000 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