652 
 WTNT43 KNHC 310853
 TCDAT3
 TROPICAL STORM FIONA DISCUSSION NUMBER   3
 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
 500 AM AST TUE AUG 31 2010
  
 FIONA HAS CHANGED LITTLE IN STRUCTURE DURING THE LAST SEVERAL HOURS.
 DEEP CONVECTION REMAINS CONFINED TO A FEW CURVED BANDS MAINLY OVER
 THE WESTERN SEMICIRCLE...ALTHOUGH AN AREA OF THUNDERSTORMS HAS
 RECENTLY FORMED NEAR THE ESTIMATED CENTER POSITION. THE INITIAL
 INTENSITY IS HELD AT 35 KT...IN AGREEMENT WITH AN 0056 UTC ASCAT
 PASS AND A 1007 MB PRESSURE REPORT FROM BUOY 41040. ONLY A LITTLE
 STRENGTHENING IS FORECAST IN THE SHORT TERM DUE TO MARGINALLY
 FAVORABLE UPPER-LEVEL WINDS...SOME DRY AIR AROUND THE CYCLONE...AND
 CURRENT LACK OF ORGANIZATION. THE SHIPS MODEL SHOWS NORTHEASTERLY
 SHEAR INCREASING SIGNIFICANTLY IN 24-36 HOURS...AND IF
 CORRECT...THAT SHOULD LIMIT ADDITIONAL STRENGTHENING. THIS
 INTENSITY FORECAST IS UNCHANGED FROM EARLIER AND REMAINS NEAR THE
 LOW END OF THE MODEL GUIDANCE.
  
 THE AFOREMENTIONED ASCAT PASS AND A TRMM OVERPASS AT 0303 UTC
 SUGGESTED THAT THE LOW-LEVEL CENTER...ALBEIT NOT VERY EASY TO
 LOCATE...WAS SITUATED A LITTLE TO THE NORTH OF THE PREVIOUS
 ESTIMATES. THEREFORE...THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN
 285/20. A NARROW MID-LEVEL RIDGE LOCATED ALONG 25 N OVER THE
 CENTRAL AND EASTERN ATLANTIC IS EXPECTED TO KEEP FIONA ON A RATHER
 FAST WEST-NORTHWESTWARD COURSE FOR THE NEXT DAY OR SO.
 THEREAFTER...THE CYCLONE IS EXPECTED TO APPROACH A WEAKNESS IN THE
 RIDGE...WHICH WILL BE ENHANCED BY HURRICANE EARL...AND THAT SHOULD
 CAUSE FIONA TO GRADUALLY SLOW DOWN AND TURN TO THE NORTHWEST. THE
 ECMWF...WHICH HAS BEEN THE LEFT-MOST MODEL FOR THE PAST COUPLE OF
 CYCLES...IS NOW ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE. IN
 GENERAL...THE MODEL GUIDANCE HAS SHIFTED SLIGHTLY TO THE RIGHT AND
 IS A LITTLE FASTER AT THE END OF THE PERIOD...AND THE NHC FORECAST
 HAS BEEN ADJUSTED IN THAT DIRECTION.
 
 FORECAST POSITIONS AND MAX WINDS
  
 INITIAL      31/0900Z 15.8N  53.0W    35 KT
  12HR VT     31/1800Z 16.5N  55.7W    35 KT
  24HR VT     01/0600Z 17.8N  59.1W    40 KT
  36HR VT     01/1800Z 19.6N  61.9W    45 KT
  48HR VT     02/0600Z 21.8N  64.2W    45 KT
  72HR VT     03/0600Z 26.5N  67.5W    45 KT
  96HR VT     04/0600Z 29.0N  68.5W    45 KT
 120HR VT     05/0600Z 30.5N  69.0W    45 KT
  
 $$
 FORECASTER CANGIALOSI/BLAKE