Flooding lingers at Fort Lauderdale-Hollywood International Airport on Thursday after heavy rain pounded South Florida. A weather system dumped 25 inches of rain over the area this week.
A weather system that hit in the Tampa Bay area dropped an estimated 18 inches of rain on May 8, 1979. A woman inspects the damage to her house in St. Petersburg.
The weather system that dumped 25 inches of rain on Fort Lauderdale this week was so epic and rare that meteorologists said it would be expected to occur only once every 1,000 years.
Flooding shut down the Fort Lauderdale airport for days and had residents paddling through streets on kayaks and canoes.
Could that much rain ever fall in the Tampa Bay area in a single day? And if it did, what would it look like?
Though 25 inches of rain has never fallen on the Tampa Bay area in one day, a weather system that hit in the area on May 8, 1979, dropped an estimated 18 inches of rain. The then-St. Petersburg Times called it the storm of the century.
At least two people were killed during the torrential rains in St. Petersburg and 10,000 people were without power. Newspapers reported more than a dozen tornadoes were spun out from the storm, wreaking havoc across Tampa Bay.
Businesses shut down, classes were canceled and Tampa International Airport evacuated it’s control tower after winds reached 108 mph.
Photos from the 1979 storm are eerily similar to those taken on Wednesday in Fort Lauderdale, where cars were stranded and people were forced to trek through knee-high water.
In the last 40 years, the Tampa Bay area has grown tremendously. There are more roads to flood and homes to damage. About 3 million people live across Pinellas, Pasco and Hillsborough counties now, nearly twice as many compared to when the 1979 storm hit.
Forecasters said a storm like the one that caused so much chaos in Fort Lauderdale this week would lead to similar problems for Tampa Bay. Our area is urbanized much like Fort Lauderdale and extreme rainfall would be too much for local drainage systems to handle, said Ross Giarratana, a meteorologist with the National Weather Service’s Tampa Bay office.
There have been instances, he noted, where thunderstorms have sat over South Tampa and flooded streets with 5 inches of rain. Pinellas County has had similar experiences in areas like Shore Acres.
“That type of rainfall, roads would certainly be able to be flooded,” Giarratana said. “As far as talking about specific areas, it’s hard to say — but Tampa Bay, I would say, would be very much just as vulnerable given its low-lying and populated, urbanized topography.”
The rainfall from the Fort Lauderdale storm is the third most to ever fall on a major U.S. city over a 24-hour period in recorded history (behind Hilo, Hawaii’s, 27 inches in 2000 and Port Arthur, Texas’ 26.5 inches in 2017).
Florida has the right topography, plenty of warm water nearby and other favorable conditions to create such a deluge, said Greg Carbin, forecast branch chief at the National Oceanic and Atmospheric Administration’s Weather Prediction Center.
Normally a supercell like that would “snuff itself out” in maybe 20 minutes or at least keep moving, Carbin said.
But the Fort Lauderdale supercell was in a lull between opposing weather systems, Carbin said. It dumped heavy rain for up to eight hours in some places.
A hurricane is one of the few instances in which forecasters could expect to see such extreme rainfall.
“We’ve seen those types of rainfall amounts in parts of Florida before, and typically they happen from tropical systems, because those are the types of systems that carry the amounts of moisture that would be necessary,” Giarratana said.
According to records from the National Weather Service, Hurricane Ian dropped about 19 inches of rain at the Myakka River State Park and flooded the area on Sept. 28. In June 1945, a hurricane dropped about 12 inches of rain locally, according to records from the Hillsborough River State Park. In 2012, Tropical Storm Debby dropped more than 11 inches in Tarpon Springs.
But outside of a tropical storm, a number of factors have to line up just right for such a ferocious weather system to form.
“You had this extreme warmth and moisture that was just feeding into the cell and because it had a bit of a spin to it, it was essentially acting like a vacuum and sucking all that moisture back up into the main core of the system,” said Steve Bowen, a meteorologist and chief science officer for Gallagher Re, a global reinsurance broker. “It just kept reigniting itself, essentially.”
Former National Oceanic and Atmospheric Administration chief scientist Ryan Maue said “the availability of warm ocean air from the Gulf Stream was essentially infinite” in Fort Lauderdale during the flooding, which was a key factor.
Many of those conditions by themselves are not unusual, including the location of the Gulf Stream. But when they combined in a precise way, it acted like a continuous feeding loop that poured rain in amounts that the National Weather Service in Miami called a 1-in-1,000 chance.
“We continue to see more and more of these thousand-year” weather extremes in major cities, Bowen said. “The whole definition of normal is changing.”
Material from The Associated Press supplements this report. Contact Michaela Mulligan at mmulligan@tampabay.com. Follow @Michaela_Mull.