Issued at 1100 PM AST Wed Sep 17 2025
000 WTNT42 KNHC 180252 TCDAT2 Tropical Storm Gabrielle Discussion Number 4 NWS National Hurricane Center Miami FL AL072025 1100 PM AST Wed Sep 17 2025 The overall structure of Gabrielle hasn't changed too much. The cloud pattern of the cyclone consists of a large comma shape. GOES-19 CIRA proxy-vis imagery and a recent 17/2342 UTC ASCAT-B overpass clearly indicate that the surface wind center is at the bottom of the upper portion of the comma head. The strongest ASCAT wind vectors are the same magnitudes as the pass from 12 hours prior, so the intensity is held at 45 kt for this advisory. Gabrielle still has a very large and broad envelope of convection and winds. It is quite atypical to see a structure like this for a tropical cyclone in this part of the world. Strong westerly shear should continue on Thursday, then gradually abate at some point on Friday. The other factor that is detrimentally impacting Gabrielle is the very dry air seen on water vapor imagery in the open area of the comma, to the south and west of the center. Even after the shear abates, Gabrielle will continue moving through an environment of dry air through Friday, with moistening along its path over the weekend. The official intensity forecast has been decreased during the 24-48 h period, in agreement with most of the reliable intensity guidance. The new NHC intensity forecast is near the middle of the guidance envelope through 48 hours, then near the high end of the guidance thereafter, and still calls for Gabrielle to be a hurricane at days 4-5. The center has jogged westward since the previous advisory, but the longer term motion is estimated to be west-northwestward, or 300/14 kt. A similar motion is expected for the next couple of days, followed by a gradual turn toward the west-northwest as Gabrielle moves on the south side of a subtropical ridge. Over the weekend, the cyclone should round the southwestern periphery of the ridge and turn northwestward as it catches up to a slow-moving upper-level low that should be located just west of Gabrielle. A northward motion is expected in 4-5 days as Gabrielle gets closer to the mid-latitude westerlies, which should induce a northeastward turn in about 5 days. The new NHC track forecast is shifted significantly to the left (southwest) of the previous forecast through 72 h but near the previous track again at days 4-5. The forecast is in fairly good agreement with the Google Deep Mind ensemble mean through 72 h, then leans toward the HCCA Corrected Consensus at days 4-5. Track forecast confidence remains relatively low. This system should pass well east and north of the Leeward Islands, but interests in Bermuda should monitor forecasts during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 19.5N 49.5W 45 KT 50 MPH 12H 18/1200Z 20.3N 51.0W 45 KT 50 MPH 24H 19/0000Z 21.3N 52.9W 40 KT 45 MPH 36H 19/1200Z 22.2N 54.9W 40 KT 45 MPH 48H 20/0000Z 23.3N 56.9W 40 KT 45 MPH 60H 20/1200Z 24.5N 58.8W 45 KT 50 MPH 72H 21/0000Z 25.8N 60.3W 50 KT 60 MPH 96H 22/0000Z 28.9N 62.7W 65 KT 75 MPH 120H 23/0000Z 32.5N 62.0W 75 KT 85 MPH $$ Forecaster Hagen
NHC Atlantic
