Hurricane Milton delivered an earlier-than-expected dose of chaos before making landfall this week, as supercell thunderstorms — which feature rotating updrafts and can produce tornadoes — ripped through the state.
The resulting twisters prompted the National Weather Service to issue 126 tornado warnings, and the agency’s Storm Prediction Center issued 45 preliminary reports of tornadoes.
In St. Lucie County, five people died after a tornado ripped through a retirement community, making up nearly a third of the 17 deaths reported so far from the hurricane.
As Florida begins the long process of cleaning up and recovering from Hurricane Milton, the tornado outbreak has become one of the leading causes of death and damage in a state accustomed to tropical storms but less familiar with powerful tornadoes.
This day will likely go down in Florida history as one of the worst tornado outbreaks ever observed there during a cyclone, and included one of the strongest tornadoes in South Florida history.
According to a preliminary report from the National Weather Service, swirling winds in Palm Beach Gardens whipped up to 140 miles per hour, tearing away concrete walls and ripping off large portions of the roof of newly constructed homes.
“That’s the first EF-3 for our area in South Florida, from Lake Okeechobee and southward,” said Donal Harrigan, an NWS meteorologist in Miami. An EF-3 refers to a tornado with estimated wind speeds of 136 to 160 mph (EF stands for the Enhanced Fujita Scale, which became operational for the National Weather Service in 2007).
It is possible that several other observed twisters will be rated as EF-3s after damage assessments, Harrigan added.
“You can probably count on one hand how many EF-3s there have been in the state historically. We may have several in one day,” he said.
Overall, the U.S. has seen an abnormally high number of strong tornadoes associated with hurricanes this year.
Although tornadoes are common when hurricanes make landfall, most are on the weaker end of the spectrum; less than 1% of tornadoes associated with landfalling tropical systems are rated EF-3 or stronger. In contrast, this year, four out of five hurricanes that made landfall in the U.S. produced tornadoes of EF-3 intensity.
From 1995 through 2023, only five tornadoes caused by tropical storms were rated that highly.
Early research has suggested that tropical cyclones could produce more tornadoes in a warmer world. In a study published in June, researchers modeled Hurricanes Ivan, Katrina, Rita and Harvey in a warmer, future climate. Their results indicated that the number of potentially tornadic storms caused by tropical cyclones could increase between 56% and 299% by mid-century, assuming the rate of fossil fuel pollution remains stable.
It is not yet known whether climate change played a role in this year’s storm-related twisters. But Bill Gallus, author of the June study and professor of meteorology at Iowa State University, said that during Milton it was “really unusual how unstable conditions were in South Florida.”
Conditions are considered unstable when differences in density and temperature allow air bubbles to rise and fall quickly – conditions that make thunderstorms possible.
“I was shocked when I pulled out the instability map. It was as high as you would see in Kansas during a storm chase,” Gallus said. “We’ve had hurricanes that produced more tornadoes, but only in Florida have we ever had that many.”
He added that in a warming world, this type of instability is “expected to become more common.”
One reason Milton produced so many tornadoes is that the hurricane’s thunderstorms ventured far from the center.
“With the first tornadoes, that particular line of showers and storms seemed to originate from Milton quite well ahead of the hurricane,” Gallus said.
That outer storm band ended up isolated and without interference from other systems – those were the thunderstorms that spawned tornadoes. It’s a reminder that hurricanes can pose a threat long before they make landfall and far from the center of a storm, experts say.
The other crucial ingredient for Milton’s tornadoes: heat. The hurricane approached the Florida coast in the afternoon, and because the thunderstorms were well on the hurricane’s edge, they encountered particularly warm conditions in addition to wind shear: changes in the direction and speed of winds at high altitudes. This allowed them to become more powerful than they would in a more typical hurricane setup.
“The atmosphere had plenty of time to warm up,” Gallus said. “With most hurricanes, you don’t end up getting much heat from the sun at all; the tornadoes happen in the heat of the moment during heavy rain.”
In a hurricane with counterclockwise winds, like Milton, tornadoes tend to form on the leading edge of a storm and on the right side – which is also called the dirty side. This area also tends to see the worst winds.
That’s how it played out during Milton, Gallus said: the tornadoes “located right where we see the most tornadoes happening.”
But in Milton’s case, he noted, the tornadoes were particularly concentrated.
Because of Milton’s short path across the Florida peninsula, Gallus said, “the real estate where it produced tornadoes was small — I suspect it is the most concentrated outbreak of tornadoes produced by a hurricane.”
More research is still needed on how exactly climate change may affect the tornadoes produced by hurricanes. But the influence of global warming on extreme rainfall is more robust and clear.
A report released Friday by the World Weather Attribution project — a consortium of scientists that analyzes extreme weather and is considered an authority in determining the influence of climate change on certain events — shows that precipitation at single-day events such as Milton is now approximately 20% to 30%. % more intense due to climate change. The analysis found that Milton’s wind speeds were likely 10% stronger due to the influence of climate change.
The group similarly found that Hurricane Helene was wetter and windier because of climate change. Another preliminary report found that climate change has likely increased Helene’s rainfall by as much as 50% in a three-day period in some of the worst-affected areas.
This article was originally published on NBCNews.com
