Weather Pattern Change in the Midwest: The Real Cause

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Last week the National Weather Service began warning that a cold snap was on the way for most of the Midwestern states, moving as far south as Oklahoma. The NWS mistakenly used the term “polar vortex” to describe the blast of chilly air which should begin in Michigan around Sunday, but quickly corrected itself. The real cause in the Midwestern weather pattern change, say weather experts, is last week’s Typhoon Neoguri in the western Pacific.

A typhoon is the Western Pacific’s equivalent of a hurricane, and Neoguri made landfall in Okinawa, Japan late last Sunday evening with wind gusts up to 118 miles per hour. About 480,000 people in Okinawa were advised to evacuate in advance of the storm, and about 22,000 households were left without power. The Japan Meteorological Agency also reported a storm surge of up to seven feet with offshore waves topping 45 feet. This was no small storm.

In the U.S., the west coast was prepared for a storm surge from Neoguri to hit on Friday, but the weather remained mild. The unanticipated effect of the typhoon, however, was that its massive cyclonic winds caused a change in the northern jet stream, pulling cold air down from the northeast Pacific. This was not, by most accounts, a polar vortex.

After two offices at the National Weather Service used the term to describe the weather pattern change in the Midwest, they were immediately challenged by a number of other weather groups who said the polar vortex was not the real cause. Some meteorologists say that the term polar vortex is open to some interpretation, but most others say that a pool of cold air around a region cannot be called a polar vortex unless the source of the cold air is actually coming from the poles.

Since the cause of this cold snap is a typhoon in the northern Pacific, meteorologists at The Weather Channel were using the term “polar air invasion,” and the NWS corrected its offices’ terminology to “deep upper low.” There is still clearly some debate over the terminology, however, as AccuWeather has chosen to continue using polar vortex.

It appears that no one is debating the cause of the dip in the jet stream which will occur next week in the Midwest, but only the terminology used to describe it. A similar debate ensued in January when the eastern seaboard of the United States was hit with record low temperatures and snowfall. This dip in the jet stream was said to come from northern Alaska, where the Arctic and Pacific Oceans meet. The winter weather caused an even heavier debate, as the source of the cold air was much closer to the North Pole than the current pattern over the Midwest.

Whatever the terminology, Midwestern states can expect temperatures anywhere from 10 to 30 degrees below the average for this time of year. In more southern states like Arkansas and Oklahoma whose temperatures can reach into the high 90s in the summer, temperatures could be 40 to 50 degrees below their seasonal average. Though the real cause of the weather pattern change in the Midwest has settled back into the ocean, residents there will still be feeling the effects well into next Tuesday.

By Layla Klamt

Washington Post (January 2014) (The Weather Channel)
Washington Post (Weather Service)