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Hurricane Sergio Discussion Number  26
NWS National Hurricane Center Miami FL       EP212018
200 PM PDT Fri Oct 05 2018

This afternoon's satellite presentation shows that Sergio has become
a little better organized.  Eyewall cloud temperatures have once
again cooled, and the ragged, cloud-filled eye has warmed during the
past 6 hours.  Accordingly, the subjective and objective T-numbers
support increasing the initial intensity to 105 kt for this
advisory.

As mentioned in this morning's discussion, unforeseen short term
inner-core structure changes could cause some intensity
fluctuations.  Since the environment is forecast to remain favorable
during the next 24 hours or so, little change in strength is
forecast, and again, the cyclone could become a little stronger than
reflected in the forecast.  Beyond this period, gradual weakening is
expected through day 5 as Sergio moves toward decreasing sea-surface
temperatures and into a more stable surrounding environment.  The
Decay-SHIPS and LGEM intensity guidance, as well as the large-scale
models, show increasing southwesterly shear disrupting Sergio's
outflow pattern after 72 hours.  The intensity forecast is similar
to the previous package, and is just above the NOAA-HCCA and IVCN
consensus models and below the statistical intensity aids.

Sergio's motion is estimated to be west-southwestward, or 250/6 kt
within the mid-level steering flow produced by a building high
pressure system located north-northeast of the Hawaiian Islands. By
early next week, a decrease in forward speed and a turn toward the
northwest to north-northwest is forecast as the aforementioned
mid-level high retrogrades in response to an amplifying trough over
the southwestern United States and Baja California peninsula. Beyond
day 3, increasing southwesterly mid-tropospheric flow should induce
a northeastward accelerated motion through day 5.  The NHC forecast
is again adjusted south of the last advisory through 48 hours, and
is close to the various multi-model consensus guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 15.7N 122.3W  105 KT 120 MPH
 12H  06/0600Z 15.3N 123.1W  105 KT 120 MPH
 24H  06/1800Z 14.9N 124.3W  100 KT 115 MPH
 36H  07/0600Z 14.8N 125.4W  100 KT 115 MPH
 48H  07/1800Z 15.1N 126.3W   90 KT 105 MPH
 72H  08/1800Z 16.7N 126.5W   80 KT  90 MPH
 96H  09/1800Z 18.9N 123.9W   70 KT  80 MPH
120H  10/1800Z 22.0N 119.3W   65 KT  75 MPH

$$
Forecaster Roberts

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