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Hurricane Sergio Discussion Number  36
NWS National Hurricane Center Miami FL       EP212018
200 AM PDT Mon Oct 08 2018

Sergio continues to have a large 60 nmi diameter eye with several
mesovorticies within it.  Although the cloud pattern is quite
symmetric around the eye, the cloud tops are not very cold, likely
due to some ocean upwelling beneath the hurricane.  The Dvorak
estimates are largely unchanged from earlier and still support an
initial intensity of 80 kt.

Sergio is now drifting northwestward in weak steering currents.  A
shortwave trough is expected to approach Sergio from the north, and
that feature, and a large trough over the southwestern United States
should cause Sergio to turn northeastward tonight.  This motion with
an increase in forward speed is expected through the remainder of
the week.  The models are in good agreement overall, and the NHC
track forecast lies near the middle of the guidance envelope.
Based on this forecast, Sergio is expected to be very near the Baja
California peninsula in about 4 days.

Sergio is expected to hold its strength or weaken only slightly
during the next day or so while it remains in a favorable
atmospheric environment.  However, steady weakening is expected
after that time due to increasing shear, drier air, and
progressively cooler waters along the forecast track.  Based on the
intensity guidance and environmental conditions, Sergio is expected
to be a tropical storm by the time it nears the Baja California
peninsula. The cyclone should weaken quickly once it moves inland.
The NHC intensity forecast is an update of the previous one and near
the HCCA and IVCN guidance.

Recent ASCAT data was very helpful in analyzing the 34- and 50-kt
wind radii.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 15.2N 128.1W   80 KT  90 MPH
 12H  08/1800Z 15.7N 128.3W   75 KT  85 MPH
 24H  09/0600Z 16.4N 127.9W   75 KT  85 MPH
 36H  09/1800Z 17.2N 126.6W   70 KT  80 MPH
 48H  10/0600Z 18.2N 124.8W   65 KT  75 MPH
 72H  11/0600Z 21.4N 120.0W   60 KT  70 MPH
 96H  12/0600Z 26.5N 114.0W   45 KT  50 MPH...NEAR BAJA CALIFORNIA
120H  13/0600Z 33.0N 106.5W   25 KT  30 MPH...INLAND

$$
Forecaster Cangialosi

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