Skip Navigation Links
NOAA NOAA United States Department of Commerce

Hurricane SEYMOUR Forecast Discussion

Home   Public Adv   Fcst Adv   Discussion   Wind Probs   Graphics   Archive  

WTPZ45 KNHC 261439

800 AM PDT WED OCT 26 2016

Seymour continues to maintain an impressive central dense overcast,
consisting of very deep convection around a 15 n mi well-defined
eye.  However, the distribution of convection has become slightly
asymmetric since the last advisory, with the greatest coverage to
the north and east of the center.  The convective asymmetry is
likely indicative of some increase in southwesterly shear.  A blend
of the latest Dvorak T- and CI-numbers, including UW-CIMSS ADT
values, is used to lower the initial intensity estimate of 120 kt.

Seymour is living on borrowed time.  A large mid- to upper-level
trough seen in water vapor imagery upstream of the cyclone should
cause a considerable increase in southwesterly shear within 24
hours. By that time, Seymour will already have reached much cooler
waters.  This should result in weakening, with the rate of filling
only increasing with time.  By 36 hours, the shear should become
extremely strong and cause the vortex to shear apart, with the
middle and upper portions of the circulation moving well to the
north or northeast of the low-level center.  The official forecast
shows Seymour becoming a post-tropical remnant low in 48 hours in
general agreement with global models that depict this decoupling as
soon as 36 to 42 hours. The NHC intensity forecast shows about the
same rate of weakening as the previous one and is close to the
multi-model consensus.

The initial motion estimate is 290/13.  Seymour has begun to gain a
little more latitude recently as it nears the western periphery of a
mid-level ridge west of the Baja California peninsula.  The
cyclone's motion should slow and become northwesterly soon and
then shift north-northwestward and northward in 24 to 36 hours as
Seymour becomes embedded in the flow between the high to the
northeast and the trough to the northwest.  Once Seymour becomes a
shallow system in 48 hours, the remnant low will slow further and
turn north-northeastward until dissipation.  The NHC track forecast
is only slightly to the left of the previous one after 24 hours and
a little faster during the remnant low phase.


INIT  26/1500Z 16.9N 120.2W  120 KT 140 MPH
 12H  27/0000Z 18.0N 121.5W  105 KT 120 MPH
 24H  27/1200Z 19.7N 122.6W   80 KT  90 MPH
 36H  28/0000Z 21.1N 122.9W   60 KT  70 MPH
 48H  28/1200Z 22.2N 122.4W   35 KT  40 MPH...POST-TROP/REMNT LOW
 72H  29/1200Z 23.7N 121.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  30/1200Z...DISSIPATED

Forecaster Kimberlain