WTNT43 KNHC 302047
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 PM EDT MON AUG 30 2010
 
EARLIER TODAY...ABOUT 30 DROPSONDES WERE RELEASED DURING A G-V
RESEARCH MISSION BEING CONDUCTED BY THE NATIONAL CENTER FOR
ATMOSPHERIC RESEARCH NEAR THE AREA OF LOW PRESSURE LOCATED ABOUT
800 MILES EAST OF THE LESSER ANTILLES.  ONE OF THE DROPSONDES
MEASURED A SURFACE WIND OF 35 KT APPROXIMATELY 120 N MI TO THE
NORTHEAST OF THE ESTIMATED CENTER.  THIS MEASUREMENT AGREES WITH AN
ASCAT PASS FROM 1208 UTC...WHICH SHOWED A SWATH OF 30-35 KT WINDS
IN THAT SAME AREA.  CONVECTION HAS BEEN A LITTLE THIN FOR MOST OF
THE DAY...BUT BANDING FEATURES HAVE RECENTLY BECOME MORE PROMINENT
MAINLY OVER THE WESTERN SEMICIRCLE.  GIVEN THE INCREASE IN
CONVECTION AND SINCE TROPICAL STORM FORCE WINDS ARE ALREADY
OCCURRING...THE SYSTEM IS BEING DIRECTLY UPGRADED TO TROPICAL STORM
FIONA.

SINCE FIONA STILL LACKS SOME ORGANIZATION AND THE WIND FIELD IS
SOMEWHAT LARGE...THE CYCLONE WILL LIKELY HAVE A DIFFICULT TIME
INTENSIFYING OVER THE NEXT DAY OR SO.  I DO NOT BELIEVE THIS
STRUCTURE IS HANDLED WELL BY THE STATISTICAL INTENSITY
GUIDANCE...WHICH INTENSIFY FIONA TO A HURRICANE IN 36 TO 48
HOURS...SO I AM INCLINED TO LEAN CLOSER TO THE DYNAMICAL GFDL AND
HWRF AT THIS POINT.  IN FACT...THE GFS DISSIPATES THE CYCLONE WITHIN
2 TO 3 DAYS.  THE OFFICIAL FORECAST THEREFORE SHOWS MINIMAL
STRENGTHENING OVER THE NEXT 1 TO 2 DAYS AND THEN LEVELS OUT THE
INTENSITY FOR DAYS 3 THROUGH 5...WHEN IT APPEARS THAT INCREASING
VERTICAL SHEAR COULD BECOME A LIMITING FACTOR. 

THE SURFACE CENTER HAS BEEN A LITTLE DIFFICULT TO LOCATE...AND THE
INITIAL MOTION IS AN UNCERTAIN 270/21.  TRACK MODEL GUIDANCE IS IN
GOOD AGREEMENT FOR THE NEXT 48 HOURS AND SHOWS FIONA TURNING TOWARD
THE NORTHWEST...GENERALLY FOLLOWING EARL AROUND THE WESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE.  AFTER THAT...THE
GFDL...HWRF...AND GFS KEEP FIONA AS A WEAK SYSTEM AND SHOW IT
CONTINUING TO THE NORTH IN THE LOW-LEVEL FLOW BEHIND EARL.  THE
ECMWF...ON THE OTHER HAND...SHOWS A STRONGER FIONA AND SUGGESTS
THAT THE SUBTROPICAL RIDGE COULD BUILD BACK TO THE WEST BEFORE THE
CYCLONE CAN RECURVE.  THE OFFICIAL FORECAST IS VERY CLOSE TO THE
MODEL CONSENSUS TVCN FOR THE FIRST 48 HOURS BUT THEN LIES A LITTLE
NORTH OF THE CONSENSUS IN FAVOR OF THE TRACKS OF THE WEAKER GFDL
AND HWRF.
 
  
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      30/2100Z 14.4N  48.7W    35 KT
 12HR VT     31/0600Z 14.9N  51.9W    35 KT
 24HR VT     31/1800Z 15.8N  55.9W    40 KT
 36HR VT     01/0600Z 17.2N  59.2W    45 KT
 48HR VT     01/1800Z 19.3N  62.0W    45 KT
 72HR VT     02/1800Z 24.0N  66.0W    40 KT
 96HR VT     03/1800Z 27.5N  68.0W    40 KT
120HR VT     04/1800Z 29.0N  69.0W    40 KT
 
$$
FORECASTER BERG
 

WTNT43 KNHC 310252
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 PM EDT MON AUG 30 2010
 
CONVECTION HAS INCREASED IN THE NORTHWESTERN PORTION OF FIONA THIS
EVENING. HOWEVER...OVERALL THE SYSTEM LOOKS FAIRLY DISORGANIZED
WITH JUST A FEW WEAK BANDING FEATURES. A NOAA/NTAS BUOY LOCATED
NEAR THE CENTER REPORTED A PRESSURE OF 1008 MB A FEW HOURS
AGO...WHICH IS ABOUT THE SAME PRESSURE AS BUOY 41041 MEASURED
EARLIER TODAY. THUS...THE INITIAL INTENSITY WILL REMAIN 35 KT FOR
THIS ADVISORY. GIVEN THE CURRENT DISHEVELED APPEARANCE OF FIONA...
ONLY A SLOW INCREASE IN STRENGTH IS FORECAST FOR THE NEXT DAY OR SO
WHILE THE TROPICAL CYCLONE MOVES OVER VERY WARM WATER AND LIGHT
SHEAR. AFTER THAT TIME...NORTHEASTERLY SHEAR INCREASES MARKEDLY AND
MAY HALT ANY FURTHER DEVELOPMENT...PLUS THE CYCLONE COULD BE MOVING
OVER COOLER WATERS THAT WERE UPWELLED BY EARL. MOST OF THE
MODELS...SAVE THE GFDL/GFDN...ARE IN CLOSE AGREEMENT WITH THIS
SCENARIO...AND THE OFFICIAL NHC INTENSITY FORECAST IS NEAR THE
PREVIOUS ONE BUT BELOW THE INTENSITY CONSENSUS. HOWEVER...I DO NOT
HAVE A LOT OF CONFIDENCE IN THE FORECAST AT THIS TIME.  
 
