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HURRICANE DARBY DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052016
200 PM PDT FRI JUL 15 2016

Darby's eye has been clearing out during the past few hours with
some warming noted in infrared satellite imagery.  There are some
breaks in the surrounding convection due to infiltration of dry
air, which has caused the subjective data-T numbers to oscillate
around 4.5 and 5.0 since this morning.  However, CI numbers are 5.0
from both TAFB and SAB, and ADT estimates are up to 5.3/97 kt. Based
on these data, Darby's maximum winds are increased to 90 kt.

Vertical shear over Darby has become quite low and should remain low
during the entire forecast period.  However, based on the latest
global SST analysis, Darby will only be over waters warmer than
26.5C for another 12-18 hours and is likely to reach SSTs as cold as
24C in a couple of days. Therefore, additional significant
strengthening is not anticipated, and in fact, a gradual weakening
trend is shown in the official forecast for the entire five days.
This forecast is very similar to the previous one and remains
relatively close to the SHIPS guidance and the Florida State
Superensemble.

The hurricane is moving west-northwestward, or 290/8 kt, to the
south of a strong mid-level ridge extending west of northern
Mexico.  The ridge is forecast to weaken during the next 24 hours
due to an amplifying mid- to upper-level trough along the west
coast of the United States.  This should keep Darby moving
west-northwestward for the next few days, followed by a turn to the
west at the end of the forecast period once the weaker cyclone
becomes steered by lower-level steering flow.  It may sound like a
broken record, but the track guidance remains tightly clustered for
the entire forecast period.  The updated NHC forecast is
essentially down the middle of the guidance envelope and not too
much different from the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  15/2100Z 16.8N 121.4W   90 KT 105 MPH
 12H  16/0600Z 17.2N 122.7W   85 KT 100 MPH
 24H  16/1800Z 17.6N 124.4W   80 KT  90 MPH
 36H  17/0600Z 17.9N 126.1W   75 KT  85 MPH
 48H  17/1800Z 18.2N 128.0W   70 KT  80 MPH
 72H  18/1800Z 18.7N 132.5W   60 KT  70 MPH
 96H  19/1800Z 19.5N 137.5W   50 KT  60 MPH
120H  20/1800Z 19.5N 142.5W   40 KT  45 MPH

$$
Forecaster Berg

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