1WTNT43 KNHC 302047 2TCDAT3 3TROPICAL STORM FIONA DISCUSSION NUMBER 1 4NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 5500 PM EDT MON AUG 30 2010 6 7EARLIER TODAY...ABOUT 30 DROPSONDES WERE RELEASED DURING A G-V 8RESEARCH MISSION BEING CONDUCTED BY THE NATIONAL CENTER FOR 9ATMOSPHERIC RESEARCH NEAR THE AREA OF LOW PRESSURE LOCATED ABOUT 10800 MILES EAST OF THE LESSER ANTILLES. ONE OF THE DROPSONDES 11MEASURED A SURFACE WIND OF 35 KT APPROXIMATELY 120 N MI TO THE 12NORTHEAST OF THE ESTIMATED CENTER. THIS MEASUREMENT AGREES WITH AN 13ASCAT PASS FROM 1208 UTC...WHICH SHOWED A SWATH OF 30-35 KT WINDS 14IN THAT SAME AREA. CONVECTION HAS BEEN A LITTLE THIN FOR MOST OF 15THE DAY...BUT BANDING FEATURES HAVE RECENTLY BECOME MORE PROMINENT 16MAINLY OVER THE WESTERN SEMICIRCLE. GIVEN THE INCREASE IN 17CONVECTION AND SINCE TROPICAL STORM FORCE WINDS ARE ALREADY 18OCCURRING...THE SYSTEM IS BEING DIRECTLY UPGRADED TO TROPICAL STORM 19FIONA. 20 21SINCE FIONA STILL LACKS SOME ORGANIZATION AND THE WIND FIELD IS 22SOMEWHAT LARGE...THE CYCLONE WILL LIKELY HAVE A DIFFICULT TIME 23INTENSIFYING OVER THE NEXT DAY OR SO. I DO NOT BELIEVE THIS 24STRUCTURE IS HANDLED WELL BY THE STATISTICAL INTENSITY 25GUIDANCE...WHICH INTENSIFY FIONA TO A HURRICANE IN 36 TO 48 26HOURS...SO I AM INCLINED TO LEAN CLOSER TO THE DYNAMICAL GFDL AND 27HWRF AT THIS POINT. IN FACT...THE GFS DISSIPATES THE CYCLONE WITHIN 282 TO 3 DAYS. THE OFFICIAL FORECAST THEREFORE SHOWS MINIMAL 29STRENGTHENING OVER THE NEXT 1 TO 2 DAYS AND THEN LEVELS OUT THE 30INTENSITY FOR DAYS 3 THROUGH 5...WHEN IT APPEARS THAT INCREASING 31VERTICAL SHEAR COULD BECOME A LIMITING FACTOR. 32 33THE SURFACE CENTER HAS BEEN A LITTLE DIFFICULT TO LOCATE...AND THE 34INITIAL MOTION IS AN UNCERTAIN 270/21. TRACK MODEL GUIDANCE IS IN 35GOOD AGREEMENT FOR THE NEXT 48 HOURS AND SHOWS FIONA TURNING TOWARD 36THE NORTHWEST...GENERALLY FOLLOWING EARL AROUND THE WESTERN 37PERIPHERY OF THE SUBTROPICAL RIDGE. AFTER THAT...THE 38GFDL...HWRF...AND GFS KEEP FIONA AS A WEAK SYSTEM AND SHOW IT 39CONTINUING TO THE NORTH IN THE LOW-LEVEL FLOW BEHIND EARL. THE 40ECMWF...ON THE OTHER HAND...SHOWS A STRONGER FIONA AND SUGGESTS 41THAT THE SUBTROPICAL RIDGE COULD BUILD BACK TO THE WEST BEFORE THE 42CYCLONE CAN RECURVE. THE OFFICIAL FORECAST IS VERY CLOSE TO THE 43MODEL CONSENSUS TVCN FOR THE FIRST 48 HOURS BUT THEN LIES A LITTLE 44NORTH OF THE CONSENSUS IN FAVOR OF THE TRACKS OF THE WEAKER GFDL 45AND HWRF. 46 47 48FORECAST POSITIONS AND MAX WINDS 49 50INITIAL 30/2100Z 14.4N 48.7W 35 KT 51 12HR VT 31/0600Z 14.9N 51.9W 35 KT 52 24HR VT 31/1800Z 15.8N 55.9W 40 KT 53 36HR VT 01/0600Z 17.2N 59.2W 45 KT 54 48HR VT 01/1800Z 19.3N 62.0W 45 KT 55 72HR VT 02/1800Z 24.0N 66.0W 40 KT 56 96HR VT 03/1800Z 27.5N 68.0W 40 KT 57120HR VT 04/1800Z 29.0N 69.0W 40 KT 58 59$$ 60FORECASTER BERG 61 62 63WTNT43 KNHC 310252 64TCDAT3 65TROPICAL STORM FIONA DISCUSSION NUMBER 2 66NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 671100 PM EDT MON AUG 30 2010 68 69CONVECTION HAS INCREASED IN THE NORTHWESTERN PORTION OF FIONA THIS 70EVENING. HOWEVER...OVERALL THE SYSTEM LOOKS FAIRLY DISORGANIZED 71WITH JUST A FEW WEAK BANDING FEATURES. A NOAA/NTAS BUOY LOCATED 72NEAR THE CENTER REPORTED A PRESSURE OF 1008 MB A FEW HOURS 73AGO...WHICH IS ABOUT THE SAME PRESSURE AS BUOY 41041 MEASURED 74EARLIER TODAY. THUS...THE INITIAL INTENSITY WILL REMAIN 35 KT FOR 75THIS ADVISORY. GIVEN THE CURRENT DISHEVELED APPEARANCE OF FIONA... 76ONLY A SLOW INCREASE IN STRENGTH IS FORECAST FOR THE NEXT DAY OR SO 77WHILE THE TROPICAL CYCLONE MOVES OVER VERY WARM WATER AND LIGHT 78SHEAR. AFTER THAT TIME...NORTHEASTERLY SHEAR INCREASES MARKEDLY AND 79MAY HALT ANY FURTHER DEVELOPMENT...PLUS THE CYCLONE COULD BE MOVING 80OVER COOLER WATERS THAT WERE UPWELLED BY EARL. MOST OF THE 81MODELS...SAVE THE GFDL/GFDN...ARE IN CLOSE AGREEMENT WITH THIS 82SCENARIO...AND THE OFFICIAL NHC INTENSITY FORECAST IS NEAR THE 83PREVIOUS ONE BUT BELOW THE INTENSITY CONSENSUS. HOWEVER...I DO NOT 84HAVE A LOT OF CONFIDENCE IN THE FORECAST AT THIS TIME. 85 86MICROWAVE AND SURFACE DATA SUGGEST THE CENTER IS MOVING 280/21. 87FIONA SHOULD MOVE AROUND THE SOUTHWESTERN PERIPHERY OF A RIDGE OVER 88THE CENTRAL ATLANTIC...EVENTUALLY TURNING TO THE WEST-NORTHWEST AND 89NORTHWEST IN THE NEXT COUPLE OF DAYS. THE TRACK MODELS ARE FAIRLY 90WELL CLUSTERED...EXCEPT FOR THE ECMWF. THAT MODEL IS ON THE LEFT 91SIDE OF THE GUIDANCE ENVELOPE...PERHAPS BECAUSE IT SHOWS A DEEPER 92FIONA RESPONDING TO STRONGER UPPER-LEVEL NORTHEASTERLY WINDS. 93SINCE WE ARE NOT EXPECTING THAT SCENARIO...THE NHC FORECAST IS VERY 94CLOSE TO THE PREVIOUS ONE...AND IS A LITTLE SOUTH OF THE MODEL 95CONSENSUS. 96 97 98FORECAST POSITIONS AND MAX WINDS 99 100INITIAL 31/0300Z 15.1N 50.8W 35 KT 101 12HR VT 31/1200Z 15.7N 54.0W 35 KT 102 24HR VT 01/0000Z 16.9N 57.7W 40 KT 103 36HR VT 01/1200Z 18.4N 60.6W 45 KT 104 48HR VT 02/0000Z 20.5N 63.2W 45 KT 105 72HR VT 03/0000Z 25.0N 67.0W 45 KT 106 96HR VT 04/0000Z 28.0N 69.0W 45 KT 107120HR VT 05/0000Z 29.0N 69.5W 45 KT 108 109$$ 110FORECASTER BLAKE 111 112 113WTNT43 KNHC 310853 114TCDAT3 115TROPICAL STORM FIONA DISCUSSION NUMBER 3 116NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 117500 AM AST TUE AUG 31 2010 118 119FIONA HAS CHANGED LITTLE IN STRUCTURE DURING THE LAST SEVERAL HOURS. 