Issued at 500 AM AST Sun Sep 21 2025
000 WTNT42 KNHC 210842 TCDAT2 Tropical Storm Gabrielle Discussion Number 17 NWS National Hurricane Center Miami FL AL072025 500 AM AST Sun Sep 21 2025 Gabrielle has become slightly better organized overnight. The large convective band over the eastern side of the system has persisted, and within the last few hours deep convection has been bursting over the low-level center. There have been no microwave passes since the previous advisory, to determine if the inner core has been able to close off on the southwestern side. Satellite intensity estimates from TAFB and SAB were both T/3.5 or 55 kts. Latest objective AiDT, DPRINT, and DMINT intensity estimates from UW-CIMSS range from 52 to 58 kt. Using these estimates, the intensity is held at 55 kt for this advisory, although that could be conservative given recent convective burst. An Air Force Reserve Hurricane Hunter aircraft is en route to investigate the storm and will provide important details on the intensity and structure of the system. The storm is moving north-northwestward at an estimated motion of 335/8 kt. The system continues to be steered by a subtropical ridge over the Central Atlantic. Over the next few days, Gabrielle will begin to recurve to the north and eventually northeast between the western periphery of the ridge and a trough moving offshore the east coast of the United States. Track models remain tightly clustered and keep Gabrielle well east of Bermuda on Monday. As Gabrielle becomes steered within the west-southwesterly wind flow, the system will accelerate across the Atlantic. By day 3 of the forecast period, there is some along track model spread with differences in the forward speed of the system. The NHC track forecast is near the previous in the short term, but some minor adjustments to slow down the previous forecast towards the consensus aids were made between day 3-5. The environment surrounding the system is favorable for strengthening over the next couple of days, with light to moderate wind shear, warm sea surface temperatures, and slightly better mid-level relative humidity values. As Gabrielle looks to be establishing an inner core, it should begin to strengthen. The NHC intensity forecast follows these trends although the intensity guidance has continued to trend not as aggressive due to how long the system has taken to establish an inner core, and the peak intensity forecast has been lowered to 85 kt, which remains near the higher end of the guidance envelope. In about 48 h, westerly shear will begin to increase and sea surface temperatures will begin to cool along the forecast track, thus a weakening trend is forecast. The long-range forecast along track uncertainty makes it difficult to assess whether Gabrielle will fully complete extratropical transition by the end of the period. KEY MESSAGES: 1. Gabrielle is forecast to become a hurricane later today and pass east of Bermuda on Monday. While the chances of impacts are decreasing, interests on Bermuda should continue to monitor forecast updates since some wind and rainfall impacts are still possible. 2. Swells generated by Gabrielle will continue to affect Bermuda during the next few days. These swells are expected to reach the east coast of the United States from North Carolina northward, as well as Atlantic Canada, beginning later today and continuing through early this week. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 27.2N 60.0W 55 KT 65 MPH 12H 21/1800Z 28.3N 60.9W 65 KT 75 MPH 24H 22/0600Z 29.9N 61.6W 75 KT 85 MPH 36H 22/1800Z 31.5N 61.3W 80 KT 90 MPH 48H 23/0600Z 33.1N 59.7W 85 KT 100 MPH 60H 23/1800Z 34.5N 56.8W 80 KT 90 MPH 72H 24/0600Z 35.4N 52.9W 70 KT 80 MPH 96H 25/0600Z 36.9N 41.7W 60 KT 70 MPH 120H 26/0600Z 40.0N 29.0W 55 KT 65 MPH $$ Forecaster Kelly
NHC Atlantic