000
WTPZ41 KNHC 272032
TCDEP1

Tropical Storm Alvin Discussion Number   9
NWS National Hurricane Center Miami FL       EP012019
300 PM MDT Thu Jun 27 2019

A pair of timely ASCAT passes just before 1800 UTC indicate that
Alvin has strengthened a little more. Multiple 45-50 kt wind vectors
were present in the northwest quadrant of the cyclone in both
passes. The intensity of the tropical storm has been increased to
55 kt since the ASCAT instrument is likely undersampling the
strongest winds of this small tropical storm.

Most of the intensity models indicate that Alvin has reached its
peak intensity, however, the HWRF and GFS suggest that Alvin could
still squeak out a little more intensification during the next 12 h
or so. While I can't rule out that Alvin could get a little stronger
tonight, its window for strengthening is likely closing soon. The
cyclone's infrared cloud signature has already taken on a shear
pattern, and GFS- and ECMWF-based SHIPS diagnostics suggest that the
shear should steadily increase during the next 48 h. Furthermore,
the tropical storm is quickly approaching cooler waters. Nearly all
of the models show Alvin degenerating into a remnant low within
about 48 h and dissipating soon thereafter, and the NHC forecast
reflects this.

The initial motion of Alvin is still 300/12 kt. No changes of
significance were made to the NHC track forecast which continues to
closely follow HCCA and TVCN. Alvin should continue on this general
heading for another 24 hours or so, before gradually turning
westward as it degenerates into a remnant low over the weekend.

FORECAST POSITIONS AND MAX WINDS

INIT  27/2100Z 16.6N 114.2W   55 KT  65 MPH
 12H  28/0600Z 17.7N 115.9W   55 KT  65 MPH
 24H  28/1800Z 19.3N 118.0W   45 KT  50 MPH
 36H  29/0600Z 20.3N 119.9W   35 KT  40 MPH
 48H  29/1800Z 20.9N 121.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  30/1800Z...DISSIPATED

$$
Forecaster Zelinsky