Issued at 500 PM AST Fri Sep 19 2025
656 WTNT42 KNHC 192041 TCDAT2 Tropical Storm Gabrielle Discussion Number 11 NWS National Hurricane Center Miami FL AL072025 500 PM AST Fri Sep 19 2025 Gabrielle's cloud pattern has changed significantly since the last advisory. The previously noted shear pattern has changed to a curved convective band pattern, and the previously exposed low-level center has become at least partly covered by cirrus clouds spreading westward from the convection. This change suggests that the storm is starting to encounter the forecast decrease in vertical shear. At this time, this change has not led to an increase in the various satellite intensity estimates, so the initial intensity remains 45 kt. The initial motion is 300/10 kt. Gabrielle is on the southwest side of the subtropical ridge, and during the next 2-3 days it is expected to turn northward between the ridge to the east and and a mid-latitude trough over the eastern United States and the far western Atlantic. The track guidance remains fairly tightly clustered during this time, although the consensus models have shifted a little to the left since the last advisory. This part of the new forecast track is nudged a little to the left, but still lies east of the consensus models. After 3 days, Gabrielle is expected to recurve into the westerlies and accelerate northeastward. The guidance shows more spread during this time, with the GFS being to the left/north and faster than most of the guidance, while the ECMWF is to the right/south and slower. Despite the spread, the consensus models and the center of the guidance envelope are have changed little since the last advisory for this part of the forecast. Thus, the new forecast is similar to, but slightly slower than, the previous forecast. The reliable track models still show Gabrielle's center passing at least 130 n mi east of Bermuda in 60-72 h. However, interests on the island should continue to monitor Gabrielle's progress since NHC's average track error at 72 h is about 90 n mi, and hazards can extend well away from the center. There remains a 20-25 percent chance of tropical-storm-force winds occurring on Bermuda. Gabrielle is now forecast to be in a light-to-moderate shear environment for the next 72 h, which should allow strengthening that would be tempered mainly by occasional entrainment of dry air. The new intensity forecast has been tweaked a bit to show a peak intensity of 90 kt at 72 h. Extratropical transition should be underway by 120 h, and could be complete by that time if the cyclone takes a more northward track similar to the GFS. However, a more southward track similar to the ECMWF would delay transition, and based on the uncertainty the new intensity forecast keeps the system as a tropical cyclone at 120 h. KEY MESSAGES: 1. Gabrielle is forecast to become a hurricane by Sunday and pass east of Bermuda Sunday night and Monday. Interests on Bermuda should monitor Gabrielle's forecasts since it is too soon to specify the magnitude of potential wind and rainfall impacts. 2. Swells generated by Gabrielle are expected to reach Bermuda tonight and build through the weekend. These swells are likely to cause life-threatening surf and rip current conditions. FORECAST POSITIONS AND MAX WINDS INIT 19/2100Z 22.4N 56.6W 45 KT 50 MPH 12H 20/0600Z 23.5N 58.0W 45 KT 50 MPH 24H 20/1800Z 25.0N 59.4W 55 KT 65 MPH 36H 21/0600Z 26.8N 60.6W 65 KT 75 MPH 48H 21/1800Z 28.6N 61.4W 75 KT 85 MPH 60H 22/0600Z 30.6N 61.6W 85 KT 100 MPH 72H 22/1800Z 33.0N 59.9W 90 KT 105 MPH 96H 23/1800Z 38.1N 51.3W 90 KT 105 MPH 120H 24/1800Z 42.1N 38.4W 70 KT 80 MPH $$ Forecaster Beven
NHC Atlantic
