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Hurricane Sergio Discussion Number  23
NWS National Hurricane Center Miami FL       EP212018
800 PM PDT Thu Oct 04 2018

Sergio's cloud pattern has deteriorated somewhat since the previous
advisory, with cloud tops warming and the eye becoming more ragged
and less distinct. The initial intensity is reduced to 110 kt based
on a blend of the latest objective and subjective Dvorak estimates.
Sergio is expected to steadily weaken for the next 48 hours while
moving into a drier and more stable environment. By then, most of
the guidance suggests little change from 48-72 hours before the
shear increases by the end of the period and SSTs cool to between
26C and 27C, which should again result in weakening. The new NHC
intensity forecast is lower than the previous one during the first
48 hours to account for the observed weakening and the trend in the
guidance, but is similar after that time. This prediction is close
to or a bit above the latest HCCA intensity consensus aid.

Sergio has turned toward the left during the past few hours, with an
initial motion estimate now 305/07. A mid-level ridge building to
the northwest of Sergio will steer the hurricane toward the west and
even toward the west-southwest during the next 36 to 48 hours. After
that time, an amplifying longwave trough over western North America
will erode the ridge and cause Sergio to recurve, with a faster
northeastward motion shown by day 5. The new NHC track forecast has
been adjusted to the south of the previous one from 24 to 48 hours,
following the trend of the latest consensus aids, which are showing
a more equatorward motion during this time. At days 3 through 5, the
NHC track is largely an update of the previous one, and lies between
the faster GFS and the slower ECMWF models.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 15.9N 120.5W  110 KT 125 MPH
 12H  05/1200Z 16.0N 121.4W  100 KT 115 MPH
 24H  06/0000Z 15.9N 122.5W   95 KT 110 MPH
 36H  06/1200Z 15.6N 123.8W   85 KT 100 MPH
 48H  07/0000Z 15.5N 125.0W   80 KT  90 MPH
 72H  08/0000Z 16.0N 127.0W   80 KT  90 MPH
 96H  09/0000Z 17.5N 127.0W   70 KT  80 MPH
120H  10/0000Z 19.5N 124.5W   65 KT  75 MPH

$$
Forecaster Brennan

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