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HURRICANE SEYMOUR DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP202016
800 PM PDT TUE OCT 25 2016

Seymour has continued to rapidly intensify since the last advisory.
The eye is about 10-15 nmi wide in infrared satellite imagery, but
is less than 10 nmi wide in a recent 0005Z SSMI/S microwave image,
indicating that the eye diameter has contracted since the previous
advisory. The initial intensity is increased to 130 kt for this
advisory based on satellite intensity estimates of T6.5/127 kt from
both TAFB and SAB, and a T6.7/132 kt from UW-CIMSS ADT.

The initial motion is now 285/13 kt. The global and regional models
remain in excellent agreement on Seymour moving steadily
west-northwestward around the southwestern periphery of a deep-layer
ridge for the next 24 hours, followed by a turn toward the northwest
in 36 hours as a strong shortwave trough significantly erodes the
western portion of the ridge. By 48 hours, Seymour is expected to
slow down appreciably and turn north-northwestward as the cyclone
rapidly weakens and becomes more vertically shallow. After that
time, the shallow post-tropical low is forecast to turn back toward
the west-northwest under the influence of the low-level trade wind
flow. The official forecast track is similar to the previous
advisory, and lies close to blend of the TVCX and HCCA consensus
models.

Some additional slight strengthening is possible during the next
6-12 hours due to the small eye, low shear conditions, and warm
SSTs. After that time, increasing southwesterly vertical wind shear,
cooler waters, including significant cold upwelling by 24 hours and
beyond, should cause steady to rapid weakening.  Seymour is expected
to drop below hurricane status shortly after 48 hours, degenerate
into a post-tropical low by 72 hours, and dissipate by 120 hours.
The new intensity forecast is similar to the previous forecast, and
is close to the IVCN intensity consensus model.

FORECAST POSITIONS AND MAX WINDS

INIT  26/0300Z 16.1N 117.7W  130 KT 150 MPH
 12H  26/1200Z 16.7N 119.4W  125 KT 145 MPH
 24H  27/0000Z 17.9N 121.1W  110 KT 125 MPH
 36H  27/1200Z 19.2N 122.2W   95 KT 110 MPH
 48H  28/0000Z 20.2N 122.6W   70 KT  80 MPH
 72H  29/0000Z 21.1N 122.9W   40 KT  45 MPH...POST-TROPICAL
 96H  30/0000Z 21.7N 123.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  31/0000Z...DISSIPATED

$$
Forecaster Stewart

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