FORT LAUDERDALE, Fla. – When it comes to hurricanes and their vicious little offspring tornadoes, one good spin deserves another.

It’s an intricate and sometimes perplexing dance of swirling winds that cause tornadoes to spawn as a hurricane travels over land. One such tornado touched down twice behind the Hendry County sheriff’s station in Clewiston, Fla., on Friday about 11:45 a.m. EDT.

“We don’t have any damage that we know of,” said Marcus Padgett, spokesman for the Hendry County emergency management office.

Such a swift-moving, dangerous cyclone, though smaller and more localized than the massive hurricane storm system that produced it, can pack a whollop of a punch, with winds reaching up to 300 mph – enough to propel a refrigerator hundreds of feet.

About 1,000 tornadoes rake across the United States every year, mostly in the Midwest. But those Midwestern storms are a different breed from the type of tornadoes generated by a hurricane. Tornadoes from a hurricane result from a confluence of clashing winds rotating between the earth and upper atmosphere.

How it works is, once a hurricane makes landfall, friction from the ground slows down the winds in its lower level, said Bill Read, a Houston-based meteorologist with the National Oceanic & Atmospheric Administration temporarily assigned to the National Hurricane Center west of Miami. “It changes the shape, or the profile of the wind, in the storm itself,” he said of the earth’s friction.

Winds in the upper atmosphere, however, retain their swifter speed, causing what’s called a vertical wind shear, in which wind on the ground can be a drastically different speed from wind higher up. The low level winds then are pulled toward the hurricane’s center, or eye, which causes a rotation between the upper and lower systems.

“The winds can be going in different directions from surface to atmosphere,” Read said.

The resulting rotation can spin off deadly, swirling tornadoes.

But knowledge is still limited about the hurricane-spawned tornadoes. “There are still things we don’t know about these tornadoes,” Read said. “There are people who earn Ph.D.s studying how that works.”



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