[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 212051
TCDAT1

Potential Tropical Cyclone Sixteen Discussion Number   2
NWS National Hurricane Center Miami FL       AL162023
500 PM EDT Thu Sep 21 2023

High-resolution visible satellite imagery and surface synoptic
observations indicate that the disturbance has not yet acquired a
well-defined center of circulation.  There is a distinct
comma-shaped curved band of convection over the eastern portion of
the system, with moderate southwesterly vertical wind shear over
the area.  The current intensity is set at 30 kt based on surface
observations.

Since there is still no distinct center the initial motion, 360/7
kt, is an educated guess.  The dynamical model guidance suggests
that there may be some center re-formations during the next day or
two.  However, the system should move generally northward to
north-northwestward over the next couple of days while embedded on
the eastern side of a deep-layer trough over the eastern United
States.  The official forecast is close to the previous one and is
also close to the corrected dynamical model consensus.

Strong vertical wind shear is likely to persist over the system,
but the global models show strengthening before landfall.  This
intensification is probably at least partially due to baroclinic
energy sources.  In fact the ECMWF forecast suggests that the
system will retain at least some frontal cyclone characteristics
through landfall.  Nonetheless, the system is likely to cause
tropical-storm-force winds, locally heavy rainfall, and dangerous
storm surges over the warned areas in the southeastern and
mid-Atlantic United States.  Interests should be aware that
hazardous conditions will extend well away from the forecast center
locations.

Key Messages:

1. An area of low pressure is forecast to strengthen off the
southeastern U.S. coast and 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 a danger of life-threatening storm surge inundation
over portions of eastern North Carolina and southeastern Virginia,
including the Pamlico and Albemarle Sounds, and the lower
Chesapeake Bay, where Storm Surge Warnings are in place.  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  21/2100Z 29.2N  75.9W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  22/0600Z 30.8N  75.8W   40 KT  45 MPH...POTENTIAL TROP CYCLONE
 24H  22/1800Z 32.6N  76.0W   45 KT  50 MPH...POTENTIAL TROP CYCLONE
 36H  23/0600Z 33.8N  76.5W   50 KT  60 MPH
 48H  23/1800Z 35.6N  77.0W   50 KT  60 MPH
 60H  24/0600Z 37.3N  76.9W   35 KT  40 MPH
 72H  24/1800Z 38.7N  76.1W   30 KT  35 MPH...POST-TROPICAL
 96H  25/1800Z 40.0N  74.0W   25 KT  30 MPH...POST-TROPICAL
120H  26/1800Z...DISSIPATED

$$
Forecaster Pasch
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