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HURRICANE DARBY DISCUSSION NUMBER 12
NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016
800 AM PDT THU JUL 14 2016
Darby still appears to be feeling the effects of 10-15 kt of
northeasterly shear. Recent microwave images continue to show a
mid-level eye, but the deep convection has an asymmetric structure,
primarily focused to the south and southwest of the center.
Subjective and objective Dvorak estimates have not changed during
the past six hours, and the initial intensity is therefore held at
70 kt. Although Darby is moving over a relative cool spot in the
ocean, SSTs are still plenty warm to support strengthening for the
next 36 hours. A limiting factor may be continued vertical shear,
which does not seem to have decreased as the models had been
indicating. The SHIPS guidance now shows the shear staying up
between 10-15 kt during the next 24 hours, so only a little more
strengthening is shown in the official forecast. The new NHC
forecast shows a slightly lower peak intensity, and it should be
noted that this forecast is still near the high end of the
guidance. Much colder SSTs, on the order of 24-25 degrees Celsius,
should contribute to weakening beyond 48 hours.
The initial motion remains westward, or 280/11 kt. A well-
established ridge to the north of Darby should continue steering
the cyclone westward during the next five days. With the exception
of the GFDL and HWRF models, which are located along the northern
edge of the guidance envelope, the track models are tightly
clustered and are showing more agreement than yesterday. The NHC
forecast is south of the TVCE model consensus, and is very close to
the previous official forecast and an average of the GFS and ECMWF
models.
FORECAST POSITIONS AND MAX WINDS
INIT 14/1500Z 15.9N 116.9W 70 KT 80 MPH
12H 15/0000Z 16.3N 118.7W 75 KT 85 MPH
24H 15/1200Z 16.7N 121.1W 80 KT 90 MPH
36H 16/0000Z 17.0N 123.2W 80 KT 90 MPH
48H 16/1200Z 17.2N 125.2W 80 KT 90 MPH
72H 17/1200Z 17.4N 128.7W 65 KT 75 MPH
96H 18/1200Z 17.8N 132.5W 55 KT 65 MPH
120H 19/1200Z 18.5N 137.0W 45 KT 50 MPH
$$
Forecaster Berg
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