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TROPICAL STORM FIONA DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
1100 AM AST FRI AUG 19 2016

Fiona continues to produce bursts of convection, mainly near and
north of the center.  The current burst has weakened during the
past few hours, leaving the low-level center partly exposed south
of the convective area.  Various objective and subjective satellite
intensity estimates range from 35-50 kt, and based on these, the
initial intensity remains 40 kt.

The initial motion is 295/9.  A low- to mid-level ridge north of the
cyclone is steering Fiona west-northwestward, and this motion
should continue with some increase in forward speed during the next
48-72 hours.  After that time, a developing weakness in the ridge
is expected to cause Fiona to turn northwestward.  The guidance has
shifted a little westward between 72-120 hours.  Thus, that portion
of the track is also nudged westward, but it lies to the east of
the various consensus models.

A combination of a dry air mass, increasing vertical wind shear, and
convergent upper-level flow should cause Fiona to weaken for the
next 3-4 days.  The intensity forecast follows the guidance
consensus in calling for the cyclone to weaken to a depression by 48
hours, and then remain at about a 30 kt intensity through the rest
of the forecast period.  An alternative scenario is that the system
weakens more than currently forecast and decays to a remnant low
sometime before day 4.  As noted in the previous discussion, the
environmental conditions might get less hostile by day 5.  However,
it is uncertain how much of the cyclone might be left to take
advantage of these more favorable conditions.


FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 17.8N  43.5W   40 KT  45 MPH
 12H  20/0000Z 18.4N  44.9W   40 KT  45 MPH
 24H  20/1200Z 19.3N  46.9W   35 KT  40 MPH
 36H  21/0000Z 20.4N  49.1W   35 KT  40 MPH
 48H  21/1200Z 21.6N  51.5W   30 KT  35 MPH
 72H  22/1200Z 24.0N  56.0W   30 KT  35 MPH
 96H  23/1200Z 26.0N  58.5W   30 KT  35 MPH
120H  24/1200Z 28.0N  60.0W   30 KT  35 MPH

$$
Forecaster Beven

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