000
WTNT43 KNHC 011441
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 AM AST WED SEP 01 2010
 
EARLIER THIS MORNING...THE AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT
MEASURED A PEAK 850 MB WIND OF 58 KT...BELIEVABLE SFMR VALUES OF
45-50 KT...AND A MINIMUM PRESSURE OF 998 MB.  THIS WAS THE BASIS FOR
THE 8 AM INTENSITY OF 50 KT.  SINCE THAT TIME... THE SYSTEM HAS
BECOME MORE DISORGANIZED WITH THE CENTER ON THE NORTHWESTERN EDGE OF
WEAKENING DEEP CONVECTION.  ANOTHER AIRCRAFT WILL BE IN THE SYSTEM
EARLY THIS AFTERNOON.  DESPITE MODERATE SHEAR...ALL OF THE
GUIDANCE SHOW FURTHER INTENSIFICATION AND MOST ACTUALLY MAKE FIONA
A HURRICANE.  BY LATE TOMORROW...THE SHEAR SHOULD INCREASE AS THE
MAJORITY OF THE GLOBAL MODELS HAVE FAIRLY STRONG NORTHEASTERLY
SHEAR IN A FEW DAYS DUE PRIMARILY TO STRONG UPPER-LEVEL WINDS FROM
EARL. THIS PATTERN CAUSES FIONA TO RAPIDLY WEAKEN IN 3 OR 4
DAYS...AND THE NHC FORECAST WILL STAY ON THE LOWER END OF THE
GUIDANCE ENVELOPE...FAIRLY CLOSE TO THE SHIPS MODEL.
 
AIRCRAFT FIXES SHOW A MOTION OF ABOUT 305/15 DURING THE PAST SEVERAL
HOURS. TRACK MODELS ARE IN GOOD AGREEEMENT ON A NORTHWEST TO
NORTH-NORTHWEST MOTION FOR A DAY OR TWO DUE TO FIONA MOVING AROUND
A SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC OCEAN. HOWEVER...THE
GUIDANCE STARTS TO BECOME RATHER DIVERGENT AFTER THAT TIME...WHICH
APPEARS TO BE RELATED TO THE FUTURE INTENSITY OF FIONA. IF THE
STORM WEAKENS QUICKLY...THE LOW-LEVEL CIRCULATION WILL LIKELY GET
CAUGHT UP IN SOUTHWESTERLY FLOW AHEAD OF EARL. HOWEVER...IF FIONA
STAYS A MORE COHERENT VORTEX...THERE REMAINS THE POTENTIAL FOR IT
TO GET TRAPPED BY A MID-LEVEL SUBTROPICAL RIDGE. GIVEN THE STRONG
SHEAR FORECAST AT THE END...THE NHC FORECAST LEANS TOWARD THE
FASTER TRACK SCENARIO AT THE END OF THE FORECAST PERIOD AND
IS CLOSE TO THE PREVIOUS FORECAST. HOWEVER...I DO NOT HAVE A LOT OF
CONFIDENCE IN THE LONG-TERM TRACK OR INTENSITY FORECASTS...AS THE
MODELS HAVE BEEN STURGGLING WITH CONSISTENCY WITH THIS STORM.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/1500Z 18.8N  61.7W    50 KT
 12HR VT     02/0000Z 20.3N  63.3W    55 KT
 24HR VT     02/1200Z 22.6N  65.3W    55 KT
 36HR VT     03/0000Z 24.9N  66.6W    55 KT
 48HR VT     03/1200Z 26.9N  67.1W    45 KT
 72HR VT     04/1200Z 29.0N  67.0W    40 KT
 96HR VT     05/1200Z 31.0N  67.0W    30 KT
120HR VT     06/1200Z...DISSIPATED
 
$$
FORECASTER BLAKE