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HURRICANE SANDRA DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP222015
200 PM MST FRI NOV 27 2015

Geostationary and microwave imagery indicate that the low-level
center of Sandra has begun to separate from the mid-level
circulation. This is due to vertical shear of 30 to 35 kt, which is
forecast to increase further tonight. Dvorak estimates continue to
decrease as the deep convection wanes and separates from the center,
and the initial intensity has been conservatively lowered to 70 kt
based on a blend of the latest Final-T and CI numbers from TAFB and
SAB. Quick weakening is forecast, and Sandra should weaken to a
tropical storm in the next 12 hours and become a tropical depression
or remnant low in 24-36 hours before dissipating. The new NHC
intensity forecast is close to the latest SHIPS model.

The low-level center has wobbled to the left during the past couple
of hours, but a long-term initial motion estimate is 020/09. As
Sandra shears apart, the guidance envelope has shifted to the left
this cycle, with the exception of the HWRF. The new NHC track has
been adjusted a little to the left of the previous one now that the
cyclone is starting to weaken more quickly, and the NHC forecast is
close to the latest ECMWF solution. If Sandra decouples faster than
anticipated, the low-level circulation could move to the left of
the new forecast track and even dissipate entirely before the center
reaches the coast. However, the main threat of heavy rainfall over a
large part of west-central Mexico will occur regardless of the
details of the track and intensity forecast.

The remnant mid- and upper-level moisture associated with Sandra
will contribute to a significant precipitation event expected to
occur over portions of the south-central United States this weekend.
For more information, please see products from the NOAA Weather
Prediction Center and local NWS Weather Forecast Offices.

FORECAST POSITIONS AND MAX WINDS

INIT  27/2100Z 20.4N 108.4W   70 KT  80 MPH
 12H  28/0600Z 22.1N 107.8W   50 KT  60 MPH
 24H  28/1800Z 23.8N 107.2W   30 KT  35 MPH
 36H  29/0600Z 25.5N 106.6W   20 KT  25 MPH...POST-TROP/INLAND
 48H  29/1800Z...DISSIPATED

$$
Forecaster Brennan

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