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TROPICAL STORM HILDA DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102015
800 AM PDT THU AUG 06 2015

The cyclone's cloud pattern has significantly increased in
organization since late yesterday. There is now a small central mass
of deep convection, with a band on the northern side of the
circulation.  The center, according to an 1132 UTC SSM/I pass, is
also directly underneath this central convection, and the same pass
indicates increasing symmetry to the overall convective structure.
Satellite classifications from 1200 UTC were T2.0/30 kt and T2.5/35
kt from SAB and TAFB, respectively.  The initial intensity estimate
is set at the higher end of these estimates (35 kt), based on the
even greater organization seen in satellite imagery since that time.

The initial motion is toward the west or 275/11. The general
forecast scenario is for a subtropical ridge north of the cyclone to
steer Hilda westward for the next couple of days with a slight bend
toward the west-northwest after 36 hours.  In about 72 hours, the
cyclone should move around the western end of the ridge and
encounter a break in this feature at the end of the forecast period.
This pattern should cause Hilda to turn northwestward with a
decrease in forward speed by 96 hours.  The GFS-based guidance shows
a stronger ridge and a west-southwestward to westward track during
the next 2 to 3 days, while the ECMWF has a weaker ridge and a
track farther north. The official forecast is closer to the ECMWF
solution and near but faster than the previous one through 72 hours.
Overall, the NHC forecast lies to the right of the multi-model
consensus, which is dominated by the GFS guidance. After 72 hours,
the official track is near the multi-model consensus but not as far
west as the GFS/ECMWF model solutions.

Large-scale dynamic and thermodynamic factors are forecast to be
conducive for intensification through for the next 72 hours or so,
except for a somewhat drier lower to middle troposphere along
Hilda's path in 2 to 3 days.  When the cyclone gains latitude late
in the forecast period, it should begin to weaken due to increasing
southwesterly shear associated with a mid- to upper-level trough
expected to be near the longitude of Hawaii.  The official intensity
forecast is higher than the previous one through 72 hours and is
higher than the multi-model consensus, but little change was made to
the intensity forecast late in the period.


FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 12.7N 132.3W   35 KT  40 MPH
 12H  07/0000Z 12.9N 133.6W   45 KT  50 MPH
 24H  07/1200Z 13.0N 135.8W   50 KT  60 MPH
 36H  08/0000Z 13.5N 137.9W   55 KT  65 MPH
 48H  08/1200Z 14.1N 139.9W   60 KT  70 MPH
 72H  09/1200Z 15.4N 144.2W   65 KT  75 MPH
 96H  10/1200Z 17.1N 146.8W   65 KT  75 MPH
120H  11/1200Z 18.8N 149.4W   55 KT  65 MPH

$$
Forecaster Kimberlain

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