Central Pacific Basin Tropical Cyclones

Tropical Storm Darby Forecast Discussion

WTPA41 PHFO 162035

Tropical Storm Darby Discussion Number  30
NWS Central Pacific Hurricane Center Honolulu HI   EP052022
1100 AM HST Sat Jul 16 2022

Deep convection redeveloped in the northern semicircle near the 
center last night. High clouds from this convection briefly obscured 
the center but it has become exposed once again. The convection 
appears to be poorly organized and is not persistent near the center 
over time. This pulsing of convection is typical behavior of a 
central Pacific tropical cyclone as it goes through its weakening 
process toward dissipation. The center of Darby is visible in the 
South Point radar data and indicates the center passing south of the 
Big Island at this time. The current satellite intensity estimate 
from PHFO came in at 2.0/30 kt. This was the only subjective 
estimate available. The CIMSS ADT was 2.0/30 kt, and the latest 
available SATCON from 1208 UTC was 37 kt. The initial intensity for 
this advisory is 35 kt, though this may be generous.

Darby is a shallow system and is being steered by the low- to 
mid-level easterly flow. This steering current will remain in place 
until the system dissipates. The forecast track is just an update 
to the previous track.

Although SSTs are expected to slowly increase along the remaining 
forecast track, vertical shear is forecast to increase above 30 kt 
tonight in both the GFS and ECMWF SHIPS guidance. Thus, 
reintensification is not expected. Thus, the forecast keeps the 
weakening trajectory of the previous forecast, which makes Darby a 
post-tropical system tonight and dissipates it by Sunday. If 
additional data are received that indicate the circulation has 
opened up to a trough, or if deep convection does not persist near 
the center, the system could be dropped as a tropical cyclone 


INIT  16/2100Z 17.7N 155.5W   35 KT  40 MPH
 12H  17/0600Z 17.7N 158.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  17/1800Z...DISSIPATED

Forecaster Kodama

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