015 
 WTNT41 KNHC 181241
 TCDAT1
 
 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