Why Hurricane Milton Caused So Many Tornadoes

Why did Hurricane Milton spawn so many tornadoes?

Who Meghan Bartels

Hurricane Milton hit Florida As a Category 3 storm, bringing severe storm surge and heavy rain to the central part of the state. As discussions about the hurricane’s dangers focused on flooding, rain and strong winds, residents further south were surprised to receive numerous tornado warnings — more than 100, in all — from local National Weather Service offices.

But Hurricane Milton’s sheer power and size combined with underlying atmospheric factors to trigger dozens of tornadoes in what Jana Houser, an atmospheric scientist at Ohio University, calls “an almost perfect storm scenario with Milton.”

As part of a hurricane or independently, tornadoes develop when air swirling near the ground is pulled up into the atmosphere by a storm, Houser says. Air increases in speed as it moves inward and upward.

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In general, tornadoes are especially likely to occur there bigger hurricanes such as Milton, which had tropical storm-force winds up to 255 miles from its core on October 9.

Hurricanes have their own rotating winds, especially in the eyewall of the hurricane’s core, where wind speeds are highest. Sometimes weak tornadoes can form near the heart of a hurricane as it makes landfall, as the winds are more suited to interacting with rough terrain than with the relatively smooth surface of the ocean.

But it’s nowhere to look for stronger tornadoes, such as those spawned by Milton, which Virginia Tech meteorologist Stephanie Zick says were “exceptionally strong” for tornadoes spawned by hurricanes. These form at the storm’s edges, the outer rainbands up to 100 miles from the eye, where supercell thunderstorms—large, rotating storms—grow. In addition, Houser says the environment around which Milton spun was ideal for tornadoes, thanks to the presence of pockets of warm, moist air and a band of winds that the storm could touch.

Tornado conditions were also strongest to the east of the storm, Zick said. Combined with the distance from the eye of the hurricane, most tornado reports were located in southern Florida.

Despite the uproar its tornadoes have caused, Milton has not been the hurricane with the most tornadoes this year, Houser says. That dubious honor Hurricane BerylHe hit the Texas Gulf Coast in early July before trekking northeast across the US, his the remains finally soaking Vermont. Beryl spawned 68 tornadoes, Houser says, nearly double Milton’s previous count of 38. (It takes time to evaluate tornado reports and pick out duplicate or false alarms, he notes.) The record for tornado production was Hurricane Ivan, which swept across the southeastern United States. in September 2004 and caused 120 tornadoes.

Tornadoes spawned by hurricanes are a prime example of how hurricanes pose multiple threats to residents: not only damaging winds, but also violent storm surges; not only a long deluge but also a violent tornado.

And sometimes threats are linked. As Milton approached Florida, it encountered chaotic winds that tore through its structure, weakening the storm from a Category 5 storm with sustained winds of 100 miles per hour to a Category 3 storm with sustained winds of 120 miles per hour on land. But that also caused the storm to increase in size and create turbulent wind patterns along its edges that fueled the tornado outbreak, Houser says.

“If those winds hadn’t been there, Milton probably would have made landfall as a Category 5 hurricane,” he says. “But then you probably wouldn’t get nearly the number of tornadoes that you ended up seeing further inland.”