Ian’s storm surge was as deep and widespread as forecasters feared



Early damage surveys from Hurricane Ian and flood sensor data show that the cyclone’s massive storm surge – powerful seawater flooding over normally dry land – has one to two stories high for about 60 miles of the southwest coast of Florida and in some places extended for several miles inland.

Although early fears of floodwaters rising in Tampa Bay did not materialize, the results appear to support dire warnings from the National Weather Service that a deadly and destructive storm surge would stretch far from the landfall. unpredictable from Ian, who ended up on a barrier island near Cape Coral.

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Well south of there, in Naples, Marco Island and Everglades City, studies have shown ocean waters have risen more than seven feet, although damage has been less, according to data compiled by the US Geological Survey. .

“It was a huge increase,” said Jeffry Evans, the meteorologist in charge of the National Weather Service’s Houston/Galveston forecast office, who traveled to Florida to collect the data.

Evans said he saw evidence in two-story condominiums of up to 15 feet of water running through northern Fort Myers Beach — a level he says doesn’t include the height of waves beating even higher. .

About 40 miles away on Marco Island, surveys and data suggest flood waters reached 7.5 feet, likely as a result of Ian winds pushing along the shore as the storm crossed the Gulf of Mexico toward the coast, said Ronald Busciolano, a USGS. hydrologist and leader of the agency’s coastal storm team.

“It was a really big storm,” Busciolano said. “The wave followed it and came with it.”

If Ian had followed a little further north, “Tampa would have been hit much harder,” he said. “They were spared because they were on the north side of the storm.”

Brian LaMarre, the meteorologist in charge of the Tampa Bay Weather Service’s forecast office, said he hopes Ian’s impact will inspire those who avoided his most severe conditions to remember what might have been – and, in the future, to pay attention not only to a storm. the predicted track, but also areas facing storm surges and other threats.

“I think a lot of people here are realizing how close they came to a deadly, devastating, life-altering hurricane,” he said.

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Official data on flooding from the storm surge is not expected for weeks, after further damage surveys have been carried out and the data has been reviewed for errors and bias. National Hurricane Center officials said their thorough review of Ian’s forecast and sightings would not be complete until winter or spring.

But preliminary observations show what meteorologists feared: this wave would be widespread and devastating in areas where Ian’s winds were blowing towards the shore. Because tropical cyclones spin counter-clockwise in the Northern Hemisphere, this meant that areas south of Ian’s eye were subject to its storm surge.

That was true even in the Florida Keys, which only received a glimpse of the storm but still recorded water levels several feet above normal. In Key West, a USGS gauge installed before Ian’s arrival showed a 4.5-foot rise in ocean levels.

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In the Tampa Bay area, by contrast, Ian’s more southerly track and circulation caused winds to push water away from shore. A USGS gauge at Clearwater Beach showed a four-foot drop in water levels in what are known as boom tides or negative storm surges.

Preliminary data comes from a combination of USGS gauges, flood sensors, and observations collected during damage surveys.

The latter involve combing the destruction for signs of water height that resemble a bathtub ring. Measurements can come from sightings of debris piled up on a shoreline or lines left on or in buildings by mud or floating seeds. They can show up more prominently in places like bathrooms, closets and interior cabinets, Evans said — places where water can drain away but wave action is minimal.

It was sometimes hard to find in places like Fort Myers Beach, he said. In many cases, the storm emptied buildings of drywall and left nothing but debris in its path.

“The extent of the damage was among the most extreme I have ever seen,” Evans said.

USGS data analyzed so far shows the thrust reached 13.23 feet at Fort Myers Beach, a level that translated to more than nine feet of seawater above ground. normally dry in buildings a few feet above sea level. More data will be collected and more surveys conducted over the next two weeks, Busciolano said.

The data also shows that storm surges reached well inland in many areas. For example, an estimated nine-foot storm surge meant a foot or two of water extended for miles inland in areas like Punta Rassa and Bonita Springs.

The topography of downtown Naples, on the other hand, prevented about eight feet of storm surge from penetrating more than a few blocks inland, Mark Bove, a meteorologist who helped surveys on damages and is senior vice president of natural disaster solutions for insurance company Munich Re US, said in an email.

Water levels have risen more than seven feet in the Caloosahatchee River that separates Cape Coral and Fort Myers, measured about 20 miles inside the gulf. It’s likely the product of heavy rains inland as well as the storm surge, Busciolano said.

“The water is going to want to find its level,” pouring into whatever low spots it can find, he said. “He’s going to keep pushing upriver…and going further inland than you think.”


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