Central Pacific Basin Tropical Cyclones

Hurricane Darby Forecast Discussion

WTPA41 PHFO 141458

Hurricane Darby Discussion Number  21
NWS Central Pacific Hurricane Center Honolulu HI   EP052022
500 AM HST Thu Jul 14 2022

Darby crossed longitude 140W and officially entered the central 
Pacific basin just after midnight HST this morning. The cyclone's 
satellite appearance has gone through some fluctuations since the 
previous advisory, but an elongated and somewhat ragged 5-10 nm 
wide eye has persisted. Pulsing convection continues to encircle the 
center, but has become much less symmetric. The initial intensity is 
estimated to be 90 kt, supported by a blend of the subjective Dvorak 
intensity estimates from SAB and HFO, the latest UW-CIMSS objective 
Dvorak estimate of 87 kt, and a SATCON near 83 kt.

Darby lies on the southwestern periphery of a ridge aloft, in an 
area characterized by moderate southerly vertical wind shear. Darby 
is moving closer to an upper-level trough to its northwest, into an 
environment characterized by even stronger vertical wind shear, as 
evidenced by transverse banding in the northwest semicircle. This 
shear will allow the cyclone to efficiently ingest the dry mid-level 
air that prevails, while moving over sub-26C SSTs. Since Darby 
continues to be a small system, it will quickly respond to the 
debilitating environment into which it is moving, with rapid 
weakening expected over the next 48 hours before dissipation occurs 
by 72 hours. The updated intensity forecast closely follows the 
consensus IVCN, as well as the SHIPS guidance. 

The initial motion estimate for this advisory is 290/14kt. As Darby 
degrades to a shallow system over the next 48 hours, a persistent 
strong surface high north of Hawaii will force it to accelerate as 
it makes a turn toward the west. The updated track forecast is close 
to the previous forecast, and lies very close to the GFEX. 


INIT  14/1500Z 16.6N 140.9W   90 KT 105 MPH
 12H  15/0000Z 17.1N 142.9W   75 KT  85 MPH
 24H  15/1200Z 17.2N 145.6W   60 KT  70 MPH
 36H  16/0000Z 17.2N 148.7W   50 KT  60 MPH
 48H  16/1200Z 17.1N 152.1W   40 KT  45 MPH
 60H  17/0000Z 16.9N 155.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  17/1200Z...DISSIPATED

Forecaster Birchard

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