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CURIOUS GULF COAST: Why Didn't We See High Storm Surge?

A storm surge map from the Southwest Florida Regional Planning Council.
A storm surge map from the Southwest Florida Regional Planning Council.

With the impending arrival of Hurricane Irma, thousands of Floridians left the state because of potential high storm surge, which is the rise of sea level that results from wind forces.

Doug Constantine from Cape Coral asked: "With FEMA recently scaring several million people into an evacuation, where they predicted storm surge of almost 20 feet and they were wrong and they’ve been wrong before. How many times can they yell the sky is falling?

The Federal Emergency Management Agency isn't in charge of calculating storm surge. That’s the job of the National Hurricane Center.

The Center’s Storm Surge Specialist Jamie Rhome is in charge of the storm surge unit and said they run hundreds to thousands of scenarios in their modeling system, trying to determine what the storm surge might be.

“You’re basically solving equations of motion for how a fluid will respond to a force exerted upon it,” said Rhome.

He said the challenge is that storms change off of their predicted course. And that’s what happened with Irma.

“The storm wobbled a bit to the east and went inland further east than we were projecting," Rhome said. "And that little 10 or 15-mile wobble saved everybody from Naples northward.”

But, Rhome said that meant areas like Chokoloskee, Goodland, Everglades City, and Marco Island saw significant storm surge.

Meteorologist Jeff Huffman, with the Florida Public Radio Emergency Network, said reported storm surge estimates are on the high end of the calculations done by the National Hurricane Center.

“The projection for storm surge is what’s called a reasonable worst case scenario," said Huffman. "It’s kinda like 'why do you put your seatbelt on in a car?' It’s because it’s a very small chance of a significant event that could impact your life.”

He said storm surge projections are released when there’s a greater than 10 percent chance of it happening—it’s called a 10 percent exceedance.

“There also is a 90 percent probability that 15 feet won’t occur," Huffman said. "So, that’s the challenge that we have in terms of storm surge forecasting.”

Huffman said these worst case scenario storm surges have happened, can happen and will happen again.

The Southwest Florida Regional Planning Council’s Tim Walker has the latest storm surge maps for the area. And he said that a 15-foot storm surge has happened before.

“People have to realize we have had storm inundation that high," said Walker. "Back in 1873 there was an unnamed storm that they recorded a 14 to 15 foot storm surge that went over top Punta Rassa, so it’s possible. It’s not a question of if, but when.” 

The National Hurricane Center’s Rhome said that if people want more accurate storm surge calculations, it has to be a group effort. 

“We can make improvements in our predictions," he said. "But the country has to invest in that.”

Rhome said for now, when it comes to predicting and reporting about a potential storm surge, he'd rather err on the "worst-case-scenario" side so that everyone's prepared for the worst. Because when they aren’t, lives are lost. 

Copyright 2020 WGCU. To see more, visit WGCU.

Quincy Walters is a reporter and backup host for WGCU.
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