1WTNT42 KNHC 050236 2TCDAT2 3 4TROPICAL STORM GABRIELLE DISCUSSION NUMBER 2 5NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 61100 PM AST WED SEP 04 2013 7 8THE SATELLITE PRESENTATION OF THE CYCLONE CONSISTS OF A SMALL AREA 9OF VERY DEEP CONVECTION NEAR AND NORTHEAST OF THE SURFACE CENTER 10WHILE THE CONVECTIVE BANDS HAVE LARGELY DISSIPATED OVER THE PAST 11FEW HOURS. THE LARGE-SCALE OUTFLOW PATTERN OVER THE CYCLONE IS 12EXCELLENT WITH AN ENHANCED POLEWARD OUTFLOW CHANNEL SEEN IN WATER 13VAPOR IMAGERY. BASED ON THE LATEST SATELLITE CLASSIFICATIONS FROM 14BOTH TAFB AND SAB...THE INITIAL INTENSITY IS SET TO 35 KT...AND THE 15DEPRESSION IS NOW TROPICAL STORM GABRIELLE. 16 17DROPSONDE DATA FROM THE NASA GLOBAL HAWK AIRCRAFT SUGGEST THAT THE 18CIRCULATION OF GABRIELLE IS TILTED TO THE NORTHEAST WITH HEIGHT... 19WITH A MID-LEVEL CIRCULATION SEEN IN DATA FROM THE SAN JUAN WSR-88D 20RADAR. THIS TILTED STRUCTURE IS CONSISTENT WITH SOUTHERLY TO 21SOUTHWESTERLY VERTICAL SHEAR OF 5 TO 10 KT SHOWN OVER THE CYCLONE 22BY THE UW-CIMSS AND SHIPS MODEL ANALYSES. IN ADDITION...THE 23DROPSONDE DATA SHOWED DRY AIR IN THE MID LEVELS OF THE ATMOSPHERE 24AROUND GABRIELLE. GIVEN THE ENVIRONMENT...THE SOMEWHAT DISORGANIZED 25STATE OF THE CIRCULATION...POSSIBLE LAND INTERACTION...AND THE 26PRESENCE OF THE LARGE AREA OF DISTURBED WEATHER NORTHEAST OF 27GABRIELLE...NOT MUCH STRENGTHENING IS EXPECTED IN THE SHORT TERM. 28THE NHC FORECAST IS IN GOOD AGREEMENT WITH THE INTENSITY CONSENSUS 29AIDS FOR THE FIRST 24 HOURS. IT IS ENTIRELY POSSIBLE THAT THE 30LOW-LEVEL CIRCULATION WILL DISSIPATE IN THE NEXT 24 HOURS. ASSUMING 31THAT GABRIELLE SURVIVES...ONLY LIMITED INTENSIFICATION IS SHOWN 32LATER IN THE PERIOD AS THE SHEAR INCREASES DRAMATICALLY AHEAD OF AN 33UPPER-LEVEL TROUGH. THE NHC FORECAST REMAINS BELOW MUCH OF THE 34INTENSITY GUIDANCE LATE IN THE PERIOD...WHICH SEEMS TOO HIGH GIVEN 35THE INCREASE IN SHEAR. THE NHC FORECAST IS ALSO SUPPORTED BY THE 36GLOBAL MODELS...WHICH DO NOT SHOW MUCH INTENSIFICATION AFTER 37GABRIELLE MOVES NORTH OF THE CARIBBEAN SEA. 38 39THE LOW-LEVEL CENTER HAS BEEN DIFFICULT TO LOCATE...BUT THE GLOBAL 40HAWK DROPSONDE DATA SUGGEST IT REMAINS SOUTHWEST OF THE MID-LEVEL 41CENTER SEEN IN RADAR IMAGERY. GIVEN THE DIFFICULTY LOCATING THE 42CENTER...THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 320/7. THE 43SYNOPTIC-SCALE TRACK REASONING HAS NOT CHANGED...AS GABRIELLE IS 44EXPECTED TO MOVE GENERALLY NORTHWESTWARD DURING THE NEXT DAY OR 45SO...FOLLOWED A TURN TOWARD THE NORTH BY 72 HOURS AS THE CYCLONE 46MOVES AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE. LATE 47IN THE PERIOD AN ACCELERATION TOWARD THE NORTHEAST IS EXPECTED AHEAD 48OF AN UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC. THE NHC TRACK 49FORECAST IS LARGELY AN UPDATE OF THE PREVIOUS ONE THROUGH 72 HOURS 50AND LIES A LITTLE TO THE RIGHT OF MOST OF THE MODEL GUIDANCE DURING 51THIS PERIOD. AT DAYS 4 AND 5 THE NHC FORECAST IS A LITTLE TO THE 52RIGHT OF THE PREVIOUS ONE AND IS CLOSE TO THE GFS ENSEMBLE MEAN AND 53FSU SUPERENSEMBLE. 54 55REGARDLESS OF THE EXACT TRACK OF THE CENTER OF GABRIELLE DURING THE 56NEXT 24 HOURS...THE MAIN THREAT WILL BE HEAVY RAINFALL OVER 57PORTIONS OF PUERTO RICO AND THE DOMINICAN REPUBLIC. 58 59 60FORECAST POSITIONS AND MAX WINDS 61 62INIT 05/0300Z 17.0N 66.6W 35 KT 40 MPH 63 12H 05/1200Z 17.8N 67.4W 40 KT 45 MPH 64 24H 06/0000Z 19.0N 68.4W 45 KT 50 MPH 65 36H 06/1200Z 20.1N 69.0W 45 KT 50 MPH 66 48H 07/0000Z 21.2N 69.4W 45 KT 50 MPH 67 72H 08/0000Z 23.3N 69.2W 50 KT 60 MPH 68 96H 09/0000Z 25.5N 67.5W 50 KT 60 MPH 69120H 10/0000Z 29.5N 63.9W 50 KT 60 MPH 70 71$$ 72FORECASTER BRENNAN 73 74 75WTNT42 KNHC 050841 76TCDAT2 77 78TROPICAL STORM GABRIELLE DISCUSSION NUMBER 3 79NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 80500 AM AST THU SEP 05 2013 81 82ALTHOUGH THE AREA OF DEEP CONVECTION HAS EXPANDED SIGNIFICANTLY 83DURING THE PAST SEVERAL HOURS AND THE OUTFLOW IS EXCELLENT... 