Why Hurricane Ian poses a unique threat to Tampa Bay
Hurricane Ian would pose particular risks to the city of Tampa and the Tampa Bay area if it lands there due to the Gulf Coast’s geography, rising sea levels and lagging resilience planning.
The storm made landfall on the west coast of Cuba in the early hours of Tuesday morning shortly after becoming a major hurricane, then entered the Gulf of Mexico.
The bulk of Florida’s west coast, including the Tampa Bay area, is currently under a storm surge warning, and several counties have issued mandatory or voluntary evacuations.
Pinellas County, home to nearly 1 million people, ordered everyone living in particularly vulnerable low-lying areas to evacuate Monday evening.
The region has not seen a major hurricane in a century. That 1921 storm, a Category 3, killed at least eight people.
Since then, a 2013 World Bank study named Tampa the seventh most vulnerable coastal city to damages from flooding and the fourth most vulnerable U.S. city.
Two years later, a report from catastrophe modelers Karen Clark and Co. deemed Tampa the single most vulnerable city to storm surge flooding in the country, projecting damages to residential, commercial and industrial properties from a hypothetical 100-year hurricane to be about $175 billion.
In the 100 years since its last major hurricane, the city’s population grew nearly 400 percent, from 51,000 to just under 396,000 people. The 2015 report notes that about 50 percent of the city’s population lives in low-lying areas, with ground elevations of under 10 feet.
The wider Tampa-St. Petersburg-Clearwater area has a population of about 3 million, and much of the region is linked by causeways and bridges that are particularly susceptible to flooding, said Jeff Masters, a meteorologist with Yale Climate Connections.
“These people don’t have much hurricane experience, so they’ve been very lucky over the past 100 years,” Masters said. “So you combine the vulnerability with the high population that’s inexperienced, and you have a situation that’s among the worst for any major city in the U.S.”
Experts say the Tampa area’s geography makes it particularly vulnerable to even a weaker storm. The city is located along the Gulf of Mexico and has an unusually far-reaching continental shelf.
“The waters are kind of shallow for hundreds of miles going into the Gulf, which really worsens the storm surge possibilities and impacts as this wall of wind and water [is] moving toward land,” said Aris Papadopoulos, the founder and chair of the Resilience Action Fund and distinguished expert of resilience at Florida International University.
The shallow waters and the “U” shape of the Gulf Coast can create an effect that intensifies the storm as it nears the shore.
“Near the shore and the Gulf of Mexico, it just piles up,” Masters said. “And then when you get to Tampa Bay, Tampa Bay is pretty much funnel shaped. So that acts to concentrate the water that’s been piled up even further.”
“We’re looking at a case where we … not only have a large storm surge that’s most likely to hit a broad swath of the region, but also a prolonged and protracted rainfall,” said Chris Uejio, an associate professor of geography at Florida State University. The combination of the two, he said, could lead to “flooding that we haven’t seen in the modern era.”
A slight variation in the path of the hurricane could lessen much of the danger, according to Masters.
“If the hurricane hits just to the south of Tampa Bay, they are not going to get a massive, destructive storm surge, because the winds are going to be blowing offshore, blowing the water out of Tampa Bay,” Masters said. “But if the hurricane hits just north of town, then that’s when you get this 5- to 10-foot storm surge that the [National] Hurricane Center was forecasting.”
Recent revisions, he noted, are projecting 5 to 8 feet and a landfall south of Tampa, he added, but “just a small variation in track could change things because the hurricane’s coming in at kind of an angle to the coast, so it’s a difficult forecast situation, and it makes all the difference where the storm hits.”
Florida Gov. Ron DeSantis (R) specifically noted the “sensitivity … and fragility of this area” in a news conference Monday. Uejio told The Hill much of the population at greatest risk will be older residents and people with medical conditions, particularly those who rely on electricity for their medical needs.
Moreover, spiraling rents have increased the area’s homeless population, another group that will struggle to find shelter from extreme weather, he noted.
The Tampa Bay region has seen major sea level rises over the decade due to climate change, according to the National Oceanic and Atmospheric Administration (NOAA), compounding the vulnerability to major storms.
NOAA measurements of St. Petersburg sea levels found they have risen about 2.97 millimeters a year since 1947, equivalent to just under a foot per 100 years.
The pace appears to have quickened since around 1990. A 2019 analysis by the Tampa Bay Climate Science Advisory Panel projected that based on these trends, the level is set to rise 1 to 2.5 feet by 2050 and between 2 to 8.5 feet by the end of the century.
Papadopoulos added that much of the northern parts of the state have structures that predate the more stringent hurricane codes the south adopted after Hurricane Andrew in 1992.
Metropolitan areas like Miami-Dade, he said, “can face a Category 5 hurricane impact, but in the Tampa area and other parts of Florida, they’re still at levels for Category 2, maybe Category 3 in some locations.”
“We’re gambling, essentially, with nature by saying well, the probability is lower and so we’ll take a chance and lower the standards,” he added. “I think that’s an unwise gamble, today and definitely much more as we go into the future.”