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Hurricane Hilary Forecast Discussion


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000
WTPZ44 KNHC 270237
TCDEP4

Hurricane Hilary Discussion Number  23
NWS National Hurricane Center Miami FL       EP092017
900 PM MDT Wed Jul 26 2017

Recent microwave images indicate that Hilary is vertically titled
due to 15-20 kt of northwesterly shear.  Although the low-level
center of the hurricane is still located beneath very cold
cloud tops, the overall cloud pattern appears more ragged than it
was earlier today.  The Dvorak classifications from TAFB and SAB
have held steady at 5.0/90 kt, but based on the degraded appearance
and structure, the initial wind speed is lowered a little to 85 kt.
This intensity estimate is between the above mentioned subjective
Dvorak estimates and the ADT values from CIMSS at the University of
Wisconsin.

The moderate shear currently affecting Hilary is expected to
continue for about another day, which should cause some additional
weakening.  Even though the shear should lessen beyond 24 hours,
Hilary will be moving over progressively cooler waters and it is
forecast to cross the 26 degree C isotherm in about 2 days.  These
less favorable oceanic conditions and a progressively drier and more
stable air mass should cause additional weakening, and Hilary is
expected to become a post-tropical cyclone by the end of the
forecast period.  The NHC intensity forecast is a little lower than
previous one, and it is close to the HFIP and IVCN consensus models.

The hurricane is moving west-northwestward at 10 kt steered by a
mid-level ridge to its northeast.  The track forecast philosophy
has not changed from the past few advisories.  Although some
interaction may take place with Irwin, currently located about 500
nmi to the west of Hilary, it is not expected to have much of an
impact on the future path of Hilary.  A general track to the
west-northwest at a slightly slower pace is expected throughout the
forecast period. The new NHC track forecast is similar to the
previous one, and it is in best agreement with the various consensus
aids.

FORECAST POSITIONS AND MAX WINDS

INIT  27/0300Z 17.1N 114.2W   85 KT 100 MPH
 12H  27/1200Z 17.4N 115.6W   80 KT  90 MPH
 24H  28/0000Z 17.9N 117.2W   75 KT  85 MPH
 36H  28/1200Z 18.6N 118.8W   75 KT  85 MPH
 48H  29/0000Z 19.3N 120.5W   70 KT  80 MPH
 72H  30/0000Z 20.7N 124.3W   60 KT  70 MPH
 96H  31/0000Z 21.8N 128.1W   45 KT  50 MPH
120H  01/0000Z 22.9N 131.2W   35 KT  40 MPH...POST-TROPICAL

$$
Forecaster Cangialosi