Airport topped out at 60 mph, according to the NWS.

Tuesday night saw a low of just three degrees, warm compared to Monday night. Tonight the low will be around 18. Tomorrow (Thursday, 9 January) a high of 31 is expected. There is a slight chance of snow showers later Thursday after 1 a.m., predicts the NWS out of State College. Currently the NWS predicts a rainy – not snowy – weekend.

So what causes it to move?

Simply stated the warmer air at the North Pole is what causes the polar vortex to break free and slip south. Essentially, the jet stream gets bumped around by air masses. So as the air gets warmer, the vortex weakens. As it weakens, it falls south.

The S&S Team pointed out that this is a regular occurrence. The difference this year is the extreme coldness and the speed at which it went through. The polar vortex occurs year-round however when it is 100 degrees one summer day and 80 the next, no one complains or questions.

Will it happen again?

The short answer is yes. It is very likely that this will happen again and in our lifetime. NOAA – the National Oceanic Atmospheric Agency – has entertained the possibility that the weakening of the polar vortex is caused by the reduction in the ice cover. As the summer ice caps continue to melt, the temperature of the Arctic Ocean rises. As that temperature rises, the heat is radiated back into the atmosphere which in turn disrupts or weakens the polar vortex.

This polar vortex is not unique to the United States. It can occur anywhere in the Northern Hemisphere, meaning in addition to North America, Europe and Asia can be affected by a polar vortex. CNN, in a recent piece about polar vortex, points out that, unlike a hurricane, the polar vortex is not a single storm. It is more akin to a distortion from which several storms can spawn.

The White House has announced a We the Geeks Hangout this Friday, 10 January at 2 p.m. ET. The topic is We the Geeks: "Polar Vortex" and Extreme Weather. Readers are encouraged to join in this conversation during which meteorologists, climate scientists, and weather experts discuss why temperatures dipped to such frigid lows this week, how weather experts turn raw data into useful forecasts, and what we know about extreme weather events in the context of a changing climate, according to a White House release. Readers can Tweet their questions using the hashtag #WeTheGeeks.

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