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| #1246291 (Received by flhurricane at: 4:51 PM 27.Sep.2025) TCDAT4 Tropical Depression Nine Discussion Number 5 NWS National Hurricane Center Miami FL AL092025 500 PM EDT Sat Sep 27 2025 The organization of the depression has not changed much since this morning. Some deep convection has flared up this afternoon near the estimated center, which appears broad in the 850-mb flight-level wind data from the Air Force Hurricane Hunters. The earlier scatterometer winds and more recent aircraft data do not suggest the system has intensified. The initial intensity is held at 30 kt for this advisory. The center appears to be slightly south and west of previous estimates, with an uncertain initial motion of 315/4 kt. Over the next couple of days, the system should turn more north-northwestward within the flow between an upper trough over the southeast U.S. and a subtropical ridge over the Atlantic. This forecast brings the depression over the central and northwestern Bahamas through early Monday, then toward the southeast U.S. coast by Tuesday. The NHC track forecast is very similar to the previous one, with only a slight nudge westward based on the initial position adjustments during the day. Warm waters and strong upper-level divergence should promote strengthening during the next few days, but this could be tempered by moderate southerly shear over the system from an upper-level trough. The NHC intensity forecast shows steady strengthening through early next week, with the system becoming a hurricane by 60 h. This prediction lies close to the latest IVCN and HCCA aids. There is still above-average uncertainty in the details of the long-range forecast. In general, the models agree that the presence of Hurricane Humberto to the east will result in a weakening of the prevailing steering currents, causing the system to slow down and meander near the southeast U.S. coast on Tuesday. While the chances of a landfall appear lower than yesterday, there are still some hurricane regional models and ensemble solutions that show this possibility. Given the expected asymmetric storm structure, a risk of significant heavy rainfall, storm surge, and wind impacts exists for the southeast U.S. coast even if the storm center remains offshore. The increased track spread at 96-120 h is related to whether the system feels the effects of an amplifying upper-level trough behind Humberto over the western Atlantic. While many global models show a sharp eastward turn and acceleration away from land, the system fails to be captured by the trough in the 12z ECMWF and lingers offshore. The NHC track forecast at days 4-5 maintains a consensus approach and shows a slower eastward motion, but future track adjustments are likely as confidence increases. The system may be in close proximity to fronts by the end of the period, so extratropical transition could begin around or shortly after day 5. KEY MESSAGES: 1. The depression is expected to strengthen and bring tropical storm conditions to portions of the central and northwestern Bahamas through Sunday night. Tropical storm conditions are also possible along portions of the east coast of central Florida beginning Monday, where a Tropical Storm Watch is in effect. 2. Rainfall will continue 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 a significant threat of heavy rainfall early next week from portions of the east coast of Florida northward into the Carolinas, which could cause flash, urban, and river flooding. 4. The depression is expected to be at or near hurricane intensity when it is closest to the southeast U.S. coast early next week, where there is a risk of storm surge and wind impacts. Although it is too soon to specify the exact location and magnitude of impacts, residents should closely monitor the latest forecast updates and ensure that they have their hurricane plan in place. FORECAST POSITIONS AND MAX WINDS INIT 27/2100Z 22.2N 76.5W 30 KT 35 MPH 12H 28/0600Z 23.3N 77.1W 35 KT 40 MPH 24H 28/1800Z 24.9N 77.6W 45 KT 50 MPH 36H 29/0600Z 26.7N 78.1W 55 KT 65 MPH 48H 29/1800Z 28.5N 78.6W 60 KT 70 MPH 60H 30/0600Z 30.0N 78.8W 65 KT 75 MPH 72H 30/1800Z 30.8N 78.6W 65 KT 75 MPH 96H 01/1800Z 31.1N 76.8W 65 KT 75 MPH 120H 02/1800Z 31.5N 74.0W 60 KT 70 MPH $$ Forecaster Reinhart |
