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Hurricane Darby Discussion Number 19
NWS National Hurricane Center Miami FL EP052022
Issued by NWS Central Pacific Hurricane Center Honolulu HI
500 PM HST Wed Jul 13 2022
Darby continues to be a healthy tropical cyclone. In fact, the
subjective intensity estimates from PHFO, TAFB, and SAB, and the
objective ADT and CIMSS SATCON all came it at 102 kt. Based on this
consensus, the initial intensity has been increased to 100 kt,
making Darby a major hurricane once again. Satellite images from
the past couple of hours indicated that the upper level outflow has
started to become a bit asymmetric, which may indicate that Darby is
starting to be affected by the large upper level trough to the
northwest.
The initial motion is 285/14 kt. The cyclone is being
steered by a low- to mid-level ridge to the north of the system.
This ridge is expected to maintain a general west-northwest motion
over the next 24 hours or so. As Darby becomes impacted by vertical
shear, it will weaken over the next 24 to 48 hours. As it becomes
an increasingly shallow system, it should turn toward the west. The
trusted dynamical models are in agreement with this scenario and are
in a tightly clustered guidance envelope. The forecast track has
also been quite consistent for several cycles, and current forecast
follows the previous package with a slight northward shift based on
recent movement trends.
Sea surface temperatures (SSTs) are between 25-26C around Darby and
should remain marginal along the forecast track. The main question
is when the forecasted vertical shear will begin to significantly
affect the system. The combination of this vertical shear, marginal
SSTs, and drier low- to mid-tropospheric air should result in a
rapid weakening of Darby, especially considering the small size of
the cyclone. Simulated IR data from the GFS and HWRF indicated that
Darby could maintain an eye tonight, but it would finally collapse
some time Thursday, with the low level circulation becoming
exposed on Friday. The main intensity aids are projecting a rapid
weakening over the next 3 days despite the recent intensification.
The forecast for this advisory is consistent with the previous
forecast and has Darby resuming its weakening trend soon, becoming
a post-tropical/remnant low in 72 hours.
FORECAST POSITIONS AND MAX WINDS
INIT 14/0300Z 15.9N 138.5W 100 KT 115 MPH
12H 14/1200Z 16.3N 140.3W 90 KT 105 MPH
24H 15/0000Z 16.8N 142.9W 80 KT 90 MPH
36H 15/1200Z 17.0N 145.4W 65 KT 75 MPH
48H 16/0000Z 17.0N 148.2W 55 KT 65 MPH
60H 16/1200Z 16.8N 151.4W 40 KT 45 MPH...POST-TROPICAL
72H 17/0000Z 16.7N 154.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 18/0000Z...DISSIPATED
$$
Forecaster Kodama/M Ballard
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