05 September 2019

Dorian regains major hurricane status near South Carolina coast

Composite radar image from 9am EDT. (CoD)
Hurricane Dorian has continued its northward trek along the southeast U.S. coast, and as of Thursday morning, is centered about 70 miles east of Charleston SC.  The maximum sustained winds are up to 115 mph (Category 3), and the tropical storm force winds extend an average of 145 miles from the center. The exact intensity/category does not matter much at this point: Dorian will be a powerful hurricane and will bring with it the full array of hurricane hazards (watch out for those fast-moving tornadoes in the rainbands).

The track forecast is shown below, along with the current wind field (green is the tropical storm force winds, yellow is the gale force winds, and orange is the hurricane force winds. As you see, the hurricane force winds will be very close to the SC and NC coastline, sometime onshore, sometimes offshore.

For arrival times of the dangerous tropical storm force winds, the map below show the most likely timing (line contours) along with the probability (colored contours).  Note that as of Thursday morning, the Delmarva peninsula is under a tropical storm warning and Cape Cod is under a tropical storm watch.  The full updated maps of hurricane, tropical storm, and storm surge watches and warnings can be found on the NHC website.

The National Weather Service's  HTI (Hurricane Threats & Impacts) graphics from Thursday morning break down the big four hurricane hazards onto maps: wind, flooding rain, storm surge, and tornadoes. When it comes to storm surge, keep in mind that the timing of the surge matters quite a bit: the flooding will be worse if peaks near high tide. Water will rise gradually for a while, then ramp up quickly as the strongest onshore winds approach.

You can keep an eye on the rainfall (and eyewall and rainbands) via long radar loops at http://bmcnoldy.rsmas.miami.edu/tropics/radar/

Dorian will pass the Outer Banks in NC by Friday afternoon, then by New England on Saturday, then continue northeast toward Nova Scotia on Saturday night.  Coastal flooding will likely be a problem all along the way as the storm's winds push water onshore ahead of it.

Since yesterday, Fernand made landfall in northeast Mexico and has since dissipated, Gabrielle is still a disorganized tropical storm far from land, and a wave that just left the African coast yesterday is showing signs of development. At this early stage, it appears likely that if this forms, it would turn north well before reaching land, but not as quickly as Gabrielle did. Long-range model guidance does not suggest that it would reach the Lesser Antilles.

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