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Hurricane Fernanda Discussion Number  15
NWS National Hurricane Center Miami FL       EP072023
1100 PM HST Tue Aug 15 2023
 
Fernanda's structure is becoming more ragged and less organized this 
evening, as it moves into a drier and more stable airmass. Infrared 
satellite trends since the previous advisory have drastically 
deteriorated, with convection dissipating, particularly on the 
northern side of the system. Cloud tops have been warming over the 
last few hours as well. Subjective Dvorak final-T estimates were 
lower for this cycle as well with SAB and TAFB at T3.5 and 4.0, 
respectively.  Although, some of the objective intensity estimates 
from UW-CIMSS are still a bit higher.  Using a blend of satellite 
estimates and assuming a lag in the spin down of Fernanda's winds, 
the initial intensity for this advisory is set at 65 kt.

Fernanda continues to weaken, barely holding on to hurricane 
strength. Vertical wind shear continues to effect the system, as 
well as rapidly cooling sea-surface temperatures, and mid-level 
relative humidity levels below 40 percent. This combination will 
continue to cause rapid weakening, and Fernanda is expected to 
become a tropical storm within very soon, and a post-tropical 
cyclone in about 36 h. There is good agreement from global model 
simulated infrared satellite images that the cyclone will be void 
of deep convection in about 36 h.  The remnant low is now expected 
to open up into a trough by day 5.
 
The motion of Fernanda remains generally westward, with a mid-level 
ridge expected to continue to steer the cyclone generally westward 
throughout the forecast period. The track guidance this cycle once 
again shifted a bit south, possibly in response to the storm quickly 
weakening and becoming more steered by the low-level flow. Thus, 
the latest NHC track forecast has been shifted a bit to the south of 
the prior one, but not quite as far as south as the HCCA corrected 
consensus.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  16/0900Z 17.4N 125.5W   65 KT  75 MPH
 12H  16/1800Z 17.2N 127.5W   55 KT  65 MPH
 24H  17/0600Z 17.1N 130.2W   40 KT  45 MPH
 36H  17/1800Z 17.2N 132.9W   35 KT  40 MPH...POST-TROPICAL
 48H  18/0600Z 17.3N 135.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  18/1800Z 17.5N 138.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  19/0600Z 17.7N 141.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  20/0600Z 17.7N 147.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  21/0600Z...DISSIPATED
 
$$
Forecaster Kelly/Berg
 
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