120DEEP CONVECTION REMAINS CONFINED TO A FEW CURVED BANDS MAINLY OVER 121THE WESTERN SEMICIRCLE...ALTHOUGH AN AREA OF THUNDERSTORMS HAS 122RECENTLY FORMED NEAR THE ESTIMATED CENTER POSITION. THE INITIAL 123INTENSITY IS HELD AT 35 KT...IN AGREEMENT WITH AN 0056 UTC ASCAT 124PASS AND A 1007 MB PRESSURE REPORT FROM BUOY 41040. ONLY A LITTLE 125STRENGTHENING IS FORECAST IN THE SHORT TERM DUE TO MARGINALLY 126FAVORABLE UPPER-LEVEL WINDS...SOME DRY AIR AROUND THE CYCLONE...AND 127CURRENT LACK OF ORGANIZATION. THE SHIPS MODEL SHOWS NORTHEASTERLY 128SHEAR INCREASING SIGNIFICANTLY IN 24-36 HOURS...AND IF 129CORRECT...THAT SHOULD LIMIT ADDITIONAL STRENGTHENING. THIS 130INTENSITY FORECAST IS UNCHANGED FROM EARLIER AND REMAINS NEAR THE 131LOW END OF THE MODEL GUIDANCE. 132 133THE AFOREMENTIONED ASCAT PASS AND A TRMM OVERPASS AT 0303 UTC 134SUGGESTED THAT THE LOW-LEVEL CENTER...ALBEIT NOT VERY EASY TO 135LOCATE...WAS SITUATED A LITTLE TO THE NORTH OF THE PREVIOUS 136ESTIMATES. THEREFORE...THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 137285/20. A NARROW MID-LEVEL RIDGE LOCATED ALONG 25 N OVER THE 138CENTRAL AND EASTERN ATLANTIC IS EXPECTED TO KEEP FIONA ON A RATHER 139FAST WEST-NORTHWESTWARD COURSE FOR THE NEXT DAY OR SO. 140THEREAFTER...THE CYCLONE IS EXPECTED TO APPROACH A WEAKNESS IN THE 141RIDGE...WHICH WILL BE ENHANCED BY HURRICANE EARL...AND THAT SHOULD 142CAUSE FIONA TO GRADUALLY SLOW DOWN AND TURN TO THE NORTHWEST. THE 143ECMWF...WHICH HAS BEEN THE LEFT-MOST MODEL FOR THE PAST COUPLE OF 144CYCLES...IS NOW ON THE RIGHT SIDE OF THE GUIDANCE ENVELOPE. IN 145GENERAL...THE MODEL GUIDANCE HAS SHIFTED SLIGHTLY TO THE RIGHT AND 146IS A LITTLE FASTER AT THE END OF THE PERIOD...AND THE NHC FORECAST 147HAS BEEN ADJUSTED IN THAT DIRECTION. 148 149FORECAST POSITIONS AND MAX WINDS 150 151INITIAL 31/0900Z 15.8N 53.0W 35 KT 152 12HR VT 31/1800Z 16.5N 55.7W 35 KT 153 24HR VT 01/0600Z 17.8N 59.1W 40 KT 154 36HR VT 01/1800Z 19.6N 61.9W 45 KT 155 48HR VT 02/0600Z 21.8N 64.2W 45 KT 156 72HR VT 03/0600Z 26.5N 67.5W 45 KT 157 96HR VT 04/0600Z 29.0N 68.5W 45 KT 158120HR VT 05/0600Z 30.5N 69.0W 45 KT 159 160$$ 161FORECASTER CANGIALOSI/BLAKE 162 163 164WTNT43 KNHC 311439 165TCDAT3 166TROPICAL STORM FIONA DISCUSSION NUMBER 4 167NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 1681100 AM AST TUE AUG 31 2010 169 170A 0929 UTC SSMIS MICROWAVE OVERPASS SHOWED CURVED BANDS OF 171CONVECTION LOOSELY WRAPPING AROUND THE CENTER. SINCE THAT TIME 172VISIBLE SATELLITE IMAGERY INDICATES THAT THE CONVECTIVE BANDS NEAR 173THE CENTER HAVE WEAKENED...WHILE NEW CONVECTION HAS DEVELOPED 174AROUND THE PERIPHERY OF THE CIRCULATION. THE INITIAL INTENSITY 175REMAINS 35 KT...BASED ON THE EARLIER SCATTEROMETER DATA. AN AIR 176FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS SCHEDULED TO 177INVESTIGATE FIONA THIS AFTERNOON AND SHOULD PROVIDE A BETTER 178ASSESSMENT OF THE CURRENT STRUCTURE AND INTENSITY. 179 180THE INITIAL MOTION ESTIMATE IS 285/21 KT. THE CYCLONE IS FORECAST 181TO SLOW DOWN AND TURN NORTHWESTWARD DURING THE NEXT 24 HOURS AS IT 182NEARS THE WESTERN PORTION OF THE SUBTROPICAL RIDGE. THEREAFTER... 183FIONA IS EXPECTED TO TURN NORTH-NORTHWESTWARD...THEN NORTHWARD 184BETWEEN THE WESTERN SIDE OF THE RIDGE AND HURRICANE EARL TO THE 185NORTHWEST. THE TRACK GUIDANCE IS IN BETTER AGREEMENT ON THIS 186SCENARIO AND THE OFFICIAL FORECAST HAS BEEN ADJUSTED EASTWARD ALONG 187THE LEFT SIDE OF THE GUIDANCE ENVELOPE. LATE IN THE FORECAST 188PERIOD...FIONA SHOULD TURN NORTHEASTWARD AS DEEP SOUTHWESTERLY FLOW 189DEVELOPS OVER THE WESTERN ATLANTIC. 190 191THERE APPEARS TO BE A SMALL WINDOW OF OPPORTUNITY FOR FIONA TO 192STRENGTHEN DURING THE NEXT 12 TO 24 HOURS BEFORE AN UPPER-LEVEL 193RIDGE TO THE NORTHWEST OF FIONA STRENGTHENS...AND NORTHEASTERLY 194UPPER-LEVEL WINDS INCREASE. THE SHEAR IS FORECAST TO REMAIN 195MODERATE TO STRONG THROUGHOUT MOST OF THE FORECAST PERIOD AND NO 196ADDITIONAL STRENGTHENING IS PREDICTED. AN ALTERNATE SCENARIO...AS 197SHOWN BY THE GFS...IS THAT FIONA COULD WEAKEN AND POSSIBLY 198DISSIPATE IN A COUPLE OF DAYS DUE TO THE AFOREMENTIONED SHEAR. 199 200 201FORECAST POSITIONS AND MAX WINDS 202 203INITIAL 31/1500Z 15.9N 55.3W 35 KT 204 12HR VT 01/0000Z 16.9N 58.2W 40 KT 205 24HR VT 01/1200Z 18.7N 61.3W 45 KT 206 36HR VT 02/0000Z 21.1N 63.8W 45 KT 207 48HR VT 02/1200Z 23.4N 65.8W 45 KT 208 72HR VT 03/1200Z 27.7N 67.8W 45 KT 209 96HR VT 04/1200Z 31.0N 67.5W 45 KT 210120HR VT 05/1200Z 34.0N 66.0W 45 KT 211 212$$ 213FORECASTER BROWN 214 215 216WTNT43 KNHC 312049 217TCDAT3 218TROPICAL STORM FIONA DISCUSSION NUMBER 5 219NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 220500 PM AST TUE AUG 31 2010 221 222THUNDERSTORM ACTIVITY HAS RECENTLY DEVELOPED NEAR THE CENTER OF 223FIONA...HOWEVER THE CONVECTION SHOWS LITTLE BANDING. THE AIRCRAFT 224FOUND PEAK 925 MB FLIGHT-LEVEL WINDS OF 41 KT AND SEVERAL UNFLAGGED 225SFMR WINDS OF AROUND 35 KT TO THE NORTH OF THE CENTER. BASED ON 226THESE DATA...THE INITIAL INTENSITY REMAINS 35 KT. AN UPPER-LEVEL 227ANTICYCLONE TO THE NORTHWEST OF FIONA IS FORECAST TO PRODUCE 228INCREASING UPPER-LEVEL NORTHEASTERLY SHEAR OVER THE CYCLONE. THE 229SHEAR IS EXPECTED TO REMAIN STRONG DURING THE NEXT SEVERAL DAYS AND 230ONLY A LITTLE STRENGTHENING IS SHOWN IN THE OFFICIAL FORECAST. 