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Tropical Storm HILARY Forecast Discussion


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000
WTPZ44 KNHC 231435
TCDEP4

Tropical Storm Hilary Discussion Number   9
NWS National Hurricane Center Miami FL       EP092017
1000 AM CDT Sun Jul 23 2017

Visible imagery indicates that Hilary is becoming better organized.
A small central dense overcast has formed, along with a large curved
band in the northern semicircle of the cyclone. The initial wind
speed is set to 40 kt, a blend of the latest TAFB/SAB estimates.
Hilary could be on the verge of starting its long-anticipated
significant strengthening period.  A 1059 UTC SSMIS microwave pass
indicates more inner-core structure with the storm, which suggests
that Hilary will be able to take advantage of the nearby conducive
atmospheric and oceanic conditions.  The SHIPS guidance is also
indicating relatively high chances of rapid intensification, roughly
a 50/50 chance during the next 48 hours. Given the factors
above, the NHC forecast is raised from the previous one, best in
line with a blend of the HWRF/DSHIP/HFIP corrected consensus
models.  An increase in northerly shear, possibly enhanced by
outflow from TS Irwin, should cause some weakening late in the
period, along with more marginal SSTs.

Hilary is moving slower now to the west-northwest at about 9 kt. A
ridge over Mexico should steer Hilary in that general direction for
the next several days, at various speeds due to the strength of the
ridge.  Later in the period, there is a possibility of some binary
interaction with Irwin, which adds some uncertainty to the forecast.
Overall, there hasn't been a lot of change to the model guidance,
and the latest NHC track prediction stays relatively close to the
previous forecast and the consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z 12.7N 102.3W   40 KT  45 MPH
 12H  24/0000Z 13.1N 103.5W   50 KT  60 MPH
 24H  24/1200Z 13.8N 104.8W   65 KT  75 MPH
 36H  25/0000Z 14.6N 106.2W   75 KT  85 MPH
 48H  25/1200Z 15.4N 107.9W   90 KT 105 MPH
 72H  26/1200Z 16.5N 112.0W  100 KT 115 MPH
 96H  27/1200Z 17.6N 115.8W   90 KT 105 MPH
120H  28/1200Z 19.0N 119.0W   85 KT 100 MPH

$$
Forecaster Blake