FLORIDA, United States, Tuesday September 12, 2017 – Videos and photos of water receding as far as the eye could see, from shorelines in the Bahamas up through Florida’s west coast after Hurricane Irma’s passage, have gone viral. And they have triggered fears that a tsunami is on the horizon.
However, there’s actually a scientific explanation for those dry sea beds.
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Key Largo, FL | Ocean is literally being pulled out leaving boats on land but as winds change water will surge back 😧pic.twitter.com/Dp5G0D44Av
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Jamie Rhome, a storm surge specialist with the National Hurricane Centre (NHC) in Miami, explained to NBC News that it was a combination of Irma’s strength and positioning that caused the water to recede so much. It was essentially the opposite of a storm surge, he added.
“Storm surge is where strong winds are pushing the water towards the shore. But you can imagine that same force is pushing water away from the shoreline,” Rhome said. “If the wind is blowing offshore, it blows water away from land.”
So, Category 5 Hurricane Irma left shorelines so bare because as its robust low-pressure centre approached places like the Bahamas on Friday and Saturday, and Tampa and the rest of the Gulf Coast on Sunday, its record-smashing strong winds were blowing from northeast to southwest — just the right direction to push the water out.
While it looks similar to what happens when an earthquake causes water to recede before a tsunami, it’s not the same thing.
“A tsunami is not caused by wind. That is purely dynamics,” explained Shuyi Chen, a University of Washington professor of atmospheric sciences. “The hurricane-related water retreat is mostly caused by the winds.”
Chen said this has happened before, most notably on Long Island, New York during Superstorm Sandy.
Despites concerns, experts said the water would return slowly. And it already has.
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National Weather Service meteorologist Ryan Rogers says this phenomenon is “not terribly uncommon”, but noted that it doesn’t get the same attention of destructive storm surges.