748 WTPZ41 KNHC 302044 TCDEP1 Tropical Storm Alvin Discussion Number 9 NWS National Hurricane Center Miami FL EP012025 200 PM MST Fri May 30 2025 The satellite presentation of Alvin has gradually degraded today. Alvin is entering an environment of strong south-southwesterly wind shear. Although much of the convection has been pushed off to the north and become elongated, the low-level center still appears to be underneath the southernmost portion of the central dense overcast. A pair of recent ASCAT passes missed the center, but still provided useful information that shows somewhat larger 34-kt radii, so these have been been expanded a bit. The ASCAT data show winds up to 40 kt about 50 n mi east of the center, but there is a good chance that stronger winds are still occurring slightly closer to the center where there was a gap in ASCAT data. The latest subjective intensity estimates from TAFB and SAB are T-2.5/35 kt, and the latest objective intensity estimates from UW-CIMSS are in the 41-47 kt range. The intensity is held at 45 kt for this advisory since the low-level center has not emerged from underneath the central dense overcast yet, and based on the ASCAT data. The initial motion is estimated to be north-northwest, or 335/9 kt. Alvin is forecast to turn northward tonight as it moves through a weakness in the subtropical ridge, toward the east side of a mid-level cutoff low located just west of Baja California. Little change is made to the previous NHC track prediction, which lies down the middle of the consensus model envelope. Alvin will continue moving into an increasingly hostile environment of very strong wind shear, dry air, and sea-surface temperatures that will drop below 26C along Alvin's path in about 6 hours. These conditions should lead to Alvin losing its convection on Saturday, which is depicted by the GFS and ECMWF simulated satellite imagery. There are no significant changes to the NHC intensity forecast, and Alvin is forecast to degenerate to a remnant low in about 24 hours, with dissipation predicted to occur in about 2 days. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 18.1N 109.0W 45 KT 50 MPH 12H 31/0600Z 19.4N 109.3W 35 KT 40 MPH 24H 31/1800Z 20.8N 109.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 01/0600Z 22.4N 109.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 01/1800Z...DISSIPATED $$ Forecaster Hagen
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