• Once it is ashore, Florence’s drenching rains may cause “catastrophic flash flooding and significant river flooding” over a wide area of the Carolinas and the Mid-Atlantic states, the hurricane center said.
• President Trump promised on Wednesday morning that the federal government was “ready for the big one.” In a post on Twitter, Mr. Trump once again boasted about the government’s response last year to Hurricane Maria in Puerto Rico, where 3,000 people died.
A powerful storm on a rare track
It’s unusual for storms as strong as Florence to barrel straight at the North Carolina coast. The last Category 4 hurricane to do so was Hazel in 1954. That storm was famous for its destructiveness. Most storms that reach the coastal United States tend to track farther south, hitting Florida or entering the Gulf of Mexico.
“This could be an unprecedented disaster for North Carolina,” said Brian McNoldy, a senior research associate at the University of Miami, in a post Tuesday on his popular hurricane blog.
Storms that do follow a path across the Atlantic similar to Florence generally tend to turn north before they reach the coast. This year, though, an atmospheric phenomenon known as a blocking high spun off from the jet stream “like a swirl in the river that separates itself from the main flow,” has prevented Florence from making that turn, said Jennifer Francis, a research professor at Rutgers University.
A body of recent research suggests that disruptions to the jet stream — an apparent result of climate change — have weakened the currents that tend to move weather systems, Dr. Francis added. As a result, she said, “we are seeing this tendency for weather patterns to basically get stuck in place in the summertime,” whether it is drought in the West or the drenching summer rains in the Midwest this year.
The phenomenon, she said, “tends to take away the steering currents from a tropical storm coming into Texas, like Harvey, or a tropical storm heading toward the Carolinas, like Florence.”
A more populated, vulnerable coastline
In Carolina Beach, N.C., an island community south of Wilmington, about 75 percent of the residents had left, according to Michael Cramer, the town manager.
Mr. Cramer said he was worried about projections that Florence would be comparable to Hurricane Hazel, which nearly wiped his town of 6,200 year-round residents off the map in 1954. It destroyed 362 buildings there.
The coastline that Florence will plow into this week is, if anything, even more vulnerable. Americans have flocked to the nation’s shores and built extensively in recent decades, ensuring that any modern storm will damage much more property than those of previous generations.
The trend has also put many more people directly in harm’s way. In 2010, 123 million people, or 39 percent of Americans, lived in counties directly on the shoreline. That’s a 40 percent increase since 1970. The 2020 census is expected to show that figure growing by 10 million people.
That growth has occurred as climate change has made the coasts more vulnerable. Gabriel Vecchi, a climate scientist at Princeton University, noted that a rising sea level adds to the destructiveness of storm surges, and a warming atmosphere holds more moisture, leading to more rain.
“Right now, I would focus on everybody getting safe, and away from Florence,” Dr. Vecchi said. “But afterward, there’s other questions that need to be asked.”
Trump again says the government did a ‘great job’ in Puerto Rico
President Trump took to Twitter on Wednesday morning to assure people in the storm’s path that the federal government was prepared for the storm.
But, as he had on Tuesday at the White House, he also boasted about the government’s response last year to Hurricane Maria in Puerto Rico, where 3,000 people died.
He called the government’s work there “an unappreciated great job” and Mayor Carmen Yulín Cruz of San Juan, who has complained about the government’s poor response, “totally incompetent.”
Speaking after Mr. Trump’s initial comments on Tuesday, Jose Andrés, a Spanish chef who organized an emergency feeding program on the island after Maria — and butted heads with federal authorities while doing so — said the president’s comments were “astonishing.”
Forecasters lament dangerous misconceptions
Forecasters and public officials will try just about anything to get residents to flee coastlines ahead of a hurricane. Last year, as Hurricane Harvey barreled toward the Gulf Coast, the mayor pro tem of Rockport, Tex., said people who insisted on staying should “mark their arm with a Sharpie pen — put their Social Security number on it and their name.”
Fearing that Hurricane Florence could also be deadly, the governors of the Carolinas and Virginia ordered evacuations this week in many coastal counties.
The storm “will affect each and every one of you,” said Gov. Roy Cooper of North Carolina on Tuesday, as he ordered what he believed was the first state-mandated evacuation of the state’s barrier islands. “The waves and the wind this storm may bring is nothing like you’ve ever seen.”
But experts know that not all residents will heed the warnings, and some say part of the reason is that storm forecasts and risks are inadequately communicated to the public. Here are some common misconceptions, and recommendations for how forecasts could be improved to remedy them.