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Hurricane Darby Discussion Number 14
NWS National Hurricane Center Miami FL EP052022
1100 AM HST Tue Jul 12 2022
Darby remains a small and formidable hurricane, although there are
some subtle changes in its convective pattern. The hurricane looks
a little more asymmetric in infrared imagery, favoring the western
side, and a black ring on the Dvorak enhancement curve (colder than
-63 degrees Celsius) has struggled to stay wrapped around the eye.
Subjective Dvorak Current Intensity numbers have gradually fallen
closer to objective numbers, and the range of estimated intensities
is now from 90-102 kt. Darby's current intensity is therefore
lowered to 100 kt.
Darby lost a little bit of latitude since overnight, but the
12-hour average motion remains westward, or 270/15 kt. The
hurricane should maintain a westward motion for another 24 hours
but then take on a slightly slower west-northwestward track from
36-48 hours as it moves toward a break in the subtropical ridge.
After 48 hours, a filling of the break and a weaker Darby should
cause the motion to turn back toward the west, continuing through
dissipation in 4-5 days. There is very little spread among the
track guidance, and the only noteworthy point is that the ECMWF and
HCCA aid are faster than much of the other models. The updated
NHC forecast is generally on top of the previous forecast but just
a little faster during the first 36 hours, hedging toward the ECMWF
and HCCA solutions.
Vertical shear over Darby is expected to be 10 kt or less during
the next 36 hours, but marginal sea surface temperatures of 26
degrees Celsius are likely to foster additional gradual weakening
during that time. Southwesterly to westerly shear then increases
in earnest to 20-30 kt on days 2 and 3, which should induce more
significant weakening. The intensity guidance is in very good
agreement, and Darby could weaken below hurricane strength soon
after 48 hours, become post-tropical by day 4, and degenerate into a
trough by day 5. Some of the global model guidance suggest that the
post-tropical phase and dissipation could occur even sooner than
indicated in the official forecast.
FORECAST POSITIONS AND MAX WINDS
INIT 12/2100Z 14.6N 131.2W 100 KT 115 MPH
12H 13/0600Z 14.8N 133.3W 95 KT 110 MPH
24H 13/1800Z 15.3N 136.0W 85 KT 100 MPH
36H 14/0600Z 16.0N 138.6W 75 KT 85 MPH
48H 14/1800Z 16.6N 141.0W 65 KT 75 MPH
60H 15/0600Z 17.0N 143.5W 55 KT 65 MPH
72H 15/1800Z 17.1N 146.3W 40 KT 45 MPH
96H 16/1800Z 17.0N 152.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 17/1800Z...DISSIPATED
$$
Forecaster Berg
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