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| #1245610 (Received by flhurricane at: 4:54 PM 21.Sep.2025) TCDAT2 Hurricane Gabrielle Discussion Number 19 NWS National Hurricane Center Miami FL AL072025 500 PM AST Sun Sep 21 2025 We are fortunate to have three NOAA aircraft (two P3`s and one G-IV) which are conducting research missions into Gabrielle this afternoon. The data they have provided has been valuable, showing the storm has become better aligned in the low to mid-levels compared to this morning, though the eyewall structure has been coming and going due to occasional dry air mixing out near the cyclone`s core. The highest 750 mb flight-level winds were up to 70 kt, which using a typical 0.85 reduction supports 60 kt. However, the Tail Doppler Radar (TDR) on board one of the NOAA-P3 aircraft showed a swath of 0.5 km winds up to 79 kt in the eastern semicircle at 1741 UTC. Using a more conservative 0.80 reduction factor for this level supports an intensity of 65 kt, and Gabrielle has become a hurricane. Recon fixes this afternoon show that the hurricane is beginning to turn more north-northwest, with the estimated motion now at 330/9-kt. The track reasoning in the short-term remains the same as this morning, with Gabrielle rounding the western edge of the subtropical ridge, which should allow the hurricane to turn northward and then northeastward over the next couple of days. There was another small adjustment west in the track over the next 24 h, but this still keeps Gabrielle`s wind field well to the east of Bermuda when it passes its latitude towards the end of the day Monday. Thereafter, the hurricane should begin to gradually accelerate in the westerly flow around the north side of the aforementioned ridge. The biggest change in the track forecast towards the end of the period is that the guidance continues to shift a little more southward, especially the most recent 12 UTC ECMWF, which shifted closer to the Azores in 4-5 days. For now, the NHC track forecast will only be shifted a little southward this cycle, choosing to stay closer to the reliable consensus aids TVCN and HCCA, though it`s possible some southward adjustments will be needed in subsequent forecasts. While the structure of Gabrielle on geostationary satellite is still a little ragged with warmer cloud tops than this morning, it has become more axis-symmetric, and a recent AMSR2 microwave pass at 1733 UTC indicates a thicker 37-GHz cyan ring than the one observed this morning. 18 UTC DTOPS guidance, which did well predicting Erin`s rapid intensification period earlier this year, is now indicating a 62 to 76 percent chance of a 30 kt increase in intensity over the next 24 h. Thus, I see no reason to not forecast continued steady to rapid intensification over the next 24-36 h, which is in line with the higher end of the intensity guidance, but not as high as the most recent HAFS-A run. After 36 h, SHIPS guidance shows southwesterly shear steadily increasing, and this should lead to steady weakening through the end of the forecast period. There is still some question as to Gabrielle`s structure at the end of the forecast and whether it will be losing tropical characteristics. The southward shift in the forecast track suggests it might hang on to tropical characteristics a little longer than originally expected. The intensity forecast falls back close to the IVCN and HCCA consensus aids by the end of the forecast period. KEY MESSAGES: 1. Gabrielle is now a hurricane, but is still expected to pass east of Bermuda on Monday. While the chances of impacts are still 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 now reaching the east coast of the United States from North Carolina northward, as well as Atlantic Canada, and should continue 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 21/2100Z 28.5N 61.7W 65 KT 75 MPH 12H 22/0600Z 29.7N 62.2W 80 KT 90 MPH 24H 22/1800Z 31.2N 62.0W 95 KT 110 MPH 36H 23/0600Z 32.7N 60.6W 100 KT 115 MPH 48H 23/1800Z 34.2N 57.7W 90 KT 105 MPH 60H 24/0600Z 35.2N 53.4W 80 KT 90 MPH 72H 24/1800Z 35.8N 47.6W 70 KT 80 MPH 96H 25/1800Z 37.5N 36.0W 60 KT 70 MPH 120H 26/1800Z 41.5N 25.1W 55 KT 65 MPH $$ Forecaster Papin |