MICROWAVE AND SURFACE DATA SUGGEST THE CENTER IS MOVING 280/21.
FIONA SHOULD MOVE AROUND THE SOUTHWESTERN PERIPHERY OF A RIDGE OVER
THE CENTRAL ATLANTIC...EVENTUALLY TURNING TO THE WEST-NORTHWEST AND
NORTHWEST IN THE NEXT COUPLE OF DAYS.  THE TRACK MODELS ARE FAIRLY
WELL CLUSTERED...EXCEPT FOR THE ECMWF.  THAT MODEL IS ON THE LEFT
SIDE OF THE GUIDANCE ENVELOPE...PERHAPS BECAUSE IT SHOWS A DEEPER
FIONA RESPONDING TO STRONGER UPPER-LEVEL NORTHEASTERLY WINDS. 
SINCE WE ARE NOT EXPECTING THAT SCENARIO...THE NHC FORECAST IS VERY
CLOSE TO THE PREVIOUS ONE...AND IS A LITTLE SOUTH OF THE MODEL
CONSENSUS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/0300Z 15.1N  50.8W    35 KT
 12HR VT     31/1200Z 15.7N  54.0W    35 KT
 24HR VT     01/0000Z 16.9N  57.7W    40 KT
 36HR VT     01/1200Z 18.4N  60.6W    45 KT
 48HR VT     02/0000Z 20.5N  63.2W    45 KT
 72HR VT     03/0000Z 25.0N  67.0W    45 KT
 96HR VT     04/0000Z 28.0N  69.0W    45 KT
120HR VT     05/0000Z 29.0N  69.5W    45 KT
 
$$
FORECASTER BLAKE
 

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
 

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
 

WTNT43 KNHC 312049
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER   5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 PM AST TUE AUG 31 2010
 
THUNDERSTORM ACTIVITY HAS RECENTLY DEVELOPED NEAR THE CENTER OF
FIONA...HOWEVER THE CONVECTION SHOWS LITTLE BANDING.  THE AIRCRAFT
FOUND PEAK 925 MB FLIGHT-LEVEL WINDS OF 41 KT AND SEVERAL UNFLAGGED
SFMR WINDS OF AROUND 35 KT TO THE NORTH OF THE CENTER.  BASED ON
THESE DATA...THE INITIAL INTENSITY REMAINS 35 KT.  AN UPPER-LEVEL
ANTICYCLONE TO THE NORTHWEST OF FIONA IS FORECAST TO PRODUCE
INCREASING UPPER-LEVEL NORTHEASTERLY SHEAR OVER THE CYCLONE.  THE
SHEAR IS EXPECTED TO REMAIN STRONG DURING THE NEXT SEVERAL DAYS AND
ONLY A LITTLE STRENGTHENING IS SHOWN IN THE OFFICIAL FORECAST.
 
THE INITIAL MOTION ESTIMATE IS 290/21 KT.  FIONA IS FORECAST
TO TURN NORTHWESTWARD AND DECELERATE VERY SOON AS IT APPROACHES
THE WESTERN EDGE OF THE SUBTROPICAL RIDGE.  IN 36-48 HOURS...THE
CYCLONE SHOULD TURN NORTHWARD BETWEEN THE RIDGE AND HURRICANE EARL
TO THE NORTHWEST.  ALL OF GLOBAL MODELS DISSIPATE THE STORM IN 2-3
DAYS AS THE SMALLER CIRCULATION OF FIONA BECOMES AN OPEN TROUGH IN
THE STRONG SOUTHWESTERLY FLOW ON THE SOUTHEASTERN SIDE OF EARL.  THE
OFFICIAL FORECAST FOLLOWS THIS SCENARIO...HOWEVER DISSIPATION COULD
OCCUR EARLIER THAN SHOWN BELOW.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/2100Z 16.7N  57.7W    35 KT
 12HR VT     01/0600Z 17.9N  60.8W    40 KT
 24HR VT     01/1800Z 20.2N  63.7W    40 KT
 36HR VT     02/0600Z 23.0N  66.0W    40 KT
 48HR VT     02/1800Z 26.5N  67.7W    35 KT
 72HR VT     03/1800Z 33.5N  67.5W    35 KT
 96HR VT     04/1800Z...DISSIPATED
 
$$
FORECASTER BROWN
 

WTNT43 KNHC 010238
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 PM AST TUE AUG 31 2010

THE METEO FRANCE GUADELOUPE-MARTINIQUE RADAR MOSAIC WAS VERY HELPFUL
IN IDENTIFYING THE CIRCULATION CENTER OF FIONA.  DEEP CONVECTION
HAS BEEN PERSISTENT NEAR THE CENTER...BUT THE CLOUD PATTERN IS A
RATHER SHAPELESS BLOB...AND APPEARS TO BE ELONGATED ALONG AN AXIS
SOUTHEAST TO NORTHWEST.  THE DVORAK INTENSITY ESTIMATES REMAIN AT
30 KT FROM BOTH TAFB AND SAB...BUT THE INITIAL INTENSITY WILL
REMAIN AT 35 KT BASED ON THE PERSISTENT DEEP CONVECTION TO THE
NORTH OF THE CENTER WHERE THE EARLIER AIRCRAFT RECONNAISSANCE
RECORDED FLIGHT-LEVEL WINDS OF 41 KT.  NORTHEASTERLY SHEAR
ASSOCIATED WITH THE SOUTHEAST OUTFLOW CHANNEL OF EARL IS EXPECTED
TO IMPINGE ON THE WESTERN PORTION OF THE CYCLONE IN 36 HOURS.  THE
SHIPS MODEL AS WELL AS THE GLOBAL MODELS ALL SUGGEST THAT THE SHEAR
WILL SIGNIFICANTLY INCREASE OVER THE CYCLONE THROUGH DAY 3...
CAUSING DISSIPATION BY DAY 4.  THERE IS SOMEWHAT OF A CHANCE...
HOWEVER...OF MINIMAL STRENGTHENING PRIOR TO THE INCREASING
SHEAR DURING THE EARLY PORTION OF THE FORECAST. 
 
