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TROPICAL STORM DARBY DISCUSSION NUMBER  32
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052016
800 AM PDT TUE JUL 19 2016

Conventional satellite imagery shows that the inner core cloud tops
have warmed since last night and deep convective banding has become
fragmented.  Although Darby has exhibited an intermittent ragged eye
feature, a blend of the subjective Final-T and CI-numbers, and
the objective ADT estimate, yield an intensity of 60 kt.
Additionally, the ambiguity solution of an earlier ASCAT overpass
revealed only a couple of 50-55 kt winds over the northern quadrant.
Accordingly, Darby's initial intensity has been lowered to 60 kt for
this advisory.  The cyclone is currently traversing sub-25C water,
but should be moving back over slightly warmer water east of
the Hawaiian Islands near the 36 hour period.  Darby, however, will
also be moving into a more stable thermodynamic environment and
modest southwesterly shear around the same time.  Therefore, these
contributing factors are expected to cause Darby to gradually weaken
through the period.  The official intensity forecast is based
primarily on the model consensus, IVCN, which includes the HWRF
hurricane model, and is above both the SHIPS and LGEM
statistical-dynamical intensity models.

The track forecast philosophy remains similar to the previous
forecast.  The cyclone should continue on a generally westward
heading to the south of a mid-tropospheric ridge anchored along 30N
for the next few days.  At the 96 hour period, Darby is forecast
to slow its forward speed as it encounters a growing weakness in the
ridge while a mid- to upper-level low digs north of the Hawaiian
Islands.  This synoptic feature should turn Darby gradually
northwestward, east of the Big Island.  The NHC forecast is located
between the TVCE multi-model consensus and both the GFS and ECMWF
ensemble mean guidance which are both situated north of the Hawaiian
Islands.


FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 19.8N 135.4W   60 KT  70 MPH
 12H  20/0000Z 20.1N 137.1W   55 KT  65 MPH
 24H  20/1200Z 20.1N 139.3W   50 KT  60 MPH
 36H  21/0000Z 20.1N 141.5W   50 KT  60 MPH
 48H  21/1200Z 19.7N 143.8W   45 KT  50 MPH
 72H  22/1200Z 19.4N 148.1W   45 KT  50 MPH
 96H  23/1200Z 19.9N 151.2W   40 KT  45 MPH
120H  24/1200Z 21.6N 153.4W   35 KT  40 MPH

$$
Forecaster Roberts

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