Hurricane Sally Is a Slow-Moving Threat. Climate Change Might Be Why.

In Bayou La Batre, Ala., where Sally was already turning roads into rivers on Tuesday, Ernest Nelson, a retired commercial fisherman, reached a similar conclusion as he sought refuge under a house raised 10 feet off the ground on concrete pillars.

Storms were getting bigger and more intense, he said. Mr. Nelson, who had worked the water for decades, gave his basis for that belief: “No meteorologist. No college degree. Experience.”

On Tuesday, the National Hurricane Center reported that Sally’s translation speed, the rate at which it moves forward, was about 2 miles per hour, and that the storm was not expected to accelerate much as it moved northward in the Gulf of Mexico toward an expected landfall on Wednesday. It was stalling, in effect, as it approached the Mississippi coast.

But rather than serve as a source of comfort, its languid speed only intensified the unease: Sally is dangerous, meteorologists warned, precisely because it is so slow. Its lingering could translate into major flooding, with more rain than the region typically records over several months.

Hurricane Paulette, by contrast, was zipping along in the Atlantic on Tuesday with a translation speed of more than 25 m.p.h. after passing Bermuda two days earlier.

Other recent hurricanes have also stalled. A year ago, Dorian crawled over the Bahamas for a day and a half, causing widespread destruction from wind and storm surge. And Harvey, perhaps the best-known — and most costly — example of stalling, was no longer a hurricane by the time it slowed near Houston in August 2017. It had been downgraded to a tropical storm, but still it inundated the city and surrounding communities with four feet or more of rain over several days.