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| #1246219 (Received by flhurricane at: 4:45 AM 27.Sep.2025) TCDAT4 Potential Tropical Cyclone Nine Discussion Number 3 NWS National Hurricane Center Miami FL AL092025 500 AM EDT Sat Sep 27 2025 Satellite imagery this morning shows an increase in vorticity at the western edge of a convective cluster located near the Ragged Islands in the Bahamas. However, this has not reached the stage where it could be called a well-defined center of circulation. Based on this, the system is continued as a potential tropical cyclone with maximum winds near 30 kt. The initial motion is a somewhat uncertain 315/6 kt. Later today, the system should turn north-northwestward between the subtropical ridge over the Atlantic and a deep-layer trough over the southeastern United States. The track models are in good agreement during this part of the system's life, and this portion of the new forecast track is almost the same as the previous track. After 72 h, the guidance continues to be quite divergent. Most of the deterministic and consensus models now show a turn toward the east caused by Hurricane Humberto passing to the east of the system and breaking down the ridge. However, the HMON and HAFS-A models still show landfall in the southeastern United States, as do several ECMWF and GFS ensemble members. Given the current guidance and the trends, the new forecast track calls for a slow turn to the northeast and east after 72 h, but at a much slower forward speed than most of the guidance. It should be noted that while this forecast keeps the system offshore, it would still be large enough and close enough to cause wind and coastal flooding impacts along the southeastern U.S. coast, as well as heavy rainfall/flooding concerns in inland areas. Based on current trends in the satellite imagery and the global models, the disturbance will likely take another 12-18 h to become a tropical cyclone. After that happens, strengthening is expected through 72 h as the system moves through an upper-level wind environment of moderate shear and strong divergence. The intensity forecast continues to show the system reaching hurricane strength in 3-4 days, which is in agreement with the intensity consensus. Some weakening is expected by 120 h due to shear and possible interaction with a frontal system approaching from the northwest. KEY MESSAGES: 1. The disturbance is forecast to become a tropical storm this weekend and bring tropical storm conditions to portions of the central and northwestern Bahamas, where Tropical Storm Warnings are in effect. 2. Rainfall associated with this system is expected to impact eastern Cuba, Hispaniola, Jamaica, and the Bahamas through the weekend, which will likely produce flash and urban flooding. Mudslides are possible in the higher terrain. 3. There is an increasing threat of heavy rainfall early next week from coastal Georgia through the Carolinas and into the southern Mid-Atlantic states, which could cause flash, urban, and river flooding. 4. The system is expected to be at or near hurricane intensity when it approaches the southeast U.S. coast early next week, where there is a risk of storm surge and wind impacts. Residents in that area should monitor updates to the forecast and ensure they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 27/0900Z 21.9N 75.8W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 27/1800Z 22.5N 76.4W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 24H 28/0600Z 23.8N 77.0W 35 KT 40 MPH...TROPICAL STORM 36H 28/1800Z 25.3N 77.5W 40 KT 45 MPH 48H 29/0600Z 27.0N 77.9W 50 KT 60 MPH 60H 29/1800Z 28.8N 78.5W 60 KT 70 MPH 72H 30/0600Z 30.2N 78.8W 65 KT 75 MPH 96H 01/0600Z 31.5N 78.7W 65 KT 75 MPH 120H 02/0600Z 31.5N 77.8W 55 KT 65 MPH $$ Forecaster Beven |