THE INITIAL MOTION IS SIMILAR TO THE PREVIOUS ADVISORY
ESTIMATE...BUT A LITTLE SLOWER...290/17 KT.  LARGE-SCALE MODELS
INDICATE THAT FIONA WILL TURN NORTHWESTWARD ALONG THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE DURING THE NEXT 24 HOURS.
THROUGH THE REMAINING FORECAST PERIOD...THE CYCLONE SHOULD TURN
NORTHWARD WITHIN A STIFF SOUTHERLY FLOW BETWEEN THE RIDGE EXTENDING
OVER BERMUDA AND HURRICANE EARL TO THE NORTHWEST.  THE OFFICIAL
FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE...WITH ONLY A SLIGHT
ADJUSTMENT TO THE LEFT...AND IS BASED ON THE MULTI-MODEL TVCN
CONSENSUS.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/0300Z 16.9N  59.4W    35 KT
 12HR VT     01/1200Z 18.7N  62.0W    40 KT
 24HR VT     02/0000Z 21.2N  64.7W    40 KT
 36HR VT     02/1200Z 24.4N  66.5W    40 KT
 48HR VT     03/0000Z 27.8N  67.6W    35 KT
 72HR VT     04/0000Z 35.0N  66.0W    30 KT
 96HR VT     05/0000Z...DISSIPATED
 
$$
FORECASTER ROBERTS/PASCH
 

WTNT43 KNHC 010900
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 AM AST WED SEP 01 2010
 
RECONNAISSANCE DATA...RADAR DATA FROM GUADELOUPE...AND SATELLITE
IMAGERY INDICATE FIONA HAS BECOME A LITTLE BETTER ORGANIZED THIS
MORNING. DEEP CONVECTION HAS INCREASED IN THE SOUTHERN SEMICIRCLE
AND THE CENTER HAS BECOME BETTER DEFINED IN RADAR IMAGERY AND IN
FLIGHT-LEVEL WIND DATA. THE MAXIMUM 850 MB FLIGHT-LEVEL WINDS
OBSERVED THUS FAR DURING THE CURRENT MISSION HAS BEEN 52 KT IN THE
NORTHEAST QUADRANT...WHICH EQUATES TO ABOUT A 42-KT SURFACE WIND.
THE LOWEST PRESSURES OBSERVED THUS FAR HAVE BEEN 1002 MB AT 0602Z
AND 1004 MB AT 0803Z. THE INITIAL INTENSITY IS SET AT 40 KT...WHICH
IS LOWER THAN THE 50-KT ADT INTENSITY ESTIMATE FROM UW-CIMSS.

THE INITIAL MOTION IS 290/12 KT USING RECON AND RADAR FIX POSITIONS.
FIONA APPEARS TO HAVE DECREASED ITS RATE OF CLOSURE ON EARL LOCATED
TO ITS NORTHWEST. OVER THE PAST 48 HOURS...THE DISTANCE BETWEEN
FIONA AND EARL HAS BEEN DECREASING BY ABOUT 100 NMI EVERY 12
HOURS...AND THE TWO CYCLONES ARE CURRENTLY ABOUT 750 NMI APART.
RIDDING BETWEEN THE TWO SYSTEMS HAS OBVIOUSLY INCREASED...WHICH HAS
RESULTED IN THE SIGNIFICANT DECREASE IN THE FORWARD SPEED OF FIONA
FROM MORE THAN 20 KT DOWN TO THE CURRENT 12 KT IN THE PAST 12
HOURS. THE POSSIBLE CAUSE OF THE RIDGING TO THE NORTHWEST OF FIONA
IS THE UPPER-LEVEL OUTFLOWS FROM BOTH CYCLONES CONVERGING TO THE
NORTHWEST OF FIONA. THIS RIDGING MAY ALLOW KEEP FIONA FROM
INTERACTING WITH THE LARGER CIRCULATION OF EARL LIKE MOST OF THE
GLOBAL MODELS HAVE BEEN FORECASTING THE PAST COUPLE OF DAYS. ALL OF
THE MODEL GUIDANCE...EXCLUDING NOGAPS...NOW SLOWS DOWN FIONA BY DAY
3...WITH THE CYCLONE POSSIBLY GETTING TRAPPED IN THE SUBTROPICAL
RIDGE. AS RESULT OF THESE NEW SCENARIO...A 96-HOUR POSITION HAS
BEEN ADDED AND DISSIPATION HAS BEEN DELAYED UNTIL 120 HOURS. IF
FIONA BECOMES A STRONGER SYSTEM THAN CURRENTLY FORECAST...THE
CYCLONE COULD SURVIVE AND END UP MAKING A CLOCKWISE LOOP OR EVEN
BECOME STATIONARY BY 120 HOURS. THE OFFICIAL FORECAST TRACK IS
SIMILAR TO THE PREVIOUS ADVISORY..EXCEPT SLOWER AT 48 HOURS AND
BEYOND...AND IS ALONG THE WESTERN EDGE OF THE GUIDANCE SUITE.

SOME DRY MID-LEVEL AIR APPEARS TO BE GETTING DRAWN INTO THE NORTHERN
QUADRANT OF THE FIONA...WHICH MAY BE RESPONSIBLE FOR THE LACK OF
SIGNIFICANT CONVECTION IN THAT REGION. HOWEVER...UPPER-LEVEL
OUTFLOW HAS IMPROVED SOME AND BECOME A LITTLE MORE CIRCULAR IN
APPEARANCE. THE OFFICIAL INTENSITY FORECAST WAS NUDGED UPWARD
SLIGHTLY FROM THE PREVIOUS ADVISORY...BUT IS LOWER THAN THE SHIPS
AND LGEM MODELS WHICH BRING FIONA UP TO A 60-KT SYSTEM BY 48
HOURS...AND MUCH LOWER THAN THE GFDL MODEL WHICH MAKES FIONA AN
85-KT HURRICANE AT THAT SAME TIME.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/0900Z 17.4N  60.2W    40 KT
 12HR VT     01/1800Z 18.9N  62.5W    45 KT
 24HR VT     02/0600Z 21.2N  64.7W    50 KT
 36HR VT     02/1800Z 23.5N  66.5W    50 KT
 48HR VT     03/0600Z 26.3N  67.3W    40 KT
 72HR VT     04/0600Z 29.2N  67.5W    35 KT
 96HR VT     05/0600Z 31.5N  67.0W    30 KT
120HR VT     06/0600Z...DISSIPATED
 
$$
FORECASTER STEWART
 

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
 

WTNT43 KNHC 012058
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER   9
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 PM AST WED SEP 01 2010
 
