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Potential Tropical Cyclone Eight Discussion Number 3
NWS National Hurricane Center Miami FL AL082024
500 AM EDT Mon Sep 16 2024
The structure of the area of low pressure off the coast of South
Carolina has seemingly become less organized during the past few
hours. Proxy-visible satellite imagery indicates that the
low-level circulation is elongated from northeast to southwest, and
the center has not become well defined. The associated deep
convection has a generally linear orientation and has been
displaced farther to the north and east of the center due to strong
upper-level winds. Lastly, an Air Force Reserve Hurricane Hunter
aircraft still measured a 2-3 degree Celsius temperature difference
at 850 mb from north to south, indicating that the frontal boundary
is diffuse but not totally gone. Therefore, the low is still not a
tropical or subtropical cyclone. That said, the plane measured a
peak wind of 54 kt at 6000 ft in the convection well northeast of
the center, suggesting that the current intensity is about 45 kt.
The low is drifting northwestward (325 degrees) at 3 kt, gradually
approaching the South Carolina coast. A faster motion toward the
northwest is expected to occur today as the low moves between
mid-level high pressure over the northeastern U.S. and a trough
over the southeastern U.S. The NHC track forecast shows the low
crossing the coast later this afternoon, which is shown by most of
the track models. The GFS remains the notable outlier since it
initialized the low too far to the northwest and consequently has
it crossing the coast around sunrise. After moving inland, the low
is expected to continue moving slowly northwestward and then
northward over the Carolinas through Wednesday. The new track
forecast has been nudged westward from the previous forecast,
although there is a modest amount of uncertainty given the
ill-defined nature of the center.
The chances of the system becoming a tropical or subtropical
cyclone may be starting to decrease given the current structure, and
since it only has another 12 hours or so before moving inland.
Most of the intensity guidance also suggests that the maximum winds
should gradually decrease as the low approaches the coast, although
tropical-storm-force winds are still expected to occur within the
warning areas today. Further weakening is forecast after the
system moves inland, and it will likely dissipate over the Carolinas
by late Wednesday.
Key Messages:
1. Tropical storm conditions are expected along portions of the
coasts of South Carolina and North Carolina within the Tropical
Storm Warning area through this evening.
2. The system will bring the potential for locally considerable
flash and urban flooding and minor river flooding across southeast
North Carolina and northeast South Carolina through tonight. There
is also a risk of isolated flash and urban flooding across much of
the Mid-Atlantic region through Wednesday.
3. Coastal flooding and high surf are likely along portions of
the southeastern U.S. coast over the next day or two.
FORECAST POSITIONS AND MAX WINDS
INIT 16/0900Z 32.4N 78.3W 45 KT 50 MPH...POTENTIAL TROP CYCLONE
12H 16/1800Z 33.0N 79.0W 40 KT 45 MPH...TROPICAL CYCLONE
24H 17/0600Z 33.7N 79.8W 30 KT 35 MPH...INLAND
36H 17/1800Z 34.5N 80.6W 20 KT 25 MPH...POST-TROP/REMNT LOW
48H 18/0600Z 35.2N 81.0W 15 KT 15 MPH...POST-TROP/REMNT LOW
60H 18/1800Z 35.7N 81.1W 15 KT 15 MPH...POST-TROP/REMNT LOW
72H 19/0600Z...DISSIPATED
$$
Forecaster Berg
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