Polar Vortex Explained

By
Atish Baidya

Dateline
Updated Fri, Jan 10, 2014 12:19 pm

Two words almost guaranteed to send shivers down people’s spines for the rest of winter: polar vortex.

Earlier this week the frigid Arctic air, not felt by large portions of the country in almost two decades, had many people muttering four-letter words at said polar vortex, Mother Nature and anyone or anything else people chose to blame for the bone-chilling temperatures.

But what exactly is a polar vortex?  According to meteorologist Ryan Fogt with Ohio University’s Scalia Laboratory for Atmospheric Analysis most people have heard about it before.

“The polar vortex is basically just another description for the jet stream,” Fogt said. “It is called the polar vortex because typically the jet stream spins around the North Pole in basically a straight almost west to east fashion. In the winter it is the strongest and it’s the weakest typically in the summer season but it does exist year around.”

The jet stream acts like a dividing line between cold arctic air to the north and warmer tropical air to the south.  It isn’t a straight line, it is more like a wave, and when conditions are right the jet stream can dip farther south allowing the cold arctic air to spread over parts of the contiguous United States.  Fogt said those changes in the jet stream can be difficult to predict.

“There are just natural imbalances that are trying to be redistributed,” he said. “They aren't things that are easy to predict, certainly not much more than a week out.”

This particular cold snap isn’t a good prediction of what the rest of the winter will be like either.

“It doesn't look like there is a lot of predicative capacity as far as how old or warm it will be for the rest of the season,” Fogt said. “Normally for winter predictions or seasonal predictions you are going to base those off sea surface temperature patterns. Right now, in the Pacific, which is the main ocean basin that influences the US, the patterns of the sea surface temperature are near normal,” Fogt explained.

“Sea surface temperatures, which respond much more slowly to changes in the atmosphere or changes in energy, are not giving us a sign one way or another what winter might be like.”

But in the age of social media, the intense mainstream media coverage of this week’s shift in the jet stream translated into tweets, retweets, pins and Facebook posts with people generally using the frigid weather as signs for or against global warming.   Fogt, however, cautions against using a weather event like dip of the jet stream as evidence of climate change.

“Weather is the day-to-day variations in the earth's atmosphere, he said. “They drive regions of high pressure and low pressure; cold air and warm air; cold fronts and warm fronts; precipitation, cloud cover, all those sorts of things from day-to-day.”

“Climate is the average conditions that describe conditions over much longer time scales and when we average things over several decades, approximately 30 years or longer, we can get an idea of what the average conditions are for a region and whether or not they are changing.”

 

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