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Hurricane SANDRA Forecast Discussion

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WTPZ42 KNHC 260239

800 PM MST WED NOV 25 2015

The intensification of Sandra seems to have slowed during the past
few hours.  The cloud tops in the eyewall have continued to cool
with temperatures now colder than -80C.  However, as this has
occurred the eye has become less distinct.  Satellite intensity
estimates are 115 kt from SAB and 102 kt from TAFB, and there is a
recent CIMSS ADT estimate of 110 kt.  A blend of these data is used
for the initial intensity of 105 kt.

The initial motion is now 320/7.  Sandra is moving around the
western end of a mid- to upper-level ridge over southern Mexico, and
during the next 96 hours it should move into southwesterly flow
between the ridge and a deep-layer trough over the western United
States.  While the guidance is generally in good agreement with
this scenario,  there remains some spread between the slower and
farther west ECMWF and the faster and farther east GFS.  As seen in
the previous advisory, this is due to the GFS keeping Sandra a
stronger system than does the ECMWF.  The new track forecast is
more or less an update of the previous forecast, but remains slower
than the model consensus in deference to the ECMWF, whose weaker
forecast again looks more realistic at this time.  The new forecast
has the center of Sandra passing near the southern end of the Baja
California peninsula between 48-72 hours and subsequently moving
into mainland Mexico between 72-96 hours.

Some additional strengthening is possible tonight. After that,
Sandra is expected to encounter rapidly increasing southwesterly
vertical wind shear, which should cause rapid weakening as the
center approaches Baja California and mainland Mexico.  The new
intensity forecast is near the intensity consensus IVCN through 48
hours, and then it is a little stronger than the guidance at 72
hours.  After Sandra makes landfall in Mexico, it is forecast to
dissipate quickly over the mountains.

Although Sandra is forecast to weaken, it is still too soon to know
exactly how it will affect portions of the southern Baja California
peninsula or the west coast of mainland Mexico.  Watches will not
be required on this advisory.  However, interests in those areas
should continue to monitor the progress of Sandra.


INIT  26/0300Z 13.6N 110.4W  105 KT 120 MPH
 12H  26/1200Z 14.9N 110.9W  110 KT 125 MPH
 24H  27/0000Z 16.7N 111.2W  100 KT 115 MPH
 36H  27/1200Z 18.5N 110.9W   85 KT 100 MPH
 48H  28/0000Z 20.4N 110.3W   70 KT  80 MPH
 72H  29/0000Z 24.0N 108.5W   35 KT  40 MPH
 96H  30/0000Z 28.0N 107.0W   20 KT  25 MPH...POST-TROP/INLAND
120H  01/0000Z...DISSIPATED

Forecaster Beven