Issued at 200 PM PDT Sat Oct 25 2025
000 WTPZ43 KNHC 252042 TCDEP3 Tropical Storm Sonia Discussion Number 5 NWS National Hurricane Center Miami FL EP182025 200 PM PDT Sat Oct 25 2025 Sonia appears to have become better organized during the past several hours. GMI microwave imagery valid near 18Z showed a better-defined center in 37 GHz imagery. Satellite-based intensity estimates range from near 45 kt to near 55 kt. ASCAT-C wind data valid at 1701 UTC only captured a part of the circulation of Sonia on the edge of the pass swath, but it did not show any winds of tropical-storm force. Based on all these data, the intensity estimate remains 45 kt for this advisory. The aforementioned GMI data helped identify the center of Sonia, so the initial position and movement of the tropical storm is higher confidence now. However, there is still unusually large spread in the track guidance. The models appear to be split over whether Sonia will begin a short period of intensification in about a day, or not. The stronger solutions, including the GFS and all of the hurricane regional models, show Sonia gaining more latitude, while the weaker ones, including the Google DeepMind and ECMWF, keep the cyclone moving generally westward to west-northwestward. The NHC track forecast already split these solutions, and no significant change has been made for this advisory since there is no obvious reason to discount either solution at this time. Likewise, no change of note was made to the official intensity forecast. Sonia could strengthen slightly over the weekend, since its structure and organization appear to be improving and there are no immediate significant inhibiting factors. However, by early next week the cyclone will move into a drier environment and move toward an upper-level low that will result in an increase in shear. This should cause weakening, and all available dynamical guidance still indicates Sonia will become post-tropical by day 4, regardless of how strong it gets between now and then. The NHC intensity forecast is now near the middle of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 25/2100Z 13.5N 118.9W 45 KT 50 MPH 12H 26/0600Z 13.6N 119.7W 50 KT 60 MPH 24H 26/1800Z 13.7N 120.3W 55 KT 65 MPH 36H 27/0600Z 14.1N 120.9W 60 KT 70 MPH 48H 27/1800Z 14.7N 121.9W 60 KT 70 MPH 60H 28/0600Z 15.0N 123.1W 50 KT 60 MPH 72H 28/1800Z 15.1N 124.7W 40 KT 45 MPH 96H 29/1800Z 15.0N 128.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 30/1800Z...DISSIPATED $$ Forecaster D. Zelinsky
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