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With wind speeds that have approached 140 miles per hour, Hurricane Florence isn’t exactly slow. But forecasters don’t expect the storm to blow through quickly once it reaches land.

Instead, they think it will stall, much as Hurricane Harvey did over Houston last year, besieging the area for days with wind and rain. That is part of the reason Florence is expected to be so dangerous.

Unfortunately, Florence and Harvey are not alone. Tropical cyclones, which include hurricanes, have grown more sluggish since the mid-20th century, researchers say.

A study published this summer in the journal Nature focused on what is known as translation speed, which measures how quickly a storm is moving over an area, say, from Miami to the Florida Panhandle. Between 1949 and 2016, tropical cyclone translation speeds declined 10 percent worldwide, the study says. The storms, in effect, are sticking around places for a longer period of time.