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HURRICANE DARBY DISCUSSION NUMBER  30
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052016
800 PM PDT MON JUL 18 2016

Darby still appears as a well-organized tropical cyclone on
geostationary imagery, with a symmetric CDO and occasional eye
showing up on enhanced infrared imagery.  Microwave imagery,
however, shows that the system has a slight northward tilt with
height with the mid-level center located a few tenths of a degree
north of the low-level center.  Dvorak classifications from SAB and
TAFB still support hurricane strength, so the official intensity
estimate remains at 65 kt.  Darby will be moving over marginal SSTs
and into drier air with increasing shear during the next several
days.  Therefore, the cyclone is forecast to gradually weaken during
the forecast period.  The official forecast is a blend of the
latest SHIPS and LGEM model output through 72 hours and is a
little above that guidance at days 4 and 5.

Based on the microwave images, the center is positioned slightly
south of the fixes from GOES imagery, and the resulting motion
estimate is 280/11 kt.  The track forecast reasoning is about the
same as in the previous advisory.  Darby should continue on a
generally westward heading to the south of a zonally-oriented
mid-level subtropical ridge for the next couple of days.  Later in
the period, the cyclone should slow its forward speed as it nears a
weakness in the ridge.  The official track forecast lies roughly in
the middle of the dynamical guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  19/0300Z 19.1N 133.2W   65 KT  75 MPH
 12H  19/1200Z 19.6N 134.9W   60 KT  70 MPH
 24H  20/0000Z 20.0N 136.9W   55 KT  65 MPH
 36H  20/1200Z 20.1N 139.1W   50 KT  60 MPH
 48H  21/0000Z 19.9N 141.3W   45 KT  50 MPH
 72H  22/0000Z 19.5N 145.5W   35 KT  40 MPH
 96H  23/0000Z 19.0N 150.0W   35 KT  40 MPH
120H  24/0000Z 20.0N 152.5W   30 KT  35 MPH

$$
Forecaster Pasch

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