THOUGH THE SATELLITE APPEARANCE OF FIONA LOOKS QUITE DISHEVELED WITH
THE SURFACE CIRCULATION POPPING OUT FROM UNDER THE DEEP
CONVECTION...THE AIR FORCE HURRICANE HUNTER AIRCRAFT OBSERVATIONS
SHOW THAT THE SYSTEM STILL IS MAINTAINING MODERATE TROPICAL STORM
INTENSITY. PEAK 850 MB FLIGHT LEVEL WINDS OF 57 KT AND SFMR SURFACE
WIND ESTIMATES OF ABOUT 50 KT INDICATE THAT FIONA REMAINS AT 50 KT.
AIRCRAFT OBSERVATIONS ALSO INDICATE THAT FIONA IS RATHER SMALL IN
HORIZONTAL EXTENT WITH TROPICAL STORM FORCE WINDS EXTENDING OUT
LESS THAN 100 NM ON AVERAGE AROUND THE SYSTEM.

CURRENT MOTION OF THE CYCLONE IS A SPEEDY 17 KT TOWARD THE
NORTHWEST.  THE SYSTEM IS BEING ADVECTED ALONG MAINLY BY THE RIDGE
TO ITS NORTHEAST WITH SOME CONTRIBUTION OF STEERING AS WELL BY THE
MUCH LARGER HURRICANE EARL.  THE MODEL GUIDANCE IS IN GOOD
AGREEMENT THROUGH TWO DAYS THAT THE CYCLONE WILL CONTINUE TOWARD
THE NORTHWEST AT A SLOWER FORWARD SPEED.  AFTER THAT...THE
SOLUTIONS DIVERGE WITH SOME GUIDANCE QUICKLY HAVING FIONA ABSORBED
WITHIN THE CIRCULATION OF EARL AND SOME KEEPING FIONA AS A DISTINCT
VORTEX AND EVENTUALLY BECOMING A FRONTAL LOW IN ABOUT FOUR TO FIVE
DAYS.  THE FORECAST TRACK IS CLOSE TO THE MODEL CONSENSUS...MINUS
THE GFDN HURRICANE MODEL WHICH TAKES FIONA UNREALISTICALLY DUE
WEST...AND IS SIMILAR TO THE PREVIOUS ADVISORY.

THE INTENSITY FORECAST IS...AS USUAL...A DIFFICULT CALL. DESPITE THE
CYCLONE REMAINING OVER QUITE WARM WATERS FOR THE NEXT SEVERAL
DAYS...THE VERTICAL SHEAR APPEARS TO BE THE LIMITING FACTOR FOR THE
INTENSITY OF FIONA. A RESEARCH MISSION BY THE NSF GULFSTREAM-V JET
SHOWED UNIDIRECTIONAL 35 KT EASTERLIES ADVECTING OVER THE TOP OF
THE CYCLONE. SUCH UPPER LEVEL FLOW...ALONG WITH THE FAST FORWARD
SPEED...SHOULD LIMIT ANY INTENSIFICATION IN THE NEAR TERM AND THE
FORECAST INTENSITY SHOWS LITTLE CHANGE FOR THE NEXT TWO DAYS. AFTER
THAT...IT IS ANTICIPATED THAT FIONA WILL GRADUALLY DECAY AS IT GETS
ENTRAINED INTO THE CIRCULATION OF EARL AND VERTICAL WIND SHEAR
INCREASES. THE INTENSITY FORECAST IS SIGNIFICANTLY BELOW THE MODEL
CONSENSUS BUT IS QUITE SIMILAR TO THE PREVIOUS ADVISORY. IF CURRENT
TRENDS CONTINUE...IT IS EVEN POSSIBLE THAT FIONA WILL NO LONGER
HAVE A CLOSED SURFACE CIRCULATION. UNDER THIS SCENARIO...
ADVISORIES...AND FIONA...WOULD CEASE TO EXIST.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      01/2100Z 20.2N  62.9W    50 KT
 12HR VT     02/0600Z 21.6N  64.6W    50 KT
 24HR VT     02/1800Z 23.8N  66.3W    50 KT
 36HR VT     03/0600Z 25.9N  67.4W    50 KT
 48HR VT     03/1800Z 27.4N  67.6W    45 KT
 72HR VT     04/1800Z 30.0N  66.5W    35 KT
 96HR VT     05/1800Z 33.5N  64.5W    25 KT
120HR VT     06/1800Z...DISSIPATED
 
$$
FORECASTER LANDSEA/BLAKE
 

WTNT43 KNHC 020245
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 PM AST WED SEP 01 2010
 
DESPITE THE POOR SATELLITE PRESENTATION...RECONNAISSANCE DATA SINCE
THE LAST ADVISORY INDICATE THAT THERE HAS BEEN LITTLE CHANGE TO THE
INTENSITY OF FIONA.  THE AIRCRAFT FOUND PEAK 850 MB FLIGHT-LEVEL
WINDS OF 58 KT AND SFMR WINDS TO 53 KT TO THE NORTHEAST OF THE
CENTER.  THE AIRCRAFT DATA AND OBSERVATIONS FROM NOAA BUOY 41043
THIS EVENING SUGGEST THAT THE CIRCULATION OVER THE SOUTHWESTERN
QUADRANT HAS BECOME LESS DEFINED...AND A RECENT SSMIS IMAGE
DEPICTED A CIRCULATION THAT APPEARED ELONGATED FROM SOUTHEAST TO
NORTHWEST.  THE ENVIRONMENT AHEAD OF FIONA APPEARS QUITE
HOSTILE...WITH STRONG UPPER-LEVEL WINDS SHOWN BY THE GLOBAL MODELS.
THE NHC FORECAST INDICATES GRADUAL WEAKENING AND IS AT THE LOWER
END OF THE GUIDANCE. IT IS POSSIBLE THAT THE CIRCULATION WILL
DEGENERATE INTO AN OPEN TROUGH IN THE STRONG SOUTH TO SOUTHWEST
LOW-LEVEL FLOW ON THE EAST SIDE OF HURRICANE EARL. THIS SOLUTION IS
SUPPORTED BY MOST OF THE GLOBAL MODELS AND DISSIPATION OF FIONA
COULD OCCUR EARLIER THAN SHOWN BELOW.
 
