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Tropical Storm Fernanda Discussion Number   4
NWS National Hurricane Center Miami FL       EP072023
800 AM PDT Sun Aug 13 2023
 
The compact storm is currently exhibiting a CDO-type cloud pattern
with very cold embedded tops to near -80 deg C.  Upper-level
outflow is well defined over the western semicircle of the
circulation.  The current intensity estimate is set at 50 kt based
on a blend of subjective Dvorak estimates from TAFB and SAB along
with various objective estimates from UW-CIMSS.
 
Fernanda continues its west-northwestward trek, and the initial
motion estimate remains at around 285/9 kt.  A weak mid-level ridge
is currently situated to the north of the system.  Over the next
few days, the ridge is expected to strengthen somewhat.  This
should result in a gradual increase in forward speed during the
forecast period with a turn toward the west in a few days.  The
official forecast track is essentially an update of the previous one
and is very close to the dynamical model consensus, TVCE.
 
The tropical cyclone should continue to traverse sea surface
temperatures near 29 deg C for the next 36 hours or so with very
low vertical wind shear.  Rapid intensification (RI) seems likely,
and the SHIPS RI indices show a significant likelihood of an
increase of intensity of around 30 kt during the next day or so.
The official forecast goes along with this guidance and calls for
Fernanda to become a hurricane in 12 hours or so, and to reach
category 2 strength within the next couple of days.  By 48 hours and
beyond a drier air mass, seen in GOES-18 low-level water vapor
imagery to the west-northwest of the cyclone, should result in
weakening.  The official forecast is near or a little below the
latest corrected consensus, HCCA, prediction.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/1500Z 15.4N 115.9W   50 KT  60 MPH
 12H  14/0000Z 15.6N 117.2W   65 KT  75 MPH
 24H  14/1200Z 16.0N 118.7W   80 KT  90 MPH
 36H  15/0000Z 16.4N 120.4W   90 KT 105 MPH
 48H  15/1200Z 16.9N 122.2W   90 KT 105 MPH
 60H  16/0000Z 17.3N 124.3W   80 KT  90 MPH
 72H  16/1200Z 17.5N 126.5W   70 KT  80 MPH
 96H  17/1200Z 17.8N 132.0W   50 KT  60 MPH
120H  18/1200Z 18.0N 138.0W   35 KT  40 MPH
 
$$
Forecaster Pasch
 
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