31 August 2019

Dorian now near Category 5 intensity and threatening southeast U.S. coast

Dorian intensified dramatically on Friday and Friday night, and as of Saturday at 11am EDT it has peak sustained winds of 150 mph -- making it an extremely strong Category 4 hurricane, and just 10 mph shy of Category 5 status. Recall that two days ago it was 85 mph and one day ago it was at 110 mph. There is virtually nothing in its way.

Hurricane Dorian is centered about 415 miles east of West Palm Beach FL and moving toward the west at 8 mph.  Tropical storm force winds now extend an average of 105 miles from the center. It is headed for the western Bahamas on Sunday, and then is forecast to have significant impacts along Florida's east coast on Monday-Tuesday.  Beyond that, places further north into Georgia and the Carolinas should be starting to prepare for hurricane conditions by Tuesday-Wednesday.

Over the past few model cycles, the forecast tracks have generally slowed and nudged north.  This has been a consistent trend that all models agree on. That does not preclude the opposite trend from happening this weekend (not likely, but not impossible), and all of the Florida peninsula should still be prepared for at least tropical storm force winds on Sunday-Monday.  For now, the threat to south Florida has decreased, though it should be noted that south Florida was never even under a tropical storm watch and was always on the far southern periphery of the model guidance.

The map below shows the latest rainfall guidance over the coming week.  This is not welcome news to eastern SC and NC where Florence dumped record-breaking rainfall last September.

With this shift in model guidance, many more people are in harm's way.  A major hurricane tracking along the southeast coastline is a big problem.  And even if the center never technically crosses the coastline and makes landfall, strong winds will affect land, and storm surge will impact every coastal city along the way.  A direct major hurricane landfall in South Carolina (think Hugo 1989) or North Carolina (think Floyd 1999) would be catastrophic.

The map below shows the 50-member European model ensemble forecast tracks through the next 7 days:

The history of major hurricanes passing within 150 miles of Dorian's current position includes several "recurvers", but also some infamous names like Floyd '99, Andrew '92, Hugo '89, Gloria '85, and Betsy '65 that have all been retired.

Tracks of historic hurricanes that were all at least Category 3 intensity and within 150 miles of Dorian's location.
Elsewhere, the two waves near/over Africa are still favored by models to eventually develop, and the western one that's near Cabo Verde has a 60% chance of becoming at least a tropical depression in the next five days.  Most long-range model forecasts start recurving this to the north by the time it reaches 50W or so, but I'll continue to watch it closely. The next name on the list is Fernand.

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