FIXES FROM THE AIRCRAFT SHOW THAT FIONA ACCELERATED THIS
AFTERNOON...WITH AN ESTIMATED MOTION OF 320/20 KT.  THE CYCLONE
IS FORECAST TO MOVE AROUND THE WESTERN PORTION OF THE SUBTROPICAL
RIDGE DURING THE NEXT DAY OR SO.  THEREAFTER...FIONA IS FORECAST
TO TURN NORTHWARD...THEN NORTHEASTWARD IN DEEP-LAYER SOUTHWESTERLY
FLOW BETWEEN THE RIDGE AND EARL TO THE NORTHWEST.  THE NEW TRACK
FORECAST IS FASTER THAN THE PREVIOUS ADVISORY AND IS A BLEND OF
THE GFS...ECMWF...NOGAPS...AND UKMET MODELS.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0300Z 21.8N  64.1W    50 KT
 12HR VT     02/1200Z 23.8N  65.7W    45 KT
 24HR VT     03/0000Z 26.2N  67.1W    45 KT
 36HR VT     03/1200Z 28.8N  67.4W    40 KT
 48HR VT     04/0000Z 31.5N  66.3W    40 KT
 72HR VT     05/0000Z 35.5N  63.5W    35 KT
 96HR VT     06/0000Z...DISSIPATED
 
$$
FORECASTER BROWN
 

WTNT43 KNHC 020853
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 AM AST THU SEP 02 2010
 
AFTER LITTLE TO NO CONVECTION NEAR THE CENTER OF FIONA...A STRONG
BURST OF DEEP CONVECTION DEVELOPED OVER THE CENTER FOR A FEW HOURS
EARLIER THIS MORNING...WHICH HAS NOW BEEN SHEARED SLIGHTLY TO THE
SOUTHWEST OF THE CENTER. HOWEVER...NIGHTTIME VISIBLE IMAGERY AND A
02/0156Z ASCAT OVERPASS INDICATE FIONA HAS A SMALL BUT VERY
WELL-DEFINED CIRCULATION. THE INITIAL INTENSITY OF 45 KT IS BASED
ON A BELTON OF SATELLITE INTENSITY ESTIMATES OF 35 KT FROM FROM
TAFB AND SAB...AT LEAST 40 KT FROM THE ASCAT PASS...AND UW-CIMSS
ADT ESTIMATE OF 49 KT.
 
THE INITIAL MOTION ESTIMATE IS 320/15 BASED ON MOSTLY ON MICROWAVE
FIXES AND CONTINUITY WITH THE PREVIOUS ADVISORY MOTION. THE FUTURE
TRACK OF FIONA IS HEAVILY DEPENDENT ON THE INTENSITY AND STRUCTURE
OF THE CYCLONE. IT IS UNLIKELY THAT FIONA WILL GROW MUCH MORE IN
HORIZONTAL SIZE DUE TO THE LARGE CIRCULATION OF POWERFUL HURRICANE
EARL SITUATED ABOUT 750 NMI TO THE NORTHWEST. HOWEVER...ALL OF THE
GLOBAL MODELS ARE NOW FORECASTING FIONA TO ROUND THE WESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE LOCATED EAST-WEST BETWEEN 27N
AND 30N LATITUDE...AND IN 36-48 HOURS MOVE UNDERNEATH A REGION OF
LOW VERTICAL SHEAR BETWEEN THE STRONG NORTHERLY OUTFLOW FROM EARL
AND THE SOUTHWESTERLY FLOW AHEAD OF A LARGE MID-LATITUDE TROUGH
FORECAST TO MOVE OFF THE U.S. EAST COAST IN 24 HOURS AND CAPTURE
HURRICANE EARL. IF THIS PATTERN EVOLVES...FIONA WILL REMAIN A
DISTINCT ENTITY AND NOT BECOME ABSORBED BY THE LARGE CIRCULATION OF
EARL AS QUICKLY AS MOST OF THE GLOBAL MODELS ARE FORECASTING. THE
HWRF AND GFDL MODELS KEEP FIONA A SEPARATE SYSTEM THROUGH 120 HOURS
AND EVEN MAKE THE CYCLONE A HURRICANE IN 24-36 HOURS. THE OFFICIAL
FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK THROUGH 24 HOURS...
AND THEN A LITTLE TO EAST OR RIGHT OF TRACK AFTER THAT. ON THE
FORECAST TRACK...FIONA IS EXPECTED TO PASS VERY NEAR BERMUDA IN
ABOUT 48 HOURS...WHICH HAS PROMPTED THE ISSUANCE OF A TROPICAL
STORM WATCH FOR THAT ISLAND BY THE BERMUDA WEATHER SERVICE.

AS MENTIONED ABOVE...FIONA MAY REMAIN JUST WEST OF THE STRONGEST
NORTHEASTERLY VERTICAL WIND SHEAR ASSOCIATED WITH THE OUTFLOW OF
EARL FOR THE NEXT 24 HOURS. ALTHOUGH THERE MAY BE FLUCTUATIONS IN
THE INTENSITY OF FIONA...THE SHEAR IS NOT EXPECTED TO BE STRONG
ENOUGH TO STRIP AWAY ALL OF THE CONVECTION. BY 36-48 HOURS...FIONA
MAY MOVE INTO THE AFOREMENTIONED REGION OF LOW SHEAR BENEATH A
SMALL UPPER-LEVEL ANTICYCLONE FORECAST BY ALL THE MODELS TO DEVELOP
NEAR BERMUDA. THIS WOULD PROVIDE A BRIEF WINDOW OF OPPORTUNITY FOR
MORE SIGNIFICANT DEVELOP THAN CURRENTLY INDICATED. THE OFFICIAL
FORECAST CALLS FOR FIONA TO MAINTAIN ITS CURRENT INTENSITY FOR THE
NEXT 48 HOURS...ALTHOUGH THERE MAY SOME FLUCTUATIONS DURING THAT
TIME AS THE SHEAR WAXES AND WANES. THIS SCENARIO IS CONSISTENT WITH
THE GFDL AND HWRF MODELS.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/0900Z 22.6N  65.4W    45 KT
 12HR VT     02/1800Z 24.6N  66.6W    45 KT
 24HR VT     03/0600Z 27.1N  67.3W    45 KT
 36HR VT     03/1800Z 29.7N  67.0W    45 KT
 48HR VT     04/0600Z 32.4N  65.8W    45 KT
 72HR VT     05/0600Z 36.5N  62.0W    35 KT
 96HR VT     06/0600Z...DISSIPATED
 
$$
FORECASTER STEWART
 

WTNT43 KNHC 021437
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  12
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 AM AST THU SEP 02 2010
 
