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TROPICAL STORM FIONA DISCUSSION NUMBER   6...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
500 AM AST THU AUG 18 2016

Corrected track guidance discussion in third paragraph

Deep convection associated with Fiona has increased with the
approach of the diurnal convective maximum, and the cyclone's cloud
pattern is better organized than it was yesterday.  Satellite data
suggest that the low-level center is now located underneath an
irregularly shaped central dense overcast, while a few broken
banding features have recently developed over the eastern semicircle
of the circulation. Satellite classifications are T3.0/45 kt and
T2.0/30 kt from TAFB and SAB, respectively, while ADT values are
around T3.0. A blend of these data is used to increase the initial
wind speed to 40 kt.

Global models indicate that large-scale conditions should be
adequately conducive to support some additional strengthening during
the next 12 to 24 hours.  However, after that time, a substantially
drier atmosphere and increasing southwesterly shear associated with
the mid-oceanic trough are expected to induce weakening, even though
sea surface temperatures will be higher.  Although not shown
explicitly in the forecast, atmospheric conditions could become so
hostile that Fiona would degenerate into a remnant low later in the
forecast period as depicted in the ECMWF model. The new NHC
intensity forecast is slightly higher than the previous one and the
bulk of the guidance in the short term but is a little lower after
48 hours.

Fiona has been moving west-northwestward to northwestward into a
weakness in the mid-level subtropical ridge between 40w and 50w,
and the initial motion estimate is 300/14.  Fiona should maintain a
similar heading but at a reduced forward speed once it becomes a
shallower cyclone in a few days and is steered around the Atlantic
low-level subtropical ridge.  The NHC track forecast has been
adjusted to the north of the previous one, mostly after 48 hours and
largely in response to a significant shift in the latest ECMWF
solution.  The forecast track lies on the western side of the
guidance envelope, well to the left of the multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  18/0900Z 16.2N  40.3W   40 KT  45 MPH
 12H  18/1800Z 17.0N  41.4W   45 KT  50 MPH
 24H  19/0600Z 17.9N  43.0W   50 KT  60 MPH
 36H  19/1800Z 18.7N  44.6W   45 KT  50 MPH
 48H  20/0600Z 19.8N  46.6W   40 KT  45 MPH
 72H  21/0600Z 22.1N  50.1W   35 KT  40 MPH
 96H  22/0600Z 23.8N  53.5W   35 KT  40 MPH
120H  23/0600Z 25.6N  56.1W   35 KT  40 MPH

$$
Forecaster Kimberlain

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