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Hurricane Hilary Discussion Number  16
NWS National Hurricane Center Miami FL       EP092017
300 AM MDT Tue Jul 25 2017

Hilary's compact, symmetric, inner core continues to become better
defined on satellite imagery.  Microwave imagery suggests
that the eye is quite small, less than 10 n mi in diameter, with
little evidence of vertical tilt of the vortex.  The current
intensity estimate is now 90 kt in agreement with a Dvorak estimate
from the NESDIS SAB.  Hilary should be in a moist air mass and over
a warm ocean for the next couple of days.  Dynamical guidance
predicts some increase in northerly shear over the cyclone in 1- to
2-days, but probably not enough of an increase to impede at least
some additional strengthening.  The official intensity forecast
calls for Hilary to become a major hurricane in 12 hours or so and
reach a peak in a day or so.  This is in good agreement with the
latest Florida State University Superensemble (FSSE) prediction.
Later in the forecast period, gradually cooling sea surface
temperatures should induce slow weakening.

The initial motion estimate remains west-northwestward, or 290/9 kt.
A mid-tropospheric ridge extending westward from the southwestern
United States would cause Hilary to continue on its
west-northwestward track for the next several days.  In a few days,
however, Hilary is likely to pass close to Hurricane Irwin.  The
current thinking is that the circulation of Hilary will dominate so
that little influence on Hilary's track, due to binary interaction
with Irwin, will occur.  On the other hand, the latter tropical
cyclone is expected to begin rotating around Hilary's circulation
later in the forecast period (please refer to the Forecast
Discussion on Irwin for additional information).  The official track
forecast is quite close to the simple consensus TVCN, and to the
corrected consensus predictions, HCCA and FSSE.

FORECAST POSITIONS AND MAX WINDS

INIT  25/0900Z 15.3N 106.7W   90 KT 105 MPH
 12H  25/1800Z 15.8N 108.2W  100 KT 115 MPH
 24H  26/0600Z 16.3N 110.4W  105 KT 120 MPH
 36H  26/1800Z 16.8N 112.6W  105 KT 120 MPH
 48H  27/0600Z 17.4N 114.8W  100 KT 115 MPH
 72H  28/0600Z 18.6N 118.7W   85 KT 100 MPH
 96H  29/0600Z 19.5N 122.5W   75 KT  85 MPH
120H  30/0600Z 20.0N 126.0W   65 KT  75 MPH

$$
Forecaster Pasch

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