231 232THE INITIAL MOTION ESTIMATE IS 290/21 KT. FIONA IS FORECAST 233TO TURN NORTHWESTWARD AND DECELERATE VERY SOON AS IT APPROACHES 234THE WESTERN EDGE OF THE SUBTROPICAL RIDGE. IN 36-48 HOURS...THE 235CYCLONE SHOULD TURN NORTHWARD BETWEEN THE RIDGE AND HURRICANE EARL 236TO THE NORTHWEST. ALL OF GLOBAL MODELS DISSIPATE THE STORM IN 2-3 237DAYS AS THE SMALLER CIRCULATION OF FIONA BECOMES AN OPEN TROUGH IN 238THE STRONG SOUTHWESTERLY FLOW ON THE SOUTHEASTERN SIDE OF EARL. THE 239OFFICIAL FORECAST FOLLOWS THIS SCENARIO...HOWEVER DISSIPATION COULD 240OCCUR EARLIER THAN SHOWN BELOW. 241 242FORECAST POSITIONS AND MAX WINDS 243 244INITIAL 31/2100Z 16.7N 57.7W 35 KT 245 12HR VT 01/0600Z 17.9N 60.8W 40 KT 246 24HR VT 01/1800Z 20.2N 63.7W 40 KT 247 36HR VT 02/0600Z 23.0N 66.0W 40 KT 248 48HR VT 02/1800Z 26.5N 67.7W 35 KT 249 72HR VT 03/1800Z 33.5N 67.5W 35 KT 250 96HR VT 04/1800Z...DISSIPATED 251 252$$ 253FORECASTER BROWN 254 255 256WTNT43 KNHC 010238 257TCDAT3 258TROPICAL STORM FIONA DISCUSSION NUMBER 6 259NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 2601100 PM AST TUE AUG 31 2010 261 262THE METEO FRANCE GUADELOUPE-MARTINIQUE RADAR MOSAIC WAS VERY HELPFUL 263IN IDENTIFYING THE CIRCULATION CENTER OF FIONA. DEEP CONVECTION 264HAS BEEN PERSISTENT NEAR THE CENTER...BUT THE CLOUD PATTERN IS A 265RATHER SHAPELESS BLOB...AND APPEARS TO BE ELONGATED ALONG AN AXIS 266SOUTHEAST TO NORTHWEST. THE DVORAK INTENSITY ESTIMATES REMAIN AT 26730 KT FROM BOTH TAFB AND SAB...BUT THE INITIAL INTENSITY WILL 268REMAIN AT 35 KT BASED ON THE PERSISTENT DEEP CONVECTION TO THE 269NORTH OF THE CENTER WHERE THE EARLIER AIRCRAFT RECONNAISSANCE 270RECORDED FLIGHT-LEVEL WINDS OF 41 KT. NORTHEASTERLY SHEAR 271ASSOCIATED WITH THE SOUTHEAST OUTFLOW CHANNEL OF EARL IS EXPECTED 272TO IMPINGE ON THE WESTERN PORTION OF THE CYCLONE IN 36 HOURS. THE 273SHIPS MODEL AS WELL AS THE GLOBAL MODELS ALL SUGGEST THAT THE SHEAR 274WILL SIGNIFICANTLY INCREASE OVER THE CYCLONE THROUGH DAY 3... 275CAUSING DISSIPATION BY DAY 4. THERE IS SOMEWHAT OF A CHANCE... 276HOWEVER...OF MINIMAL STRENGTHENING PRIOR TO THE INCREASING 277SHEAR DURING THE EARLY PORTION OF THE FORECAST. 278 279THE INITIAL MOTION IS SIMILAR TO THE PREVIOUS ADVISORY 280ESTIMATE...BUT A LITTLE SLOWER...290/17 KT. LARGE-SCALE MODELS 281INDICATE THAT FIONA WILL TURN NORTHWESTWARD ALONG THE SOUTHWESTERN 282PERIPHERY OF THE SUBTROPICAL RIDGE DURING THE NEXT 24 HOURS. 283THROUGH THE REMAINING FORECAST PERIOD...THE CYCLONE SHOULD TURN 284NORTHWARD WITHIN A STIFF SOUTHERLY FLOW BETWEEN THE RIDGE EXTENDING 285OVER BERMUDA AND HURRICANE EARL TO THE NORTHWEST. THE OFFICIAL 286FORECAST IS SIMILAR TO THE PREVIOUS PACKAGE...WITH ONLY A SLIGHT 287ADJUSTMENT TO THE LEFT...AND IS BASED ON THE MULTI-MODEL TVCN 288CONSENSUS. 289 290FORECAST POSITIONS AND MAX WINDS 291 292INITIAL 01/0300Z 16.9N 59.4W 35 KT 293 12HR VT 01/1200Z 18.7N 62.0W 40 KT 294 24HR VT 02/0000Z 21.2N 64.7W 40 KT 295 36HR VT 02/1200Z 24.4N 66.5W 40 KT 296 48HR VT 03/0000Z 27.8N 67.6W 35 KT 297 72HR VT 04/0000Z 35.0N 66.0W 30 KT 298 96HR VT 05/0000Z...DISSIPATED 299 300$$ 301FORECASTER ROBERTS/PASCH 302 303 304WTNT43 KNHC 010900 305TCDAT3 306TROPICAL STORM FIONA DISCUSSION NUMBER 7 307NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 308500 AM AST WED SEP 01 2010 309 310RECONNAISSANCE DATA...RADAR DATA FROM GUADELOUPE...AND SATELLITE 311IMAGERY INDICATE FIONA HAS BECOME A LITTLE BETTER ORGANIZED THIS 312MORNING. DEEP CONVECTION HAS INCREASED IN THE SOUTHERN SEMICIRCLE 313AND THE CENTER HAS BECOME BETTER DEFINED IN RADAR IMAGERY AND IN 314FLIGHT-LEVEL WIND DATA. THE MAXIMUM 850 MB FLIGHT-LEVEL WINDS 315OBSERVED THUS FAR DURING THE CURRENT MISSION HAS BEEN 52 KT IN THE 316NORTHEAST QUADRANT...WHICH EQUATES TO ABOUT A 42-KT SURFACE WIND. 317THE LOWEST PRESSURES OBSERVED THUS FAR HAVE BEEN 1002 MB AT 0602Z 318AND 1004 MB AT 0803Z. THE INITIAL INTENSITY IS SET AT 40 KT...WHICH 319IS LOWER THAN THE 50-KT ADT INTENSITY ESTIMATE FROM UW-CIMSS. 320 321THE INITIAL MOTION IS 290/12 KT USING RECON AND RADAR FIX POSITIONS. 322FIONA APPEARS TO HAVE DECREASED ITS RATE OF CLOSURE ON EARL LOCATED 323TO ITS NORTHWEST. OVER THE PAST 48 HOURS...THE DISTANCE BETWEEN 324FIONA AND EARL HAS BEEN DECREASING BY ABOUT 100 NMI EVERY 12 325HOURS...AND THE TWO CYCLONES ARE CURRENTLY ABOUT 750 NMI APART. 