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Tropical Storm Sergio Discussion Number   3
NWS National Hurricane Center Miami FL       EP212018
1000 PM CDT Sat Sep 29 2018

Satellite images indicate that Sergio has become better organized
during the past several hours with more concentrated convection near
the center.  Intensity estimates are slightly higher than the past
advisory, so the initial wind speed is set to 40 kt, closest to the
CIMSS SATCON.  The storm should be in a low-shear, warm-water, and
high-moisture environment for the next 2 or 3 days.  While there
are no signs of an inner core forming yet, that usually doesn't
stop steady intensification, and rapid strengthening is a distinct
possibility in a day or two.  Thus the intensity forecast is raised
from the previous one and is close to the consensus.   Although
there are a number of reliable models showing a higher peak
intensity, an uncertain environment at long range leads me to a more
conservative forecast.  It would not be surprising at all if my
prediction ended up being too low, given the intense nature of this
eastern Pacific hurricane season.

The initial motion is close to the prevous one, 275/9.  Sergio
should be steered generally westward for the next two or three days
by the subtropical ridge over Mexico.  After that time, the cyclone
is forecast to approach a weakness in the ridge caused by a large
mid- to upper-level trough over California, and this should lead to
a turn toward the northwest.  Similar to the previous advisory, the
track guidance has shifted slightly south and west, so the official
forecast is nudged in that direction at most time periods.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z 12.3N 103.3W   40 KT  45 MPH
 12H  30/1200Z 12.4N 104.7W   50 KT  60 MPH
 24H  01/0000Z 12.3N 106.9W   65 KT  75 MPH
 36H  01/1200Z 12.0N 109.1W   75 KT  85 MPH
 48H  02/0000Z 11.8N 111.1W   90 KT 105 MPH
 72H  03/0000Z 12.9N 114.8W  100 KT 115 MPH
 96H  04/0000Z 15.0N 117.8W  100 KT 115 MPH
120H  05/0000Z 17.0N 120.0W   95 KT 110 MPH

$$
Forecaster Blake

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