Hurricane Florence is moving relentlessly toward the Southeastern U.S. It's a large, powerful cyclone that will likely bring storm surge and high winds to coastal communities.
But climate scientists say one of the biggest threats posed by Florence is rain.
"Freshwater flooding poses the greatest risk to life," explains James Kossin, an atmospheric scientist for the National Oceanic and Atmospheric Administration and the University of Wisconsin, Madison. And Florence could cause extensive freshwater flooding for two reasons.
First, Florence is moving slowly and could all but stop when it reaches land.
"The storm could be over North Carolina and traveling incredibly slowly — on the order of just a few miles per hour," explains Kossin, who says an official from the city of Charlotte, N.C., contacted him about rainfall projections for that city.
If Florence stalls over the Southeast, it would be reminiscent of Hurricane Harvey, which spent days dumping rain on the Houston region last year. Some areas ended up with more than 60 inches, a catastrophic amount of water that shut down the entire region and resulted in at least 93 deaths.
Slow-moving storms like Harvey are getting more common. A study published earlier this year by Kossin found that tropical cyclones around the world have slowed down 10 percent in the past 70 years.
"We're seeing that in every ocean basin except the northern Indian Ocean," says Kossin, possibly because climate change is causing the wind currents that hurricanes ride to slow down. If Florence slows down and stalls when it hits land, it will be the latest example of that trend.
Kevin Trenberth of the National Center for Atmospheric Research in Boulder, Colo., says global warming also affects the size and intensity of storms like Florence.
"We have global warming, and so this actually makes these storms bigger and more intense," he explains. Humans burn fossil fuels in our cars, our power plants and our airplanes, all of which release greenhouse gases that trap heat. Warmer oceans, especially, provide fuel for hurricanes in the form of evaporating moisture.
"The oceans are warmer now than they've ever been, and they're going steadily upwards," Trenberth explains. In a study published in May, he and colleagues found rain from Hurricane Harvey was powered by the highest ocean temperatures ever recorded in the Gulf of Mexico.
Right now, the part of the Atlantic under Florence is slightly warmer than usual, and the area north of the storm is significantly above normal, he says.
Together, the increased size and the slower forward motion of storms like Florence spell potential flood disaster for communities in their path. Florence could be like a faulty sprinkler, stuck watering one area for days on end.
"This idea, first of all, of a very strong hurricane making landfall is always going to be very, very bad news," says Kossin, "but then adding the potential for it to stall out once it hits land — that's a very, very frightening prospect to think about."
Florence, a Category 4 storm with winds of 130 miles per hour (210 kph), was expected to make landfall on Friday, most likely in North Carolina near the South Carolina border, the National Hurricane Center in Miami said.
U.S. President Donald Trump on Tuesday signed declarations of emergency for both North Carolina and South Carolina, freeing up federal money and resources for storm response.
“This storm is not going to be a glancing blow. This storm is going to be a direct hit on our coast,” said Jeff Byard, associate administrator for response and recovery at the Federal Emergency Management Agency.
“We are planning for devastation.”
The slow-moving storm was about 905 miles (1,455 km) east-southeast of Cape Fear, North Carolina, at 11 a.m. EDT, according to the NHC, which warned the storm was expected to strengthen with life-threatening storm surge possible along the coasts of North and South Carolina.
Residents boarded up their homes and stripped grocery stores bare of food, water and supplies. The South Carolina Highway Patrol sent “flush cars” eastbound on major highways to clear traffic before reversing lanes on major roadways to speed the evacuation.
“This is still a very dangerous storm. We must take it very seriously,” South Carolina Governor Henry McMaster said at a Tuesday news conference. “We are in a very deadly and important game of chess with Hurricane Florence.”
McMaster lifted an earlier evacuation order for parts of three southern coastal counties - Jasper, Beaufort and Colleton - but left them in effect for the state’s northern coast and urged residents to flee.
Duke University in Durham, North Carolina, said classes would be canceled after 5 p.m. on Wednesday, joining other colleges in the state making similar plans.
12-FOOT STORM SURGE
In addition to flooding the coast with wind-driven storm surges of seawater as high as 12 feet (3.7 m), Florence could drop 20 inches to as much as 30 inches (51 cm to 76 cm) of rain in places, posing the risk of deadly flooding miles inland, forecasters said. They warned the storm could linger for days after making landfall.
Wall Street was sniffing out companies that could gain or lose at the storm’s hands. Generator maker Generac Holdings Inc rose 2.2 percent and reached its highest price since April 2014.
Insurers Allstate Corp and Travelers Companies Inc were up slightly in early trade after falling sharply on Monday on worries about claims losses.
At least 250,000 more people were due to be evacuated from the northern Outer Banks barrier islands in North Carolina on Tuesday.
Vance McGougan, 57, of Fayetteville, North Carolina, and his family did not wait for the noon deadline to evacuate a rented house at Holden Beach, about two hours away.
“We had already decided ... that it was prudent for us to get on the road,” McGougan said.
Two years ago, when Hurricane Matthew crossed Fayetteville, McGougan said his house was without power for five days.
Classified as a Category 4 on the five-step Saffir-Simpson scale of hurricane strength, Florence is the most severe storm to threaten the U.S. mainland this year.
The United States was hit with a series of high-powered hurricanes last year, including Hurricane Maria, which killed some 3,000 people in Puerto Rico, and Hurricane Harvey, which killed about 68 people and caused an estimated $1.25 billion in damage with catastrophic flooding in Houston.
Additional reporting by Gene Cherry in Raleigh, North Carolina, Liz Hampton in Houston, Susan Heavey in Washington, Bernie Woodall in Fort Lauderdale, Florida, Alden Bentley in New York and Brendan O'Brien in Milwaukee; Writing by Nick Zieminski; Editing by Scott Malone and Bill Trott