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TROPICAL STORM HILDA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102015
200 AM PDT FRI AUG 07 2015

A GPM Microwave Imager pass from 0431 UTC revealed that Hilda's
center was located just under the eastern edge of the deep
convection due to some easterly shear.  The overall cloud pattern
has not really improved since earlier advisories, and the initial
intensity remains 50 kt.  This is supported by Dvorak estimates of
T3.5/55 kt from TAFB and T3.0/45 kt from SAB.  Although Hilda's
intensity has been steady for the past 12 hours, easterly shear
is relaxing, and the cyclone should be able to strengthen soon.
Hilda is forecast to be in a low-shear environment and over sea
surface temperatures of 27-29C during the next three days or so,
during which time intensification is expected.  On days 4 and 5,
weakening is anticipated as southwesterly shear of 25-35 kt begins
to affect the cyclone.  The NHC intensity forecast is near the
upper bound of the guidance and shows a peak intensity occurring in
about 48 hours.

Hilda is moving due west, or 270/11 kt.  The cyclone should turn
west-northwestward by 36 hours as it approaches a weakness in the
subtropical ridge.  Then, a mid- to upper-level low is expected to
develop north of the Hawaiian Islands in about three days, which
should cause Hilda to turn northwestward and north-northwestward on
days 4 and 5.  The track guidance generally agrees on this scenario,
but there is significant discrepancy on how sharply Hilda will turn
after 72 hours.  The GFS and GFDL, which depict a stronger cyclone,
have sharper turns and end up on the east side of the guidance
envelope.  The ECMWF, on the other hand, does not intensify Hilda as
much and is well to the west of the other track models.  The updated
NHC track forecast shows a sharper turn than in the previous
advisory, but the turn is not nearly as sharp as suggested by the
GFS, GFDL, and the various consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  07/0900Z 12.6N 135.6W   50 KT  60 MPH
 12H  07/1800Z 12.8N 137.3W   60 KT  70 MPH
 24H  08/0600Z 13.2N 139.3W   65 KT  75 MPH
 36H  08/1800Z 13.9N 141.3W   70 KT  80 MPH
 48H  09/0600Z 14.7N 143.3W   75 KT  85 MPH
 72H  10/0600Z 16.1N 147.1W   70 KT  80 MPH
 96H  11/0600Z 18.0N 149.0W   60 KT  70 MPH
120H  12/0600Z 20.5N 150.0W   45 KT  50 MPH

$$
Forecaster Berg

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