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Hurricane SANDRA Forecast Discussion

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WTPZ42 KNHC 250839

200 AM MST WED NOV 25 2015

Although an eye is not apparent on infrared imagery, the cloud
pattern has continued to become better organized with the center of
the cyclone embedded within an area of very deep convection. The
outflow pattern continues to be established in all quadrants. Based
on the average of objective estimates from CIMSS and subjective
Dvorak numbers from TAFB and SAB, the initial intensity has been
increased to 75 kt. The wind radii was adjusted based on a recent
ASCAT B pass, which shows that the cyclone is a little smaller in
size than previously estimated.

The hurricane will be within a very favorable environment of low
shear during the next 36 hours. In fact, the Rapid Intensification
Index of the SHIPS model continues to show better than 60 percent
chance of a 40 kt increase in the winds during the next 24 hours.
Then, the NHC forecast calls for strengthening. Beyond 36 hours, the
hurricane will encounter strong shear and a rapid weakening should
begin, and Sandra is forecast to be below hurricane strength before
it reaches the coast of Mexico.

The best estimate of the initial motion is 295 degrees at 9 kt. The
subtropical ridge which is controlling the west-northwest motion
of Sandra will shift eastward and weaken. This forecast pattern
should force the cyclone to turn northwestward and northward around
the ridge later today. The cyclone is expected to reach the
mid-latitude westerlies in about 48 hours, and it should then
sharply turn to the north-northeast and northeast toward the coast
of Mexico. This is the solution provided by most of the guidance and
is very similar to the previous NHC forecast.

Although Sandra is forecast to weaken, 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. A watch
may be required later today for portions of Mexico, and interests in
those areas should monitor the progress of Sandra.


INIT  25/0900Z 12.5N 109.0W   75 KT  85 MPH
 12H  25/1800Z 13.5N 109.9W   95 KT 110 MPH
 24H  26/0600Z 15.0N 110.8W  105 KT 120 MPH
 36H  26/1800Z 16.7N 111.1W  100 KT 115 MPH
 48H  27/0600Z 18.7N 110.8W   80 KT  90 MPH
 72H  28/0600Z 23.0N 108.5W   45 KT  50 MPH
 96H  29/0600Z 26.5N 105.5W   20 KT  25 MPH...INLAND
120H  30/0600Z...DISSIPATED

Forecaster Avila