326RIDDING BETWEEN THE TWO SYSTEMS HAS OBVIOUSLY INCREASED...WHICH HAS 327RESULTED IN THE SIGNIFICANT DECREASE IN THE FORWARD SPEED OF FIONA 328FROM MORE THAN 20 KT DOWN TO THE CURRENT 12 KT IN THE PAST 12 329HOURS. THE POSSIBLE CAUSE OF THE RIDGING TO THE NORTHWEST OF FIONA 330IS THE UPPER-LEVEL OUTFLOWS FROM BOTH CYCLONES CONVERGING TO THE 331NORTHWEST OF FIONA. THIS RIDGING MAY ALLOW KEEP FIONA FROM 332INTERACTING WITH THE LARGER CIRCULATION OF EARL LIKE MOST OF THE 333GLOBAL MODELS HAVE BEEN FORECASTING THE PAST COUPLE OF DAYS. ALL OF 334THE MODEL GUIDANCE...EXCLUDING NOGAPS...NOW SLOWS DOWN FIONA BY DAY 3353...WITH THE CYCLONE POSSIBLY GETTING TRAPPED IN THE SUBTROPICAL 336RIDGE. AS RESULT OF THESE NEW SCENARIO...A 96-HOUR POSITION HAS 337BEEN ADDED AND DISSIPATION HAS BEEN DELAYED UNTIL 120 HOURS. IF 338FIONA BECOMES A STRONGER SYSTEM THAN CURRENTLY FORECAST...THE 339CYCLONE COULD SURVIVE AND END UP MAKING A CLOCKWISE LOOP OR EVEN 340BECOME STATIONARY BY 120 HOURS. THE OFFICIAL FORECAST TRACK IS 341SIMILAR TO THE PREVIOUS ADVISORY..EXCEPT SLOWER AT 48 HOURS AND 342BEYOND...AND IS ALONG THE WESTERN EDGE OF THE GUIDANCE SUITE. 343 344SOME DRY MID-LEVEL AIR APPEARS TO BE GETTING DRAWN INTO THE NORTHERN 345QUADRANT OF THE FIONA...WHICH MAY BE RESPONSIBLE FOR THE LACK OF 346SIGNIFICANT CONVECTION IN THAT REGION. HOWEVER...UPPER-LEVEL 347OUTFLOW HAS IMPROVED SOME AND BECOME A LITTLE MORE CIRCULAR IN 348APPEARANCE. THE OFFICIAL INTENSITY FORECAST WAS NUDGED UPWARD 349SLIGHTLY FROM THE PREVIOUS ADVISORY...BUT IS LOWER THAN THE SHIPS 350AND LGEM MODELS WHICH BRING FIONA UP TO A 60-KT SYSTEM BY 48 351HOURS...AND MUCH LOWER THAN THE GFDL MODEL WHICH MAKES FIONA AN 35285-KT HURRICANE AT THAT SAME TIME. 353 354 355FORECAST POSITIONS AND MAX WINDS 356 357INITIAL 01/0900Z 17.4N 60.2W 40 KT 358 12HR VT 01/1800Z 18.9N 62.5W 45 KT 359 24HR VT 02/0600Z 21.2N 64.7W 50 KT 360 36HR VT 02/1800Z 23.5N 66.5W 50 KT 361 48HR VT 03/0600Z 26.3N 67.3W 40 KT 362 72HR VT 04/0600Z 29.2N 67.5W 35 KT 363 96HR VT 05/0600Z 31.5N 67.0W 30 KT 364120HR VT 06/0600Z...DISSIPATED 365 366$$ 367FORECASTER STEWART 368 369 370WTNT43 KNHC 011441 371TCDAT3 372TROPICAL STORM FIONA DISCUSSION NUMBER 8 373NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 3741100 AM AST WED SEP 01 2010 375 376EARLIER THIS MORNING...THE AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT 377MEASURED A PEAK 850 MB WIND OF 58 KT...BELIEVABLE SFMR VALUES OF 37845-50 KT...AND A MINIMUM PRESSURE OF 998 MB. THIS WAS THE BASIS FOR 379THE 8 AM INTENSITY OF 50 KT. SINCE THAT TIME... THE SYSTEM HAS 380BECOME MORE DISORGANIZED WITH THE CENTER ON THE NORTHWESTERN EDGE OF 381WEAKENING DEEP CONVECTION. ANOTHER AIRCRAFT WILL BE IN THE SYSTEM 382EARLY THIS AFTERNOON. DESPITE MODERATE SHEAR...ALL OF THE 383GUIDANCE SHOW FURTHER INTENSIFICATION AND MOST ACTUALLY MAKE FIONA 384A HURRICANE. BY LATE TOMORROW...THE SHEAR SHOULD INCREASE AS THE 385MAJORITY OF THE GLOBAL MODELS HAVE FAIRLY STRONG NORTHEASTERLY 386SHEAR IN A FEW DAYS DUE PRIMARILY TO STRONG UPPER-LEVEL WINDS FROM 387EARL. THIS PATTERN CAUSES FIONA TO RAPIDLY WEAKEN IN 3 OR 4 388DAYS...AND THE NHC FORECAST WILL STAY ON THE LOWER END OF THE 389GUIDANCE ENVELOPE...FAIRLY CLOSE TO THE SHIPS MODEL. 390 391AIRCRAFT FIXES SHOW A MOTION OF ABOUT 305/15 DURING THE PAST SEVERAL 392HOURS. TRACK MODELS ARE IN GOOD AGREEEMENT ON A NORTHWEST TO 393NORTH-NORTHWEST MOTION FOR A DAY OR TWO DUE TO FIONA MOVING AROUND 394A SUBTROPICAL RIDGE OVER THE CENTRAL ATLANTIC OCEAN. HOWEVER...THE 395GUIDANCE STARTS TO BECOME RATHER DIVERGENT AFTER THAT TIME...WHICH 396APPEARS TO BE RELATED TO THE FUTURE INTENSITY OF FIONA. IF THE 397STORM WEAKENS QUICKLY...THE LOW-LEVEL CIRCULATION WILL LIKELY GET 398CAUGHT UP IN SOUTHWESTERLY FLOW AHEAD OF EARL. HOWEVER...IF FIONA 399STAYS A MORE COHERENT VORTEX...THERE REMAINS THE POTENTIAL FOR IT 400TO GET TRAPPED BY A MID-LEVEL SUBTROPICAL RIDGE. GIVEN THE STRONG 401SHEAR FORECAST AT THE END...THE NHC FORECAST LEANS TOWARD THE 402FASTER TRACK SCENARIO AT THE END OF THE FORECAST PERIOD AND 403IS CLOSE TO THE PREVIOUS FORECAST. HOWEVER...I DO NOT HAVE A LOT OF 404CONFIDENCE IN THE LONG-TERM TRACK OR INTENSITY FORECASTS...AS THE 405MODELS HAVE BEEN STURGGLING WITH CONSISTENCY WITH THIS STORM. 406 407 408FORECAST POSITIONS AND MAX WINDS 409 410INITIAL 01/1500Z 18.8N 61.7W 50 KT 411 12HR VT 02/0000Z 20.3N 63.3W 55 KT 412 24HR VT 02/1200Z 22.6N 65.3W 55 KT 413 36HR VT 03/0000Z 24.9N 66.6W 55 KT 414 48HR VT 03/1200Z 26.9N 67.1W 45 KT 415 72HR VT 04/1200Z 29.0N 67.0W 40 KT 416 96HR VT 05/1200Z 31.0N 67.0W 30 KT 417120HR VT 06/1200Z...DISSIPATED 418 419$$ 420FORECASTER BLAKE 421 422 423WTNT43 KNHC 012058 424TCDAT3 425TROPICAL STORM FIONA DISCUSSION NUMBER 9 426NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 427500 PM AST WED SEP 01 2010 428 429THOUGH THE SATELLITE APPEARANCE OF FIONA LOOKS QUITE DISHEVELED WITH 430THE SURFACE CIRCULATION POPPING OUT FROM UNDER THE DEEP 431CONVECTION...THE AIR FORCE HURRICANE HUNTER AIRCRAFT OBSERVATIONS 432SHOW THAT THE SYSTEM STILL IS MAINTAINING MODERATE TROPICAL STORM 433INTENSITY. PEAK 850 MB FLIGHT LEVEL WINDS OF 57 KT AND SFMR SURFACE 434WIND ESTIMATES OF ABOUT 50 KT INDICATE THAT FIONA REMAINS AT 50 KT. 435AIRCRAFT OBSERVATIONS ALSO INDICATE THAT FIONA IS RATHER SMALL IN 436HORIZONTAL EXTENT WITH TROPICAL STORM FORCE WINDS EXTENDING OUT 437LESS THAN 100 NM ON AVERAGE AROUND THE SYSTEM. 