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Hurricanes Are Lingering Longer. That Makes Them More Dangerous.

June 6, 2018

With wind speeds that can top 180 miles per hour, hurricanes are not usually thought of as slow. Yet tropical cyclones, which include hurricanes, have grown more sluggish since the mid-20th century, researchers say. That may mean bad news for people residing in their path.

A study published Wednesday in the journal Nature focuses 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.

Lingering hurricanes can be a problem, as Texans learned last year when Hurricane Harvey stalled over the state, causing devastating flooding and billions of dollars of damage. The storm dropped more than 30 inches of rain in two days and nearly 50 inches over four days in some places. A report released this month by Harris County, which includes Houston, found that Harvey’s rainfall exceeded every known flooding event in American history since 1899.

The really, really high rainfall totals were because the storm moved so slowly,” said Deanna Hence, a professor of atmospheric sciences at the University of Illinois at Urbana-Champaign, who was not involved in the new research. “The large amount of rain that is going to come out of a tropical storm or hurricane anyway fell in the same place over a long period of time.”