Caught in a bone-chilling ‘river of wind’

river_of_wind_650Chip Konrad has made a career tracking what he calls “weather and climate extremes.”

Last week got his full attention.

As a graduate student at the University of Virginia in the late 1980s, Konrad did his master’s thesis on “cold-air outbreaks” like the kind that enveloped most of the country last week.

 

Like the rest of us, it was the first time he heard the media use the term “polar vortex” to explain how cold air that should be hovering around the North Pole ends up in North Carolina.

Konrad
Konrad

“I think of a polar vortex as a strong, counterclockwise wind that circulates over the Northern Hemisphere and makes a big loop around the polar region,” said Konrad, associate professor of geography in the College of Arts and Sciences, who also serves as director of The Southeast Regional Climate Center in Chapel Hill.

“You can also think of it as a river of wind,” he said. “Like everything in the atmosphere, the air in a polar vortex is in continual flux and changing. You can think of that state of flux as waves of air with crests and troughs,” Konrad explained.

“When these waves get really big, they can break and form a mini vortex, which is what happened here. Over the course of four or five days, the mini vortex tore through Canada into the eastern United States.”

On the Sunday afternoon before the vortex plowed through North Carolina, the temperature at Raleigh-Durham International Airport reached 62 degrees, Konrad said. By Tuesday morning, the temperature at RDU had plunged to 9 degrees.

To put last week’s event into historic perspective, Konrad did a little research and found that last Monday – Jan. 6 – was the coldest day of the 21st century across the continental United States.

“It is easy to think, ‘Wow, that was really amazing,’” he said. “But another way of looking at it is that there were 39 days that were actually colder – and all of those days occurred in the 20th century.

“This is obviously a very strong outbreak – the strongest this century – but it is the kind of weather event that occurred more often in the 20th century, and you can associate that pattern with this long-term period of warming that we have been experiencing.

“That part is real clear.”

By Gary Moss, University Gazette