84SURROUNDING SURFACE OBSERVATIONS DO NOT SUGGEST THAT THERE HAS 85BEEN ANY IMPROVEMENT OF THE CIRCULATION. IN ADDITION...MICROWAVE OR 86DOPPLER RADAR DATA DO NOT SHOW ANY DEVELOPMENT OF AN INNER 87CORE...ALTHOUGH RADAR IMAGES SHOW A WELL-DEFINED MID-LEVEL CENTER 88TO THE EAST OF THE SURFACE LOCATION. I WOULD NOT BE SURPRISED IF 89THERE IS A REFORMATION OF THE SURFACE CENTER. A RECONNAISSANCE 90PLANE LATER THIS MORNING WILL HELP US TO DETERMINE IF THIS IS THE 91CASE. SUBJECTIVE ESTIMATES FROM TAFB AND SAB AS WELL AS OBJECTIVE 92ESTIMATES FROM THE UNIVERSITY OF WISCONSIN...CIMSS...ARE 2.5 ON THE 93DVORAK SCALE. ON THIS BASIS...THE INITIAL INTENSITY IS KEPT AT 35 94KNOTS...AND THESE WINDS ARE PROBABLY CONFINED TO A VERY SMALL AREA 95NEAR THE CENTER. THE INTENSITY FORECAST IS HIGHLY UNCERTAIN. MOST 96OF THE GLOBAL MODELS KEEP A WEAK CYCLONE FOR A FEW DAYS WITH THE 97EXCEPTION OF THE ECMWF WHICH DISSIPATES GABRIELLE JUST NORTH OF 98HISPANIOLA IN A COUPLE OF DAYS. GIVEN THE STRONG WESTERLY SHEAR 99WHICH IS FORECAST TO BECOME ESTABLISHED ALONG THE FORECAST PATH OF 100GABRIELLE...THE DISSIPATION OPTION OF THE ECMWF IS NOT OUT OF THE 101QUESTION. AT THIS TIME...THE NHC FORECAST FOLLOWS THE MODEL 102CONSENSUS SHOWING SOME SLIGHT STRENGTHENING GIVING CREDIT TO THE 103OTHER MODELS. 104 105ALTHOUGH THE SURFACE CENTER IS DIFFICULT TO FIND ON IR IMAGES...IT 106APPEARS TO BE ON THE WESTERN EDGE OF THE DEEP CONVECTION. THE BEST 107ESTIMATE OF THE INITIAL MOTION IS TOWARD THE NORTHWEST OR 320 108DEGREES AT 7 KNOTS. GABRIELLE IS EMBEDDED WITHIN A WEAK STEERING 109FLOW SOUTH OF A NARROW RIDGE OF HIGH PRESSURE OVER THE WESTERN 110ATLANTIC. IN A DAY OR TWO...A MID-LEVEL TROUGH IS FORECAST TO MOVE 111FROM THE UNITED STATES EASTWARD ACROSS THE ATLANTIC...CAUSING 112GABRIELLE TO RECURVE AND MOVE TOWARD THE OPEN ATLANTIC. THE 113OFFICIAL FORECAST IS VERY CLOSE TO THE MULTI-MODEL CONSENSUS AND IS 114NOT TOO DIFFERENT FROM THE PREVIOUS ONE. 115 116REGARDLESS OF THE EXACT TRACK OF THE CENTER OF GABRIELLE DURING THE 117NEXT 24 HOURS...THE MAIN THREAT WILL BE HEAVY RAINFALL OVER PORTIONS 118OF PUERTO RICO AND THE EASTERN PORTION OF THE DOMINICAN REPUBLIC. 119 120 121FORECAST POSITIONS AND MAX WINDS 122 123INIT 05/0900Z 17.5N 66.9W 35 KT 40 MPH 124 12H 05/1800Z 18.5N 67.7W 35 KT 40 MPH 125 24H 06/0600Z 19.7N 68.5W 40 KT 45 MPH 126 36H 06/1800Z 20.9N 69.1W 45 KT 50 MPH 127 48H 07/0600Z 21.8N 69.5W 50 KT 60 MPH 128 72H 08/0600Z 24.0N 69.0W 50 KT 60 MPH 129 96H 09/0600Z 27.0N 66.0W 50 KT 60 MPH 130120H 10/0600Z 31.5N 62.5W 50 KT 60 MPH 131 132$$ 133FORECASTER AVILA 134 135 136WTNT42 KNHC 051441 137TCDAT2 138 139TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER 4 140NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 1411100 AM AST THU SEP 05 2013 142 143A COMBINATION OF SATELLITE...SAN JUAN DOPPLER RADAR...RAWINSONDE... 144AND AIRCRAFT DATA INDICATES THAT GABRIELLE HAS BECOME VERY 145DISORGANIZED. THE LOW-LEVEL CENTER...WHICH IS POORLY DEFINED...IS 146LOCATED SOUTH OF THE MONA PASSAGE ABOUT 130 N MI FROM THE MID-LEVEL 147CENTER THAT IS LOCATED BETWEEN PUERTO RICO AND THE VIRGIN ISLANDS. 148THIS STRUCTURE MAY BE DUE TO SOME WESTERLY VERTICAL WIND SHEAR... 149ALTHOUGH THE SHEAR APPEARS TO BE TOO LIGHT TO HAVE SUCH A DRASTIC 150EFFECT ON THE CYCLONE. NONE OF THE DATA CURRENTLY SUGGEST TROPICAL 151STORM FORCE WINDS ARE OCCURRING...SO GABRIELLE IS DOWNGRADED TO A 15230-KT TROPICAL DEPRESSION. 