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So what’s a waterspout? Science explains what happened on Hilton Head Thursday

Waterspouts off Hilton Head Island

Submitted video provided by Kristina Springer showing two water spouts off the coast of Hilton Head Island around 10 a.m. on Thursday, July 21, 2016.
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Submitted video provided by Kristina Springer showing two water spouts off the coast of Hilton Head Island around 10 a.m. on Thursday, July 21, 2016.

Two waterspouts were spotted off just off the Hilton Head coast Thursday morning, and caused quite the stir on the island.

What causes a waterspout? Are they dangerous? What exactly is going on out there?

James Carpenter, meteorologist with the National Weather Service in Charleston, offered scientific insight to help us understand these fascinating funnel formations.

What exactly is a waterspout? How do they form?

In general, a waterspout is a tornado over water.

There are two types of water spouts: fair weather and tornadic waterspouts. Tornadic waterspouts form from the clouds, while fair weather waterspouts form from the water.

Tornadic waterspouts are usually associated with thunderstorms and have the same characteristics of a land tornado, but just happen to be over water.

Fair weather waterspouts require warm water and cumulus cloud formations to occur.

“It’s basically a thin-spinning cloud forming from the water surface,” Carpenter said. “But there is still a lot of research and debate about how waterspouts form.”

Are waterspouts dangerous?

Tornadic waterspouts are more likely to hit land, according to Carpenter, but both pose a threat to boaters and should be taken seriously.

“Fair weather waterspouts usually dissipate before hitting land because they really depend on warm water,” Carpenter said. “But they can hit land, so you should be cautious if you see one.”

How fast do they move?

Carpenter said fair weather waterspouts require light wind, so they move slowly.

“Often, fair weather spouts look like they’re barely moving,” Carpenter said.

On the other hand, tornadic waterspouts can move fast and transition smoothly from water to shore. So, stay cautious if you see one close to shore.

How often do they occur?

Carpenter said “it’s hard to tell” because most waterspouts are undocumented (because no one sees them in the middle of the ocean.

“They are more likely to form in areas like Key West where the water is really warm, but they form more often in the summer around the Carolinas,” Carpenter said.

What can you tell us about Thursday’s double water spout?

Double water spouts are “fairly uncommon” according to Carpenter.

“It just comes down to physics and the right weather conditions,” he said.

Carpenter said yesterday’s waterspouts were fair weather waterspouts and didn’t pose a threat.

Mandy Matney: 843-706-8147, @MandyMatney

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