438 439CURRENT MOTION OF THE CYCLONE IS A SPEEDY 17 KT TOWARD THE 440NORTHWEST. THE SYSTEM IS BEING ADVECTED ALONG MAINLY BY THE RIDGE 441TO ITS NORTHEAST WITH SOME CONTRIBUTION OF STEERING AS WELL BY THE 442MUCH LARGER HURRICANE EARL. THE MODEL GUIDANCE IS IN GOOD 443AGREEMENT THROUGH TWO DAYS THAT THE CYCLONE WILL CONTINUE TOWARD 444THE NORTHWEST AT A SLOWER FORWARD SPEED. AFTER THAT...THE 445SOLUTIONS DIVERGE WITH SOME GUIDANCE QUICKLY HAVING FIONA ABSORBED 446WITHIN THE CIRCULATION OF EARL AND SOME KEEPING FIONA AS A DISTINCT 447VORTEX AND EVENTUALLY BECOMING A FRONTAL LOW IN ABOUT FOUR TO FIVE 448DAYS. THE FORECAST TRACK IS CLOSE TO THE MODEL CONSENSUS...MINUS 449THE GFDN HURRICANE MODEL WHICH TAKES FIONA UNREALISTICALLY DUE 450WEST...AND IS SIMILAR TO THE PREVIOUS ADVISORY. 451 452THE INTENSITY FORECAST IS...AS USUAL...A DIFFICULT CALL. DESPITE THE 453CYCLONE REMAINING OVER QUITE WARM WATERS FOR THE NEXT SEVERAL 454DAYS...THE VERTICAL SHEAR APPEARS TO BE THE LIMITING FACTOR FOR THE 455INTENSITY OF FIONA. A RESEARCH MISSION BY THE NSF GULFSTREAM-V JET 456SHOWED UNIDIRECTIONAL 35 KT EASTERLIES ADVECTING OVER THE TOP OF 457THE CYCLONE. SUCH UPPER LEVEL FLOW...ALONG WITH THE FAST FORWARD 458SPEED...SHOULD LIMIT ANY INTENSIFICATION IN THE NEAR TERM AND THE 459FORECAST INTENSITY SHOWS LITTLE CHANGE FOR THE NEXT TWO DAYS. AFTER 460THAT...IT IS ANTICIPATED THAT FIONA WILL GRADUALLY DECAY AS IT GETS 461ENTRAINED INTO THE CIRCULATION OF EARL AND VERTICAL WIND SHEAR 462INCREASES. THE INTENSITY FORECAST IS SIGNIFICANTLY BELOW THE MODEL 463CONSENSUS BUT IS QUITE SIMILAR TO THE PREVIOUS ADVISORY. IF CURRENT 464TRENDS CONTINUE...IT IS EVEN POSSIBLE THAT FIONA WILL NO LONGER 465HAVE A CLOSED SURFACE CIRCULATION. UNDER THIS SCENARIO... 466ADVISORIES...AND FIONA...WOULD CEASE TO EXIST. 467 468 469FORECAST POSITIONS AND MAX WINDS 470 471INITIAL 01/2100Z 20.2N 62.9W 50 KT 472 12HR VT 02/0600Z 21.6N 64.6W 50 KT 473 24HR VT 02/1800Z 23.8N 66.3W 50 KT 474 36HR VT 03/0600Z 25.9N 67.4W 50 KT 475 48HR VT 03/1800Z 27.4N 67.6W 45 KT 476 72HR VT 04/1800Z 30.0N 66.5W 35 KT 477 96HR VT 05/1800Z 33.5N 64.5W 25 KT 478120HR VT 06/1800Z...DISSIPATED 479 480$$ 481FORECASTER LANDSEA/BLAKE 482 483 484WTNT43 KNHC 020245 485TCDAT3 486TROPICAL STORM FIONA DISCUSSION NUMBER 10 487NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 4881100 PM AST WED SEP 01 2010 489 490DESPITE THE POOR SATELLITE PRESENTATION...RECONNAISSANCE DATA SINCE 491THE LAST ADVISORY INDICATE THAT THERE HAS BEEN LITTLE CHANGE TO THE 492INTENSITY OF FIONA. THE AIRCRAFT FOUND PEAK 850 MB FLIGHT-LEVEL 493WINDS OF 58 KT AND SFMR WINDS TO 53 KT TO THE NORTHEAST OF THE 494CENTER. THE AIRCRAFT DATA AND OBSERVATIONS FROM NOAA BUOY 41043 495THIS EVENING SUGGEST THAT THE CIRCULATION OVER THE SOUTHWESTERN 496QUADRANT HAS BECOME LESS DEFINED...AND A RECENT SSMIS IMAGE 497DEPICTED A CIRCULATION THAT APPEARED ELONGATED FROM SOUTHEAST TO 498NORTHWEST. THE ENVIRONMENT AHEAD OF FIONA APPEARS QUITE 499HOSTILE...WITH STRONG UPPER-LEVEL WINDS SHOWN BY THE GLOBAL MODELS. 500THE NHC FORECAST INDICATES GRADUAL WEAKENING AND IS AT THE LOWER 501END OF THE GUIDANCE. IT IS POSSIBLE THAT THE CIRCULATION WILL 502DEGENERATE INTO AN OPEN TROUGH IN THE STRONG SOUTH TO SOUTHWEST 503LOW-LEVEL FLOW ON THE EAST SIDE OF HURRICANE EARL. THIS SOLUTION IS 504SUPPORTED BY MOST OF THE GLOBAL MODELS AND DISSIPATION OF FIONA 505COULD OCCUR EARLIER THAN SHOWN BELOW. 506 507FIXES FROM THE AIRCRAFT SHOW THAT FIONA ACCELERATED THIS 508AFTERNOON...WITH AN ESTIMATED MOTION OF 320/20 KT. THE CYCLONE 509IS FORECAST TO MOVE AROUND THE WESTERN PORTION OF THE SUBTROPICAL 510RIDGE DURING THE NEXT DAY OR SO. THEREAFTER...FIONA IS FORECAST 511TO TURN NORTHWARD...THEN NORTHEASTWARD IN DEEP-LAYER SOUTHWESTERLY 512FLOW BETWEEN THE RIDGE AND EARL TO THE NORTHWEST. THE NEW TRACK 513FORECAST IS FASTER THAN THE PREVIOUS ADVISORY AND IS A BLEND OF 514THE GFS...ECMWF...NOGAPS...AND UKMET MODELS. 515 516 517FORECAST POSITIONS AND MAX WINDS 518 519INITIAL 02/0300Z 21.8N 64.1W 50 KT 520 12HR VT 02/1200Z 23.8N 65.7W 45 KT 521 24HR VT 03/0000Z 26.2N 67.1W 45 KT 522 36HR VT 03/1200Z 28.8N 67.4W 40 KT 523 48HR VT 04/0000Z 31.5N 66.3W 40 KT 524 72HR VT 05/0000Z 35.5N 63.5W 35 KT 525 96HR VT 06/0000Z...DISSIPATED 526 527$$ 528FORECASTER BROWN 529 530 531WTNT43 KNHC 020853 532TCDAT3 533TROPICAL STORM FIONA DISCUSSION NUMBER 11 534NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 535500 AM AST THU SEP 02 2010 536 537AFTER LITTLE TO NO CONVECTION NEAR THE CENTER OF FIONA...A STRONG 538BURST OF DEEP CONVECTION DEVELOPED OVER THE CENTER FOR A FEW HOURS 539EARLIER THIS MORNING...WHICH HAS NOW BEEN SHEARED SLIGHTLY TO THE 540SOUTHWEST OF THE CENTER. HOWEVER...NIGHTTIME VISIBLE IMAGERY AND A 54102/0156Z ASCAT OVERPASS INDICATE FIONA HAS A SMALL BUT VERY 542WELL-DEFINED CIRCULATION. THE INITIAL INTENSITY OF 45 KT IS BASED 543ON A BELTON OF SATELLITE INTENSITY ESTIMATES OF 35 KT FROM FROM 544TAFB AND SAB...AT LEAST 40 KT FROM THE ASCAT PASS...AND UW-CIMSS 545ADT ESTIMATE