What a Hurricane Pushes Into Florida Is More Dangerous Than Its Wind

Hurricane storm surge put 15.5 feet of water above the ground inside a Fort Myers Beach home. The hurricane ratings on every forecast never measured it. In September 2022, Hurricane Ian pushed the Gulf of Mexico into southwest Florida. The National Hurricane Center's post-storm report attributes 66 direct US deaths to the storm — 41 of them from water, 36 of those in Lee County alone. Almost none of that water was rain. Hurricane wind speed is the number stamped on every map, and it has not been the hazard responsible for most hurricane deaths in decades. Wind accounts for roughly eight percent. Surge and rainfall flooding account for nearly all of the rest. The scale did not start out that way. When Herbert Saffir and Robert Simpson built it in the early 1970s, Simpson attached expected surge ranges to every category — nine to twelve feet for a Category three. Real storms broke the correlation. Someone at the National Hurricane Center decided to take those numbers back out, phasing them out by 2009, making it official in 2010, and adding the word "Wind" to the scale's own name after a public comment period. The hurricane ratings system is honest about its limits. It just says so quietly. What fills the gap is geography. Three variables decide how high the water climbs, and none of them appear on a forecast: the shape of the seafloor, the shape of the shoreline, and where the moon happens to be that week. Florida has a wide, shallow shelf on its Gulf side and a steep, narrow one on the Atlantic — one coast built to hold water in, the other built to push it back out. Tampa Bay and the bays north of Pensacola funnel it higher still. Hurricane Ivan and Hurricane Sally hit the same stretch of coastline sixteen years apart, one category apart, and put their water in completely different places. So a separate system had to be built to see what the category number couldn't. It's called SLOSH — Sea, Lake, and Overland Surges from Hurricanes — developed by a team led by Chester Jelesnianski, and Florida's evacuation zones are drawn from its output. It models lake surge too, because in 1928 a hurricane sloshed Lake Okeechobee over its levees and killed thousands. Understanding your storm surge risk means reading a zone letter, not a category. A category describes the storm. A zone describes the ground you're standing on. That distinction is the whole of hurricane safety on this coast: run from the water, hide from the wind. Subscribe for all things Florida.