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Winter storms follow their own patterns
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Compared to the loss of life and property that occurred in Bartow County, the Gainesville area didn’t get hit too hard during the Jan. 30 storm.

It was a typical winter system, called midlatitude wave cyclone among meteorologists. The winter storms form through air mass contrasts; in other words, a clash of bodies of air that are very different in temperature and moisture. This leads to the development of an outer edge on the warm air mass. That’s a warm front.

Everybody noticed it in Gainesville when the thermometer rushed up into the 60s. Then, gradually, the clouds got thicker until rain built up to a series of heavy downpours. Just behind those downpours came the cold front, with a chilly dry air mass from Canada behind it. When the clouds finally disappeared last week, it got dry and cold.

In the summer, one can think of local storms as having "dissolved" when they’re gone. A winter storm like the Jan. 30 one tends to keep going for a while, though. After sweeping over the eastern seaboard, it entered the Atlantic Ocean. Had it been a hurricane, its tropical characteristics would have let it refuel over the water, increasing in strength.

But winter storms are "extratropicals" and don’t act the same way. They tend to get increasingly weak as they move on toward Iceland. One of the reasons is the clockwise curvature of the jet stream, which is the path that they have to follow. American cyclones turn counterclockwise. So they lose power while they, visually speaking, grind along the guard rail in the curve.

Occasionally the jet stream straightens out, though. In that case, our storms are able to keep going and invade Europe with severe weather. The worst ones are given names when they reach land.

In January 2009, winter storm Klaus hit Spain with winds up to 124 mph, killing 26 people in three countries. Because it’s so much easier to keep up with the progress of a storm when it has a name, the Weather Channel also started naming American winter storms last year. The system passing through Georgia on Jan. 30 was named Khan. The system hitting the Northeast is named Nemo.

It seems like quite a good idea, considering that winter storms travel long distances and can be every bit as destructive as hurricanes.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.

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