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TROPICAL STORM SANDRA DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP222015
800 PM MST FRI NOV 27 2015

Sandra has sheared apart since the last advisory, with the low
level center now exposed well to the west of the remaining
convection by 40 kt of shear.  The initial intensity is reduced to
55 kt based on a blend of satellite intensity estimates from TAFB
and SAB.  The shear should increase during the next 24-36 hours,
which should keep Sandra on a rapid weakening trend.  The cyclone
is likely to weaken to a tropical depression, if not a remnant low,
before the center moves into northwestern Mexico in 24 hours or so.
This is reflected in the new intensity forecast, which is an update
of the previous forecast.

The low-level center has been moving west of due north for the past
several hours, with a longer-term initial motion of 005/9.  A
low-level ridge over Mexico should steer Sandra or its remnants
generally northward for 24 to 36 hours into northwestern Mexico.
The track guidance has again shifted to the west, and the new
forecast track lies to the west of the previous track based on this
and the initial location and motion.  However, the new forecast
lies to the east of the model consensus.

Tropical storm warning remain in effect for the Las Islas Marias and
portions of the coast of mainland Mexico due to the possibility that
the tropical storm force winds could reach the coast before Sandra
weakens to a depression.

Regardless of how Sandra evolves during the next couple of days,
heavy rains are expected over a large part of west central Mexico.
In addition, the remnant mid- and upper-level moisture associated
with Sandra will contribute to a significant precipitation event
that has begun over portions of the south-central United States.
For more information, please see products from the NOAA Weather
Prediction Center and local NWS Weather Forecast Offices.


FORECAST POSITIONS AND MAX WINDS

INIT  28/0300Z 21.2N 108.8W   55 KT  65 MPH
 12H  28/1200Z 22.6N 108.3W   40 KT  45 MPH
 24H  29/0000Z 24.3N 108.1W   25 KT  30 MPH
 36H  29/1200Z 25.9N 107.9W   20 KT  25 MPH...POST-TROP/INLAND
 48H  30/0000Z...DISSIPATED

$$
Forecaster Beven

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