OF 49 KT. 546 547THE INITIAL MOTION ESTIMATE IS 320/15 BASED ON MOSTLY ON MICROWAVE 548FIXES AND CONTINUITY WITH THE PREVIOUS ADVISORY MOTION. THE FUTURE 549TRACK OF FIONA IS HEAVILY DEPENDENT ON THE INTENSITY AND STRUCTURE 550OF THE CYCLONE. IT IS UNLIKELY THAT FIONA WILL GROW MUCH MORE IN 551HORIZONTAL SIZE DUE TO THE LARGE CIRCULATION OF POWERFUL HURRICANE 552EARL SITUATED ABOUT 750 NMI TO THE NORTHWEST. HOWEVER...ALL OF THE 553GLOBAL MODELS ARE NOW FORECASTING FIONA TO ROUND THE WESTERN 554PERIPHERY OF THE SUBTROPICAL RIDGE LOCATED EAST-WEST BETWEEN 27N 555AND 30N LATITUDE...AND IN 36-48 HOURS MOVE UNDERNEATH A REGION OF 556LOW VERTICAL SHEAR BETWEEN THE STRONG NORTHERLY OUTFLOW FROM EARL 557AND THE SOUTHWESTERLY FLOW AHEAD OF A LARGE MID-LATITUDE TROUGH 558FORECAST TO MOVE OFF THE U.S. EAST COAST IN 24 HOURS AND CAPTURE 559HURRICANE EARL. IF THIS PATTERN EVOLVES...FIONA WILL REMAIN A 560DISTINCT ENTITY AND NOT BECOME ABSORBED BY THE LARGE CIRCULATION OF 561EARL AS QUICKLY AS MOST OF THE GLOBAL MODELS ARE FORECASTING. THE 562HWRF AND GFDL MODELS KEEP FIONA A SEPARATE SYSTEM THROUGH 120 HOURS 563AND EVEN MAKE THE CYCLONE A HURRICANE IN 24-36 HOURS. THE OFFICIAL 564FORECAST TRACK IS SIMILAR TO THE PREVIOUS TRACK THROUGH 24 HOURS... 565AND THEN A LITTLE TO EAST OR RIGHT OF TRACK AFTER THAT. ON THE 566FORECAST TRACK...FIONA IS EXPECTED TO PASS VERY NEAR BERMUDA IN 567ABOUT 48 HOURS...WHICH HAS PROMPTED THE ISSUANCE OF A TROPICAL 568STORM WATCH FOR THAT ISLAND BY THE BERMUDA WEATHER SERVICE. 569 570AS MENTIONED ABOVE...FIONA MAY REMAIN JUST WEST OF THE STRONGEST 571NORTHEASTERLY VERTICAL WIND SHEAR ASSOCIATED WITH THE OUTFLOW OF 572EARL FOR THE NEXT 24 HOURS. ALTHOUGH THERE MAY BE FLUCTUATIONS IN 573THE INTENSITY OF FIONA...THE SHEAR IS NOT EXPECTED TO BE STRONG 574ENOUGH TO STRIP AWAY ALL OF THE CONVECTION. BY 36-48 HOURS...FIONA 575MAY MOVE INTO THE AFOREMENTIONED REGION OF LOW SHEAR BENEATH A 576SMALL UPPER-LEVEL ANTICYCLONE FORECAST BY ALL THE MODELS TO DEVELOP 577NEAR BERMUDA. THIS WOULD PROVIDE A BRIEF WINDOW OF OPPORTUNITY FOR 578MORE SIGNIFICANT DEVELOP THAN CURRENTLY INDICATED. THE OFFICIAL 579FORECAST CALLS FOR FIONA TO MAINTAIN ITS CURRENT INTENSITY FOR THE 580NEXT 48 HOURS...ALTHOUGH THERE MAY SOME FLUCTUATIONS DURING THAT 581TIME AS THE SHEAR WAXES AND WANES. THIS SCENARIO IS CONSISTENT WITH 582THE GFDL AND HWRF MODELS. 583 584 585FORECAST POSITIONS AND MAX WINDS 586 587INITIAL 02/0900Z 22.6N 65.4W 45 KT 588 12HR VT 02/1800Z 24.6N 66.6W 45 KT 589 24HR VT 03/0600Z 27.1N 67.3W 45 KT 590 36HR VT 03/1800Z 29.7N 67.0W 45 KT 591 48HR VT 04/0600Z 32.4N 65.8W 45 KT 592 72HR VT 05/0600Z 36.5N 62.0W 35 KT 593 96HR VT 06/0600Z...DISSIPATED 594 595$$ 596FORECASTER STEWART 597 598 599WTNT43 KNHC 021437 600TCDAT3 601TROPICAL STORM FIONA DISCUSSION NUMBER 12 602NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 6031100 AM AST THU SEP 02 2010 604 605BURSTS OF CONVECTION CONTINUE TO FORM NEAR THE WELL-DEFINED 606CIRCULATION OF FIONA THIS MORNING. HOWEVER THIS CONVECTION HAS HAD 607TROUBLE MAINTAINING ITSELF...PROBABLY DUE TO PERSISTENT NORTHERLY 608SHEAR. DVORAK CLASSIFICATIONS ARE UNCHANGED FROM EARLIER...SO THE 609INITIAL INTENSITY WILL STAY 45 KT. 610 611FIONA HAS TURNED TO THE RIGHT AND IS NOW MOVING 330/15. AS THE 612CYCLONE ROUNDS THE SOUTHWESTERN PERIPHERY OF A RIDGE OVER THE 613CENTRAL ATLANTIC...IT IS EXPECTED TO TURN TOWARD THE NORTH AND 614NORTHEAST BY LATE TOMORROW. MOST OF THE MODEL GUIDANCE IS 615CLUSTERED ON A TRACK NEAR OR WEST OF BERMUDA IN ABOUT 36-48 616HRS...THOUGH WITH SOME SPEED DIFFERENCES. SINCE FIONA HAS SHOWN NO 617SIGNS OF SLOWING DOWN...AND WILL LIKELY REMAIN A WEAK SYSTEM 618STEERED BY SWIFT LOW-LEVEL WINDS...THE NHC FORECAST WILL STAY 619FASTER THAN THE MODEL CONSENSUS. THE NEW FORECAST IS ALSO SHIFTED 620A LITTLE TO THE RIGHT OF THE PREVIOUS ONE TO COME INTO BETTER 621AGREEMENT WITH THE LATEST GUIDANCE. THE GFDL SOLUTION OF A 622SLOWER...MORE WESTWARD TRACK WELL TO THE SOUTHWEST OF BERMUDA IS 623CONSIDERED UNLIKELY. 624 625THE STORM IS WALKING A TIGHTROPE BETWEEN RATHER STRONG NORTHERLY 626SHEAR TO ITS EAST AND AN AREA OF LIGHTER SHEAR FARTHER WEST. WITH 627THE RIGHTWARD SHIFT OF THE GUIDANCE THIS MORNING...THIS COULD CAUSE 628EVEN STRONGER SHEAR IN A DAY OR SO NEAR THE CYCLONE. ALL THE 629GUIDANCE SHOWS A CONSIDERABLE WEAKENING OF FIONA...EXCEPT FOR THE 630GFDL WHICH HAS AN UNREALISTIC TRACK FORECAST. THE NHC INTENSITY 631FORECAST IS REDUCED FROM THE PREVIOUS ONE...BUT IS STILL HIGHER 632THAN NEARLY ALL OF THE GUIDANCE. 