The eye of the Category 4 storm was expected to pass between Bermuda and the Bahamas on Wednesday and arrive at the Carolina coast by Friday. But tropical storm-force winds, extending 175 miles from the center, were predicted to arrive on land by Thursday morning, giving more than 1 million people scarce time at that point to evacuate.

“Preparations to protect life and property should be rushed to completion,” the National Hurricane Center warned Wednesday morning.

The storm’s maximum sustained winds had eased slightly to 130 mph by Wednesday morning, but forecasters warned it was expected to strengthen later in the day. (It would be upgraded to Category 5 if the winds increased to 157 mph.)

In addition to powerful winds, a huge, “life-threatening storm surge” is highly likely on the low-lying coasts of North and South Carolina, the National Hurricane Center has predicted.

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.

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, Francis added.

This article originally appeared in The New York Times.

John Schwartz © 2018 The New York Times