153 154CONVECTION CONTINUES NEAR THE MID-LEVEL CENTER...SO THERE IS STILL A 155CHANCE OF THE LOW-LEVEL CENTER REFORMING IN THAT AREA. IF THAT 156DOES NOT OCCUR...GABRIELLE IS EXPECTED TO WEAKEN AS IT INTERACTS 157WITH THE TERRAIN OF THE DOMINICAN REPUBLIC AND ENCOUNTERS 158INCREASING WESTERLY SHEAR. THE REVISED INTENSITY FORECAST NOW 159CALLS FOR THE CYCLONE TO DEGENERATE TO A REMNANT LOW PRESSURE AREA 160IN 24 HOURS AND TO DISSIPATE COMPLETELY THEREAFTER. 161 162THE INITIAL MOTION IS AN UNCERTAIN 305/8. LOW-LEVEL RIDGING NORTH 163AND NORTHEAST OF GABRIELLE SHOULD ALLOW THIS GENERAL MOTION TO 164CONTINUE UNTIL THE CYCLONE DISSIPATES. IF THE SYSTEM SURVIVES 165LONGER THAN CURRENTLY FORECAST...THE DYNAMICAL MODELS SUGGEST IT 166WILL TURN NORTHWARD IN RESPONSE TO A DEVELOPING DEEP-LAYER TROUGH 167OVER THE WESTERN ATLANTIC. 168 169A HEAVY RAIN THREAT CONTINUES OVER PUERTO RICO AND THE VIRGIN 170ISLANDS. 171 172 173FORECAST POSITIONS AND MAX WINDS 174 175INIT 05/1500Z 17.5N 68.1W 30 KT 35 MPH 176 12H 06/0000Z 18.3N 68.8W 25 KT 30 MPH 177 24H 06/1200Z 19.6N 69.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 178 36H 07/0000Z...DISSIPATED 179 180$$ 181FORECASTER BEVEN 182 183 184WTNT42 KNHC 052036 185TCDAT2 186 187TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER 5 188NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 189500 PM AST THU SEP 05 2013 190 191GABRIELLE IS BEING GENEROUSLY MAINTAINED AS A TROPICAL CYCLONE AT 192THIS TIME...AS THERE IS JUST ENOUGH OF A CIRCULATION AND ORGANIZED 193CONVECTION TO KEEP IT FROM BEING DECLARED A REMNANT LOW. THE 194CYCLONE REMAINS VERY BADLY ORGANIZED...WITH THE LOW-LEVEL CENTER 195NOW SEPARATED FROM THE MID-LEVEL CENTER BY ABOUT 180 N MI. THE 196INITIAL INTENSITY IS REDUCED TO 25 KT BASED ON EARLIER 197SCATTEROMETER DATA...AND THE CENTRAL PRESSURE IS NEAR 1010 MB BASED 198ON MULTIPLE SURFACE OBSERVATIONS. 199 200WHILE CONVECTION CONTINUES NEAR THE MID-LEVEL CENTER...THERE ARE NO 201SIGNS AT THIS TIME THAT THE LOW-LEVEL CENTER IS TRYING TO RE-FORM 202THERE. IF THAT DOES NOT OCCUR...GABRIELLE IS EXPECTED TO 203DEGENERATE TO A REMNANT LOW PRESSURE AREA AS IT INTERACTS WITH THE 204TERRAIN OF THE DOMINICAN REPUBLIC...ENCOUNTERS INCREASING WESTERLY 205SHEAR...AND MOVES INTO A DRIER AIR MASS. THE INTENSITY FORECAST 206CONTINUES TO CALL FOR THE CYCLONE TO COMPLETELY DISSIPATE AFTER 24 207HOURS. IT SHOULD BE NOTED THAT THE DYNAMICAL MODELS FORECAST A LOW 208PRESSURE AREA TO DEVELOP SOUTH OR SOUTHWEST OF BERMUDA DURING THE 209NEXT 2-4 DAYS. WHETHER THIS WILL VERIFY...AND WHETHER THE LOW 210DEVELOPS FROM THE REMNANTS OF GABRIELLE OR FROM ANOTHER DISTURBANCE 211TO ITS NORTHEAST...IS UNCLEAR AT THIS TIME. 212 213THE INITIAL MOTION REMAINS 305/8. LOW-LEVEL RIDGING NORTH AND 214NORTHEAST OF GABRIELLE SHOULD ALLOW A MOTION TOWARD THE NORTHWEST 215OR NORTH-NORTHWEST TO OCCUR UNTIL THE CYCLONE DISSIPATES. 216 217A HEAVY RAIN THREAT CONTINUES OVER PUERTO RICO AND THE VIRGIN 218ISLANDS. 219 220FORECAST POSITIONS AND MAX WINDS 221 222INIT 05/2100Z 18.2N 68.6W 25 KT 30 MPH 223 12H 06/0600Z 19.2N 69.3W 25 KT 30 MPH 224 24H 06/1800Z 20.8N 70.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 225 36H 07/0600Z...DISSIPATED 226 227$$ 228FORECASTER BEVEN 229 230 231WTNT42 KNHC 100845 232TCDAT2 233 234TROPICAL STORM GABRIELLE DISCUSSION NUMBER 7 235NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 236500 AM AST TUE SEP 10 2013 237 238DURING THE PAST 12 HOURS...INFRARED SATELLITE IMAGERY INDICATES DEEP 239CONVECTION HAS DEVELOPED AND PERSISTED OVER AND TO THE EAST OF THE 240WELL-DEFINED LOW-LEVEL CIRCULATION CENTER ASSOCIATED WITH THE 241REMNANTS OF GABRIELLE. IN ADDITION...AN EARLIER ASCAT OVERPASS 242CONTAINED SOME 34- TO 36-KT WIND VECTORS TO THE SOUTH OF THE CENTER 243AND OBSERVATIONS FROM NOAA BUOY 41049 LOCATED MORE THAN 100 NMI 244SOUTHEAST OF THE CENTER HAVE BEEN STEADILY INCREASING TO AT LEAST 24531 KT OUTSIDE OF CONVECTION. BASED ON THE ABOVE DATA...ADVISORIES 246HAVE BEEN RE-INITIATED ON TROPICAL STORM GABRIELLE. AN AIR FORCE 247RESERVE AIRCRAFT IS SCHEDULED TO RECONNOITER THE CYCLONE THIS 248AFTERNOON TO PROVIDE MORE DETAILED INFORMATION ON THE EXACT 249LOCATION AND STRENGTH OF GABRIELLE. 