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Tropical Storm HILARY


Tropical Storm Hilary Discussion Number  33
NWS National Hurricane Center Miami FL       EP092017
800 AM PDT Sat Jul 29 2017

Although Hilary has crossed the 25 deg SST isotherm, the
inner-core of the tropical storm has remained mostly intact.  Recent
SSMI and AMSR microwave imagery indicate that deep convection is
still present near the center of circulation, and in a band
extending to the east and south.  IR imagery from GOES-W even
briefly showed a warm spot embedded within the shallow to medium
convection that surrounds the center.  Given that the cloud pattern
hasn't changed significantly and an earlier ASCAT-A pass at 0540 UTC
showed maximum winds of 49 kt, the initial intensity has been held
at 55 kt. Despite Hilary's resilience so far, the SSTs beneath the
cyclone will continue to decrease for the next several days, so
weakening is inevitable.  The intensity forecast has not been
changed from the previous advisory, and shows Hilary becoming a
remnant low within 48 hours.

After days of high uncertainty, the track guidance is finally
coming into better agreement.  For the next 12 to 24 hours, Hilary
should be steered generally toward the west-northwest or northwest
by a mid-level ridge located to the north.  After that time, a turn
toward the west-northwest or west is expected due to a combination
of interaction with Irwin and amplification of the ridge.  Beyond
day 3, the UKMET and ECMWF show the two cyclones dissipating in
close proximity to one another, while the GFS still shows the
systems merging.  The NHC forecast favors the ECMWF and UKMET
solutions for now, but both systems are expected to be very weak
regardless of how close they actually get.  The new track is just a
little faster than the previous forecast and is close to the model


INIT  29/1500Z 21.4N 121.5W   55 KT  65 MPH
 12H  30/0000Z 22.4N 123.2W   50 KT  60 MPH
 24H  30/1200Z 23.6N 125.6W   40 KT  45 MPH
 36H  31/0000Z 24.6N 128.0W   30 KT  35 MPH
 48H  31/1200Z 25.2N 130.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  01/1200Z 25.4N 132.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  02/1200Z 25.5N 134.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  03/1200Z...DISSIPATED

Forecaster Zelinsky