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Hurricane SEYMOUR Forecast Discussion

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WTPZ45 KNHC 250236

900 PM MDT MON OCT 24 2016

After rapidly intensifying during the past 30 hours, the rate of
strengthening has slowed for the time being. The eye of Seymour has
become cloud-filled on geostationary satellite images and microwave
data indicate that the northwestern portion of the eyewall has
eroded some.  The observed arrested development this evening is
likely due to the entrainment of dry air.  However, there are
already some signs that the hurricane is recovering from these
effects with central convection increasing and becoming more
circular during the past couple of hours.  The initial intensity is
set at 90 kt, slightly above the Dvorak estimates at 0000 UTC due to
the improvement in organization of the system since that time.

Since Seymour is expected to remain in low wind shear conditions,
over warm water, and in an environment of good upper-level
divergence during the next 24 hours, significant strengthening is
anticipated. After that time, however, an increase in southwesterly
shear should end the strengthening process. Seymour is forecast to
rapidly weaken when it moves over cooler water and into hostile
atmospheric conditions beginning in about 2 days. The NHC intensity
forecast is a little higher than the multi-model consensus, and is
in best agreement with the SHIPS and LGEM models.

Seymour is moving westward, or 280 degrees, at 14 kt.  The hurricane
is expected to remain on the southwestern side of a mid-level high
pressure system during the next 36 to 48 hours, which should allow
Seymour to maintain a westward to west-northwestward motion. After
that time, a large deep-layer low pressure system is expected to
move eastward toward California and erode the ridge.  This pattern
change should cause Seymour to turn northwestward and then northward
in 3 to 4 days.  The track models are in relatively good agreement,
and only small changes were made to the previous NHC forecast track.

A pair of ASCAT passes from several hours ago indicate that the wind
field of Seymour is very compact, with tropical-storm-force winds
extending no more than 60 n mi from the center.


INIT  25/0300Z 15.5N 112.6W   90 KT 105 MPH
 12H  25/1200Z 15.9N 114.6W  100 KT 115 MPH
 24H  26/0000Z 16.4N 117.2W  110 KT 125 MPH
 36H  26/1200Z 17.2N 119.5W  105 KT 120 MPH
 48H  27/0000Z 18.4N 121.3W   90 KT 105 MPH
 72H  28/0000Z 21.5N 122.8W   60 KT  70 MPH
 96H  29/0000Z 22.5N 122.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  30/0000Z...DISSIPATED

Forecaster Cangialosi