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Hurricane Darby Discussion Number  10
NWS National Hurricane Center Miami FL       EP052022
1100 AM HST Mon Jul 11 2022
 
Darby's satellite presentation continues to be very impressive, and 
has improved further since this morning. While convective cloud tops 
associated with the eyewall convection have not cooled much more, 
hovering between -65 to -75 C, the eye temperature has warmed 
further, with the warmest pixel fluctuating between +18-20C. The 
presentation on visible images is similarly spectacular, with a few 
mesovorticies seen rotating around in the eye exhibiting a classic 
stadium effect, and the GOES-GLM occasionally showing some inner 
core flashes. The latest UW-CIMSS objective Dvorak estimate has 
stabilized somewhat at T6.1/117 kt despite the warming eye 
temperature. However, very small tropical cyclones like Darby are 
often underestimated using objective Dvorak guidance, as was seen 
during similarly small systems, like Dorian in 2019 when it near the 
Bahamas. I also suspect the eyewall cloud tops have warmed a tad due 
to diurnal fluctuations and could cool once again during the typical 
nighttime max. The current intensity this advisory will be set at 
120 kt, indicating a remarkable intensification rate of 65 kt in the 
past 24 hours.
 
A little bit of additional intensification is possible in the short
term and the latest intensity forecast now peaks Darby as a 125-kt
hurricane in 12 hours, very close to the GFS-SHIPS guidance. It is
notable that this was also the peak intensity that a similarly-small
Hurricane Felicia also reached in this same general vicinity last
July. While shear is expected to remain very low through 48 hours,
sea-surface temperatures do start to decrease and drop below 26C in
36 hours, which should begin a weakening trend by Wednesday.
Vertical wind shear then begins to increase more after 48 hours,
which will likely induce more rapid weakening of the small cyclone.
Both the GFS- and ECMWF model simulated IR-brightness temperature
shows deep convection collapsing on Friday, and the latest forecast
now makes Darby post-tropical by 96 hours.
 
Darby is still moving westward at 275/13 kt. The track philosophy
has not changed this cycle, as a mid-level ridge is steering the
hurricane generally westward. A slight weakness in the ridge after
24 hours should allow Darby to take a more west-northwestward track
in the 36-72 hour forecast period. As Darby becomes more shallow at
the end of the forecast period, its track is forecast to bend back
westward as the low-level trade wind flow becomes dominant. The
latest track forecast is similar to the previous advisory, still
favoring a blend of the GFS and ECMWF forecasts, but ends up near
the TVCE consensus aid towards the end of the forecast period.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/2100Z 14.7N 125.0W  120 KT 140 MPH
 12H  12/0600Z 14.8N 127.0W  125 KT 145 MPH
 24H  12/1800Z 14.9N 129.7W  120 KT 140 MPH
 36H  13/0600Z 15.1N 132.2W  100 KT 115 MPH
 48H  13/1800Z 15.6N 134.7W   80 KT  90 MPH
 60H  14/0600Z 16.3N 137.3W   65 KT  75 MPH
 72H  14/1800Z 17.0N 140.0W   50 KT  60 MPH
 96H  15/1800Z 17.4N 145.3W   35 KT  40 MPH...POST-TROPICAL
120H  16/1800Z 17.3N 151.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Papin
 
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