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| #1153855 (Received by flhurricane at: 5:05 PM 21.Sep.2023) 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 |