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Hurricane Sergio Discussion Number  27
NWS National Hurricane Center Miami FL       EP212018
800 PM PDT Fri Oct 05 2018

Sergio has maintained a 25-30-nmi wide eye this evening, and a ring
of cold cloud tops has cooled around the well-defined eye. Satellite
intensity estimates range from T5.5/102 kt from TAFB and SAB to
T5.9/122 kt from ADT and a T6.0/115 kt NHC objective T-number, so
the intensity has been bumped up to 110 kt for this advisory.
Upper-level outflow and the overall convective pattern have both
improved since the previous advisory while Sergio has lost latitude
and moved over warmer waters.

The motion is now southwestward, or 235/06 kt. Sergio's recent
southwestward motion is forecast to be short lived, with a return to
a west-southwestward to westward motion expected within the next 12
hours. The deep-layer ridge to the north of Sergio is forecast to
become more narrow due to a passing shortwave trough, but it is
basically expected to remain intact. This feature will steer the
hurricane slowly westward through Sunday. By Monday, however, a
stronger trough is forecast by the global models to drop southward
off the coasts of California and Baja California, causing a
significant weakening and erosion of the western portion of the
ridge. This is expected to result in Sergio turning slowly
northeastward on Monday, and accelerate on days 4 and 5. The new NHC
forecast track is similar to the previous advisory track, and lies
close to consensus models TVCE and NOAA-HCCA.

Other than very brief intrusions of dry mid-level air and possible
upwelling beneath the hurricane due to its slow forward speed, there
do not appear to be any other negative factors that would
significantly disrupt Sergio's intensity for the next 36-48 hours.
By 72 hours and beyond, however, increasing southwesterly vertical
wind shear is expected to induce a steady weakening trend after the
cyclone begins accelerating toward the northeast, and on days 4 and
5 passing over the cold wake left behind by former Hurricane Rosa.
The new official intensity forecast is similar to the previous one,
and is near an average of the NOAA-HCCA and IVCN consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 15.3N 122.7W  110 KT 125 MPH
 12H  06/1200Z 15.0N 123.6W  110 KT 125 MPH
 24H  07/0000Z 14.7N 124.8W  105 KT 120 MPH
 36H  07/1200Z 14.8N 125.8W  100 KT 115 MPH
 48H  08/0000Z 15.4N 126.5W   95 KT 110 MPH
 72H  09/0000Z 17.1N 126.0W   85 KT 100 MPH
 96H  10/0000Z 19.4N 122.7W   70 KT  80 MPH
120H  11/0000Z 23.0N 118.0W   60 KT  70 MPH

$$
Forecaster Stewart

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