[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 222037
TCDAT1

TROPICAL DEPRESSION FIONA DISCUSSION NUMBER  24
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
500 PM AST MON AUG 22 2016

A new burst of convection has developed near the center of Fiona
during the past several hours.  However, this increase was not
significant enough to affect the subjective satellite intensity
estimates, which remain at 30 kt.  This is also in good
agreement with earlier ASCAT data.

The dynamical models forecast that the current westerly vertical
shear will subside somewhat by 36-48 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. The
intensity forecast is still based on the premise that the cyclone
will not be able to respond to the brief period of more favorable
conditions, and it calls for Fiona to gradually decay and become a
remnant low in about 48 hours. This should be followed by the system
weakening to a trough after 96 hours.

The initial motion is 285/15.  The guidance remains in good
agreement on the forecast track through 72 hours, with Fiona moving
west-northwestward to northwestward toward a weakness 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 is again a compromise between these extremes in showing a slow
north-northwestward motion.  Overall, the track guidance has
shifted westward since the previous advisory, and as a result the
forecast track has also shifted a little to the west.

FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z 25.1N  61.3W   30 KT  35 MPH
 12H  23/0600Z 25.6N  63.1W   30 KT  35 MPH
 24H  23/1800Z 26.5N  65.0W   30 KT  35 MPH
 36H  24/0600Z 27.4N  66.7W   30 KT  35 MPH
 48H  24/1800Z 28.3N  67.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  25/1800Z 30.5N  69.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  26/1800Z 31.5N  70.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  27/1800Z...DISSIPATED

$$
Forecaster Beven
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