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Tropical Storm Alvin Discussion Number   6
NWS National Hurricane Center Miami FL       EP012019
900 PM MDT Wed Jun 26 2019

Alvin's presentation on satellite images consists of a well-defined
CDO with very cold cloud tops near/over the center, with very
limited banding features.  Upper-level outflow is fairly distinct
over the western semicircle of the system.  The current intensity
estimate is boosted slightly, to 45 kt, based on Dvorak CI numbers
from both TAFB and SAB.  Alvin is likely to strengthen some more
during the next 12 to 24 hours since it should be moving over
sufficiently warm waters, within low vertical shear, and in a
modestly moist air mass for the next day or so.  Beyond 24 hours,
cooling SSTs and gradually increasing shear should cause a
weakening trend to commence.  All of the models call for rapid
weakening in 2 to 3 days, and the cyclone should degenerate into a
remnant low by Saturday. The official intensity forecast is a
little below the latest model consensus.

Recent center fixes indicate that there is no longer a southward
component of motion, and the initial motion estimate is now westward
or 270/11 kt.  There have been no significant changes to the general
track prediction philosophy.  Over the forecast period, the cyclone
is expected to move along the southwestern periphery of a mid-level
ridge extending westward from northwestern Mexico.  Most of the
track guidance has shifted a little northward on this cycle, and
the new official forecast is slightly north of the previous one,
but a little south of the simple and corrected dynamical consensus
aids.

FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 14.4N 111.3W   45 KT  50 MPH
 12H  27/1200Z 15.0N 112.9W   50 KT  60 MPH
 24H  28/0000Z 16.0N 115.1W   55 KT  65 MPH
 36H  28/1200Z 17.0N 117.3W   50 KT  60 MPH
 48H  29/0000Z 18.0N 119.2W   40 KT  45 MPH
 72H  30/0000Z 19.3N 122.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  01/0000Z...DISSIPATED

$$
Forecaster Pasch

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