250 251THE INITIAL MOTION ESTIMATE IS 360/10 KT...WHICH IS BASED MAINLY ON 252LIMITED MICROWAVE FIXES. THE NHC MODEL GUIDANCE IS IN VERY GOOD 253AGREEMENT ON GABRIELLE MOVING NORTHWARD TO NORTH-NORTHWESTWARD AND 254SLOWING DOWN DURING THE NEXT 36 TO 48 HOURS AS THE CYCLONE MOVES 255AROUND THE EASTERN PERIPHERY OF A RETROGRADING MID-/UPPER-LEVEL LOW 256CURRENTLY LOCATED JUST NORTH OF THE BAHAMAS. ON THE FORECAST 257TRACK...GABRIELLE IS EXPECTED TO PASS OVER OR NEAR BERMUDA IN ABOUT 25824 HOURS. BY 72 HOURS...GABRIELLE IS FORECAST TO BEGIN TO LIFT OUT 259AND ACCELERATE NORTHWARD AND THEN NORTHEASTWARD AHEAD OF A STRONG 260MID-TROPOSPHERIC TROUGH AND FRONTAL SYSTEM THAT IS FORECAST TO MOVE 261OFF OF THE U.S. EAST COAST BY 96 HOURS. THE OFFICIAL FORECAST 262TRACK IS CLOSE TO THE MULTI-MODEL CONSENSUS TVCA. 263 264GABRIELLE IS EXPECTED TO REMAIN IN A MODERATE SHEAR ENVIRONMENT BUT 265OVER 28-29C SSTS FOR THE NEXT 24 HOURS OR SO...WHICH SHOULD ALLOW 266FOR SOME ADDITONAL STRENGTHENING TO OCCUR. THE INTENSITY IS 267EXPECTED TO LEVEL OFF BY 48 HOURS AS SOUTHWESTERLY VERTICAL WIND 268SHEAR BEGINS TO GRADUALLY INCREASE AHEAD OF THE AFOREMENTIONED 269APPROACHING FRONTAL SYSTEM. AT 72 HOURS AND BEYOND...GABRIELLE WILL 270BE MOVING OVER SUB-25C SSTS AND THE CYCLONE IS FORECAST TO BECOME A 271POST-TROPICAL/EXTRATROPICAL LOW BY 96 HOURS WHEN WATER TEMPERATURES 272WILL BE LESS THAN 20C. THE NHC INTENSITY FORECAST IS CLOSE TO THE 273CONSENSUS MODEL ICON. 274 275FORECAST POSITIONS AND MAX WINDS 276 277INIT 10/0900Z 29.6N 65.0W 35 KT 40 MPH 278 12H 10/1800Z 31.1N 65.0W 40 KT 45 MPH 279 24H 11/0600Z 32.7N 65.2W 45 KT 50 MPH 280 36H 11/1800Z 33.7N 65.7W 45 KT 50 MPH 281 48H 12/0600Z 34.5N 66.3W 45 KT 50 MPH 282 72H 13/0600Z 37.7N 65.9W 45 KT 50 MPH 283 96H 14/0600Z 46.8N 58.6W 45 KT 50 MPH...POST-TROP/EXTRATROP 284120H 15/0600Z 56.5N 41.9W 45 KT 50 MPH...POST-TROP/EXTRATROP 285 286$$ 287FORECASTER STEWART 288 289 290WTNT42 KNHC 101439 291TCDAT2 292 293TROPICAL STORM GABRIELLE DISCUSSION NUMBER 8 294NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 2951100 AM AST TUE SEP 10 2013 296 297THE CONVECTIVE PATTERN OF GABRIELLE CONTINUES TO FEATURE VERY COLD 298CLOUD TOPS IN A CDO TYPE FEATURE. MICROWAVE AND GEOSTATIONARY 299SATELLITE IMAGERY CONTINUE TO SUGGEST THAT THE LOW-LEVEL CENTER IS 300LOCATED ON THE SOUTHWESTERN SIDE OF THE DEEP CONVECTION...AND THIS 301STRUCTURE IS CONSISTENT WITH THE 25 KT OR SO OF SOUTHWESTERLY SHEAR 302ANALYZED OVER THE SYSTEM BY UW-CIMSS. THE INITIAL INTENSITY REMAINS 30335 KT IN AGREEMENT WITH THE LATEST DVORAK CLASSIFICATIONS FROM TAFB 304AND SAB. AN AIR FORCE RESERVE AIRCRAFT WILL INVESTIGATE GABRIELLE 305THIS AFTERNOON TO PROVIDE MORE DETAILED INFORMATION ON THE EXACT 306LOCATION AND STRENGTH OF THE CYCLONE. 307 308THE ENVIRONMENT WILL REMAIN MARGINAL FOR STRENGTHENING DURING THE 309NEXT COUPLE OF DAYS...AS GABRIELLE REMAINS OVER SSTS ABOVE 27C WITH 310MODERATE SOUTHWESTERLY TO WESTERLY VERTICAL SHEAR. THE NHC 311INTENSITY FORECAST IS UNCHANGED FROM THE PREVIOUS ADVISORY AND IS 312CLOSE TO THE CONSENSUS AIDS FOR THE FIRST 48 HOURS. LATE IN THE 313PERIOD...THE GLOBAL MODELS SHOW LITTLE CHANGE IN INTENSITY DURING 314AND AFTER EXTRATROPICAL TRANSITION...WHICH SHOULD BE COMPLETE BY 96 315HOURS. GABRIELLE SHOULD DISSIPATE OR BE ABSORBED BY DAY 5. 