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Tropical Storm Sergio Discussion Number  47
NWS National Hurricane Center Miami FL       EP212018
800 PM PDT Wed Oct 10 2018

This evening's satellite presentation depicts a rather ragged and
elongated banding eye-like feature with fragmented curved bands
encircling the periphery of cyclone.  The subjective intensity
estimates from TAFB and SAB, however, still yield an initial
intensity of 55 kt.

The UW-CIMSS shear analysis shows that the westerly shear has
increased to 15-20 kt, and the Decay-SHIPS as well as the global
models indicate that the shear magnitude will increase further to
near 50 kt prior to landfall.  This inhibiting upper wind pattern
along with slightly cooler oceanic temperatures should influence
some further weakening as it approaches the Baja California
peninsula.  Sergio is forecast to move inland over Baja California
Sur on Friday and into the northwestern Mexico state of Sonora early
Saturday as a depression.  At the end of the forecast period, Sergio
is expected to further degenerate into a post-tropical weak low over
the southwestern United States.  The intensity forecast is based on
the NOAA-HCCA, and the GFS/ECMWF global models which show Sergio
making landfall Friday as a tropical storm.

The initial motion is estimated to be northeastward, or 050/14 kt,
and this general motion is forecast through the entire 72 hour
period with a continued increase in forward speed.  Sergio will be
approaching the central Baja California peninsula Friday, although
the tropical-storm-force winds are likely to arrive Thursday night.
There is continued high confidence in the forecast track as the
available large-scale and hurricane models are clustered tightly
together through 72 hours.  The NHC forecast lies in the middle of
the guidance cluster and is close to the TVCN/HCCA consensus models.

The primary threat associated with Sergio and its remnants continues
to be life-threatening flash flooding and mudslides within
mountainous terrain in the Mexico states of Baja California Sur,
Sonora, the U.S. Southern Plains, and the Ozarks through the
weekend. For more information about this potential hazard, see
products from the Weather Prediction Center and your local weather
forecast office.


FORECAST POSITIONS AND MAX WINDS

INIT  11/0300Z 20.0N 121.5W   55 KT  65 MPH
 12H  11/1200Z 21.8N 119.3W   55 KT  65 MPH
 24H  12/0000Z 24.4N 116.4W   50 KT  60 MPH
 36H  12/1200Z 27.2N 113.1W   45 KT  50 MPH...INLAND
 48H  13/0000Z 30.0N 109.1W   30 KT  35 MPH...INLAND
 72H  14/0000Z 34.4N  98.8W   20 KT  25 MPH...POST-TROP/INLAND
 96H  15/0000Z...DISSIPATED

$$
Forecaster Roberts

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