The hurricane in my backyard

According to Chip Konrad, the director of the National Oceanic and Atmospheric Administration’s Southeast Regional Climate Center and an assistant professor of geography at the University of North Carolina, Florence’s historic winds are a “huge threat” to the region, especially in areas that lie farther inland, where trees and infrastructure are less accustomed to violent gusts.

In terms of lives lost, though, the biggest danger from Florence is more likely to come from flooding than high winds, Konrad said. Although Florence is clipping along at a steady 13 miles an hour through the Atlantic, it’s forecast to hit the brakes once it moves farther inland. That’s thanks to high-pressure air bands to the north and east of the storm that will prevent it from taking the usual hurricane track off the Eastern Seaboard. Konrad called the atmospheric setup “unusual” and “extreme.” While Florence is parked, it could unload up to 32 inches of rain onto parts of North Carolina and Virginia, which usually only see around 40 to 50 inches in a given year.

This halt-and-downpour scenario is reminiscent of what Houston faced last summer, and a pattern that will only get more likely as the world warms. During Hurricane Harvey, urban sprawl and an abundance of impermeable ground cover made it difficult for the torrential downpour, once dumped, to exit the city. In the Southeast, according to Konrad, steep hillsides and already waterlogged soil will similarly fail to absorb much of the rain Florence will bring.

Researchers are still counting the dead from Hurricane Maria.

But the Southeast’s more rugged terrain is likely to produce much different consequences than Houston suffered. “Flash floods are the real danger here,” Konrad told me, as opposed to pooling. All the excess water that doesn’t find its way into the ground will be sent quickly into valleys and ravines. That will likely mean sudden, dramatic flooding downstream, along with landslides.

If Florence makes it to the Appalachian Mountains, Konrad said, things will likely get even worse: The topography will force the storm’s clouds upward, resulting in an effect called “orographic lift” that will wring even more precipitation from the storm. It’s the same effect that makes the western flanks of the Rocky Mountains so wet, and dumps feet upon feet of snow along the Great Lakes’ eastern shores.

According to Konrad, Florence “has the potential to be the most destructive hurricane we’ve had in modern history for this region.” Feltgen, the National Hurricane Center spokesperson, said juxtaposing Florence with past storms would be a “fatal mistake,” because it could lead those in its path to underestimate the danger. But if the worst comes to pass, Florence may become the region’s standard of comparison for years to come.

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