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Hurricane SEYMOUR Forecast Discussion

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WTPZ45 KNHC 251444

800 AM PDT TUE OCT 25 2016

Microwave satellite imagery suggests that Seymour underwent an
eyewall replacement during the night, with an AMSR-2 overpass at
0917 UTC showing a larger eye than seen on a Windsat overpass at
0120 UTC.  The hurricane is looking better organized than 6 hours
ago in infrared satellite imagery, with the eye gradually becoming
more apparent and greater symmetry in the cold cloud tops around the
eye.  The latest satellite intensity estimates include 115 kt from
TAFB, 102, kt from SAB, and 108 kt from the CIMSS satellite
consensus.  Based on these and current trends, the initial intensity
is increased to 110 kt.

Seymour is expected to remain within an area of low wind shear and
over SSTs of around 28C during the next 24 hours.  These conditions
favor additional intensification and the NHC wind speed forecast
calls for a peak intensity at category 4 strength later today or
early tonight.  After that time, increasing southwesterly shear and
cooler waters should cause steady to rapid weakening.  The majority
of the guidance shows Seymour weakening below hurricane strength in
less than 72 hours, degenerating to a remnant low by 96 hours, and
dissipating completely by 120 hours.  The new intensity forecast is
an update of the previous forecast and continues to lie near the
upper end of the intensity guidance.

The initial motion is 275/12.  A mid- to upper-level ridge extending
westward from Mexico is expected to steer Seymour westward to
west-northwestward for another 24 hours or so.  Subsequently, a
deep-layer trough over the northeastern Pacific is expected to cause
a break in the ridge, with Seymour turning northwestward and
northward into the break.  Most of the track guidance suggests the
forward motion should slow between 72-96 hours as Seymour shears
apart, and this is reflected in the track forecast.  The new
forecast track is a little to the south of the previous track during
the first 24 hours, and then is similar to the previous track.


INIT  25/1500Z 15.6N 115.0W  110 KT 125 MPH
 12H  26/0000Z 16.0N 117.0W  120 KT 140 MPH
 24H  26/1200Z 16.8N 119.3W  115 KT 130 MPH
 36H  27/0000Z 18.0N 121.0W  100 KT 115 MPH
 48H  27/1200Z 19.5N 122.2W   85 KT 100 MPH
 72H  28/1200Z 21.5N 122.5W   45 KT  50 MPH
 96H  29/1200Z 22.0N 122.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  30/1200Z...DISSIPATED

Forecaster Beven