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WTNT41 KNHC 220834

TCDAT1

 

Potential Tropical Cyclone Sixteen Discussion Number   4

NWS National Hurricane Center Miami FL       AL162023

500 AM EDT Fri Sep 22 2023

 

The low pressure system off the southeast U.S. coast is gradually 

organizing and strengthening this morning.  The cyclone is 

developing subtropical characteristics with deep convection 

consolidating on the system's north side and the center gaining 

definition, but there are still some frontal features associated 

with it.  NOAA buoy 41002 well off the coast of Cape Hatteras has 

seen a significant pressure drop during the past several hours, and 

the latest report was down to 1002 mb with 30-kt winds.  A 

saildrone measured winds of 32 kt well northeast of the center 

several hours ago.  Based on these pressure and wind observations as 

well as satellite intensity estimates, the initial intensity is 

increased to 45 kt.  Based on recent trends, it seems likely that 

the low will become a subtropical or tropical cyclone later today.

 

The system has been moving erratically overnight, but recent

satellite images suggest that it is now moving northward at about 7

kt.  A northward to northwestward motion is expected during the next

couple of days as the system moves on the west side of a subtropical

high, taking the cyclone inland over eastern North Carolina early

Saturday and over portions of the Mid-Atlantic Saturday night

and Sunday. The NHC track forecast is quite similar to the previous

one and not far from the GFS and ECMWF models.

 

The notable strengthening that has occurred overnight is due to a

combination of baroclinic influences from the mid- to upper-level

trough just to the west of the system and the warm Gulf Stream

waters.  The system will likely strengthen a little more before it

reaches the coast of North Carolina.  After landfall, land

interaction, dry air, and strong shear should lead to weakening and

cause the system to transition back to an extratropical low in a

couple of days.

 

It should be noted that the cyclone has a large wind field, and

tropical-storm-force winds will begin well ahead of the center.

 

Key Messages:

 

1. Low pressure off the southeastern U.S. coast is producing

a large area of tropical-storm-force winds and is forecast to

strengthen further before it reaches the coast of North Carolina

early Saturday.  Tropical storm conditions are expected along

portions of the southeastern and mid-Atlantic U.S. coasts within

the Tropical Storm Warning area beginning later this morning and

continuing into Saturday night.

 

2. There is a danger of life-threatening storm surge inundation

over portions of eastern North Carolina and southeastern Virginia,

including 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. 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 through Sunday.

 

4.  Swells generated by this system will affect much of the U.S.

east coast through the weekend, likely causing life-threatening

surf and rip currents.

 

 

FORECAST POSITIONS AND MAX WINDS

 

INIT  22/0900Z 30.5N  75.0W   45 KT  50 MPH...POTENTIAL TROP CYCLONE

 12H  22/1800Z 31.6N  75.8W   50 KT  60 MPH...TROPICAL CYCLONE

 24H  23/0600Z 33.4N  76.5W   50 KT  60 MPH

 36H  23/1800Z 35.3N  76.8W   45 KT  50 MPH...INLAND

 48H  24/0600Z 37.0N  76.9W   35 KT  40 MPH...INLAND

 60H  24/1800Z 38.3N  76.3W   30 KT  35 MPH...POST-TROP/EXTRATROP

 72H  25/0600Z 39.0N  75.2W   30 KT  35 MPH...POST-TROP/EXTRATROP

 96H  26/0600Z...DISSIPATED

 

$$

Forecaster Cangialosi