A once-in-200-years event: NC towns get a foot of rain in 12 hours

Parts of southeastern North Carolina were experiencing "life-threatening flash flooding'' Monday as a potential tropical system brought rain totals usually not seen in hundreds of years, weather officials said.

The towns of Carolina Beach, Boiling Springs Lakes and Southport received more than a foot of rain in the first 12 hours of Monday, the type of deluge that on average happens once every 200 years, said the National Weather Service's office in Wilmington, North Carolina. The 18-plus inches in half a day that dropped on Carolina Beach occurs "once every 1000 years!'' the office said.

Though the "low-pressure system" is not organized enough to be classified as a tropical storm and receive a name, the National Hurricane Center still warned about the storm's flash-flood potential and gusty winds, reported as high as 77 mph. As of 5 p.m. ET, the system carried sustained winds of 35 mph and was 45 miles west of Cape Fear, North Carolina.

“People have been dealing with flash flooding, tornado warnings, rough surf and beach erosion across the coastal Carolinas,'' AccuWeather meteorologist Bernie Rayno said "These are impacts you would expect from a named tropical storm. In every sense, that’s exactly what this system is.''

The NWS's Wilmington office said the flooding on some Carolina Beach roads was at least three feet deep. The office urged motorists to "never drive around barricades, and please do not drive through flooded roads,'' as it showed photos of people in vehicles doing just that.

The North Carolina Department of Transportation exhorted people in affected areas to avoid driving if possible, posting a photo of a collapsed and mostly submerged section of a street in Southport as the storm flooded dozens of roads.

The storm was predicted to move through the Carolinas from Monday evening through early Wednesday, and the heavy rainfall it caused could put the entire Mid-Atlantic region at risk of isolated floods, the NHC said.

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More: Tropical storm tracker: Cyclone in Atlantic could hit Carolinas Monday

Latest developments:

? The National Hurricane Center said the storm is expected to gain little strength before it makes landfall. It will weaken further as it moves inland until it dissipates on Wednesday, forecasters said.

? Elevated tides associated with the full moon, large swells and strong northeast winds are forecast to cause high tides along the coast leading to minor or moderate coastal flooding through early in the week, the weather service said. Additional storm development could also further increase the risk of more significant coastal flooding.

? Tropical Depression Gordon lost ferocity out in the Atlantic and weakened from a tropical storm, according to the National Hurricane Center. Gordon posed no threat to land, the weather service added.

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Tropical storm or not, 'impacts will be the same'

The storm impacting the Carolinas, known as Potential Tropical Cyclone Eight, has had maximum sustained wind exceeding the 39 mph required for it to be classified a tropical storm, but its center is too divided.

"It doesn't have a very defined center right now," AccuWeather lead hurricane expert Alex DaSilva said. To become a tropical storm, "it will need to essentially form a closed center of circulation," he said. He estimated the likelihood of that at around 70% on Monday morning.

Regardless of whether it becomes a tropical storm and is named, "the impacts will be the same," DaSilva said.

Those include possible dangerous flash floods from the heavy overnight rain expected from the Southeast to the Mid-Atlantic and winds traveling up to 60 mph in the Carolinas, according to DaSilva. Although not widespread, "there could be some power outages, some trees down," he said.

Tornadoes could pop up overnight, he said. "These tornadoes can develop very quickly, which can make them extra dangerous."

The storm could also cause erosion to the local beach – already vulnerable after Hurricane Debby battered the area last month. "The coastline is already kind of weakened by previous storms, so it's not going to take a whole lot to cause some pretty significant issues there," DaSilva said.

'Homegrown' storms spin up close to coastline

The storm system is "homegrown," meaning it formed quickly close to the coast, like most storms and hurricanes that hit the U.S. every year, according to Weather.com meteorologist Jonathan Erdman.

It's much rarer for hurricanes to form far out into the Atlantic before making landfall – just 10 of the 55 hurricanes that impacted the U.S. from 1995 to 2023 formed in the Atlantic between the Lesser Antilles and Africa, he wrote.

"Homegrown" storms can pose a greater threat, since they form close by, according to Weather.com. They are more common in the early part of the hurricane season, which stretches from the beginning of June through the end of November.

Some North Carolina schools close

Some schools in North Carolina did not open Monday because of the stormy conditions. Brunswick County Schools posted on Facebook that students should stay home, while teachers have an optional workday.

Brunswick Community College also shuttered its doors because of the severe weather. Classes were to take place remotely where possible. Students in Bladen, Columbus and Whiteville counties also took classes remotely.

-- Sherry Jones, Wilmington StarNews

Risk for swimmers on Outer Banks of North Carolina

The Outer Banks of North Carolina are known for currents that can be dangerous for swimmers. The storm heightened the risk, the weather service said Sunday, warning inexperienced swimmers to stay out of the water.

"Rip currents can sweep even the best swimmers away from shore into deeper water," the service warned. "Dangerous shore break can throw a swimmer or surfer head first into the bottom causing neck and back injuries."

Contributing: John Bacon and Thao Nguyen, USA TODAY

This article originally appeared on USA TODAY: Storm drops a foot of rain in 12 hours in North Carolina