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Tropical Storm Alvin Discussion Number  12
NWS National Hurricane Center Miami FL       EP012019
800 AM PDT Fri Jun 28 2019

Alvin continues to lose organization as a steady weakening trend has
commenced. The satellite presentation has become more ragged and the
center is now very close to the southwestern edge of the deep
convection. Satellite intensity estimates continue to decrease, with
a blended average indicating a 55 kt initial intensity for this
advisory. Alvin is already over SSTs of 24 C and will move over even
cooler waters over the next 36 hours. In addition, the latest
guidance depicts southwesterly shear of 15 to 20 kt impacting the
circulation, and this is forecast to increase to over 30 kt in 24
hours. These factors, along with Alvin moving into an increasingly
stable atmospheric environment, will result in continued steady
weakening into this weekend. By Saturday night, Alvin is expected to
become devoid of deep convection, and the cyclone is forecast to
dissipate by Sunday.

Alvin accelerated slightly overnight, with an initial motion of
305/14 kt. This faster motion is expected to be only temporary and
the official track forecast is near the clustering of the consensus
aids. Alvin will be steered around the southwestern periphery of
mid-level ridging to its north through today. Thereafter, a much
weaker cyclone will become steered by the lower level environmental
flow, which will result in a turn to the west-northwest and decrease
in forward speed tonight into Saturday.


FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 19.0N 117.7W   55 KT  65 MPH
 12H  29/0000Z 20.1N 119.3W   45 KT  50 MPH
 24H  29/1200Z 21.0N 121.0W   35 KT  40 MPH
 36H  30/0000Z 21.6N 122.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  30/1200Z...DISSIPATED

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Forecaster Latto/Beven

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