Unusual jet stream activity to blame for bad weather

August 12, 1993|By Newsday

Unusually cool temperatures in the Pacific Northwest, floods in the Midwest, drought in the East.

What separates this year from others, meteorologists say, is unusual activity from the jet stream -- strong winds that sweep like a broad river across the country, mixing hot and cold air in the atmosphere.

This year, though, the jet stream has swung farther south than usual and its winds are wringing moisture normally suspended over the Gulf of Mexico down onto the heads of Midwesterners.

The jet stream normally shifts northward during the summer as the sun heats the northern hemisphere. That hasn't happened this year.

It has remained in its original lane, producing atmospheric patterns and storm frequencies more like those found in winter than summer.

"I don't think I've seen anything like this in the records dating back to the turn of the century," said Ed O'Lenic, meteorologist and chief forecaster for the National Weather Service's Climate Analysis Center.

National Weather Service maps show the jet stream arcing south through Oregon, Nevada and Utah, before curving northeast through Colorado, Nebraska, Minnesota and on into Canada.

In a typical year, the maps show the jet stream running roughly along the U.S.-Canadian border.

The jet stream's southern position also explains the unusually cool weather that has passed for summer in the Pacific Northwest.

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