316 317THE INITIAL MOTION ESTIMATE IS 360/10...AS THE CYCLONE IS CURRENTLY 318SITUATED BETWEEN A MID-LEVEL RIDGE TO THE EAST AND A MID/UPPER- 319LEVEL LOW TO THE WEST. THE FORWARD MOTION OF GABRIELLE WILL SLOW AS 320THE STEERING FLOW WEAKENS...AND THE CYCLONE SHOULD TURN GRADUALLY 321TOWARD THE NORTHWEST BY 48 HOURS. LATER IN THE PERIOD...GABRIELLE 322WILL ACCELERATE NORTHEASTWARD AHEAD OF A DEEP-LAYER TROUGH MOVING 323INTO EASTERN NORTH AMERICA IN 3-4 DAYS. THE NHC FORECAST IS LARGELY 324AN UPDATE OF THE PREVIOUS ONE THROUGH 48 HOURS AND THEN TRENDS A 325LITTLE SLOWER AT DAYS 3 AND 4...LYING BETWEEN THE FASTER ECMWF AND 326THE SLOWER TVCA MULTI-MODEL CONSENSUS. 327 328 329FORECAST POSITIONS AND MAX WINDS 330 331INIT 10/1500Z 30.6N 65.0W 35 KT 40 MPH 332 12H 11/0000Z 31.9N 64.9W 40 KT 45 MPH 333 24H 11/1200Z 33.1N 65.2W 45 KT 50 MPH 334 36H 12/0000Z 34.0N 65.8W 45 KT 50 MPH 335 48H 12/1200Z 35.2N 66.2W 45 KT 50 MPH 336 72H 13/1200Z 39.5N 65.0W 45 KT 50 MPH 337 96H 14/1200Z 49.0N 56.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 338120H 15/1200Z...DISSIPATED 339 340$$ 341FORECASTER BRENNAN 342 343 344WTNT42 KNHC 101715 345TCDAT2 346 347TROPICAL STORM GABRIELLE SPECIAL DISCUSSION NUMBER 9 348NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 349130 PM AST TUE SEP 10 2013 350 351A PAIR OF ASCAT PASSES FROM 1342Z AND 1436Z INDICATE THAT GABRIELLE 352IS STRONGER THAN PREVIOUSLY ESTIMATED. BOTH PASSES SHOWED SEVERAL 35345-KT WIND RETRIEVALS...AND THAT IS THE INITIAL INTENSITY FOR THIS 354SPECIAL ADVISORY. THE INTENSITY FORECAST HAS BEEN ADJUSTED UPWARD 355AT 12 AND 24 HOURS TO 50 KT BASED ON THE INCREASE IN THE INITIAL 356INTENSITY. THE ANALYZED 34-KT WIND RADII HAVE ALSO BEEN ADJUSTED 357OUTWARD BASED ON THE ASCAT DATA...AND THEIR FORECAST HAS BEEN 358MODIFIED AS WELL TO REFLECT THE LARGER WIND FIELD. AN AIR FORCE 359RESERVE AIRCRAFT WILL INVESTIGATE GABRIELLE LATER THIS AFTERNOON TO 360PROVIDE MORE DETAILED INFORMATION ON THE STRENGTH AND STRUCTURE OF 361THE CYCLONE. 362 363NO CHANGES WERE MADE TO THE PREVIOUS TRACK FORECAST FOR THIS SPECIAL 364ADVISORY. 365 366NOTE THAT THIS SPECIAL ADVISORY TAKES THE PLACE OF THE 200 PM 367AST/1800 UTC INTERMEDIATE ADVISORY. 368 369 370FORECAST POSITIONS AND MAX WINDS 371 372INIT 10/1730Z 30.9N 64.8W 45 KT 50 MPH 373 12H 11/0000Z 31.9N 64.9W 50 KT 60 MPH 374 24H 11/1200Z 33.1N 65.2W 50 KT 60 MPH 375 36H 12/0000Z 34.0N 65.8W 45 KT 50 MPH 376 48H 12/1200Z 35.2N 66.2W 45 KT 50 MPH 377 72H 13/1200Z 39.5N 65.0W 45 KT 50 MPH 378 96H 14/1200Z 49.0N 56.5W 45 KT 50 MPH...POST-TROP/EXTRATROP 379120H 15/1200Z...DISSIPATED 380 381$$ 382FORECASTER BRENNAN 383 384 385WTNT42 KNHC 102056 386TCDAT2 387 388TROPICAL STORM GABRIELLE DISCUSSION NUMBER 10 389NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 390500 PM AST TUE SEP 10 2013 391 392AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING 393GABRIELLE FOUND PEAK SFMR WINDS OF 45-50 KT NORTHWEST AND SOUTHEAST 394OF THE CENTER ON THEIR FIRST PASS THROUGH THE STORM...AND THE 395INITIAL INTENSITY IS INCREASED TO 50 KT FOR THIS ADVISORY. THE 396CENTRAL PRESSURE OF 1004 MB IS BASED ON A DROPSONDE FROM THE 397AIRCRAFT. GABRIELLE HAS BEEN ABLE TO STRENGTHEN TODAY DESPITE THE 398PRESENCE OF MODERATE SOUTHWESTERLY SHEAR WHICH HAS EXPOSED THE 399LOW-LEVEL CENTER TO THE SOUTHWEST OF THE DEEP CONVECTION. WHILE 400MODERATE SHEAR IS EXPECTED TO CONTINUE OR EVEN INCREASE OVER THE 401NEXT COUPLE OF DAYS...THE STATISTICAL/DYNAMICAL AND GLOBAL MODELS 402SHOW SOME STRENGTHENING DURING THAT TIME. THIS SEEMS TO BE SUPPORTED 403BY MARGINAL SSTS AND AN INCREASE IN UPPER-LEVEL DIVERGENCE AHEAD OF 404A MID/UPPER-LEVEL TROUGH. THE NHC FORECAST SHOWS THE POTENTIAL FOR 405SOME STRENGTHENING AND THEN LITTLE CHANGE THROUGH EXTRATROPICAL 406TRANSITION IN ABOUT 96 HOURS. 