Tropical Storm Debby Discussion Number  25
NWS National Hurricane Center Miami FL       AL042024
1100 AM EDT Thu Aug 08 2024

Debby continues to move farther inland with the center now located
over northern South Carolina.  Surface observations and radar data
indicate that the strongest winds are likely occurring near the
coast and just offshore of southern North Carolina.  The highest
sustained winds during the past couple of hours from reliable
surface observation sites are near 30 kt with higher gusts.  Based
on the decreasing observed wind speeds, the initial intensity is 
lowered to 35 kt for this advisory.  By far, the most significant 
threat with Debby continues to be flash flooding from heavy 
rainfall.

Debby is starting to accelerate toward the north-northwest, with the 
current motion estimated at 345/9-kt.  A ridge that is currently 
strengthening over the western Atlantic will cause Debby to 
accelerate northward, moving across central North Carolina this 
evening.  Then, a deep-layer trough will approach the Great Lakes 
region on Friday, which will cause Debby to accelerate northeastward 
over the Mid-Atlantic and Northeast U.S. Friday and Friday night and 
then over Atlantic Canada on Saturday.  There are only minor changes 
to the track forecast, hedging toward the latest consensus models.

Debby should continue to weaken as it moves farther inland, and most 
of the models indicate that the winds near the coast should decrease 
a bit more later today.  Debby is expected to weaken to a tropical 
depression by this afternoon or evening.  Model phase space diagrams 
show that Debby should complete transition to an extratropical 
cyclone in about 24 to 30 h.  The current satellite imagery shows 
that Debby is already starting to interact with the jet stream, 
which extends toward the east-northeast over the North Atlantic. 
Debby is now expected to complete extratropical transition in about 
24 h as the cyclone merges with a cold front while over the 
mid-Atlantic states.  Beyond Friday, models show a post-tropical 
Debby becoming extremely elongated along the cold front, which will 
eventually lead to dissipation.  The new NHC forecast has Debby 
dissipating Sunday morning, but that could occur sooner.


Key Messages:

1. Heavy rainfall across portions of the Carolinas is expected to
persist through today along with areas of considerable flooding.
Heavy rainfall will also result in considerable to locally
catastrophic flooding impacts across portions of the Mid-Atlantic
States and Northeast through Saturday morning.

2. Tropical storm conditions will continue for several more hours in
the Tropical Storm Warning area along the coast of northeastern
South Carolina and portions of North Carolina.

3. Coastal flooding due to storm surge is likely to continue along
portions of the North Carolina coastline for several more hours.


FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 34.5N  79.9W   35 KT  40 MPH...INLAND
12H  09/0000Z 35.8N  79.9W   30 KT  35 MPH...INLAND
24H  09/1200Z 38.7N  78.8W   30 KT  35 MPH...POST-TROP/EXTRATROP
36H  10/0000Z 42.8N  75.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
48H  10/1200Z 47.0N  69.3W   30 KT  35 MPH...POST-TROP/EXTRATROP
60H  11/0000Z 50.7N  61.9W   30 KT  35 MPH...POST-TROP/EXTRATROP
72H  11/1200Z...DISSIPATED

$$
Forecaster Hagen/Cangialosi