The Factors Behind Hurricane Milton’s Powerful Tornadoes

Hurricane Milton wreaked havoc earlier than expected before making landfall this week, as supercell thunderstorms featuring rotating updrafts and the potential to spawn tornadoes raced across the state.

The resulting twister caused the National Weather Service to issue 126 tornado warnings, and the agency The Storm Prediction Center has filed 45 preliminary reports of tornadoes..

In St. Lucie County, a tornado destroyed a retirement community and killed five people, accounting for nearly one-third of the 17 deaths reported so far in the aftermath of the hurricane.

As Florida begins the long process of recovering and recovering from Hurricane Milton, tornado outbreaks are causing deaths and damage in a state accustomed to tropical storms but less accustomed to powerful twisters. has emerged as the main cause.

One of the strongest tornadoes in South Florida history occurred on a day that will likely go down in Florida history as one of the worst tornado outbreaks ever observed in Florida during a cyclone.

Swirling winds reached 160 miles per hour in Palm Beach Gardens, tearing apart concrete walls and tearing off large sections of roofs from new homes. Breaking news from the National Weather Service.

“This is the first EF-3 on record for the South Florida area south of Lake Okeechobee,” said Donal Harrigan, NWS meteorologist in Miami. EF-3 refers to tornadoes with estimated wind speeds of 136 to 160 miles per hour (EF stands for Enhanced Fujita Scale; Started operation at the National Weather Service in 2007).

Harrigan added that several other observed twisters may be rated EF-3 after damage assessment.

“You can probably count on one hand how many EF-3s have been in this state historically, potentially multiple times a day,” he said.

Overall this year, the United States has seen an unusually high number of powerful tornadoes associated with hurricanes.

Tornadoes are common when hurricanes make landfall, but most are on the weaker end of the spectrum. Less than 1% of tornadoes associated with tropical systems that make landfall are rated EF-3 or higher. By contrast, four out of five hurricanes that made landfall in the United States this year produced tornadoes with EF-3 strength.

From 1995 to 2023, only five tornadoes caused by tropical cyclones received such high ratings.

Early research suggests 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 show that the number of potential tornado storms caused by a tropical cyclone is 56% to 299% increase by mid-century Assuming the pace of fossil fuel pollution remains steady.

It is not yet known whether climate change played a role in the twisters associated with this year’s storms. But Bill Gallus, an author of the June study and a professor of meteorology at Iowa State University, said “it was really unusual that conditions in South Florida were this volatile” during Milton.

A situation is considered unstable if, due to differences in density and temperature, a mass of air rises or falls rapidly, which means that thunderstorms can form.

“When I looked at the instability graph, I was shocked. It was about as high as you’d see in Kansas chasing storms,” ​​Gallus said. “Hurricanes have produced more tornadoes, but Florida alone has never produced so many tornadoes.”

He added that this type of instability is “expected to become more common” in a warming world.

One reason Milton produced so many tornadoes is that hurricane thunderstorms traveled far from the center.

“With the first tornado, it looked like a certain band of showers and storms from Milton were actually erupting well in front of the hurricane,” Gallus said.

The outer storm belt eventually became isolated and ended without interference from other systems. Those were thunderstorms that produced tornadoes. This is a reminder that hurricanes can become a threat long before landfall and even far from the storm’s center, experts said.

Another important factor for Milton’s tornadoes is heat. The hurricane approached the Florida coast in the afternoon and encountered particularly warm conditions, as the thunderstorms were quite far away at the edge of the hurricane, in addition to wind shear (changes in wind direction and speed with altitude). This allowed it to grow stronger than a typical hurricane setup.

“There was plenty of time to warm up the atmosphere,” Gallus said. “Most hurricanes get very little heat from the sun. Tornadoes form under heavy rain and cover.”

In hurricanes like Milton, where winds blow counterclockwise, tornadoes tend to form on the leading edge of the storm and to its right, sometimes called the dirty side. This region is also the windiest.

How it unfolded during Milton, Gallus said, noting that the twister “started in the exact place you see most tornadoes form.”

But in Milton’s case, he noted, the tornadoes were particularly concentrated.

Because Milton crossed the Florida peninsula for a short distance, “the tornado area was small, and I think it was one of the most concentrated tornadoes ever produced by a hurricane,” Gallus said.

More research is needed into exactly how climate change will affect tornadoes produced by hurricanes. However, the impact of global warming on extreme rainfall is more certain and clear.

A report released Friday by the World Weather Attribution Project, a consortium of scientists considered an authority on analyzing extreme weather events and determining the impact of climate change on specific events, says: It turned out. Rainfall amounts for single-day events like Milton are currently about 20% to 30% higher due to climate change.. The analysis found that Milton’s wind speeds were likely 10% stronger due to climate change.

The researchers also found that Hurricane Helen was wetter and windier because of climate change. Separate preliminary reports say climate change is likely to increase Helen’s rainfall by up to 50% over three days in some of the worst-hit areas.