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| #1245581 (Received by flhurricane at: 11:09 AM 21.Sep.2025) TCDAT2 Tropical Storm Gabrielle Discussion Number 18 NWS National Hurricane Center Miami FL AL072025 1100 AM AST Sun Sep 21 2025 Structurally, Gabrielle continues to become better organized, with cold convective cloud tops now finally starting to wrap around the circulation of the storm. In fact, earlier this morning, a WSF-M microwave pass revealed a cyan ring on the 37-GHz channel, which was supported by the most recent Air Force Reserve reconnaissance mission, which did indicate an eyewall, albeit still open to the east-southeast. Unfortunately the plane wasn`t able to complete a full pattern, and its possible the highest flight-level winds haven`t been sampled in the northeastern quadrant. For now the intensity will be held at 55 kt, in good agreement with the 12 UTC subjective Dvorak fix from TAFB and latest D-PRINT estimate from UW-CIMSS. The earlier recon flight found the center a little further west of the prior forecast track, but the estimated motion still remains northwestward at 320/10 kt. Gabrielle is rounding the western periphery of a subtropical ridge centered to its east, and thus should continue to turn northward and ultimately northeastward over the next 24-48 hours. In addition to a slight westward shift due to the initial position, the guidance has shifted a little slower again this cycle, and the NHC forecast track was nudged in that direction. However, this latest track still keeps Gabrielle well to the east of Bermuda when it passes its latitude in about 36 hours. Thereafter, the cyclone should begin to gradually accelerate in the westerly flow around the north side of the aforementioned ridge, and should ultimately be picked up by another mid-latitude trough digging into the central subtropical Atlantic in about 4-5 days. The latter portion of the NHC track forecast has been little changed, blending the reliable HCCA and Google Deep Mind (GDMI) aids. While the morning Air Force mission found that Gabrielle was still a bit tilted with height, recent satellite images suggest the low and mid-level centers are becoming better aligned as I write this passage. In addition, environmental conditions remain quite favorable in the short-term. While the SHIPS rapid intensification indices are not especially high, they are 2 times above climatology, and DTOPS is higher showing a 26-43 percent chance of a 25 to 30 kt increase in intensity over the next 24 h. Both HAFS-A/B are explicitly forecasting rapid intensification over the next 24 hours, and given the improving inner core structure, this seems like a reasonable prediction. Thus, the NHC intensity forecast will now forecast rapid intensification over the next 24 h, and peaking Gabrielle as a 95 kt hurricane in 36 h. This value is on the high side of the intensity guidance, but not as high as the latest HAFS-A/B runs which both show it becoming a major hurricane in 36 hours, and that remains a possibility. Thereafter, vertical wind shear out of the southwest markedly increases, and there is also dry air lurking in that region that will likely disrupt Gabrielle`s core, leading to weakening through the remainder of the forecast period. Gabrielle may be close to becoming extratropical at the end of the forecast as it begins to phase with an deep-layer trough forecast to be picking it up from the west. However, that appears to complete just beyond the forecast period. KEY MESSAGES: 1. Gabrielle is forecast to become a hurricane soon 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, starting 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 21/1500Z 27.7N 61.0W 55 KT 65 MPH 12H 22/0000Z 28.8N 61.8W 70 KT 80 MPH 24H 22/1200Z 30.3N 62.0W 85 KT 100 MPH 36H 23/0000Z 31.9N 61.3W 95 KT 110 MPH 48H 23/1200Z 33.3N 59.2W 90 KT 105 MPH 60H 24/0000Z 34.8N 55.5W 80 KT 90 MPH 72H 24/1200Z 35.6N 50.5W 70 KT 80 MPH 96H 25/1200Z 36.9N 38.4W 65 KT 75 MPH 120H 26/1200Z 41.0N 27.1W 60 KT 70 MPH $$ Forecaster Papin |