633 634 635FORECAST POSITIONS AND MAX WINDS 636 637INITIAL 02/1500Z 24.4N 65.8W 45 KT 638 12HR VT 03/0000Z 26.4N 66.5W 45 KT 639 24HR VT 03/1200Z 28.9N 66.7W 45 KT 640 36HR VT 04/0000Z 31.3N 65.7W 40 KT 641 48HR VT 04/1200Z 33.8N 64.1W 35 KT 642 72HR VT 05/1200Z 37.9N 61.4W 25 KT...DISSIPATING 643 96HR VT 06/1200Z...DISSIPATED 644 645$$ 646FORECASTER BLAKE/PASCH 647 648 649WTNT43 KNHC 022035 650TCDAT3 651TROPICAL STORM FIONA DISCUSSION NUMBER 13 652NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 653500 PM AST THU SEP 02 2010 654 655THERE HAS BEEN LITTLE CHANGE WITH FIONA DURING THE DAY. THE STORM 656CONTINUES THE PATTERN OBSERVED DURING THE LAST DAY OR SO OF BURSTS 657OF CONVECTION FORMING NEAR THE CENTER...THEN SHEARING AWAY. AN 658ASCAT PASS FROM LATE THIS MORNING SHOWED MAXIMUM WINDS OF ABOUT 40 659KT. GIVEN THE WELL-DOCUMENTED LOW BIAS OF THAT INSTRUMENT...45 KT 660SEEMS LIKE A REASONABLE INITIAL WIND SPEED. THE INTENSITY FORECAST 661IS DIFFICULT BECAUSE IT SEEMS LIKE FIONA HAS BEEN WITHSTANDING THE 662SHEAR BETTER THAN MOST TROPICAL CYCLONES. THE LATEST INTENSITY 663GUIDANCE DOES NOT WEAKEN THE STORM AS QUICKLY AS EARLIER...BUT IS 664ACTUALLY PRETTY CLOSE TO THE PREVIOUS FORECAST. THUS NO CHANGES ARE 665MADE TO THE LAST NHC FORECAST. AFTER 72 HOURS...ALL OF THE GLOBAL 666MODELS SHOW THE TROPICAL CYCLONE SHEARING OUT AS IT MOVES 667NORTHEASTWARD. 668 669FIONA HAS TURNED A LITTLE MORE AND IS NOW MOVING 335/15. THERE IS 670NO CHANGE IN SYNOPTIC REASONING WITH THE CYCLONE MOVING AROUND A 671SUBTROPICAL ANTICYCLONE. THE STORM SHOULD TURN TOWARD THE NORTH... 672THEN NORTHEAST AS IT STARTS TO MOVE INTO THE MID-LATITUDES. THE 673MODELS ARE GENERALLY SLOWER THAN THE PREVIOUS CYCLE...BUT SINCE 674THE CYCLONE CONTINUES SPEEDING ALONG...THE NHC FORECAST WILL STAY 675ON THE FASTER SIDE OF THE GUIDANCE ENVELOPE...WITH LITTLE CHANGE TO 676THE TRACK. THERE IS REASONABLE AGREEMENT THAT FIONA WILL BE CLOSE 677TO BERMUDA IN 36-48 HOURS. 678 679 680FORECAST POSITIONS AND MAX WINDS 681 682INITIAL 02/2100Z 25.6N 66.4W 45 KT 683 12HR VT 03/0600Z 27.5N 66.8W 45 KT 684 24HR VT 03/1800Z 29.7N 66.4W 45 KT 685 36HR VT 04/0600Z 31.7N 65.4W 40 KT 686 48HR VT 04/1800Z 33.7N 64.1W 35 KT 687 72HR VT 05/1800Z 38.0N 61.0W 25 KT...DISSIPATING 688 96HR VT 06/1800Z...DISSIPATED 689 690$$ 691FORECASTER BLAKE/BROWN 692 693 694WTNT43 KNHC 030236 695TCDAT3 696TROPICAL STORM FIONA DISCUSSION NUMBER 14 697NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 6981100 PM AST THU SEP 02 2010 699 700FIONA REMAINS A SHEARED TROPICAL CYCLONE...WITH THE LOW-LEVEL 701CENTER EXPOSED TO THE NORTH OF THE DEEP CONVECTION. THE INITIAL 702INTENSITY IS KEPT AT 45 KT...BASED ON A DVORAK T-NUMBER OF 3.0 FROM 703TAFB AND SCATTEROMETER DATA FROM EARLIER TODAY. THE NORTH- 704NORTHEASTERLY SHEAR IS EXPECTED TO REMAIN STRONG DURING THE NEXT 70524-36 HOURS. TYPICALLY ONE WOULD EXPECT SIGNIFICANT WEAKENING DUE 706TO THE ANTICIPATED SHEAR. HOWEVER...FIONA HAS BEEN WITHSTANDING THE 707SHEAR DURING THE PAST 24 HOURS...SO ONLY GRADUAL WEAKENING IS 708FORECAST UNTIL DISSIPATION. THE NEW OFFICIAL FORECAST IS IN GOOD 709AGREEMENT WITH THE SHIPS/LGEM GUIDANCE. 710 711FIONA IS NOW MOVING NORTHWARD OR 355/14 KT. THE CYCLONE IS EXPECTED 712TO TURN NORTH-NORTHEASTWARD BETWEEN THE SUBTROPICAL RIDGE AND 713HURRICANE EARL TO ITS NORTHWEST. THE GLOBAL MODELS ARE IN GOOD 714AGREEMENT ON THIS SCENARIO. THE OFFICIAL FORECAST IS NEAR THE 715MIDDLE OF THE GUIDANCE ENVELOPE AND IS ESSENTIALLY AN UPDATE OF THE 716PREVIOUS ADVISORY. ON THE FORECAST TRACK...THE CENTER OF FIONA 717IS EXPECTED TO PASS NEAR OR OVER BERMUDA IN AROUND 36 HOURS. 718 719 720FORECAST POSITIONS AND MAX WINDS 721 722INITIAL 03/0300Z 26.9N 66.8W 45 KT 723 12HR VT 03/1200Z 28.7N 66.7W 40 KT 724 24HR VT 04/0000Z 30.8N 65.9W 40 KT 725 36HR VT 04/1200Z 32.7N 64.8W 35 KT 726 48HR VT 05/0000Z 34.8N 63.6W 35 KT 727 72HR VT 06/0000Z 39.5N 60.0W 25 KT...DISSIPATING 728 96HR VT 07/0000Z...DISSIPATED 729 730$$ 731FORECASTER BROWN 732 733 734WTNT43 KNHC 030832 735TCDAT3 736TROPICAL STORM FIONA DISCUSSION NUMBER 15 737NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 738500 AM AST FRI SEP 03 2010 739 740FIONA REMAINS A SHEARED TROPICAL CYCLONE WITH DEEP CONVECTION 741DISPLACED OVER THE SOUTHERN SEMICIRCLE OF THE CIRCULATION. THE 742INITIAL INTENSITY OF 45 KT IS BASED ON A SATELLITE INTENSITY 743ESTIMATE OF T3.0/45 KT FROM TAFB...WHICH IS SUPPORTED BY A 3-HR 744AVERAGE ADT OF T3.3/51 KT FROM UW-CIMSS. 745 746THE INITIAL MOTION ESTIMATE IS 010/11 KT...WHICH IS BASED MAINLY ON 747CONTINUITY WITH THE PREVIOUS ADVISORY. THERE IS NO CHANGE TO THE 748PREVIOUS TRACK AND INTENSITY FORECAST REASONINGS. FIONA IS FORECAST 749TO GRADUALLY WEAKEN AS IT MOVES NORTHWARD TODAY AND THEN TURNS 750NORTHEASTWARD BY SATURDAY...WITH THE CENTER OF FIONA EXPECTED TO 751PASS NEAR OR OVER BERMUDA IN ABOUT 24 HOURS. THE OFFICIAL FORECAST 752TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND IS IN THE MIDDLE OF 753THE NHC MODEL SUITE. 