July 19, 2013 in Nation/World

U.S. sweltering under rare east-to-west heat wave

Seth Borenstein Associated Press
 

WASHINGTON – The oppressively hot weather in the Northeast has surprised meteorologists: It’s moving backward across America, something that rarely happens.

Normally U.S. weather systems move west to east. The western Atlantic high pressure system behind the hot dry weather started moving east to west last week and by Tuesday was centered over lower Michigan, said Jon Gottschalck, the operations chief at the National Weather Service’s prediction branch.

“It’s definitely unusual and going the wrong way,” Gottschalck said Thursday. “This is pretty rare.”

He said the high pressure is about to return eastward, extending the Northeastern heat wave an extra day or so.

And just before the high pressure moved east to west, a rainy and cooler low pressure system moved from the Mid-Atlantic to Texas, he said. That storm system broke off the jet stream, which is parked up in Canada, and made the U-turn first.

Gottschalck said there’s no evidence pointing at man-made climate change, but this is likely just natural chaos in the atmosphere. He couldn’t say how often these backward weather flows occur, but they’re less frequent than once a year.

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