Central Pacific Basin Tropical Cyclones

Hurricane Darby Forecast Discussion

WTPA41 PHFO 150849

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.


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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