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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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