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The Science Behind Irma's 'Reverse Storm Surge'

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Bobbie O'Brien
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WUSF Public Media
Tampa Bay empties of water (right) before Hurricane Irma on Sunday and is full again (left) on Monday.

Tampa Bay area residents witnessed an unusual sight ahead of Hurricane Irma’s arrival Sunday.

In a case of a kind of reverse storm surge, Hillsborough Bay at Bayshore Boulevard was one of many places in Florida that experienced temporary lowered water levels in the hours leading up to the hurricane.

Bay News 9 meteorologist Josh Linker explained the phenomenon, which isn’t uncommon, was a result of strong offshore winds that persisted for hours.

“(The winds) acted to push the water out, just the opposite as if a storm was coming in that would push the water up on shore,” said Linker.

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Credit Bobbie O'Brien / WUSF Public Media
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WUSF Public Media
Hillsborough Bay sits dry Sunday ahead of Hurricane Irma's arrival.

The hurricane was rotating in a counter-clockwise direction. Because the storm was coming in from the south, the northwest side of Irma blew water in the Tampa Bay area out to the Gulf, thereby resulting in multiple drained bays. In Tampa Bay, water levels dropped as much as six feet.

“When the wind changes the other way, the water comes back,” said Linker. “Because it took a little bit longer for the water to come back… we ended up with between about 1 and 4 feet, depending upon the exact location, above the tide level, which for most areas wasn’t anything more than a bit of a nuisance.”

Tampa Police were concerned with the inevitable storm surge and ordered everyone off the bare seabed. However, Linker doesn’t see the danger in exploring the rarity.

“The water wasn’t going to come rushing back as long as the wind was still offshore…I can’t really see that as being a danger,” said Linker. “It’s just like walking out on low tide.”

Seabeds and mud-flats weren’t the only things uncovered by the wind-induced setback; a couple of manatees were stranded in Sarasota Bay. Rescuers eventually managed to drag them to deeper water.

The displaced water has since been returned to the bay following the passing of Hurricane Irma.

“Everything came back, it’s back to normal,” said Linker. “The water pushes back and as soon as that influence that is acting on it goes away, the water just comes back.”

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