000
WTPZ41 KNHC 071437
TCDEP1

Hurricane Sergio Discussion Number  33
NWS National Hurricane Center Miami FL       EP212018
800 AM PDT Sun Oct 07 2018

Somewhat quickly and unexpectedly, Sergio took on the appearance of
an annular hurricane overnight. The eye of the hurricane expanded,
nearly doubling in size (now 70 n mi across), and most of the
banding features disappeared. However, IR imagery over the past
hour or two indicates that the hurricane is still somewhat
asymmetrical, suggesting that the hurricane may not have a classical
annular structure, at least not yet. The initial intensity has been
lowered to 90 kt, in agreement with the latest current intensity
estimates from TAFB and SAB.

The hurricane continues to move due west with an initial forward
speed of 7 kt. Sergio is still expected to slow down and turn first
northward, and then northeastward over the next couple of days. By
mid-week, a mid-level shortwave trough moving southward off coast of
California should cause Sergio to accelerate northeastward toward
the Baja California peninsula. The global models remain in fairly
good agreement on the track of the cyclone through the middle of
next week, and only small changes were made to the NHC track
forecast to move it closer to the model consensus.

As long as Sergio can maintain its annular-like structure, only slow
weakening is anticipated due to continued effects of ocean upwelling
combined with the slow forward motion of the hurricane. By the end
of the forecast period, Sergio will be moving over much cooler SSTs
located west of the Baja California peninsula, and a faster
weakening rate is forecast. Given the lower initial intensity of
Sergio, the official intensity forecast is a little lower for the
first two days of the forecast, but is very similar beyond that
time.


FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 14.5N 126.8W   90 KT 105 MPH
 12H  08/0000Z 14.8N 127.6W   85 KT 100 MPH
 24H  08/1200Z 15.2N 128.2W   80 KT  90 MPH
 36H  09/0000Z 15.9N 128.1W   75 KT  85 MPH
 48H  09/1200Z 16.7N 127.3W   70 KT  80 MPH
 72H  10/1200Z 18.8N 123.8W   65 KT  75 MPH
 96H  11/1200Z 22.0N 119.5W   55 KT  65 MPH
120H  12/1200Z 26.5N 114.0W   45 KT  50 MPH

$$
Forecaster Zelinsky