863 
 WTNT41 KNHC 190243
 TCDAT1
 
 TROPICAL STORM FIONA DISCUSSION NUMBER   9
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
 1100 PM AST THU AUG 18 2016
 
 A sizable burst of deep convection has been ongoing since late this
 afternoon, and recent microwave imagery suggests that the low-level
 center may be a little closer to the thunderstorm activity than it
 was for most of the day.  Still, Dvorak estimates are unchanged at
 T3.0/45 kt from TAFB and T2.5/35 kt from SAB, and the initial
 intensity remains 40 kt.
 
 Fiona's window for any strengthening is narrowing.  SHIPS guidance
 is currently analyzing 10-15 kt of south-southwesterly shear, while
 the UW-CIMSS analysis has the shear as high as 20-25 kt.  Despite
 the discrepancy, these values suggest the shear is already
 increasing, and it is expected to increase further and become more
 westerly during the next three days.  Therefore, if the current
 burst of convection continues, Fiona has a chance to strengthen
 slightly during the next 12 hours and then gradually weaken through
 days 3 and 4.  The forecast trends in the intensity models suggest
 that Fiona could weaken to a tropical depression, which is now
 shown in the official forecast.  Environmental conditions appear to
 be a little less hostile by the end of the forecast period, and the
 NHC forecast allows for the possibility that Fiona could
 restrengthen after the shear lightens up.  The GFDL continues to
 be an outlier by intensifying Fiona more than the other models, and
 the official intensity forecast is therefore near or just below the
 intensity consensus for most of the forecast period.
 
 Microwave fixes indicate that Fiona has been moving more slowly
 toward the northwest, or 305/7 kt.  The cyclone is moving toward a
 break in the subtropical ridge located between 40W-55W, and an
 amplifying deep-layer trough over the north Atlantic is expected to
 maintain this break for the next several days.  By continuing on a
 northwestward heading, Fiona is expected to reach the axis of the
 subtropical ridge and turn northward by day 5.  The GFDL is still
 well to the northeast of the rest of the track guidance since it
 carries a much stronger system, but the other models are otherwise
 in very good agreement.  Therefore, no significant changes were
 made to the NHC track forecast, which remains close to the TVCN
 multi-model consensus.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  19/0300Z 17.1N  41.8W   40 KT  45 MPH
  12H  19/1200Z 17.8N  43.1W   45 KT  50 MPH
  24H  20/0000Z 18.7N  44.9W   40 KT  45 MPH
  36H  20/1200Z 19.8N  46.9W   35 KT  40 MPH
  48H  21/0000Z 20.9N  48.9W   35 KT  40 MPH
  72H  22/0000Z 23.0N  53.2W   30 KT  35 MPH
  96H  23/0000Z 25.0N  56.5W   30 KT  35 MPH
 120H  24/0000Z 27.5N  57.0W   35 KT  40 MPH
 
 $$
 Forecaster Berg