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Hurricane Sergio Discussion Number  28
NWS National Hurricane Center Miami FL       EP212018
200 AM PDT Sat Oct 06 2018

Sergio has changed little in structure since the last advisory.  It
still has a 25-30 n mi wide eye surrounded by cold convective tops,
and with not much change in intensity estimates, the estimated
maximum winds remain 110 kt.  Sergio's intensity is not likely to
change much during the next day or two, although some slight
weakening is possible as the hurricane's speed slows down and it
upwells some colder water from below, or due to possible internal
structural changes.  More definitive weakening is anticipated by
days 4 and 5 due to an increase in westerly and southwesterly
shear and the hurricane reaching colder waters.  The NHC intensity
forecast remains close to a blend of the ICON consensus and the HCCA
model.  However, the statistical-dynamical models remain a bit
higher, and it is possible that Sergio won't lose quite as much
punch during the next several days as is indicated by the official
forecast.

Sergio continues to dive southwestward with an initial motion of
235/7 kt.  A shortwave trough swinging across the Baja California
peninsula will bypass Sergio during the day, leaving a weakness in
the ridge that will allow the hurricane to begin making a sharp
northward and then northeastward turn during the next 24-72 hours.
Another shortwave trough forecast to dig southward off the
California coast will then cause Sergio to accelerate northeastward
on days 4 and 5.  Notable changes in this forecast update include a
slightly wider turn from 24-72 hours, and more spread in the model
speeds once Sergio accelerates toward the Baja California
peninsula.  As is usually the case in these scenarios, the ECMWF is
much slower than the other models, and because of that, the new NHC
forecast is a bit slower than the previous one, especially on day 5.


FORECAST POSITIONS AND MAX WINDS

INIT  06/0900Z 14.9N 123.5W  110 KT 125 MPH
 12H  06/1800Z 14.6N 124.4W  105 KT 120 MPH
 24H  07/0600Z 14.4N 125.6W  100 KT 115 MPH
 36H  07/1800Z 14.7N 126.5W   95 KT 110 MPH
 48H  08/0600Z 15.2N 127.0W   90 KT 105 MPH
 72H  09/0600Z 16.9N 126.1W   80 KT  90 MPH
 96H  10/0600Z 19.0N 123.0W   65 KT  75 MPH
120H  11/0600Z 23.0N 118.0W   55 KT  65 MPH

$$
Forecaster Berg

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