BURSTS OF CONVECTION CONTINUE TO FORM NEAR THE WELL-DEFINED
CIRCULATION OF FIONA THIS MORNING.  HOWEVER THIS CONVECTION HAS HAD
TROUBLE MAINTAINING ITSELF...PROBABLY DUE TO PERSISTENT NORTHERLY
SHEAR.  DVORAK CLASSIFICATIONS ARE UNCHANGED FROM EARLIER...SO THE
INITIAL INTENSITY WILL STAY 45 KT.
 
FIONA HAS TURNED TO THE RIGHT AND IS NOW MOVING 330/15.  AS THE
CYCLONE ROUNDS THE SOUTHWESTERN PERIPHERY OF A RIDGE OVER THE
CENTRAL ATLANTIC...IT IS EXPECTED TO TURN TOWARD THE NORTH AND
NORTHEAST BY LATE TOMORROW.  MOST OF THE MODEL GUIDANCE IS
CLUSTERED ON A TRACK NEAR OR WEST OF BERMUDA IN ABOUT 36-48
HRS...THOUGH WITH SOME SPEED DIFFERENCES.  SINCE FIONA HAS SHOWN NO
SIGNS OF SLOWING DOWN...AND WILL LIKELY REMAIN A WEAK SYSTEM
STEERED BY SWIFT LOW-LEVEL WINDS...THE NHC FORECAST WILL STAY
FASTER THAN THE MODEL CONSENSUS.  THE NEW FORECAST IS ALSO SHIFTED
A LITTLE TO THE RIGHT OF THE PREVIOUS ONE TO COME INTO BETTER
AGREEMENT WITH THE LATEST GUIDANCE.  THE GFDL SOLUTION OF A
SLOWER...MORE WESTWARD TRACK WELL TO THE SOUTHWEST OF BERMUDA IS
CONSIDERED UNLIKELY.
 
THE STORM IS WALKING A TIGHTROPE BETWEEN RATHER STRONG NORTHERLY
SHEAR TO ITS EAST AND AN AREA OF LIGHTER SHEAR FARTHER WEST.  WITH
THE RIGHTWARD SHIFT OF THE GUIDANCE THIS MORNING...THIS COULD CAUSE
EVEN STRONGER SHEAR IN A DAY OR SO NEAR THE CYCLONE.  ALL THE
GUIDANCE SHOWS A CONSIDERABLE WEAKENING OF FIONA...EXCEPT FOR THE
GFDL WHICH HAS AN UNREALISTIC TRACK FORECAST.  THE NHC INTENSITY
FORECAST IS REDUCED FROM THE PREVIOUS ONE...BUT IS STILL HIGHER
THAN NEARLY ALL OF THE GUIDANCE.

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/1500Z 24.4N  65.8W    45 KT
 12HR VT     03/0000Z 26.4N  66.5W    45 KT
 24HR VT     03/1200Z 28.9N  66.7W    45 KT
 36HR VT     04/0000Z 31.3N  65.7W    40 KT
 48HR VT     04/1200Z 33.8N  64.1W    35 KT
 72HR VT     05/1200Z 37.9N  61.4W    25 KT...DISSIPATING
 96HR VT     06/1200Z...DISSIPATED
 
$$
FORECASTER BLAKE/PASCH
 

WTNT43 KNHC 022035
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 PM AST THU SEP 02 2010
 
THERE HAS BEEN LITTLE CHANGE WITH FIONA DURING THE DAY. THE STORM
CONTINUES THE PATTERN OBSERVED DURING THE LAST DAY OR SO OF BURSTS
OF CONVECTION FORMING NEAR THE CENTER...THEN SHEARING AWAY. AN
ASCAT PASS FROM LATE THIS MORNING SHOWED MAXIMUM WINDS OF ABOUT 40
KT. GIVEN THE WELL-DOCUMENTED LOW BIAS OF THAT INSTRUMENT...45 KT
SEEMS LIKE A REASONABLE INITIAL WIND SPEED. THE INTENSITY FORECAST
IS DIFFICULT BECAUSE IT SEEMS LIKE FIONA HAS BEEN WITHSTANDING THE
SHEAR BETTER THAN MOST TROPICAL CYCLONES. THE LATEST INTENSITY
GUIDANCE DOES NOT WEAKEN THE STORM AS QUICKLY AS EARLIER...BUT IS
ACTUALLY PRETTY CLOSE TO THE PREVIOUS FORECAST. THUS NO CHANGES ARE
MADE TO THE LAST NHC FORECAST. AFTER 72 HOURS...ALL OF THE GLOBAL
MODELS SHOW THE TROPICAL CYCLONE SHEARING OUT AS IT MOVES
NORTHEASTWARD.
 
FIONA HAS TURNED A LITTLE MORE AND IS NOW MOVING 335/15.  THERE IS
NO CHANGE IN SYNOPTIC REASONING WITH THE CYCLONE MOVING AROUND A
SUBTROPICAL ANTICYCLONE.  THE STORM SHOULD TURN TOWARD THE NORTH...
THEN NORTHEAST AS IT STARTS TO MOVE INTO THE MID-LATITUDES. THE
MODELS ARE GENERALLY SLOWER THAN THE PREVIOUS CYCLE...BUT SINCE
THE CYCLONE CONTINUES SPEEDING ALONG...THE NHC FORECAST WILL STAY
ON THE FASTER SIDE OF THE GUIDANCE ENVELOPE...WITH LITTLE CHANGE TO
THE TRACK. THERE IS REASONABLE AGREEMENT THAT FIONA WILL BE CLOSE
TO BERMUDA IN 36-48 HOURS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      02/2100Z 25.6N  66.4W    45 KT
 12HR VT     03/0600Z 27.5N  66.8W    45 KT
 24HR VT     03/1800Z 29.7N  66.4W    45 KT
 36HR VT     04/0600Z 31.7N  65.4W    40 KT
 48HR VT     04/1800Z 33.7N  64.1W    35 KT
 72HR VT     05/1800Z 38.0N  61.0W    25 KT...DISSIPATING
 96HR VT     06/1800Z...DISSIPATED
 
$$
FORECASTER BLAKE/BROWN
 

WTNT43 KNHC 030236
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  14
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 PM AST THU SEP 02 2010
 
