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HURRICANE DARBY DISCUSSION NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016
300 PM MDT WED JUL 13 2016
Darby is taking on a different shape as the vertical shear gradually
decreases. Convective bursts with overshooting tops have been
occurring near the center, and a broken band of convection wraps
around the southern and western part of the circulation. Subjective
and objective Dvorak estimates are unanimously T4.0, and Darby is
therefore being upgraded to a 65-kt hurricane. Ocean temperatures
near Darby are between 28-29 degrees Celsius, and even though SSTs
decrease some out ahead of the hurricane, microwave data suggest
that the ocean is warming up after the passages of Blas and Celia.
Vertical shear is also expected to be low during the next few days,
and Darby should continue strengthening for the next 36-48 hours.
The NHC intensity forecast is not too different from the previous
forecast, and it is near or just above the upper bound of the
intensity guidance.
The latest fixes indicate that Darby is beginning to gain latitude
again, and the 12-hour average motion is 270/10 kt. Mid-level
ridging to the north of the hurricane is expected to change very
little over the next five days, and Darby should therefore maintain
a consistent westward track through the forecast period. The track
guidance has shifted a little to the north on this cycle, and there
is very little cross-track difference noted among the models.
However, there are some along-track speed differences, with the
ECMWF showing a faster motion due to a stronger depiction of the
mid-level ridge. The updated NHC track forecast has been nudged
northward and is a little faster than the previous forecast, lying
close to a consensus of the GFS and ECMWF.
FORECAST POSITIONS AND MAX WINDS
INIT 13/2100Z 15.4N 113.6W 65 KT 75 MPH
12H 14/0600Z 15.6N 115.3W 75 KT 85 MPH
24H 14/1800Z 16.0N 117.8W 85 KT 100 MPH
36H 15/0600Z 16.4N 120.3W 90 KT 105 MPH
48H 15/1800Z 16.8N 122.7W 90 KT 105 MPH
72H 16/1800Z 17.3N 126.7W 75 KT 85 MPH
96H 17/1800Z 17.8N 130.7W 65 KT 75 MPH
120H 18/1800Z 18.5N 135.0W 55 KT 65 MPH
$$
Forecaster Berg
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