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HURRICANE SANDRA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP222015
800 PM MST TUE NOV 24 2015

Satellite imagery indicates that Sandra has continued to strengthen
during the past several hours.  The deep convection now wraps
around the center, and there have been occasional attempts at eye
formation.  The initial intensity is increased to 65 kt based on a
satellite intensity estimate from TAFB, a 65 kt estimate from the
CIMSS ADT, and an earlier CIMSS AMSU estimate of 60 kt.

The initial motion is 290/10.  The hurricane is currently being
steered by a mid-level ridge extending from southern Mexico
westward over the Pacific.  However, a strong deep-layer trough
moving southeastward over the western United States should erode the
ridge north of Sandra during the next couple of days.  This
evolution should cause the cyclone to turn northward in about 48
hours and recurve northeastward into the westerlies thereafter.
There has been little change in the track guidance since the last
advisory.  Thus, the new track forecast is similar to the previous
forecast in calling for Sandra to pass near the southern end of the
Baja California Peninsula in about 72 hours, followed by landfall in
northwestern Mexico between 72-96 hours.  The new forecast lies near
the center of the track guidance envelope.

Sandra has rapidly intensified during the past 24 hours, and this
trend is likely to continue as the hurricane remains in a light
vertical shear environment and over warm sea surface temperatures.
The Rapid Intensification Index of the SHIPS model shows better than
a 60 percent chance of a 40 kt increase in strength during the next
24 hours and an almost 80 percent chance of a 25 kt increase.  Based
on this, the intensity forecast has been adjusted upward to show
Sandra becoming a major hurricane in 36 hours, and this part of the
forecast could be conservative.  After 36 hours, the cyclone is
expected to encounter strong southwesterly vertical shear, and all
of the guidance forecasts rapid weakening before landfall over
mainland Mexico.  After landfall, Sandra should dissipate quickly
over the mountains of northwestern Mexico.  Overall, the new
intensity forecast lies near the upper edge of the guidance envelope
and is in best overall agreement with the Florida State
Superensemble.

It is too soon to know exactly how Sandra will affect portions of
the southern Baja California peninsula or the west coast of
mainland Mexico.  However, a watch may be required on Wednesday,
and interests in those areas should monitor the progress of Sandra.


FORECAST POSITIONS AND MAX WINDS

INIT  25/0300Z 12.0N 107.9W   65 KT  75 MPH
 12H  25/1200Z 12.6N 109.3W   75 KT  85 MPH
 24H  26/0000Z 14.0N 110.4W   90 KT 105 MPH
 36H  26/1200Z 15.8N 110.9W  100 KT 115 MPH
 48H  27/0000Z 17.7N 111.1W   90 KT 105 MPH
 72H  28/0000Z 22.0N 109.0W   60 KT  70 MPH
 96H  29/0000Z 26.0N 106.0W   20 KT  25 MPH...INLAND
120H  30/0000Z...DISSIPATED

$$
Forecaster Beven

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