Before officially becoming Tropical Storm Alex — the first named tropical system of the 2022 Atlantic hurricane season — a record-setting rainstorm caused extensive Miami flooding over the weekend.
June is typically Miami’s rainiest month, with an average of 6.3 inches falling each year. What’s now Tropical Storm Alex brought that much rain in less than two days. A month’s worth of rain in 36 hours, boosted by a warming climate.
The intense rains created extensive flash flooding, displacing thousands of people in Cuba and Florida and creating scenes of floating cars, people wading through waist-deep water, and even more surreal moments like a dog surfing (yes, really) and a school of fish making their way through a flooded parking garage.
A recently upgraded pump-and-drainage system in Miami Beach, designed to handle the more intense rainstorms that are already occurring due to climate change, did not meet expectations.
“We moved the water off pretty quickly, but in some areas, obviously, it was really challenging,” Miami Beach mayor Dan Gelber told the Associated Press. Elsewhere in the region, residents said officials did not do enough to clear storm drains before the well-predicted rains arrived. The heavy rains also created sewage overflows which shut down the region’s beaches.
The “potential tropical cyclone” dropped more than 10 inches of rain on Miami in two days — the biggest rainstorm during the first half of hurricane season in Miami in nearly 100 years.
According to meteorologists Bob Henson and Jeff Masters, “[t]he two-day rainfall total (June 3-4) of 8.65″ at Miami was its heaviest two-day rainfall in any meteorological summer (June-August) since 10.33″ fell on August 29-30, 1932.”
Unofficially, some measurements from backyard rain gauges were even higher, including Currently’s John Morales, who measured nearly a foot. This intense of a rainstorm in Miami is “obviously rare,” according to Morales. “And getting 11.77 in my house over the course of 30 hours was astounding.”
Using the same database that engineers use to plan for flooding gives an estimate of 1-in-50 to 1-in-200 years for a 9-inch rainfall in 3-6 hours in Miami, which Morales estimates is what happened at his home rain gauge. That estimate, however, is based on a stable climate — which obviously isn’t a good assumption anymore. Just last year, researchers at Florida International University in Miami released a report recommending updated building codes to handle more intense rainfall rates that are already happening in Florida due to a warming climate. Warmer air can hold more water vapor, and that is increasing the amount of rainfall that falls on the rainiest days. Over the past 60 years, Florida already gets an average of two additional “torrential” rainfall days each year, defined as more than three inches.
“These events are becoming more frequent, and when you add them to other climate-driven challenges like heat and sea level rise, they’re making South Florida a more difficult place to live with each passing year,” says Morales.