Central Pacific Basin Tropical Cyclones

Tropical Storm Darby Forecast Discussion

WTPA41 PHFO 152036

Tropical Storm Darby Discussion Number  26
NWS Central Pacific Hurricane Center Honolulu HI   EP052022
1100 AM HST Fri Jul 15 2022

Darby lost its deep convection around 1400Z, as a result of 
persistent shear of 25 to 30 kt, per the UW-CIMSS deep shear 
analysis. The loss of deep convection has left behind an exposed 
low level center. Dvorak intensities from PHFO and PGTW were 55 kt, 
SAB at 45 kt and UW-CIMSS ADT at 35 kt. The CIMSS SATCON from
1638Z had a CI of 49 kt. With the convection gone, and a high
confidence in the downward trend, have opted to go with a 
conservative blend of these intensities for an initial value of 50 

The initial motion is 275/13. With the convection sheared off, but 
cloud tops still reaching near 20K feet, the mid levels are helping 
to guide Darby. Over the next day or so, the low-level flow will 
become the steering force for the system. Both the mid- and 
low-levels are dominated by a large anticyclone far to the north 
of the cyclone, which will maintain a westerly track. The track 
guidance has become a little less tightly clustered as it has 
been over the last several runs, with some variations in how the 
models are handling the rate of weakening. The current forecast 
track remains close to the past track, near the center of the 
guidance envelope. 

The forecast track keeps Darby in a moderately sheared environment 
for the next couple of days, and continuing along the 25-26C sea 
surface temperatures (SST). The shear, SST and climatologically low 
mid-level relative humidity values near the track all work against 
redevelopment of Darby. The intensity forecast has been lowered some 
from the past forecast, to be in line with the latest guidance 
consensus, which leads to dissipation of the remnant circulation by 
Sunday night.


INIT  15/2100Z 17.6N 147.7W   50 KT  60 MPH
 12H  16/0600Z 17.6N 150.2W   40 KT  45 MPH
 24H  16/1800Z 17.5N 153.9W   35 KT  40 MPH
 36H  17/0600Z 17.2N 157.7W   30 KT  35 MPH
 48H  17/1800Z 16.9N 161.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  18/0600Z...DISSIPATED

Forecaster M Ballard/R Ballard

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