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Monday, September 2

"One Mile Per Hour: Dorian’s Catastrophic Crawl Over the Bahamas"

From Bob Henson at the Weather Channel less than an hour ago:

At a glance:
Hurricane Dorian moved at just 1 mph on Monday across Grand Bahama Island.
It's quite unusual for a hurricane this strong to move so slowly over a populated area.
Dorian's stalling is exacerbating damage in Grand Bahamas Island.
Dorian is expected to speed up as it turns northward toward the Southeast U.S.


Hurricane Dorian came to a near-halt across Grand Bahama Island on Monday. From 4 a.m. to 2 p.m. EDT, Dorian moved at an average speed of about 1 mph.

What makes such a powerful storm move so slowly? And is it typical for a fierce hurricane, which boasted gusts of up to 220 mph on Sunday, to creep along more slowly than a toddler on a leisurely walk?

Dorian's eye has been centered just off the northern coast of Grand Bahama Island, which means some locations have been stuck in the fierce Category 4 winds of the storm’s southern eyewall for many hours. Dorian’s peak winds were 150 mph as of 2 p.m. EDT.

It isn’t uncommon for a hurricane to slow or stall, but it is very unusual for a hurricane this intense to linger for so long over a populated area.

Dorian’s slowdown is linked to a shift in the steering currents that were driving the storm west but will push it northward by Tuesday. Hurricanes typically slow down when making this sharp a turn, much as a driver needs to slow before making a hard right or hard left.

The slow motion has subjected parts of the island to a prolonged siege of storm surge and destructive winds. Officials said they were overwhelmed with distress calls and urged residents to find other means to stay alive.

In October 1998, Hurricane Mitch stalled for about a day over the island of Guanaja, only about 30 miles north of the coast of Honduras, as it weakened from Category 5 to Category 2 strength. Mitch ended up producing catastrophic rains and mudslides as it moved into Honduras, causing more than 11,000 deaths.

Across the globe, hurricanes have been slowing down on average, a trend associated with climate change in a 2018 study led by James Kossin (NOAA). The study found the average hurricane motion has slowed by about 10% since 1949.


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