Eastern Pacific Basin Tropical Cyclones

Hurricane Darby Forecast Discussion


000
WTPZ45 KNHC 122037
TCDEP5

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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