[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 220842
TCDAT1

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

Although deep convection has continued to pulse near the center of
Fiona, recent scatterometer wind data and various satellite
classifications support maintaining the small but remarkably
resilient cyclone as a 30-kt tropical depression. The intensity
forecast still remains something of an enigma. Strong westerly wind
shear is forecast to persist for the next 12-18 hours, after which
the upper-level winds relax somewhat and become a little more
conducive for strengthening to occur. However, dry mid-level
air of 40-50 percent humidity is also forecast to surround the
cyclone, which could act to hinder the development of persistent
deep convection for the next 24-36 hours. Therefore, if Fiona
can survive the aforementioned hostile conditions during the next 24
hours or so, then some restrengthening or maintaining the status as
a tropical cyclone is possible.  The global models still disagree on
the future of Fiona and have flipped-flopped, with the ECMWF no
longer showing dissipation in 5 days, which is similar to the UKMET
solution, whereas the GFS now shows Fiona degenerating into an open
trough between 96-120 hours. The NHC forecast maintains continuity
and indicates dissipation in 5 days as a compromise between these
possibilities.

The initial motion estimate remains 290/16 kt. Although there is
uncertainty in the future status of Fiona, the NHC model guidance
is in pretty good agreement on the track of the cyclone for the
next 72 hours. The small cyclone is forecast to move quickly
west-northwestward around the southwestern periphery of a
deep-layer ridge for the next 3 days, and then slow down
considerably on day 4 and turn northward into a weakness in the
ridge. The new official forecast track is basically just an update
of the previous track through 72 hours, and then is a little to
the right of the previous forecast on day 4, which leans closer to
the solutions of the various consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0900Z 24.4N  58.4W   30 KT  35 MPH
 12H  22/1800Z 25.0N  60.2W   30 KT  35 MPH
 24H  23/0600Z 25.8N  62.3W   30 KT  35 MPH
 36H  23/1800Z 26.6N  64.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  24/0600Z 27.6N  65.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  25/0600Z 29.8N  67.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  26/0600Z 31.3N  67.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  27/0600Z...DISSIPATED

$$
Forecaster Stewart
This weather bulletin was brought to you by:
www.nashvilleweather.net