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Tropical Storm Sergio Discussion Number  48
NWS National Hurricane Center Miami FL       EP212018
200 AM PDT Thu Oct 11 2018

Sergio's cloud pattern has changed little during the past several
hours, and the Dvorak satellite intensity estimates from TAFB and
SAB haven't changed either.  A partial ASCAT-B scatterometer pass
revealed numerous 45-kt winds and a 50-kt northerly wind in the
coldest cloud tops of the curved band wrapping around the north
portion of the circulation. Based on these data, the initial
intensity is held at 55 kt for this advisory.

The intensity forecast philosophy remains unchanged.  A combination
of increasing southwesterly shear, a drier and more stable
surrounding environment, and slightly cooler oceanic temperatures
should influence some weakening as it approaches the Baja California
peninsula.  The cyclone is expected to move inland over
Baja California Sur on Friday and into the northwestern Mexico state
of Sonora early Saturday.  Afterward, rapid weakening, and
ultimately dissipation, is expected after Sergio makes its second
landfall along the coast of the mainland Mexico.  A 72 hour
post-tropical/remnant low point is maintained to simply represent
the inland motion of Sergio.  The intensity forecast is once
again 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 050/15
kt, within the deep-layer southwesterly flow produced by a
mid-latitude trough stretching southwestward over the eastern
Pacific from the southwestern United States.  Sergio should continue
moving in this general motion 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.
The NHC forecast lies in the middle of the tightly clustered
guidance and is close to the multi-model consensus aids.

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  11/0900Z 21.0N 120.2W   55 KT  65 MPH
 12H  11/1800Z 23.0N 117.9W   55 KT  65 MPH
 24H  12/0600Z 25.7N 114.8W   50 KT  60 MPH
 36H  12/1800Z 28.4N 111.4W   35 KT  40 MPH...INLAND
 48H  13/0600Z 31.0N 107.2W   30 KT  35 MPH...INLAND
 72H  14/0600Z 35.3N  96.0W   20 KT  25 MPH...POST-TROP/INLAND
 96H  15/0600Z...DISSIPATED

$$
Forecaster Roberts

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