The Slatest

Why a Downgraded Hurricane Florence Is Still Incredibly Dangerous

High waves crash around a pier in front of a gray, stormy sky.
Waves created by the outer edges of Hurricane Florence crash around the Oceana Pier on Thursday in Atlantic Beach, North Carolina.
Chip Somodevilla/Getty Images

The outer bands of Hurricane Florence have begun lashing the coasts of the Carolinas, but as experts continue to urge any reluctant residents to evacuate while they can, some of what appears to be good news has developed: The storm has been downgraded to a Category 2.

Meteorologists, however, are urging people to not become complacent. A Category 2 might sound mild, but the category measurements are only meant to mark peak wind speeds near the center of the hurricane. Winds are a defining part of a hurricane, yes. But one of the elements of Florence that has experts particularly worried is the amount of water it is going to drop, and push up, onto dry land. And somewhat lower wind speeds aren’t going to alleviate that problem.

Florence is, after all, massive. The region of hurricane-force winds (74 mph or greater) has expanded to 80 miles from the eye, and tropical-storm winds reach out 195 miles from the center. According to the New York Times, the cloud coverage from the storm is as large as the Carolinas themselves. Satellite image comparisons show the hurricane dwarfing 1989’s Hurricane Hugo, which caused more than 80 deaths:

The sheer size of Florence is enough to terrify experts, as the huge storm means huge amounts of rain. But compounding that is the storm’s speed, or lack thereof. Florence is lumbering toward the coast at a tortuous 10 miles per hour, and it is expected to continue to slow down further, according to the National Hurricane Center. That means when it does make landfall on the Carolinas this evening, it will linger dangerously long, unloading flood-inducing rains for days.

And the amount of rain Florence is expected to drop is shocking: One meteorologist put it at 10 trillion gallons over the next week in North Carolina alone. Deadly flash floods—the second leading direct cause of death from hurricanes—are essentially a guaranteed, experts warn. Wide areas of the Carolinas are expected to get 20 inches of rain or more, and according to the National Hurricane Center, some isolated spots will receive as much as 40 inches. The storm, as the Weather Channel explained, may be a Category 2, but it will have the floods of a Category 5.

On top of the rainfall, the storm surge is now thought to be even more dangerous than previously predicted. While it will be hard to know just how bad the surges will be without knowing the exact timing of the hurricane’s landfall with the tides, the National Hurricane Center has said the storm could push water as high as 13 feet above ground in places—meaning entire first floors could be submerged.

But the Category 2 designation should also not let anyone assume the winds will be manageable. As the Washington Post explained, the category measures top sustained winds in “a very narrow core” near the storm’s center. The storm has grown, and as a result, the areas to be affected by hurricane winds have expanded.

The strength of the winds matter, but so does the duration of the winds. Just as its slow pace threatens dangerous levels of rainfall, Florence’s lengthy assault will mean structures will weaken and damage will expand. By the time the storm’s center makes landfall with the worst winds on Friday, homes and buildings will have been buffeted by hurricane winds for hours. Trees will fall, and power will be knocked out, likely for millions of people.

While the storm is expected to thrash the Carolina coasts Thursday night, its exact path is still unpredictable. It is expected to hit North Carolina’s Outer Banks, before churning south across South Carolina and possibly even into Georgia before turning northward again Sunday or Monday. Experts are warning everyone in the storm’s path—including those in inland areas, where residents might feel comfortably insulated from hurricane devastation—to be prepared for catastrophic flooding.