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Hurricane Sergio Discussion Number  12
NWS National Hurricane Center Miami FL       EP212018
300 AM MDT Tue Oct 02 2018

Geostationary satellite imagery indicates that Sergio continues to
strengthen.   The center is located within a fairly symmetric CDO
with cloud tops of -70 to -80 degrees C.  Earlier microwave data
showed a well-defined eye and inner core, but a more recent AMSU
overpass suggests that there has been some slight erosion of the
eastern portion of the eye, possibly due to some intrusion of dry
mid-level air.  Dvorak intensity estimates ranged from 75 to 90 kt,
and the initial intensity has been increased to a possibility
conservative 75 kt for this advisory.

The intensity forecast remains somewhat uncertain.  Although
Sergio has developed an inner core and strengthened during the past
12 hour or so, the dynamical models suggest northeasterly shear
will increase over the hurricane today.  This is expected to temper
the intensification somewhat over the next 12-24 hours, however,
most of the guidance shows at least gradual strengthening during
the next day or so.  The NHC intensity forecast calls for a gradual
increase in wind speed over the next 36-48 hours, and is close to
the IVCN model consensus.  After 72 h, cooler waters and the
entrainment of drier air is expected to cause gradual weakening.

Sergio is moving slightly south of due west or 265/12 kt.  The
hurricane is currently located to the south of a mid-level ridge,
and Sergio should continue westward today.  The global models show
the western portion of the ridge weakening over the next several
days, which should cause Sergio to turn west-northwestward, then
northwestward on Wednesday. By late in the week, another ridge
is predicted to build to the northwest of Sergio and the hurricane
is forecast to turn back toward the west.  The overall guidance
envelope has changed little this cycle, and the new NHC track is
similar to the previous advisory and close to the various consensus
aids.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0900Z 10.7N 113.2W   75 KT  85 MPH
 12H  02/1800Z 10.9N 114.7W   85 KT 100 MPH
 24H  03/0600Z 11.7N 116.4W   90 KT 105 MPH
 36H  03/1800Z 12.7N 117.8W   95 KT 110 MPH
 48H  04/0600Z 13.8N 119.0W  100 KT 115 MPH
 72H  05/0600Z 15.6N 121.7W  100 KT 115 MPH
 96H  06/0600Z 16.5N 124.6W   90 KT 105 MPH
120H  07/0600Z 16.7N 127.5W   80 KT  90 MPH

$$
Forecaster Brown

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