407 408THE INITIAL MOTION ESTIMATE IS 360/09. THE MODEL GUIDANCE SHOWS A 409TURN TOWARD THE NORTH-NORTHWEST WITH A DECREASE IN FORWARD SPEED 410OVER THE NEXT 12 TO 24 HOURS...AS GABRIELLE IS TUGGED WESTWARD BY A 411WEAKENING MID/UPPER-LEVEL LOW CURRENTLY SITUATED EAST OF FLORIDA. 412AT 48 HOURS AND BEYOND...AN ACCELERATION TOWARD THE NORTHEAST IS 413EXPECTED AHEAD OF A DEEP-LAYER TROUGH MOVING THROUGH EASTERN NORTH 414AMERICA. THE TRACK MODELS REMAIN IN REASONABLE AGREEMENT ON THE 415OVERALL SCENARIO...HOWEVER MUCH OF THE GUIDANCE HAS SHIFTED A 416LITTLE TO THE LEFT THIS CYCLE. OVERALL...THE NHC TRACK FORECAST IS 417SIMILAR TO THE PREVIOUS ONE THROUGH 48 HOURS AND AFTERWARD HAS BEEN 418ADJUSTED A BIT TO THE LEFT...BUT STILL LIES EAST OF THE MULTI-MODEL 419CONSENSUS. 420 421FORECAST POSITIONS AND MAX WINDS 422 423INIT 10/2100Z 31.5N 64.9W 50 KT 60 MPH 424 12H 11/0600Z 32.6N 65.0W 55 KT 65 MPH 425 24H 11/1800Z 33.5N 65.5W 55 KT 65 MPH 426 36H 12/0600Z 34.3N 66.0W 55 KT 65 MPH 427 48H 12/1800Z 35.7N 66.5W 55 KT 65 MPH 428 72H 13/1800Z 42.0N 63.5W 55 KT 65 MPH 429 96H 14/1800Z 52.0N 52.4W 50 KT 60 MPH...POST-TROP/EXTRATROP 430120H 15/1800Z...DISSIPATED 431 432$$ 433FORECASTER BRENNAN 434 435 436WTNT42 KNHC 110254 437TCDAT2 438 439TROPICAL STORM GABRIELLE DISCUSSION NUMBER 11 440NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 4411100 PM AST TUE SEP 10 2013 442 443SATELLITE IMAGERY SHOWS THAT THE PRIMARY AREA OF DEEP CONVECTION 444ASSOCIATED WITH GABRIELLE HAS BECOME DISPLACED WELL TO THE EAST OF 445THE LOW-LEVEL CENTER THIS EVENING...DUE TO STRONG SOUTHWESTERLY 446SHEAR. RADAR IMAGES FROM BERMUDA HAVE BEEN EXTREMELY HELPFUL IN 447TRACKING THE PROGRESS OF THE STORM THIS EVENING. THE RADAR DATA 448SHOW THAT GABRIELLE HAS DECELERATED AND THAT SOME SHALLOW 449CONVECTIVE BANDS ARE WRAPPING AROUND THE NORTHEASTERN PORTION OF 450THE CIRCULATION. THE INITIAL WIND SPEED REMAINS 50 KT...WHICH IS 451BASED ON THE EARLIER AIRCRAFT DATA AND RECENT OBSERVATIONS OF 35 452TO 45 KT SUSTAINED WINDS AT WEATHER STATIONS ON BERMUDA. ANOTHER 453AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL BE INVESTIGATING 454THE TROPICAL STORM OVERNIGHT. 455 456THE INITIAL MOTION ESTIMATE IS 355/7 KT. GABRIELLE SHOULD TURN 457NORTH-NORTHWESTWARD ON WEDNESDAY AS IT IS STEERED AROUND THE 458NORTHEASTERN SIDE OF A MID- TO UPPER-LEVEL LOW LOCATED EAST OF 459FLORIDA. IN A COUPLE OF DAYS...THE DEEP LAYER FLOW OFF THE EAST 460COAST OF THE UNITED STATES IS FORECAST TO TURN SOUTHWESTWARD AND 461STRENGTHEN AHEAD OF A MID-LATITUDE TROUGH. THIS SHOULD CAUSE 462GABRIELLE TO TURN NORTHEASTWARD AND BEGIN TO ACCELERATE. THE TRACK 463MODEL GUIDANCE IS IN GENERAL AGREEMENT ON THIS SCENARIO...BUT HAS 464SHIFTED A LITTLE WESTWARD DURING THE FIRST 36 HOURS. 465CONSEQUENTLY...THE NHC TRACK HAS BEEN NUDGED WESTWARD TO BE IN 466BETTER AGREEMENT WITH THE GUIDANCE. AFTER 36 HOURS...THE UPDATED 467NHC TRACK IS CLOSE TO THE PREVIOUS ADVISORY. 468 469GABRIELLE IS FORECAST TO REMAIN OVER WARM WATER BUT WITHIN 470MODERATE TO STRONG SOUTHWESTERLY SHEAR DURING THE NEXT FEW DAYS. 471THE SHEAR IS LIKELY TO PREVENT ANY SIGNIFICANT STRENGTHENING AND 472THE LATEST INTENSITY GUIDANCE NOW SHOWS LITTLE CHANGE IN STRENGTH 473DURING THE NEXT DAY OR SO. AS A RESULT...THE NHC INTENSITY 474FORECAST HAS BEEN ADJUSTED SLIGHTLY LOWER. IF ORGANIZED DEEP 475CONVECTION DOES NOT REDEVELOP IN ASSOCIATION WITH THE CYCLONE... 476GABRIELLE COULD DEGENERATE INTO A REMNANT LOW TOMORROW. 477 478FORECAST POSITIONS AND MAX WINDS 479 480INIT 11/0300Z 32.0N 65.0W 50 KT 60 MPH 481 12H 11/1200Z 32.8N 65.3W 50 KT 60 MPH 482 24H 12/0000Z 33.6N 66.0W 45 KT 50 MPH 483 36H 12/1200Z 34.5N 66.6W 45 KT 50 MPH 484 48H 13/0000Z 36.3N 66.6W 45 KT 50 MPH 485 72H 14/0000Z 44.5N 61.5W 45 KT 50 MPH 486 96H 15/0000Z 54.0N 47.