The rash of violent tornadoes unleashed by Hurricane Milton marked a turn in South Florida’s encounters with twisters.
Blamed for killing at least six people and injuring four others, 14 tornadoes have so far been confirmed amid more than 120 warnings triggered hours before Milton made landfall near Siesta Key Oct. 9 with 120 mph winds. Three were ranked severe, with an EF-3 rating, meaning winds reached about 165 mph. One in Clewiston traveled about 70 miles before it dissipated, an unprecedented distance in modern hurricane records.
“It’s just remarkable,” said Michael Lowry, a hurricane specialist with WPLG and former senior scientist with the National Hurricane Center. “These are midwest-style tornadoes in South Florida.”
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The EF-3 tornadoes mark the first time such tornadoes have appeared under the new tornado rating scale adopted by the National Weather Service in 2007, NWS Miami Meteorologist-in-Charge Robert Molleda said in an email. Prior to that, three F-3 rated tornadoes were recorded under the previous scale that factored in fewer variables, with the most recent forming in Broward County in 1980, he said.
To fire up such fierce twisters, Milton set the stage for a perfect mix of ingredients.
After churning across the Gulf of Mexico for nearly five days, it pushed ashore a soupy mix of moist Caribbean air, Lowry explained. When that collided with dry inland air out of reach of the hurricane’s protective cloud cover, it destabilized the atmosphere amid daytime heating and increased wind shear to form the twisters.
Some lasted just minutes, like one in Okeechobee County that appeared and vanished in just five minutes. The St. Lucie County tornado lasted 31 agonizing minutes, traveled more than 21 miles and measured as wide as four football fields.
“So it was very similar but different in how the tornadoes come about in the Midwest, where you have this drier air to the north colliding with very rich, soupy air from the south,” Lowry said. “You have to have a very unique setup for that to happen. Not every hurricane is hitting Florida from the west, as this one was, and moving from southwest to northeast. That direction is really important.”
READ MORE: Tornado spawned by Hurricane Milton ravaged homes in Wellington
Tornadoes are not uncommon in hurricanes, which can trigger the swarms produced by Milton, he said. When Hurricane Ivan made landfall in Alabama and brushed Florida’s panhandle in 2004, it spawned 118 tornadoes. Frances produced 103 that same year when it hit Stuart as a Category 2 hurricane. Hurricane Beulah produced 115 when it hit just south of the Rio Grande in 1967.
“These were confirmed tornadoes. So you look at right now, we have 14 confirmed. So that's always a hazard associated with hurricanes,” he said.
What’s unusual is to have so many severe tornadoes at once.
“We don't talk about tornadoes so much with hurricanes because they tend to be weak,” he said. “Ninety percent of hurricane spawned tornadoes are EF-0 or EF-1. And because they are weak, they sort of get mixed up in the overall winds of a hurricane.”
Only about 3 % of deaths have been blamed on tornadoes from hurricanes. The majority are due to water, from either storm surge or flooding.
Scientists are still investigating what impact a warming planet will have on tornadoes produced by hurricanes. Some studies have suggested they are likely to become more frequent, and occur at night, when people are less alert. But teasing out the connections is complicated.
Milton will likely give scientists more evidence to examine, Lowry said.
“I can imagine that the severe weather experts looking at tornadoes are going to look into this during the off season to see if there's a connection to climate change or why we had so many strong long-track tornadoes this hurricane season,” he said.
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