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| #1192537 (Received by flhurricane at: 10:39 PM 06.Aug.2024) TCDAT4 Tropical Storm Debby Discussion Number 19 NWS National Hurricane Center Miami FL AL042024 1100 PM EDT Tue Aug 06 2024 Surface, satellite, and radar observations indicate that the center of Debby has emerged over the Atlantic southeast of Savannah, Georgia. The system is currently comprised of a large swirl of shallow to moderate convection with occasional patches of deep convection, particularly in bands to the east of the center. GOES-16 airmass imagery indicates that interaction with an upper-level trough has spread cool/dry air aloft over the low-level center, making the cyclone look somewhat subtropical. The initial intensity is held at 35 kt based on Doppler radar winds in the bands east of the center and a recent 1-minute wind of 31 kt at NOAA buoy 41008 to the southwest of the center. Dolly is moving slowly and somewhat erratically eastward, with the initial motion of 090/4. The track guidance continues to show a generally eastward motion for the next 12-18 h, taking the center a little farther away from the coast. After that, a building mid-level ridge should cause the system to turn northward and move back inland between 24-36 h. Subsequently, Debby is likely to accelerate northward and northeastward over the eastern and northeastern U.S. on the east side of an approaching mid-latitude trough. The new forecast track has been adjusted a little to the left of the previous track through 48 h to better match the consensus models, and it has been adjusted to the right during the extratropical phase to better match the global model guidance. The dry air aloft, the lack of an inner wind core, and the lack of deep convection suggest that Debby is at best going to strengthen slowly, and this scenario is supported by the majority of the intensity forecast guidance. The new intensity forecast calls for gradual strengthening until the cyclone makes landfall between the 24 and 36 h forecast points. Weakening is expected after landfall, with Debby expected to become post-tropical around 72 h and complete transition to an extratropical cyclone by 96 h. The new intensity forecast is at the high end of the intensity guidance through 36 h and near the intensity consensus after that. Key Messages: 1. Potentially historic heavy rainfall across portions of eastern South Carolina through Friday will likely result in areas of catastrophic flooding. Heavy rainfall will likely result in considerable flooding impacts from central to the Upstate of South Carolina, western North Carolina, Southwest Virginia through portions of Mid-Atlantic States, western and northern New York State and northern New England through Saturday. 2. Tropical storm conditions will spread northward along the southeast U.S. coast from South Carolina to North Carolina through Thursday. Tropical storm warnings and watches are in effect for portions of that area. 3. A dangerous storm surge is possible along the coast of South Carolina and southeastern North Carolina from South Santee River to Cape Fear. Residents in that area should follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 31.8N 80.2W 35 KT 40 MPH 12H 07/1200Z 32.0N 79.6W 40 KT 45 MPH 24H 08/0000Z 32.6N 79.5W 45 KT 50 MPH 36H 08/1200Z 33.4N 79.7W 45 KT 50 MPH...INLAND 48H 09/0000Z 34.7N 79.9W 35 KT 40 MPH...INLAND 60H 09/1200Z 36.9N 79.4W 30 KT 35 MPH...INLAND 72H 10/0000Z 39.9N 77.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 11/0000Z 47.1N 69.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 12/0000Z 51.5N 61.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven |
