Before Hurricane Milton made landfall, it produced twisters in southern Florida.
Wednesday broke a record for the most tornado warnings in a single day in Florida, prompting a question from some: is it normal to see tornadoes during a hurricane?
Hurricanes, also called tropical cyclones, are tropical storms that initially form over tropical or subtropical waters.
Tornadoes can occur when hurricanes strike, though it isn’t easy to predict if and when they will happen, according to a weather expert.
“It’s not like a tropical cyclone, which you can predict, sometimes even a week ahead of time,” University of Bristol’s Dann Mitchell told Reuters. “Tornadoes, we really can’t get that level of predictability.”
How tornadoes form
Mitchell explained how hurricanes like Hurricane Milton can produce tornadoes.
“When the tropical cyclone starts hitting land, suddenly winds at the surface slow down a lot, because there’s a lot of friction there, there’s a lot of buildings in the way, but the winds in the higher levels carry on,” said the professor of atmospheric science in a video published Thursday.
What happens as a result are big changes in wind speed or direction, called wind shear, he said.
“And that’s why when you see things hit, then we normally see tornadoes spawn at that point.”
The U.S. National Weather Service says these tornadoes often occur in thunderstorms away from the centre of the hurricane, in an area that is the most unstable.
Is it a common phenomenon?
In the case of the twisters linked to Hurricane Milton, one scientist said their ferocity was unusual.
“It’s definitely out of the ordinary,” Northern Illinois University meteorology professor Victor Gensini told The Associated Press. “Hurricanes do produce tornadoes, but they’re usually weak.”
He said Hurricane Milton’s impact Wednesday was similar to the one seen in the Great Plains, a grasslands region that includes 10 U.S. states, in the spring.
The central U.S. is an ideal environment for severe thunderstorms that form tornadoes because the dry, cold air moving south from Canada meets warm, moist air moving north from the Gulf of Mexico, according to the U.S. Center for Science Education.
Are tornadoes a threat?
While tornadoes produced by hurricanes are “relatively weak and short-lived,” according to the U.S. National Weather Service, they’re still considered a “significant threat.”
Tornadoes can cause many deaths, Mitchell said.
“It’s extra bad in this situation because of course, you’ve got all of the additional impacts of the tropical cyclone hitting at the same time,” he said. “And so when that tropical cyclone hits, you have heavy precipitation, often storm surges and flooding. And then if you have tornadoes on top of that, it creates this compound impact on mortality.”