Hurricane Milton caused severe damage in central Florida yesterday, making landfall as a Category 3 storm near Sarasota that killed at least five people and left more than three million people without power. But one of the most serious and compelling weather events associated with the storm preceded its arrival: dozens of tornadoes that appeared across the state of Florida yesterday afternoon.
Tornadoes are violently rotating columns of air that extend from the bottom of a storm to the ground. Weather phenomena are extremely powerful and have the ability to destroy buildings and launch everything from streetlights to cars into the air like projectiles.
Tornadoes often happen on the outskirts of hurricanes, but for many, yesterday's large number of tornadoes was a surreal preamble to a storm that would end up dumping months of rain on central Florida in just one day. More than 125 tornado warnings were issued by National Weather Service stations in central Florida, CNN reported, making it the most warnings ever issued in the state in one day and nearly doubling the previous record of 69 warnings in one day issued during Hurricane Irma in September 2017.
So what is the total tornado count so far, and why has Milton provided such fertile breeding ground for the dangerous phenomenon?
Hurricane Milton caused at least three dozen tornadoes – but probably more
For tornadoes to form — whether in the Great Plains or South Carolina, as happened during Hurricane Helene last week — a few factors are necessary.
“We want two basic things to happen: You have to have the right storms and the right winds,” said Rich Thompson, chief of forecast operations at the Storm Prediction Center, part of the National Centers for Environmental Prediction. under NOAA's National Weather Service, in a phone call with Gizmodo.
At the Storm Prediction Center headquarters in Norman, Oklahoma — right up tornado alley — winds are often sufficient for tornadoes to form, Thompson said, but the region only gets warm and humid enough to support storms in the spring.
In Florida it's the opposite. The state is hot and humid all the time but lacks wind shear. “That’s where the hurricane comes in,” Thompson said. “You get increases in the wind profile that you wouldn’t get otherwise.”
As of 8 p.m. ET yesterday, at least 116 tornado warnings had been issued and the state had experienced 19 confirmed tornadoes, Gov. Ron DeSantis said at a news conference last night — numbers that have since increased. These tornadoes occurred mainly south of Orlando and were concentrated on the state's Atlantic coast, especially around Port Saint Lucie, Florida's sixth largest city. CNN reported that the most recent numbers from the National Weather Service were 27 tornadoes across the state and at least four deaths associated with the arrival of some of those tornadoes.
“It's hard to really say what the numbers are, but our conservative version right now is 38 tornadoes,” Thompson said, which is an estimate based on a rough initial count of 45 tornadoes. “I think that number will probably increase, but it’s hard to say to what extent.”
How did Hurricane Milton develop?
Like Hurricane Helene a week earlier, Hurricane Milton was the beneficiary of above-average ocean temperatures in the Gulf of Mexico, an already warm body of water. These warm temperatures are fodder for hurricanes, which tend to develop when surface water temperatures are 27.8° Celsius (82° Fahrenheit) or higher.
“Milton was an almost perfect case [for tornado formation]especially for Florida, given its guidance and timing.”
Milton also benefited from low vertical wind shear during its formation, meaning there was not much difference in wind speed or direction acting on Milton at different altitudes. This helped the storm grow vertically, going from a Category 1 hurricane to a Category 5 storm (with winds exceeding 175 miles per hour, or 282 kilometers per hour) in less than a day.
Hurricane season runs from June 1st to November 3rd, which means we could face a few more major storms in the Gulf of Mexico and Atlantic Ocean before it's all said and done. Both NOAA and Colorado State University predicted a much busier than average hurricane season, meaning the expected number of named storms, hurricanes, and major hurricanes was higher than the 1991 through 2020 averages.
Hurricane Milton created “near-perfect” conditions for tornadoes
Thompson said Milton's tornado frenzy boiled down to – sorry in advance for the clumsy cliché –perfect storm of factors.
For one thing, Hurricane Milton charted an untraditional path as it quickly grew from a Western Gulf hurricane to a Category 5 hurricane off Mexico's Yucatan Peninsula. Most hurricanes that hit Florida originate in the Atlantic – to the east or southeast – but Milton approached from the southwest, having formed in the far west of the gulf.
“Typically we’re talking about a few weak tornadoes” in the case of a tropical cyclone, Thompson said. But Milton's rapid expansion meant that as the storm moved into Florida, its outer spiral bands reached the state in the afternoon. “With a little sun in between,” the storm bands managed to heat up even more than normal. Combined with increasing winds, the atmospheric cocktail created a tornado threat.
“If you had the same movement [in the hurricane] and we make up in 9 to 12 hours, there's probably still a few tornadoes, but it's down a lot from what we had,” Thompson said.
But that's not all, Thompson said. North of central Florida, the atmosphere “equivalent to a weak frontal zone,” a cloudy region with cooler temperatures and rain. A common pattern of tornado formation occurs when storms come from the south and interact with a frontal zone, causing clusters of tornadoes.“Typically, the most favorable area for tornado storms in a hurricane is the side of the storm where you bring the warmer, moister air toward the poles,” Thompson said — basically the east or northeast side. The side of the storm least likely to cause thunderstorms — and therefore least likely to cause tornadoes — typically makes landfall first. But this was not the case with Milton.
With these storms moving north or northwest, the most likely tornado threat is near or after landfall, Thompson added. In Milton the opposite happened. Conditions favorable for the formation of tornadoes – those storms brought to the coast by warm, humid gusts of wind – came from the west, before the hurricane itself made its eastward march across the state.
Bottom line: the tornadoes were a particularly bad combination of a very unusual hurricane track, a rapid intensification and expansion of that storm, and the time of the arrival of those hurricane-force winds and storm clouds over an area already warmed by daytime temperatures.
Okay, wow. What's the good news?
There's not much to do here except that the storm has passed. We're not getting a Hurricane Harvey-style outage over Tampa Bay or Port St. Lucie that caused Houston to flood in 2017. There's no threat of tornadoes today — in fact, Thompson said, the “carcass” of the hurricane is pulling an area cooler and drier on its southern side, which is why today it is “relatively pleasant by Florida standards.”
But if future storms hit Florida from the west, rather than the south or east, you can expect a similar pattern to develop — especially if the storm approaches in the afternoon, and with sea temperatures as warm as they are. currently.
