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Hurricane Hilary Forecast Discussion


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000
WTPZ44 KNHC 240847
TCDEP4

Hurricane Hilary Discussion Number  12
NWS National Hurricane Center Miami FL       EP092017
400 AM CDT Mon Jul 24 2017

Hilary's overall cloud pattern continues to become better organized,
although inner-core convection is still fluctuating somewhat.
There is well-defined upper-level outflow, particularly over the
northwest and northeast quadrants of the circulation.  Dvorak
T-numbers from both TAFB and SAB are now 4.0, which supports
upgrading the system to the fourth hurricane of the 2017 eastern
North Pacific season.  Hilary is expected to continue traversing
a warm ocean with weak vertical shear for the next couple of days,
which favors continued strengthening.  Rapid intensification is a
distinct possibility, since the SHIPS Rapid Intensification Index
(RII) shows a 60 percent chance of a 30 kt increase in intensity
during the next 24 hours.  The NHC forecast is in line with the
RII guidance, and is close to the HFIP Corrected Consensus
intensity forecast through 72 hours, and a little below it
thereafter when SSTs beneath the cyclone are expected to cool below
26 deg C.

A west-northwestward motion continues, near 300/7 kt.  The flow on
the southern periphery of a large 500 mb ridge that extends westward
from the southwestern United States should be the main steering
mechanism for the next several days.  A slight strengthening of the
flow should lead to some increase in the forward speed of Hilary
over the next few days.  There is still the possibility of some
binary interaction with Tropical Storm Irwin to the west, but for
now this interaction is not expected to be very significant within
the forecast period.  The official track forecast is similar to the
previous one and is a blend of the simple and corrected dynamical
model consensus predictions.

FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 14.0N 103.8W   65 KT  75 MPH
 12H  24/1800Z 14.4N 104.8W   80 KT  90 MPH
 24H  25/0600Z 15.1N 106.3W   95 KT 110 MPH
 36H  25/1800Z 15.8N 108.0W  110 KT 125 MPH
 48H  26/0600Z 16.4N 110.0W  115 KT 130 MPH
 72H  27/0600Z 17.5N 114.0W  105 KT 120 MPH
 96H  28/0600Z 18.5N 117.5W   90 KT 105 MPH
120H  29/0600Z 19.5N 121.0W   75 KT  85 MPH

$$
Forecaster Pasch