FIONA REMAINS A SHEARED TROPICAL CYCLONE...WITH THE LOW-LEVEL
CENTER EXPOSED TO THE NORTH OF THE DEEP CONVECTION.  THE INITIAL
INTENSITY IS KEPT AT 45 KT...BASED ON A DVORAK T-NUMBER OF 3.0 FROM
TAFB AND SCATTEROMETER DATA FROM EARLIER TODAY.  THE NORTH-
NORTHEASTERLY SHEAR IS EXPECTED TO REMAIN STRONG DURING THE NEXT
24-36 HOURS.  TYPICALLY ONE WOULD EXPECT SIGNIFICANT WEAKENING DUE
TO THE ANTICIPATED SHEAR. HOWEVER...FIONA HAS BEEN WITHSTANDING THE
SHEAR DURING THE PAST 24 HOURS...SO ONLY GRADUAL WEAKENING IS
FORECAST UNTIL DISSIPATION.  THE NEW OFFICIAL FORECAST IS IN GOOD
AGREEMENT WITH THE SHIPS/LGEM GUIDANCE.
 
FIONA IS NOW MOVING NORTHWARD OR 355/14 KT. THE CYCLONE IS EXPECTED
TO TURN NORTH-NORTHEASTWARD BETWEEN THE SUBTROPICAL RIDGE AND
HURRICANE EARL TO ITS NORTHWEST.  THE GLOBAL MODELS ARE IN GOOD
AGREEMENT ON THIS SCENARIO.  THE OFFICIAL FORECAST IS NEAR THE
MIDDLE OF THE GUIDANCE ENVELOPE AND IS ESSENTIALLY AN UPDATE OF THE
PREVIOUS ADVISORY.  ON THE FORECAST TRACK...THE CENTER OF FIONA
IS EXPECTED TO PASS NEAR OR OVER BERMUDA IN AROUND 36 HOURS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/0300Z 26.9N  66.8W    45 KT
 12HR VT     03/1200Z 28.7N  66.7W    40 KT
 24HR VT     04/0000Z 30.8N  65.9W    40 KT
 36HR VT     04/1200Z 32.7N  64.8W    35 KT
 48HR VT     05/0000Z 34.8N  63.6W    35 KT
 72HR VT     06/0000Z 39.5N  60.0W    25 KT...DISSIPATING
 96HR VT     07/0000Z...DISSIPATED
 
$$
FORECASTER BROWN
 

WTNT43 KNHC 030832
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 AM AST FRI SEP 03 2010
 
FIONA REMAINS A SHEARED TROPICAL CYCLONE WITH DEEP CONVECTION
DISPLACED OVER THE SOUTHERN SEMICIRCLE OF THE CIRCULATION. THE
INITIAL INTENSITY OF 45 KT IS BASED ON A SATELLITE INTENSITY
ESTIMATE OF T3.0/45 KT FROM TAFB...WHICH IS SUPPORTED BY A 3-HR
AVERAGE ADT OF T3.3/51 KT FROM UW-CIMSS.
 
THE INITIAL MOTION ESTIMATE IS 010/11 KT...WHICH IS BASED MAINLY ON
CONTINUITY WITH THE PREVIOUS ADVISORY. THERE IS NO CHANGE TO THE
PREVIOUS TRACK AND INTENSITY FORECAST REASONINGS. FIONA IS FORECAST
TO GRADUALLY WEAKEN AS IT MOVES NORTHWARD TODAY AND THEN TURNS
NORTHEASTWARD BY SATURDAY...WITH THE CENTER OF FIONA EXPECTED TO
PASS NEAR OR OVER BERMUDA IN ABOUT 24 HOURS. THE OFFICIAL FORECAST
TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND IS IN THE MIDDLE OF
THE NHC MODEL SUITE.
 

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/0900Z 28.1N  66.7W    45 KT
 12HR VT     03/1800Z 29.8N  66.1W    40 KT
 24HR VT     04/0600Z 32.0N  65.0W    40 KT
 36HR VT     04/1800Z 34.2N  63.7W    35 KT
 48HR VT     05/0600Z 36.4N  62.0W    35 KT
 72HR VT     06/0600Z 41.5N  58.5W    25 KT...DISSIPATING
 96HR VT     07/0600Z...DISSIPATED
 
$$
FORECASTER STEWART
 

WTNT43 KNHC 031442
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  16
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 AM AST FRI SEP 03 2010
 
AIRCRAFT DATA FROM THIS MORNING SHOWED PEAK SFMR WINDS OF 39 KT AND
FLIGHT-LEVEL WINDS OF 48 KT...SUPPORTING AN INITIAL WIND SPEED OF
ABOUT 40 KT. SATELLITE IMAGES SHOW THAT CONVECTION HAS BECOME
RATHER THIN NEAR THE CENTER...WITH THE CIRCULATION OF FIONA ALSO
TAKING ON AN ELONGATED APPEARANCE. SLOW WEAKENING SEEMS LIKELY
GIVEN THE PERSISTENT NORTHERLY SHEAR AND MODEL GUIDANCE IS ON GOOD
AGREEMENT WITH THIS SCENARIO. THE NHC FORECAST IS BASICALLY AN
UPDATE OF THE PREVIOUS ADVISORY. ALL MODELS WEAKEN THE SYSTEM
DRAMATICALLY IN A COUPLE OF DAYS...AND DISSIPATION IS EXPECTED
AFTER THAT TIME. GIVEN THE LATEST SATELLITE PRESENTATION...IT WOULD
NOT BE A SURPRISE IF FIONA DECAYED FASTER THAN THE FORECAST BELOW.

