000
WTPZ44 KNHC 271435
TCDEP4

Hurricane Hilary Discussion Number  25
NWS National Hurricane Center Miami FL       EP092017
800 AM PDT Thu Jul 27 2017

Hilary remains somewhat sheared, and shortwave IR imagery
suggests that much of the western semicircle of the circulation has
exposed this morning.  The intensity has been lowered to 70 kt based
on a blend of Final-T and current intensity (CI) values from TAFB
and SAB, and the CI from the UW-CIMSS ADT.

The intensity forecast is defined by a split in the dynamical and
statistical guidance.  The dynamical COAMPS-TC and HWRF models show
a brief period of re-intensification due to a decrease in shear
that allows convection to re-wrap around the circulation.  On the
other hand, the statistical models show gradual weakening
throughout the forecast period.  For the first 36 h, the NHC
forecast splits the difference between these scenarios.  After that
time, quickly dropping SSTs along the forecast track should lead to
steady weakening.  By 120 h, Hilary is shown to be a remnant low,
and is expected to have absorbed the circulation of Irwin, which is
forecast to move within just a few degrees of Hilary by day 4.
Overall, the new official forecast is a little lower than the
previous advisory.

Although the track forecast remains complicated due to the imminent
interaction of Hilary and Irwin, very little change has been made
to the forecast track.  A mid-level ridge extending from the
southwestern U.S. will keep Hilary moving generally west-northwest
or northwestward for a day or two.  The ridge weakens a little
after that, but the approach of Irwin should affect the track of
Hilary at least a little.  The GFS shows a stronger Hilary that
dominates the interaction with Irwin while the ECMWF shows two
somewhat weaker systems that have a more binary interaction that
results in a more westward motion.  Given the cool SSTs ahead of
Hilary, the forecast continues to favor slightly the ECMWF solution,
and is close to the corrected consensus HCCA, especially at 72 h and
beyond.


FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 17.6N 116.0W   70 KT  80 MPH
 12H  28/0000Z 18.0N 117.3W   65 KT  75 MPH
 24H  28/1200Z 18.7N 118.9W   65 KT  75 MPH
 36H  29/0000Z 19.5N 120.7W   65 KT  75 MPH
 48H  29/1200Z 20.2N 122.8W   60 KT  70 MPH
 72H  30/1200Z 21.2N 127.3W   50 KT  60 MPH
 96H  31/1200Z 21.8N 131.4W   35 KT  40 MPH
120H  01/1200Z 22.6N 134.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky