The Monster Surge That Wasn’t: Why Irma Caused Less Flooding Than Expected

NAPLES, Fla. — Across coastal Florida, the dreaded storm surge from Hurricane Irma — caused when ferocious winds pile up ocean water and push it onshore — was not as bad as forecast. While some areas were hard hit, notably the Florida Keys and Marco Island, residents of neighborhoods north to Fort Myers, Sarasota and Tampa Bay were expressing relief.

That bit of good fortune was the product of some meteorological luck.

Because a hurricane’s winds blow counterclockwise, the precise path of the storm matters greatly for determining storm surge. Had Irma lingered far enough off Florida’s Gulf Coast, its eastern wall, where the strongest winds occur, could have shoved six to nine feet of water into parts of Fort Myers and Naples, while swamping Tampa Bay and St. Petersburg as well.

At the last minute, Irma unexpectedly veered inland right before it got to Naples, taking its eastern wall safely away from the ocean. That meant that as the storm tracked north over Naples, Fort Myers and Tampa Bay, the winds at the head of the storm were moving west and actually pulling water away from the shoreline. In Tampa, water levels dropped five feet below normal, and bewildered spectators walked out to see beaches sucked dry. In Sarasota, a manatee became stranded.

Then, once the eye of the hurricane had passed through those areas, the back side of the storm hit, pulling water east toward the coast. But by this point, the storm’s winds were weakening, and the resulting surge was not nearly as strong as feared.

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Hurricane damage on Marco Island, Fla., on Monday. Though the island and the Florida Keys were hard hit, the state was largely spared a devastating storm surge. Credit Eric Thayer for The New York Times

That weakening was readily apparent in Fort Myers. When it passed over the city at about 7:15 p.m., the center of the storm, rather than being a well-formed eye, was a jumbled mass of thinner clouds. This suggested that the hurricane’s cyclonic structure was beginning to come apart.

Some parts of Fort Myers and Naples saw sea levels surge four to five feet above normal levels — a damaging flood, but less than early warnings had suggested.

When Peter Falisi, his father and other family members went to check on the restaurant they were renovating Monday, they weren’t sure what they would find.

The neighborhood, near the Naples airport, had been forecast to get a storm surge of up to six feet above ground. That would potentially cause catastrophic flooding at the business, Two Guys Kitchen and Catering, which they hoped to open in a month.

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Trying to keep the water out at a hotel in Miami on Sunday. Credit Eric Thayer for The New York Times

When they arrived, there was little sign of any flooding. Although there was some water in the building, it was not from the surging ocean: Irma’s winds had peeled off paneling from a roof overhang and broken a water pipe.

“The only water we have inside is from the broken sprinkler system,” Mr. Falisi said.

Along the Southwest Florida coast, only Marco Island, south of Naples, appeared to have suffered from significant flooding. Police officers on Monday went door to door on the island, checking on residents who stayed behind to ride out the storm. No deaths or serious injuries were reported.

In Fort Myers early Monday morning, there were few signs of flood damage. Across the Caloosahatchee River in North Fort Myers, residents returned to mobile home parks to find them dry and intact, with what damage there was coming largely from wind, not water.

And in East Naples neighborhoods, where inundation maps suggested as much as nine feet of water, at most homes there was little more than a foot or two, shallow enough to only lap at the front steps.

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