Residents of a small Islamorada neighborhood, only a few streets wide, were awoken late Sunday night to a sudden force of wind and rain so strong, many assumed it was a tornado.
But the strange weather event wasn’t a twister. Rather, it’s what officials at the National Weather Service in Key West have determined was a “microburst,” a term likely more familiar to any midwesterner than those who hail from a South Florida island chain.
Landscaping crews worked through the end of the week to clear damaged trees.
“It wasn’t a rotating thunderstorm, which is the type that we normally associate with a tornado,” said Jon Rizzo, the NWS Key West Warning Coordination Meteorologist.
But the microburst that quickly swept through the Plantation Key neighborhood around Indian Mound Trail brought on the kind of damage South Florida residents are all too familiar with: downed trees that toppled over fences, cars and at least one person’s roof.
But unlike a major hurricane, the damage from the event was highly concentrated.
“There’s houses here that have destruction and you walk 300 feet and there’s not even a leaf on the ground,” said Troy Johnson, owner of Artistic Lawn and Landscape.
Johnson and his crew worked until the end of the week to clear damage for several of his clients in the area. Johnson said that clearing damage from a surprise storm like this can get costly for residents with the price of clearing a tree coming between $1,400 and almost $3,000.
The microburst also caused power outages, which were restored by the Florida Keys Electric Cooperative. Emergency management did not need to activate on the county level, according to a county spokesperson.
“It just kind of zig-zagged right through here,” said resident Robert Klein. “I lived here all my life and I’ve never seen anything like it. I’ve been through hurricanes since 1960 on.”
READ MORE: A beginner’s guide to hurricane season in South Florida
NWS Key West estimates the wind speed for this microburst reached between 65 and 80 miles per hour.
Microbursts are common in the Midwest, Great Plains and parts of the interior mainland of the Southeast, according to Rizzo. But they’re few and far between in the Florida Keys. Rizzo said he’s seen events like this come through the Keys about every two to three years but they’ve typically formed in non-residential areas.
“It happened to occur in a densely populated area known for its forest canopy,” he said.
Why did this microburst form?
A microburst is an intense downdraft of sinking air. According to NWS Key West data, this one was formed because of a tropical heat wave bringing a layer of dry Saharan air and a high altitude low pressure system moving together over “vigorous thunderstorm activity.”
The dry air, which was about 10 to 20,000 feet above the ground, caused sudden evaporation of the rain and ice in the thunderstorm, which made the temperature drop quickly. That sent cool air rushing thousands of feet toward the ground that moved along the path of the storm.
“It is a form of straight line wind, but it's very concentrated and small in size,” Rizzo said. “It’s basically the size of the downdraft itself. It's not the size of the entire thunderstorm environment. And we call it a microburst because anything that's roughly about two-thirds of a mile to two and a half miles across fits that definition.”
All the factors for this microburst were coupled with a more buoyant than average atmosphere, meaning there was more available energy creating instability. It was about 33% more buoyant than a typical July evening, according to NWS data. There was also about three times more downward potential motion than areas like Atlanta or New Orleans that are more prone to microbursts in the summer.
“Looking back at the data, I haven’t seen something of this magnitude, getting winds near 80 miles an hour in several years,” he said.
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