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Hurricane Sergio Discussion Number  29
NWS National Hurricane Center Miami FL       EP212018
800 AM PDT Sat Oct 06 2018

Sergio has remained nearly steady-state since last night and the
clear eye is still surrounded by very cold cloud tops. The initial
intensity remains 110 kt, based on a blend of subjective and
objective Dvorak intensity estimates. The primary moderating factor
for Sergio's intensity over the next few days will likely be sea
surface temperatures since GFS and ECMWF SHIPS diagnostics suggest
that the environment will be otherwise favorable. Sergio is now
moving west-southwestward at around 6 kt, likely just fast enough to
outrun its own cold wake. Little change in Sergio's intensity is
expected for the next day or so while the hurricane is forecast to
continue moving at around this same forward speed. By early next
week, a slower motion will likely cause some weakening to occur, as
Sergio becomes trapped over colder upwelled waters, with further
weakening likely when Sergio reaches much cooler waters to the
north. The ocean-coupled regional models show more weakening than
currently indicated by the official forecast, while DSHP and LGEM
show a stronger storm, probably in part because those models use a
constant ocean field.  Confidence in the intensity forecast is not
very high, and it is likely that the faster Sergio moves, the
stronger it will be.

The global models are in fairly good agreement on the general track
of Sergio through the middle of next week, but they disagree on how
quickly Sergio will move along that path. Sergio is still forecast
to make a sharp u-turn toward the northeast over the next 3 days and
then accelerate in that direction between 72 and 120 h. Most of the
models are showing a slightly slower forward speed than earlier
cycles. However there are still large differences in their
representation of a shortwave trough off the coast of California
that will cause Sergio's acceleration, and the model spread remains
high. The new official track forecast is similar to the previous
advisory but generally shows a slower speed, especially after 48 h,
in line with the latest track consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 14.7N 124.0W  110 KT 125 MPH
 12H  07/0000Z 14.5N 125.0W  110 KT 125 MPH
 24H  07/1200Z 14.5N 126.0W  105 KT 120 MPH
 36H  08/0000Z 14.9N 126.8W  100 KT 115 MPH
 48H  08/1200Z 15.5N 127.0W   90 KT 105 MPH
 72H  09/1200Z 17.2N 125.6W   80 KT  90 MPH
 96H  10/1200Z 19.5N 122.0W   70 KT  80 MPH
120H  11/1200Z 23.6N 117.0W   50 KT  60 MPH

$$
Forecaster Zelinsky

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