[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 211503
TCDAT1

Potential Tropical Cyclone Sixteen Discussion Number   1
NWS National Hurricane Center Miami FL       AL162023
1100 AM EDT Thu Sep 21 2023

A broad non-tropical area of low pressure has formed well east of
the east coast of Florida this morning.  Although this system is
forecast to remain non-tropical during the next 12-24 hours, the
dynamical model guidance indicates that it will likely acquire
tropical characteristics late Friday and early Saturday as it
approaches the coast of North Carolina.  Although it is unclear as
to whether the cyclone detaches from a front that is forecast to
extend northeastward from the center, the guidance suggests a
tropical-cyclone like core and structure when it nears the coast.
As a result, advisories are being initiated on Potential Tropical
Cyclone Sixteen to issue Tropical Storm Warnings and Storm Surge
Watches for portions of the coasts of North Carolina, Virginia and
Maryland. Winds associated with the front farther north are being
covered by non-tropical products issued by local National Weather
Service offices and the Ocean Prediction Center.  Additional
tropical watches and warnings could be issued for other portions of
the Chesapeake Bay later today.

Since the low is still in its formative stage, the initial motion
estimate is a highly uncertain 360/8 kt.  The model guidance
suggests that center reformations are likely to occur during the
next day or so, but the overall motion of the system is expected to
be a little east of due north. As the system interacts with a
mid-latitude trough that it becomes embedded within, a bend toward
the north-northwest is forecast.  That motion should bring the
center over eastern North Carolina within the warning area Saturday
morning.  The NHC track forecast follows a blend of the various
global models that are in good agreement.

The system is forecast to gradually strengthen during the next 24
hours. After that time, the guidance suggests it is likely to form
a smaller inner core with additional strengthening expected until
the center reaches the coast.  The NHC intensity forecast follows
the ECMWF and GFS models trends.

Key Messages:

1. An area of low pressure is forecast to develop off the
southeastern U.S. coast later today and will bring
tropical-storm-force winds, storm surge, heavy rain, and high surf
to large portions of the southeast and mid-Atlantic United States
coast beginning Friday and continuing into the weekend.

2. There is the potential for life-threatening storm surge
inundation from Surf City, North Carolina to Chincoteague, Virginia,
the Pamlico and Albemarle Sounds, and the lower Chesapeake Bay.
Residents in these areas should follow advice given by local
officials.

3. Tropical storm conditions are expected within portions of the
southeast and mid-Atlantic coasts within the Tropical Storm Warning
area beginning on Friday and continuing into Saturday.

4. Heavy rainfall from this system could produce localized urban
and small stream flooding impacts across the eastern mid-Atlantic
states from North Carolina to New Jersey Friday through Sunday.

FORECAST POSITIONS AND MAX WINDS

INIT  21/1500Z 28.7N  75.9W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  22/0000Z 30.0N  75.5W   35 KT  40 MPH...POTENTIAL TROP CYCLONE
 24H  22/1200Z 31.7N  75.4W   45 KT  50 MPH...POTENTIAL TROP CYCLONE
 36H  23/0000Z 33.2N  75.6W   50 KT  60 MPH...TROPICAL CYCLONE
 48H  23/1200Z 35.1N  76.4W   50 KT  60 MPH...TROPICAL CYCLONE
 60H  24/0000Z 37.3N  76.4W   40 KT  45 MPH...TROPICAL CYCLONE
 72H  24/1200Z 38.8N  76.1W   30 KT  35 MPH...POST-TROPICAL
 96H  25/1200Z 40.4N  71.8W   25 KT  30 MPH...POST-TROPICAL
120H  26/1200Z...DISSIPATED

$$
Forecaster Brown
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