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 487120H 16/0000Z...DISSIPATED 488 489$$ 490FORECASTER BROWN 491 492 493WTNT42 KNHC 110851 494TCDAT2 495 496TROPICAL STORM GABRIELLE DISCUSSION NUMBER 12 497NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 498500 AM AST WED SEP 11 2013 499 500SATELLITE IMAGERY INDICATES THAT GABRIELLE IS COMPRISED OF A SWIRL 501OF LOW/MID-LEVEL CLOUDS WITH NO DEEP CONVECTION NEAR THE CENTER AT 502THIS TIME. THIS IS LIKELY DUE TO THE ONGOING AFFECT OF 15-20 KT OF 503SOUTHWESTERLY VERTICAL WIND SHEAR. AN EARLIER ASCAT OVERPASS... 504RECENT REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER 505AIRCRAFT...AND OBSERVATIONS FROM BERMUDA SHOW THAT THE WINDS HAVE 506DECREASED DURING THE PAST 12 HOURS. THE INITIAL INTENSITY IS 507REDUCED TO 45 KT...AND THIS COULD BE GENEROUS. 508 509THE CYCLONE HAS TURNED TO THE LEFT SINCE THE PREVIOUS ADVISORY...AND 510THE INITIAL MOTION IS NOW 325/7. THIS IS PARTLY DUE TO AN UPPER- 511LEVEL LOW TO THE SOUTHWEST OF GABRIELLE AND A STRENGTHENING 512LOW/MID-LEVEL RIDGE TO THE NORTH. THIS COMBINATION SHOULD STEER 513GABRIELLE SLOWLY TOWARD THE NORTHWEST FOR THE NEXT 24 HOURS OR SO. 514AFTER THAT...THE CYCLONE IS LIKELY TO RECURVE ON THE EASTERN SIDE 515OF A LARGE DEEP-LAYER TROUGH MOVING INTO THE EASTERN UNITED STATES 516AND THE WESTERN ATLANTIC. WHILE THE TRACK MODEL GUIDANCE IS IN 517GOOD AGREEMENT WITH THIS SCENARIO...IT HAS SHIFTED QUITE A BIT TO 518THE LEFT/WEST DURING THE FIRST 48 HOURS. THE NEW FORECAST TRACK IS 519ALSO SHIFTED TO THE LEFT DURING THAT TIME...BUT STILL LIES TO THE 520RIGHT OF THE CONSENSUS MODELS AND THE MIDDLE OF THE GUIDANCE 521ENVELOPE. 522 523GABRIELLE IS FORECAST TO REMAIN OVER WARM SEA SURACE TEMPERATURES 524FOR THE NEXT 48 HOURS. HOWEVER...THE DYNAMICAL MODELS CALL FOR 525CONTINUED STRONG SHEAR...WITH THE UKMET...NAVGEM...AND ECMWF MODELS 526FORECASTING THE CYCLONE TO DECAY TO A TROUGH DURING THIS TIME. 527AFTER THAT...WHATEVER IS LEFT OF THE CYCLONE IS EXPECTED TO MERGE 528WITH A FRONTAL SYSTEM BETWEEN 48-72 HOURS. THE INTENSITY FORECAST 529FOLLOWS THE GFS SCENARIO THAT GABRIELLE WILL REMAIN A TROPICAL 530CYCLONE UNTIL IT MERGES WITH THE FRONT...WITH THE NEW FORECAST A 531LITTLE WEAKER THAN THE PREVIOUS FORECAST. HOWEVER...AN ALTERNATIVE 532SCENARIO IS THAT THE CYCLONE DECAYS TO A REMNANT LOW OR TROUGH 533DURING THE NEXT 48 HOURS DUE TO A LACK OF CONVECTION. 534 535 536FORECAST POSITIONS AND MAX WINDS 537 538INIT 11/0900Z 32.5N 65.7W 45 KT 50 MPH 539 12H 11/1800Z 33.1N 66.2W 45 KT 50 MPH 540 24H 12/0600Z 33.7N 66.8W 45 KT 50 MPH 541 36H 12/1800Z 34.7N 67.3W 40 KT 45 MPH 542 48H 13/0600Z 37.2N 66.5W 40 KT 45 MPH 543 72H 14/0600Z 46.5N 59.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 544 96H 15/0600Z...DISSIPATED 545 546$$ 547FORECASTER BEVEN 548 549 550WTNT42 KNHC 111436 551TCDAT2 552 553TROPICAL STORM GABRIELLE DISCUSSION NUMBER 13 554NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 5551100 AM AST WED SEP 11 2013 556 557GABRIELLE IS BARELY HANGING ON AS A TROPICAL CYCLONE...WITH A SMALL 558AREA OF DEEP CONVECTION TO THE EAST OF THE EXPOSED LOW-LEVEL 559CENTER. THIS IS LIKELY DUE TO THE 15-20 KT OF SOUTHWESTERLY SHEAR 560OVER THE CYCLONE. THE INTITAL INTENSITY HAS BEEN CONSERVATIVELY 561LOWERED TO 40 KT FOR THIS ADVISORY. LITTLE CHANGE IN STRENGTH IS 562FORECAST DURING THE NEXT 36 HOURS OR SO AS MODERATE SHEAR 563CONTINUES...BUT SOME INTENSIFICATION IS SHOWN AT 48 HOURS AS AN 564UPPER-LEVEL TROUGH MAY PROVIDE SOME BAROCLINIC SUPPORT FOR 565INTENSIFICATION. BY 72 HOURS...GABRIELLE SHOULD BE EXTRATROPICAL 566AND BE ABSORBED OR DISSIPATE SHORTLY THEREAFTER. ALTERNATIVELY...IF 567DEEP CONVECTION DISSIPATES ENTIRELY...GABRIELLE COULD BECOME A 568POST-TROPICAL CYCLONE AT ANY TIME DURING THE FORECAST PERIOD. 