USA: 26 feet of water: What the worst-case hurricane scenario looks like for Tampa Bay
By Brian Resnick
This is part three in a three-part series about worst-case extreme weather scenarios in three regions of the United States — Arizona, California, and Florida — that are particularly vulnerable to the effects of climate change. In this story, we’ll consider why a Category 5 hurricane would be an especially catastrophic Big One for Tampa, Florida.
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It’s become a haunting question of when, not if, a big hurricane will return. Residents surrounding Tampa Bay have been spared the worst-case hurricane scenario many times before. Now, there’s so much more to lose. And sometime soon, we don’t know when, the worst-case scenario will arrive: a Category 5 hurricane, with winds in excess of 160 mph.
Here’s what it will look like: A monster hurricane — as big as they come — pushes an enormous amount of water into the bay. In downtown Tampa, at the north end of Tampa Bay, a Category 5 produces a 26-foot flood, more than twice the height of the 1921 storm. There, the downtown is built right along the waterfront, and the first floors of the buildings flood. In St. Petersburg, which is also built right up to the water, the surge reaches 20 feet, inundating much of downtown.
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The scenario I just laid wasn’t made up by me. In 2009, the Tampa Bay Regional Planning Council drafted a plan for how to respond to a potential hurricane catastrophe, dubbing it “Hurricane Phoenix.” You might have read about it in a 2017 Washington Post feature on the region’s potential to flood.
The reason for this catastrophe plan: Tampa Bay is one of the areas in the US most at risk when hurricanes arrive because of its location, growing population, and the geography of the bay. This is the map of the storm planners fear the most.
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Here’s what scientists are most confident in: The clearest consequence of climate change that will make hurricane impacts worse is sea-level rise. As the ocean warms and expands, and ice sheets in places like Greenland melt, seas are rising and more more water is available to inundate the land. Every inch more water can creep all that much higher during a storm surge.
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There’s also some evidence that the forward pace of storms might be slowing down in a warming world. When a storm lingers over an area longer, it can dump more water on it. There’s also evidence that they may grow more intense, more quickly. The recent Category 5 Hurricane Dorian exhibited both of these traits: increasing its winds from 150 to 180 mph in just nine hours, and then lingering on Grand Bahama Island for 41 hours. It’s a nightmare scenario — intense sucker-punch hurricanes that linger — and it may grow more common in the future.
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