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Hurricane Darby Discussion Number 22
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 AM HST Thu Jul 14 2022
Although Darby's appearance was fairly impressive overnight, the
hurricane has recently taken on a very ragged appearance, with the
central dense overcast becoming much less symmetrical around the
center as shear begins to impact the core convection. The initial
intensity was estimated to be 85 kt, a blend of the Dvorak estimates
from PHFO (77 kt), PGTW (90 kt) and the latest UW-CIMSS ADT (87
kt).
The initial motion is 280/14, with Darby located on the southwest
periphery of a mid-level ridge. An upper level trough to the NW of
Darby has been drawing the TC a little north of due west. This
motion is expected to continue for the next day or so, then turn
more toward due west as Darby gets farther away from the influence
of this trough, and becomes increasingly steered by the lower level
flow. At that time, strong high pressure north of Hawaii will aid in
an increase in forward speed. The track guidance remains tightly
clustered, and our official forecast lies just north of the the
middle of the guidance envelope.
Darby remains a small tropical cyclone over 26C sea surface
temperatures, and is riding along a strong gradient of deep layer
shear, currently about 20 kt near the center. The shear is
expected to remain moderate, with marginal SSTs along the
forecast track, so the guidance is unanimous about additional
weakening. Our forecast remains just a touch more conservative with
the rate of weakening shown by the guidance owing to the recent
persistence of the well-developed core, but still shows Darby
becoming a remnant low on Saturday.
FORECAST POSITIONS AND MAX WINDS
INIT 14/2100Z 17.0N 142.1W 85 KT 100 MPH
12H 15/0600Z 17.3N 144.1W 75 KT 85 MPH
24H 15/1800Z 17.4N 147.0W 60 KT 70 MPH
36H 16/0600Z 17.4N 150.3W 50 KT 60 MPH
48H 16/1800Z 17.2N 153.6W 40 KT 45 MPH
60H 17/0600Z 17.0N 157.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 17/1800Z...DISSIPATED
$$
Forecaster R Ballard/M Ballard
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