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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
kt.
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.
FORECAST POSITIONS AND MAX WINDS
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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