Hurricane Florence: what we know about the powerful storm heading for the Carolinas

Hurricane Florence will impact the southeastern and mid-Atlantic United States as a major storm — potentially thrashing coastal areas stretching from South Carolina to northern Virginia with punishing winds, heavy rain, and life-threatening storm surge. More than a million people are being ordered to evacuate ahead of the storm. Hurricane warning — meaning hurricane conditions are imminent within 36 hours — have been issued from South Carolina to the North Carolina-Virginia border.

Currently, Florence is sustaining 130 mph winds, making it a Category 4 storm. It’s likely to near landfall Friday or Saturday in North Carolina as a Category 3, with winds around 120 mph.

“Florence has rapidly intensified into an extremely dangerous hurricane,” the National Hurricane Center warned Monday. And now it warns of life-threatening storm surge, flooding, and wind.

Coastal evacuations are underway. The entire South Carolina coast has been ordered to evacuate, the Post and Courier reports, starting Tuesday at noon. That will impact a huge number of people: “One out of every five South Carolinians, about 1 million in all, are in the evacuation zones,” reports the Post and Courier. “We are not going to gamble with the lives of the people of South Carolina,” the state’s governor, Henry McMaster, said Monday. Additionally, communities in the Outer Banks in North Carolina have issued evacuation notices in preparation, as well as parts Virginia near the shore.

It’s looking like the Carolinas won’t be able to escape impacts from the storm, but the exact forecast remains uncertain. Since forecasters are generally better at predicting the path of a storm than its intensity, Florence could easily weaken or get even stronger in the next few days. Forecasters are also worried that the storm will stall after it makes landfall, setting the stage for a lot of rain, and inland flooding, across the Mid-Atlantic. Regardless of its exact category number, Florence will remain a dangerous, life-threatening storm.

“It is important for users to realize that significant impacts extend well away from the center of Florence, and serious hazards such as a dangerous storm surge and flooding rains will cover a large area regardless of exactly where the center moves,” the National Hurricane Center reports.

The Carolina coast, while no stranger to hurricanes, does not often get threatened by a storm this powerful. And it’s somewhat unusual for a storm this powerful to be so far North. “North Carolina has never experienced a Category 4 or 5 hurricane landfall, and only three Category 3 landfalls on record,” Brian McNoldy, a University of Miami atmospheric scientist, writes. “Events such as this are infrequent — testing people, structures, vegetation, resources, and plans.”

Here’s the current forecast track from the National Hurricane Center

The worst impacts of the storm are most likely to be felt along the coast, where storm surge (a literal wall of water pushed onshore by the storm) can create dangerous flooding, and where winds will be the most severe. Storm surges may exceed 9 feet in some areas.

Here are the greatest areas of concern (see the whole interactive map here):

But heavy rains can cause dangerous flooding inland as well. Twenty inches are expected in coastal North Carolina. Some locations on the shoreline might see as many as 40 inches. “Catastrophic” flash flooding may occur.

As the Washington Post points out, much of the soil in the region is already saturated. “This makes it all the more likely that trees and power lines will come down as winds pick up, and flooding will begin soon after the rain begins,” the paper’s Capital Weather Gang writes.

Again, the exact site of Florence’s landfall is not yet known, but here’s what’s possible.

And here are the earliest arrival times of tropical storm-force winds.

These are the key messages the NHC’s forecasters want you to know:

1. A life-threatening storm surge is now highly likely along portions of the coastlines of South Carolina and North Carolina, and a Storm Surge Warning is in effect for a portion of this area. All interests from South Carolina into the mid-Atlantic region should complete preparations and follow any advice given by local officials.

2. Life-threatening, catastrophic flash flooding and significant river flooding is likely over portions of the Carolinas and Mid-Atlantic states from late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland.

3. Damaging hurricane-force winds are likely along portions of the coasts of South Carolina and North Carolina, and a Hurricane Warning is in effect. Strong winds could also spread inland into portions of the Carolinas.

4. Large swells affecting Bermuda and portions of the U.S. East Coast will continue this week, resulting in life-threatening surf and rip currents.

Florence is expected to slow down as it approaches the coast. That could lead to “a prolonged and exceptionally heavy rainfall event, which may extend inland over the Carolinas and Mid Atlantic for hundreds of miles.” Recall that slow speed and heavy rain were what made Hurricane Harvey such a devastating event for Houston last year, not the wind speed.

And it’s not just the coastal regions that have to be on the lookout. Inland flooding, particularly along creeks and rivers, may also become life-threatening.

Zachary Crockett/Vox

The tropics are extremely active right now

We’re currently at peak hurricane season. In September, the Atlantic Ocean is the hottest it gets all year — when it’s most conducive to hurricane formation.

Via Colorado State

And formed they have. In addition to Florence, in the Atlantic, there’s also Hurricane Isaac, which currently has 75 mph winds and may impact the southern Caribbean by the weekend.

NOAA

And Hurricane Helene, which looks like it’s going to stay safely out at sea.

NOAA

“The last time we saw three simultaneous hurricanes [in the Atlantic] was in 2017, and there were actually four simultaneous hurricanes in 1998,” McNoldy writes. “So this is active, but far from unprecedented.”

But that’s not all. Hurricanes form in tropical waters around the globe; in the Pacific, there’s Hurricane Olivia, which may impact Hawaii as a tropical storm later this week.

NOAA

There’s also a tropical storm called Paul off the coast of Mexico in the Pacific. It’s quite the active season across the globe.

In an email, McNoldy says it’s hard to call all this activity more than a coincidence. “Periods like this do happen,” he says. And he points out that overall, the Atlantic has been pretty quiet this year and is still behind average when it comes to hurricane formation. So now it just may be catching up.

How to follow Hurricane Florence:

• The National Hurricane Center has a page updating every few hours with the latest watches and warnings for Florence. Check it out.
• Follow the National Hurricane Center on Twitter; it will keep you up to date with all the latest forecasts, hazards, and warnings. Also follow its Charleston, South Carolina, branch.
• Follow the Capital Weather Gang’s Twitter account. These folks tend to live-tweet storm updates.
• Here’s a Twitter list of weather experts via meteorologist Eric Holthaus. These experts will give you up-to-the-second forecasts and warnings.

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