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TROPICAL STORM FIONA DISCUSSION NUMBER  12
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
500 PM AST FRI AUG 19 2016

Fiona continues to produce bursts of convection north of the
center, although the center is now mostly exposed to the south of
the latest burst.  An earlier RapidScat overpass suggested that
tropical-storm-force winds were at best only occurring in the
northwest quadrant, and based on these data and the loss of
organization since this morning the initial intensity is decreased
to 35 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
caused by a frontal system moving eastward from the United States
should cause Fiona to turn northwestward and north-northwestward.
The guidance has again shifted westward between 72-120 hours.  Thus,
as in the previous advisory that portion of the track is also nudged
westward, but it remains 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 continue to
weaken. The intensity guidance has mostly trended toward lower
intensities since the last advisory, with the ECMWF model now
forecasting Fiona to weaken to a trough before 120 hours.  Based on
this, the intensity forecast now calls for Fiona to become a
remnant low after 72 hours.  That being said, the environmental
conditions might get less hostile by 120 hours, and the UKMET/
Canadian models suggest the possibility of re-intensification at
that time.  In deference to those models, the official forecast does
not call for dissipation during this forecast period.


FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 18.1N  44.4W   35 KT  40 MPH
 12H  20/0600Z 18.9N  46.0W   35 KT  40 MPH
 24H  20/1800Z 19.9N  48.2W   35 KT  40 MPH
 36H  21/0600Z 21.1N  50.7W   30 KT  35 MPH
 48H  21/1800Z 22.1N  53.1W   30 KT  35 MPH
 72H  22/1800Z 24.5N  57.5W   25 KT  30 MPH
 96H  23/1800Z 26.5N  60.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  24/1800Z 28.5N  61.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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