140 
 WTNT43 KNHC 311439
 TCDAT3
 TROPICAL STORM FIONA DISCUSSION NUMBER   4
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
 1100 AM AST TUE AUG 31 2010
  
 A 0929 UTC SSMIS MICROWAVE OVERPASS SHOWED CURVED BANDS OF
 CONVECTION LOOSELY WRAPPING AROUND THE CENTER. SINCE THAT TIME
 VISIBLE SATELLITE IMAGERY INDICATES THAT THE CONVECTIVE BANDS NEAR
 THE CENTER HAVE WEAKENED...WHILE NEW CONVECTION HAS DEVELOPED
 AROUND THE PERIPHERY OF THE CIRCULATION.  THE INITIAL INTENSITY
 REMAINS 35 KT...BASED ON THE EARLIER SCATTEROMETER DATA.  AN AIR
 FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO 
 INVESTIGATE FIONA THIS AFTERNOON AND SHOULD PROVIDE A BETTER
 ASSESSMENT OF THE CURRENT STRUCTURE AND INTENSITY.
 
 THE INITIAL MOTION ESTIMATE IS 285/21 KT.  THE CYCLONE IS FORECAST
 TO SLOW DOWN AND TURN NORTHWESTWARD DURING THE NEXT 24 HOURS AS IT
 NEARS THE WESTERN PORTION OF THE SUBTROPICAL RIDGE.  THEREAFTER...
 FIONA IS EXPECTED TO TURN NORTH-NORTHWESTWARD...THEN NORTHWARD
 BETWEEN THE WESTERN SIDE OF THE RIDGE AND HURRICANE EARL TO THE
 NORTHWEST.  THE TRACK GUIDANCE IS IN BETTER AGREEMENT ON THIS
 SCENARIO AND THE OFFICIAL FORECAST HAS BEEN ADJUSTED EASTWARD ALONG
 THE LEFT SIDE OF THE GUIDANCE ENVELOPE.  LATE IN THE FORECAST
 PERIOD...FIONA SHOULD TURN NORTHEASTWARD AS DEEP SOUTHWESTERLY FLOW
 DEVELOPS OVER THE WESTERN ATLANTIC.
 
 THERE APPEARS TO BE A SMALL WINDOW OF OPPORTUNITY FOR FIONA TO
 STRENGTHEN DURING THE NEXT 12 TO 24 HOURS BEFORE AN UPPER-LEVEL
 RIDGE TO THE NORTHWEST OF FIONA STRENGTHENS...AND NORTHEASTERLY
 UPPER-LEVEL WINDS INCREASE.  THE SHEAR IS FORECAST TO REMAIN
 MODERATE TO STRONG THROUGHOUT MOST OF THE FORECAST PERIOD AND NO
 ADDITIONAL STRENGTHENING IS PREDICTED.  AN ALTERNATE SCENARIO...AS
 SHOWN BY THE GFS...IS THAT FIONA COULD WEAKEN AND POSSIBLY
 DISSIPATE IN A COUPLE OF DAYS DUE TO THE AFOREMENTIONED SHEAR.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      31/1500Z 15.9N  55.3W    35 KT
  12HR VT     01/0000Z 16.9N  58.2W    40 KT
  24HR VT     01/1200Z 18.7N  61.3W    45 KT
  36HR VT     02/0000Z 21.1N  63.8W    45 KT
  48HR VT     02/1200Z 23.4N  65.8W    45 KT
  72HR VT     03/1200Z 27.7N  67.8W    45 KT
  96HR VT     04/1200Z 31.0N  67.5W    45 KT
 120HR VT     05/1200Z 34.0N  66.0W    45 KT
  
 $$
 FORECASTER BROWN