FIONA HAS TURNED TO THE NORTH-NORTHEAST AND IS MOVING 020/11 KT. THE
MODELS ARE WELL CLUSTERED NOW ON BRINGING THE CENTER NEAR BERMUDA
IN ABOUT 18 HOURS. THEREAFTER...SOME ACCELERATION IS ANTICIPATED AS
THE STORM ENCOUNTERS INCREASING SOUTHWESTERLY FLOW. THE NHC
FORECAST IS VERY CLOSE TO THE PREVIOUS ONE AND THE DYNAMICAL MODEL
CONSENSUS.

THE INITIAL WIND RADII HAVE BEEN REDUCED BASED ON AIRCRAFT
DATA...AND STILL MIGHT BE A LITTLE GENEROUS.  

 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/1500Z 29.0N  66.4W    40 KT
 12HR VT     04/0000Z 30.6N  65.7W    35 KT
 24HR VT     04/1200Z 32.7N  64.6W    35 KT
 36HR VT     05/0000Z 35.2N  63.1W    30 KT
 48HR VT     05/1200Z 38.1N  61.2W    25 KT
 72HR VT     06/1200Z...DISSIPATED
 
$$
FORECASTER BLAKE
 

WTNT43 KNHC 032035
TCDAT3
TROPICAL STORM FIONA DISCUSSION NUMBER  17
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
500 PM AST FRI SEP 03 2010
 
SATELLITE IMAGES INDICATE THAT FIONA IS WEAKENING.  THE LOW-LEVEL
CIRCULATION IS BECOMING DISTORTED WITH MULTIPLE SWIRLS...AND ONLY A
MEAGER AMOUNT OF CONVECTION REMAINS.  SATELLITE CLASSIFICATIONS ARE
DROPPING...AND THE INITIAL INTENSITY IS LOWERED TO 35 KT.  FURTHER
WEAKENING IS LIKELY DUE TO STRONG NORTHERLY SHEAR.  DISSIPATION IS
PROBABLE BY SUNDAY...IF NOT SOONER...OR THE SYSTEM COULD DEGENERATE
INTO A REMNANT LOW AS EARLY AS TONIGHT IF CONVECTION DOES NOT
REDEVELOP SOON.  THE CHANCES OF TROPICAL-STORM-FORCE WINDS
OCCURRING IN BERMUDA APPEAR TO BE DROPPING.
 
FIONA HAS TURNED A LITTLE MORE TO THE RIGHT AND IS NOW MOVING
030/12. A SMALL SHIFT IN THE GUIDANCE HAS OCCURRED...WITH ALL OF THE
MODELS NOW SHOWING THE CENTER PASSING JUST TO THE EAST OF BERMUDA. 
THIS APPEARS TO BE DUE TO FIONA BECOMING A RATHER SHALLOW SYSTEM
THAT IS BEING PRIMARILY STEERED BY SOUTHWESTERLY FLOW AROUND EARL. 
THE OFFICIAL FORECAST IS SHIFTED A LITTLE TO THE RIGHT OF THE
PREVIOUS ONE...BUT STILL PASSES CLOSE TO BERMUDA.  GLOBAL MODELS
INDICATE THAT THE WEAK SYSTEM SHOULD INCREASE ITS FORWARD SPEED AS
IT MOVES AWAY FROM BERMUDA AND DECAYS.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      03/2100Z 30.0N  65.5W    35 KT
 12HR VT     04/0600Z 31.6N  64.7W    30 KT
 24HR VT     04/1800Z 33.6N  63.5W    25 KT
 36HR VT     05/0600Z 36.4N  61.7W    20 KT...POST-TROP/REMNT LOW
 48HR VT     05/1800Z 39.6N  59.6W    20 KT...POST-TROP/REMNT LOW
 72HR VT     06/1800Z...DISSIPATED
 
$$
FORECASTER BLAKE
 

WTNT43 KNHC 040238
TCDAT3
TROPICAL DEPRESSION FIONA DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082010
1100 PM AST FRI SEP 03 2010

FIONA HAS DEGENERATED INTO A REMNANT LOW THIS EVENING. AN AIR FORCE
RESERVE RECONNAISSANCE AIRCRAFT FOUND AN ELONGATED AND
POORLY-DEFINED CIRCULATION WITH A CENTRAL PRESSURE THAT HAD RISEN
TO 1013 MB.  ALSO...ENHANCED INFRARED SATELLITE IMAGERY SHOWS THAT
THE SYSTEM LACKS ORGANIZED DEEP CONVECTION.  IN FACT...ALL THAT
REMAINS OF THE CONVECTION IS A VERY SMALL AREA OF SHOWERS LOCATED
ABOUT 50 MILES SOUTH OF THE CENTER...AND DVORAK ESTIMATES FROM BOTH
TAFB AND SAB INDICATE THAT THE SYSTEM IS TOO WEAK TO CLASSIFY AS A
TROPICAL CYCLONE.  THE INTENSITY FORECAST CALLS FOR DISSIPATION IN
48 HOURS IN AN ENVIRONMENT OF 20-30 KT OF NORTHEASTERLY SHEAR AS
INDICATED BY THE UW-CIMSS SHEAR PRODUCT.  DYNAMICAL MODELS THAT DO
NOT ALREADY SHOW FIONA AS AN OPEN WAVE ALSO SUPPORT SUPPORT
DISSIPATION WITHIN THE AFOREMENTIONED FORECAST PERIOD.
 
THE LOW IS FORECAST TO MOVE NORTH-NORTHEASTWARD AND PASS JUST TO THE
EAST OF BERMUDA ON SATURDAY.  AN INCREASE IN FORWARD MOTION...AS A
SHALLOW LOW...IS EXPECTED AROUND THE 36 HOUR PERIOD BEFORE
DISSIPATION.

THIS IS THE LAST FORECAST/ADVISORY ISSUED BY THE NATIONAL HURRICANE
CENTER ON FIONA. ADDITIONAL INFORMATION ON THIS SYSTEM CAN BE FOUND
IN HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE...
UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      04/0300Z 31.4N  64.9W    25 KT
 12HR VT     04/1200Z 33.0N  64.0W    25 KT...POST-TROP/REMNT LOW
 24HR VT     05/0000Z 35.2N  62.6W    25 KT...POST-TROP/REMNT LOW
 36HR VT     05/1200Z 38.2N  60.9W    20 KT...POST-TROP/REMNT LOW
 48HR VT     06/0000Z...DISSIPATED
 
$$
FORECASTER ROBERTS/BRENNAN
 

