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Tropical Storm Sergio Discussion Number  42
NWS National Hurricane Center Miami FL       EP212018
200 PM PDT Tue Oct 09 2018

Days of slow movement and cold water upwelling appear to have
finally taken a toll on Sergio.  Cloud top temperatures on the west
side of the cyclone have warmed considerably since this morning,
and microwave imagery indicates that Sergio's eyewall is no
longer fully closed.  Dvorak-based intensity estimates have
decreased accordingly and now support an initial intensity of only
60 kt.  A recent partial ASCAT overpass also showed maximum winds
of only 50-55 kt in the eastern semicircle of the cyclone, and
these data also support making Sergio a tropical storm.

The tropical storm is moving east-northeastward, or 060/8 kt.
No important changes were made to the track forecast, which is
merely an update of the previous advisory.  The tropical storm will
likely continue to accelerate toward the east-northeast or northeast
over the next few days, before approaching the Baja California
peninsula on Friday. The NHC forecast remains near the track
consensus at all times and confidence in the track forecast is high.

Now that Sergio is moving a little faster, it has a chance to move
over slightly warmer waters during the next few hours.  The
intensity guidance is in fairly good agreement that little
additional weakening is likely for the next day or so.  Beyond 36
h, faster weakening is still possible as the storm reaches much
colder waters and the shear over the tropical storm increases.
Rapid weakening and dissipation is expected after Sergio makes its
final landfall along the coast of mainland Mexico, though a 96 h
point remnant low is maintained again in this advisory to represent
the inland movement of Sergio.  The NHC forecast is essentially an
average of the HCCA and IVCN consensus aids at all forecast hours.

The biggest hazard associated with Sergio and its remnants will
likely be heavy rain that will affect portions of northwestern
Mexico and the U.S. Southern Plains through Sunday.  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  09/2100Z 16.9N 126.5W   60 KT  70 MPH
 12H  10/0600Z 17.5N 125.4W   60 KT  70 MPH
 24H  10/1800Z 18.7N 123.4W   55 KT  65 MPH
 36H  11/0600Z 20.3N 121.0W   55 KT  65 MPH
 48H  11/1800Z 22.7N 118.2W   50 KT  60 MPH
 72H  12/1800Z 27.3N 112.0W   40 KT  45 MPH
 96H  13/1800Z 31.0N 105.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  14/1800Z...DISSIPATED

$$
Forecaster Zelinsky

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