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TROPICAL DEPRESSION FIONA DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
1100 AM AST MON AUG 22 2016

The satellite depiction of Fiona currently features an exposed
low-level circulation with a few small areas of convection
southeast of the center.  Subjective satellite intensity estimates
from TAFB and SAB are 30 kt, while the various objective estimates
range from 25-45 kt.  The initial intensity remains 30 kt based
mainly on the subjective estimates.

The dynamical models forecast that the current westerly vertical
shear will subside somewhat by 48 hours as Fiona moves under an
upper-level trough into an area of easterly upper-level winds to
the north of the trough.  By 72 hours, the models forecast the
cyclone or its remnants to encounter a second trough, which should
produce another round of strong southwesterly shear. Based on the
premise that the cyclone will not be able to respond to the brief
period of more favorable conditions, the new intensity forecast
calls for Fiona to gradually decay and become a remnant low in about
36 hours. This would be followed by the system weakening to a trough
after 96 hours.

The initial motion is 285/16.  The guidance remains in good
agreement on the forecast track through 72 hours, with Fiona moving
west-northwestward to northwestward toward a developing break in
the subtropical ridge.  Beyond that time, the guidance diverges,
with the ECMWF turning the remnants of the system northeastward
while the GFS and UKMET show a westward turn.  The new forecast
track will compromise between these extremes in showing a slow
north-northwestward motion.  The new forecast track is shifted a
little to the west of the previous track and lies near the various
consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT  22/1500Z 24.6N  59.7W   30 KT  35 MPH
 12H  23/0000Z 25.3N  61.5W   30 KT  35 MPH
 24H  23/1200Z 26.1N  63.5W   30 KT  35 MPH
 36H  24/0000Z 27.0N  65.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  24/1200Z 28.1N  66.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  25/1200Z 30.0N  68.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  26/1200Z 31.5N  68.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  27/1200Z...DISSIPATED

$$
Forecaster Beven

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