754 755 756FORECAST POSITIONS AND MAX WINDS 757 758INITIAL 03/0900Z 28.1N 66.7W 45 KT 759 12HR VT 03/1800Z 29.8N 66.1W 40 KT 760 24HR VT 04/0600Z 32.0N 65.0W 40 KT 761 36HR VT 04/1800Z 34.2N 63.7W 35 KT 762 48HR VT 05/0600Z 36.4N 62.0W 35 KT 763 72HR VT 06/0600Z 41.5N 58.5W 25 KT...DISSIPATING 764 96HR VT 07/0600Z...DISSIPATED 765 766$$ 767FORECASTER STEWART 768 769 770WTNT43 KNHC 031442 771TCDAT3 772TROPICAL STORM FIONA DISCUSSION NUMBER 16 773NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 7741100 AM AST FRI SEP 03 2010 775 776AIRCRAFT DATA FROM THIS MORNING SHOWED PEAK SFMR WINDS OF 39 KT AND 777FLIGHT-LEVEL WINDS OF 48 KT...SUPPORTING AN INITIAL WIND SPEED OF 778ABOUT 40 KT. SATELLITE IMAGES SHOW THAT CONVECTION HAS BECOME 779RATHER THIN NEAR THE CENTER...WITH THE CIRCULATION OF FIONA ALSO 780TAKING ON AN ELONGATED APPEARANCE. SLOW WEAKENING SEEMS LIKELY 781GIVEN THE PERSISTENT NORTHERLY SHEAR AND MODEL GUIDANCE IS ON GOOD 782AGREEMENT WITH THIS SCENARIO. THE NHC FORECAST IS BASICALLY AN 783UPDATE OF THE PREVIOUS ADVISORY. ALL MODELS WEAKEN THE SYSTEM 784DRAMATICALLY IN A COUPLE OF DAYS...AND DISSIPATION IS EXPECTED 785AFTER THAT TIME. GIVEN THE LATEST SATELLITE PRESENTATION...IT WOULD 786NOT BE A SURPRISE IF FIONA DECAYED FASTER THAN THE FORECAST BELOW. 787 788FIONA HAS TURNED TO THE NORTH-NORTHEAST AND IS MOVING 020/11 KT. THE 789MODELS ARE WELL CLUSTERED NOW ON BRINGING THE CENTER NEAR BERMUDA 790IN ABOUT 18 HOURS. THEREAFTER...SOME ACCELERATION IS ANTICIPATED AS 791THE STORM ENCOUNTERS INCREASING SOUTHWESTERLY FLOW. THE NHC 792FORECAST IS VERY CLOSE TO THE PREVIOUS ONE AND THE DYNAMICAL MODEL 793CONSENSUS. 794 795THE INITIAL WIND RADII HAVE BEEN REDUCED BASED ON AIRCRAFT 796DATA...AND STILL MIGHT BE A LITTLE GENEROUS. 797 798 799FORECAST POSITIONS AND MAX WINDS 800 801INITIAL 03/1500Z 29.0N 66.4W 40 KT 802 12HR VT 04/0000Z 30.6N 65.7W 35 KT 803 24HR VT 04/1200Z 32.7N 64.6W 35 KT 804 36HR VT 05/0000Z 35.2N 63.1W 30 KT 805 48HR VT 05/1200Z 38.1N 61.2W 25 KT 806 72HR VT 06/1200Z...DISSIPATED 807 808$$ 809FORECASTER BLAKE 810 811 812WTNT43 KNHC 032035 813TCDAT3 814TROPICAL STORM FIONA DISCUSSION NUMBER 17 815NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 816500 PM AST FRI SEP 03 2010 817 818SATELLITE IMAGES INDICATE THAT FIONA IS WEAKENING. THE LOW-LEVEL 819CIRCULATION IS BECOMING DISTORTED WITH MULTIPLE SWIRLS...AND ONLY A 820MEAGER AMOUNT OF CONVECTION REMAINS. SATELLITE CLASSIFICATIONS ARE 821DROPPING...AND THE INITIAL INTENSITY IS LOWERED TO 35 KT. FURTHER 822WEAKENING IS LIKELY DUE TO STRONG NORTHERLY SHEAR. DISSIPATION IS 823PROBABLE BY SUNDAY...IF NOT SOONER...OR THE SYSTEM COULD DEGENERATE 824INTO A REMNANT LOW AS EARLY AS TONIGHT IF CONVECTION DOES NOT 825REDEVELOP SOON. THE CHANCES OF TROPICAL-STORM-FORCE WINDS 826OCCURRING IN BERMUDA APPEAR TO BE DROPPING. 827 828FIONA HAS TURNED A LITTLE MORE TO THE RIGHT AND IS NOW MOVING 829030/12. A SMALL SHIFT IN THE GUIDANCE HAS OCCURRED...WITH ALL OF THE 830MODELS NOW SHOWING THE CENTER PASSING JUST TO THE EAST OF BERMUDA. 831THIS APPEARS TO BE DUE TO FIONA BECOMING A RATHER SHALLOW SYSTEM 832THAT IS BEING PRIMARILY STEERED BY SOUTHWESTERLY FLOW AROUND EARL. 833THE OFFICIAL FORECAST IS SHIFTED A LITTLE TO THE RIGHT OF THE 834PREVIOUS ONE...BUT STILL PASSES CLOSE TO BERMUDA. GLOBAL MODELS 835INDICATE THAT THE WEAK SYSTEM SHOULD INCREASE ITS FORWARD SPEED AS 836IT MOVES AWAY FROM BERMUDA AND DECAYS. 837 838FORECAST POSITIONS AND MAX WINDS 839 840INITIAL 03/2100Z 30.0N 65.5W 35 KT 841 12HR VT 04/0600Z 31.6N 64.7W 30 KT 842 24HR VT 04/1800Z 33.6N 63.5W 25 KT 843 36HR VT 05/0600Z 36.4N 61.7W 20 KT...POST-TROP/REMNT LOW 844 48HR VT 05/1800Z 39.6N 59.6W 20 KT...POST-TROP/REMNT LOW 845 72HR VT 06/1800Z...DISSIPATED 846 847$$ 848FORECASTER BLAKE 849 850 851WTNT43 KNHC 040238 852TCDAT3 853TROPICAL DEPRESSION FIONA DISCUSSION NUMBER 18 854NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082010 8551100 PM AST FRI SEP 03 2010 856 857FIONA HAS DEGENERATED INTO A REMNANT LOW THIS EVENING. AN AIR FORCE 858RESERVE RECONNAISSANCE AIRCRAFT FOUND AN ELONGATED AND 859POORLY-DEFINED CIRCULATION WITH A CENTRAL PRESSURE THAT HAD RISEN 860TO 1013 MB. ALSO...ENHANCED INFRARED SATELLITE IMAGERY SHOWS THAT 861THE SYSTEM LACKS ORGANIZED DEEP CONVECTION. IN FACT...ALL THAT 862REMAINS OF THE CONVECTION IS A VERY SMALL AREA OF SHOWERS LOCATED 863ABOUT 50 MILES SOUTH OF THE CENTER...AND DVORAK ESTIMATES FROM BOTH 864TAFB AND SAB INDICATE THAT THE SYSTEM IS TOO WEAK TO CLASSIFY AS A 865TROPICAL CYCLONE. THE INTENSITY FORECAST CALLS FOR DISSIPATION IN 86648 HOURS IN AN ENVIRONMENT OF 20-30 KT OF NORTHEASTERLY SHEAR AS 867INDICATED BY THE UW-CIMSS SHEAR PRODUCT. DYNAMICAL MODELS THAT DO 868NOT ALREADY SHOW FIONA AS AN OPEN WAVE ALSO SUPPORT SUPPORT 869DISSIPATION WITHIN THE AFOREMENTIONED FORECAST PERIOD. 870 871THE LOW IS FORECAST TO MOVE NORTH-NORTHEASTWARD AND PASS JUST TO THE 872EAST OF BERMUDA ON SATURDAY. AN INCREASE IN FORWARD MOTION...AS A 873SHALLOW LOW...IS EXPECTED AROUND THE 36 HOUR PERIOD BEFORE 874DISSIPATION. 875 876THIS IS THE LAST FORECAST/ADVISORY ISSUED BY THE NATIONAL HURRICANE 877CENTER ON FIONA. ADDITIONAL INFORMATION ON THIS SYSTEM CAN BE FOUND 878IN HIGH SEAS FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE... 879UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC. 880 881FORECAST POSITIONS AND MAX WINDS 882 883INITIAL 04/0300Z 31.4N 64.9W 25 KT 884 12HR VT 04/1200Z 33.0N 64.0W 25 KT...POST-TROP/REMNT LOW 885 24HR VT 05/0000Z 35.2N 62.6W 25 KT...POST-TROP/REMNT LOW 886 36HR VT 05/1200Z 38.2N 60.9W 20 KT...POST-TROP/REMNT LOW 887 48HR VT 06/0000Z...DISSIPATED 888 889$$ 890FORECASTER ROBERTS/BRENNAN 891 892 893