The way hurricanes like Milton generate tornadoes

Hurricane Milton has spawned at least two major tornadoes and a tornado watch has been issued for much of the southern part of the state ahead of its landfall on Florida's west coast later tonight.

Tornadoes like this are not uncommon and have been observed in many different areas. 80 percent of hurricanes It made landfall on the Gulf Coast, but it's unusual for a hurricane to be so clearly visible in front of it. William Gallus at Iowa State University. “We've already seen an alarming number of them, and they look like tornadoes in the Great Plains,” he says. “It's spacious.”

Two main elements are needed for a hurricane to generate a tornado, which increases the destructive power of the storm. The first is instability caused by heat and moisture in the atmosphere. The second is the difference in wind speed and direction at different altitudes, called wind shear.

Hurricanes that move over water typically have relatively low wind shear because there is not much friction between the storm and the ocean surface. “It's like a giant rotating cylinder, so the wind doesn't change much between the ground and the sky,” Gallus said.

Conditions change when a storm makes landfall, with friction with the ground slowing the winds at lower altitudes and pushing them toward the center of the storm. When the air becomes hot and humid enough, these strong winds can form tornadoes.

In this case, a band of wind in front of Milton's main body reaches the coast, causing wind shear and creating a tornado, Gallus said.

Like other hurricane hazards such as storm surge and heavy rain, these tornadoes can cause significant destruction, and the pattern of debris they leave behind can sometimes indicate their path. one by one estimateapproximately 3 percent of tropical cyclone-related deaths in the United States were caused by tornadoes produced by tropical cyclones. earlier estimate Think of this number as 10% of the total number of deaths.

Such tornadoes may also become more frequent as climate change warms the lower atmosphere, making conditions more unstable for them to form. Recently studyGallus and his colleagues simulated how four different hurricanes (Ivan, Katrina, Rita, and Harvey) would behave with the expected warming by mid-century under very high emissions scenarios. did. They found a significant increase in the number of tornadoes produced by each storm in their simulations. The range was from a 56% increase in Harvey to a 299% increase in Katrina.

“Even if only half of them occur, the number of tornadoes will increase very significantly,” Gallus said.