[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 210841
TCDAT3

Tropical Storm Claudette Discussion Number  15
NWS National Hurricane Center Miami FL       AL032021
500 AM EDT Mon Jun 21 2021

The elongated low-level center of Claudette is located over eastern
North Carolina this morning, while a curved band of convection
continues pushing eastward across the adjacent coastal and offshore
waters. Surface pressures have fallen slightly overnight near the
estimated center position, and Frying Pan Shoals buoy 41013 off the
coast of southeastern North Carolina reported a brief period of
sustained tropical-storm-force winds shortly after 06 UTC.
Therefore, Claudette's initial intensity is raised to 35 kt with
this advisory, making it a tropical storm once again.

Claudette continues to accelerate east-northeastward as it is
steered by a mid- to upper-level trough that is approaching the
eastern United States. The storm will move off the North Carolina
coast within the next few hours, and a bit more strengthening is
possible today as it passes near the north wall of the Gulf Stream.
The official NHC forecast hangs onto Claudette as a tropical cyclone
through tonight, then quickly transitions it to a post-tropical
cyclone by 36 h. The time of dissipation is also moved up a day
earlier with this advisory, which is consistent with the latest
global model fields that show an open trough approaching Atlantic
Canada. Otherwise, the official NHC forecast remains very similar to
the previous one, and the track closely follows the multi-model
consensus.

Some of the global guidance suggests that Claudette could lose its
closed low-level circulation and open up into a trough soon after
emerging into the western Atlantic Ocean later today.  Given the
current poor center definition, it is a plausible alternative
scenario that Claudette dissipates faster than shown below.


Key Messages:

1. Heavy rain from Claudette will continue over the North Carolina
coast this morning. Isolated flash, urban, and small stream
flooding impacts are possible.

2. Tropical storm conditions are expected along portions of the
North Carolina coast through this morning, where a Tropical Storm
Warning is in effect.


FORECAST POSITIONS AND MAX WINDS

INIT  21/0900Z 35.6N  77.6W   35 KT  40 MPH...INLAND
 12H  21/1800Z 37.0N  74.1W   40 KT  45 MPH...OVER WATER
 24H  22/0600Z 39.5N  68.6W   40 KT  45 MPH
 36H  22/1800Z 42.8N  63.3W   40 KT  45 MPH...POST-TROP/EXTRATROP
 48H  23/0600Z...DISSIPATED

$$
Forecaster Reinhart/Blake
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