319 WTPZ41 KNHC 300234 TCDEP1 Tropical Storm Alvin Discussion Number 6 NWS National Hurricane Center Miami FL EP012025 800 PM MST Thu May 29 2025 Infrared cloud top temperatures have gradually warmed over the center of Alvin this evening. Earlier AMSR-2 passive microwave images showed a ragged convective structure on the west side of the storm, and recent satellite trends indicate the system may already be contending with some shear and intrusions of drier air. The subjective Dvorak classifications and objective intensity estimates range from 45-55 kt, so the initial intensity is held at 50 kt. Alvin is still moving to the northwest (325/10 kt) but should turn north-northwestward and northward on Friday and Saturday toward a weakness in the ridge created by a cutoff low offshore of Baja California. The track guidance remains in good agreement, and no major changes were made to the updated NHC track forecast. Recent microwave data indicate the storm lacks an inner core, so Alvin will be susceptible to the negative effects of increasing shear and drier mid-level air during the next couple of days. In addition, the track forecast brings Alvin over cooler waters as it nears the Baja California peninsula. So, gradual weakening is forecast as the associated convection is likely to become displaced from the storm center beginning on Friday. This forecast shows Alvin becoming post-tropical in 36 h and spinning down over the weekend, in agreement with the global model fields and simulated satellite imagery. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 16.0N 107.9W 50 KT 60 MPH 12H 30/1200Z 17.2N 108.5W 45 KT 50 MPH 24H 31/0000Z 18.7N 109.0W 40 KT 45 MPH 36H 31/1200Z 20.3N 109.3W 35 KT 40 MPH...POST-TROPICAL 48H 01/0000Z 21.9N 109.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 01/1200Z 23.7N 109.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 02/0000Z...DISSIPATED $$ Forecaster Reinhart
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