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Hurricane Darby Discussion Number 24
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 PM HST Thu Jul 14 2022
Darby's satellite presentation has deteriorated this evening as it
continues to be influenced by moderate west-southwesterly vertical
wind shear of around 20 knots as indicated by UW-CIMSS vertical
wind shear analysis, and cool sea surface temperatures (SSTs) of
around 25C shown in the NASA SPoRT SST composite. The latest
subjective Dvorak current intensity estimates from PHFO/SAB/JTWC
ranged from 4.0 (65 knots) to 4.5 (77 knots) while the UW-CIMSS
objective ADT current intensity estimate was 3.8 (61 knots).
Additionally, a SATCON estimate at 14/0404Z estimated the cyclones
strength at 64 knots. Given the satellite degradation and
incorporating a blend of the above intensity estimates, Darby's
initial intensity has been lowered to 65 knots with this advisory.
Darby continues on its westward course, with the estimated initial
motion set at 280/14 knots.
Darby will remain in a hostile environment during the next couple
days, characterized by cool SSTs of 25-26C, moderate to strong
westerly vertical wind shear of 20 to 30 knots, and surrounded by
dry mid-level air with relative humidity values of less than 50
percent. As a result, we expect Darby to continue to steadily
weaken during the next couple days. The tropical cyclone is expected
to weaken into a tropical storm later tonight, then weaken further
into a remnant low late Saturday, before dissipating Saturday
night. The intensity forecast has been lowered based on the rapid
rate of weakening the system is experiencing, and follows a blend of
the dynamical and statistical intensity guidance.
The tropical cyclone will continue to be directed westward during
the next couple days, influenced initially by a gradually building
mid and upper level ridge to the north of the system, while deep
convection persists. The cyclone will then begin to move slightly
south of due west at a faster forward speed as deep convection
becomes more sporadic, allowing Darby to be pushed along by the low
level trade wind flow. The forecast track closely follows a blend
of the latest GFS and ECMWF guidance (GFEX) through dissipation,
and is nearly a carbon copy of the previous official forecast track.
FORECAST POSITIONS AND MAX WINDS
INIT 15/0900Z 17.5N 144.8W 65 KT 75 MPH
12H 15/1800Z 17.6N 147.0W 55 KT 65 MPH
24H 16/0600Z 17.6N 150.3W 45 KT 50 MPH
36H 16/1800Z 17.5N 154.0W 35 KT 40 MPH
48H 17/0600Z 17.2N 157.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 17/1800Z...DISSIPATED
$$
Forecaster Jelsema
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