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HURRICANE DARBY DISCUSSION NUMBER  22
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052016
800 PM PDT SAT JUL 16 2016

Darby has finally responded to the cooler SSTs, with a weakening in
the central convection and the eye becoming less distinct.  The
current intensity is reduced to 90 kt which is a blend of Data-T
and Current Intensity numbers.  The cyclone is expected to
traverse ocean waters of near 25 deg C, along the northern edge of
the strong gradient of SST, for the next few days.  Even though the
shear is forecast to remain low for the next 2-3 days, the
combination of cooler waters and a more stable air mass should
result in continued weakening. Near the end of the forecast period,
the SSTs under Darby will begin to warm a bit.  By that time,
however, increasing west-southwesterly shear should prevent
restrengthening.

Center fixes are in good agreement, which is not surprising given
that an eye has been apparent, and the initial motion continues at
285/9 kt.  A narrow mid-level subtropical ridge to the north of
Darby is expected to remain in place for the next several days.
This steering pattern should cause the tropical cyclone to move on a
mainly westward heading for the next 4 days or so.  By the end of
the forecast period, the weakening system should be steered more by
the low-level tradewind flow, and turn to a slightly south of
westward heading.  The official track forecast is very close to the
previous one, and is a blend of the latest GFS and ECMWF solutions.

A drifting buoy, ID 46906, near the southern eyewall of Darby,
measured a pressure of 980.1 mb around 0200 UTC.

FORECAST POSITIONS AND MAX WINDS

INIT  17/0300Z 18.2N 125.8W   90 KT 105 MPH
 12H  17/1200Z 18.4N 127.2W   85 KT 100 MPH
 24H  18/0000Z 18.7N 129.1W   75 KT  85 MPH
 36H  18/1200Z 18.9N 131.2W   65 KT  75 MPH
 48H  19/0000Z 19.1N 133.2W   55 KT  65 MPH
 72H  20/0000Z 19.8N 138.0W   45 KT  50 MPH
 96H  21/0000Z 19.6N 142.5W   40 KT  45 MPH
120H  22/0000Z 18.5N 147.5W   35 KT  40 MPH

$$
Forecaster Pasch

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