As Hurricane Milton spun out over the Atlantic Ocean on Thursday, St. Lucie County reported five people dead in its wake. But those fatalities were eerily on the opposite coast from Siesta Key, where Milton made landfall Wednesday as a powerful Category 3 hurricane.
They occurred where at least one tornado had spawned from Milton’s outer ring.
At least 126 tornado warnings were issued across the region and dozens of tornadoes were spotted Wednesday.
“It’s on the higher end of the spectrum of what we’d expect from hurricane-produced tornadoes,” said Jana Houser, associate professor of atmospheric science at Ohio State University.
The Storm Prediction Center counted 45 tornado reports Wednesday, but Houser said those reports were being checked for duplicates. The total tally Thursday morning was closer to 38, she said.
But Houser and other scientists agreed that while the cluster of tornadoes was on the higher side, it wasn’t unprecedented.
Previous major hurricanes have produced far more tornadoes than reported from Milton, such as Hurricane Ivan in 2004, which produced 118, or Hurricane Beryl that produced about 68 this year, according to Christopher Nowotarski, an associate professor of atmospheric sciences at Texas A&M University.
But what is striking is that tornadoes produced by hurricanes or tropical storms typically span several states as the storm chugs a path from the Atlantic basin northward across the contiguous United States.
“Milton just moved across Florida,” Nowotarski said. “So the fact that it produced as many tornadoes as it did across land is a testament to how dense those number of tornadoes were.”
There are no official reports of the ferocity of Milton’s tornadoes. A tornado’s intensity is an estimate of wind speed, largely determined by how much the spinning column of air damaged nearby structures. Employees with the National Weather Service will be on the ground in the coming days to determine the strength of the storms.
While scientists know that hotter ocean water, caused by the heat that carbon dioxide and other greenhouse gases trap near Earth’s surface, can produce stronger hurricanes that grow more rapidly, the jury is still out on whether more powerful hurricanes could produce more destructive tornadoes or larger tornado outbreaks.
“How climate change effects tornadoes in a hurricane is a question we haven’t really gotten to yet,” Nowotarski said.
In the meantime, researchers are trying to determine how best to communicate the dual hazards of hurricanes and tornadoes.
Hurricane messaging, for example, typically warns about storm surge, flooding and strong winds. Flood warnings tell people to get to an elevated position. But if a tornado touches down, the safest thing is to be as low in a structure as possible, ideally in a basement or storm cellar.
Also, people outside of the main path of the hurricane might not be paying as much attention to their own risk as they could.
“People farther away from the hurricane center aren’t expecting the same impacts,” Nowotarski said. “So, they may be less aware of the tornado risk that hurricanes have.”
While researchers have found that larger hurricanes, or those with sustained wind speeds greater than 110 mph, can be associated with larger tornado outbreaks, all tropical storms and hurricanes have the potential to spawn tornadoes.
Tornadoes typically form from a storm’s outer rain bands, or the far-reaching arms that can extend hundreds of kilometers out from the hurricane’s eye. Those outer bands tend to have the kind of strong thunderstorms associated with tornadoes.
That’s because when the strong winds from a hurricane hit land after gliding over smooth water, they can suddenly decelerate. The storm’s winds create friction against the rough ground and bulky barriers like trees and buildings. That friction can change a hurricane’s wind speed and direction near the ground, while the winds immediately above the ground remain strong. The dissonance can change the spin of the wind, creating a corkscrew-like effect known as vertical wind shear that tornadoes love.
But tornadoes also require the right atmospheric conditions, separate from the hurricane itself. On Wednesday, a subtropical jet stream was flowing above Central Florida, about halfway between where airplanes fly and the ground. Those strong winds increased the likelihood for rotating thunderstorms called supercells that can lead to tornado formation.
“All those conditions came together to make a perfect storm scenario to produce a lot of tornadoes,” Houser said.
Images of Milton’s tornadoes flashed across social media Wednesday.
“I don’t recall seeing a lot of large, picturesque tornadoes like that associated with hurricanes in the past,” said Jason Naylor, an associate professor with a specialty in atmospheric science at the University of Louisville. He added that it was possible people posted less to social media during hurricanes in the past. “But it looked like something you might see on the plains.”
This article originally appeared in The New York Times.
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