569 570THE CYCLONE HAS BEEN MOVING LITTLE OVER THE PAST FEW HOURS...AND IS 571NOW DRIFTING WESTWARD AT ABOUT 3 KT. HOWEVER THE MODEL GUIDANCE IS 572IN GOOD AGREEMENT ON A SLOW NORTHWESTWARD MOTION DEVELOPING DURING 573THE NEXT 12 TO 24 HOURS DUE TO AN UPPER-LEVEL LOW TO THE SOUTHWEST 574OF GABRIELLE AND A LOW/MID-LEVEL RIDGE TO THE NORTH AND NORTHEAST. 575RECURVATURE IS EXPECTED BY 48 HOURS AS THE CYCLONE ACCELERATES 576NORTH-NORTHEASTWARD AHEAD OF AN ADVANCING MID/UPPER-LEVEL TROUGH. 577THE TRACK MODEL GUIDANCE HAS TRENDED A LITTLE SLOWER AND TO THE 578LEFT THIS CYCLE AND SO HAS THE NHC TRACK WHICH NOW LIES ALONG...BUT 579IS A LITTLE FASTER THAN...THE TVCA MULTI-MODEL CONSENSUS. 580 581FORECAST POSITIONS AND MAX WINDS 582 583INIT 11/1500Z 32.5N 65.9W 40 KT 45 MPH 584 12H 12/0000Z 33.1N 66.5W 40 KT 45 MPH 585 24H 12/1200Z 33.8N 67.1W 40 KT 45 MPH 586 36H 13/0000Z 35.5N 67.2W 40 KT 45 MPH 587 48H 13/1200Z 38.6N 65.9W 45 KT 50 MPH 588 72H 14/1200Z 48.5N 58.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 589 96H 15/1200Z...DISSIPATED 590 591$$ 592FORECASTER BRENNAN 593 594 595WTNT42 KNHC 112036 596TCDAT2 597 598TROPICAL STORM GABRIELLE DISCUSSION NUMBER 14 599NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 600500 PM AST WED SEP 11 2013 601 602GABRIELLE CONTINUES TO MAINTAIN A SMALL AREA OF DEEP CONVECTION TO 603THE NORTHEAST OF THE CENTER IN AN ENVIRONMENT OF MODERATE 604SOUTHWESTERLY SHEAR. THE INITIAL INTENSITY IS LOWERED TO 35 KT 605BASED ON THE LATEST DVORAK DATA-T NUMBER FROM TAFB. LITTLE CHANGE 606IN STRENGTH IS FORECAST DURING THE NEXT 24 HOURS OR SO AS MODERATE 607SHEAR CONTINUES...BUT SOME INTENSIFICATION IS SHOWN FROM 36 TO 48 608HOURS AS AN UPPER-LEVEL TROUGH MAY PROVIDE SOME BAROCLINIC SUPPORT 609FOR INTENSIFICATION. GABRIELLE SHOULD BECOME EXTRATROPICAL BY 72 610HOURS...AND MAY BE DISSIPATED ENTIRELY BY THEN...HOWEVER A 72-HOUR 611POINT WAS PROVIDED IN THIS FORECAST FOR CONTINUITY. 612ALTERNATIVELY...IF DEEP CONVECTION DISSIPATES ENTIRELY...GABRIELLE 613COULD BECOME A POST-TROPICAL CYCLONE AT ANY TIME DURING THE 614FORECAST PERIOD. 615 616GABRIELLE HAS MOVED SLOWLY WEST-NORTHWESTWARD THIS AFTERNOON...AND 617THE INITIAL MOTION ESTIMATE IS 295/04. THIS MOTION IS PROBABLY DUE 618TO THE SHALLOW CYCLONE NOT FEELING THE INFLUENCE OF THE UPPER-LEVEL 619LOW OFF THE SOUTHEAST U.S. COAST AND THE DOMINANT STEERING FLOW 620COMING FROM A WEAK LOW-LEVEL RIDGE TO THE NORTH AND EAST. THE MODEL 621GUIDANCE CONTINUES TO INSIST ON A NORTHWARD TURN SOON...WITH A 622MOTION TOWARD THE NORTHWEST EXPECTED TOMORROW FOLLOWED BY A 623NORTH-NORTHEASTWARD ACCELERATION ON FRIDAY AHEAD OF AN 624EASTWARD-MOVING UPPER-LEVEL TROUGH. DUE TO THE WESTWARD MOTION 625TODAY...AND A WESTWARD SHIFT IN THE GUIDANCE DURING THE FIRST 626COUPLE OF DAYS...THE NHC FORECAST HAS BEEN ADJUSTED WESTWARD TOWARD 627THE NEW MULTI-MODEL CONSENSUS AND LIES ABOUT A DEGREE WEST OF THE 628PREVIOUS FORECAST BY 48 HOURS. 629 630FORECAST POSITIONS AND MAX WINDS 631 632INIT 11/2100Z 32.8N 66.4W 35 KT 40 MPH 633 12H 12/0600Z 33.2N 67.1W 35 KT 40 MPH 634 24H 12/1800Z 34.4N 67.7W 35 KT 40 MPH 635 36H 13/0600Z 37.1N 67.2W 40 KT 45 MPH 636 48H 13/1800Z 41.5N 65.0W 45 KT 50 MPH 637 72H 14/1800Z 51.5N 55.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 638 96H 15/1800Z...DISSIPATED 639 640$$ 641FORECASTER BRENNAN 642 643 644WTNT42 KNHC 120247 645TCDAT2 646 647TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER 15 648NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 6491100 PM AST WED SEP 11 2013 650 651DEEP CONVECTION ASSOCIATED WITH GABRIELLE HAS DISSIPATED 652AGAIN THIS EVENING...LEAVING THE CYCLONE AS A SWIRL OF LOW-LEVEL 653CLOUDS...EXCEPT FOR ONE SMALL THUNDERSTORM THAT HAS RECENTLY 654DEVELOPED WELL EAST OF THE CENTER. SUBJECTIVE AND OBJECTIVE DVORAK 655INTENSITY ESTIMATES HAVE DECREASED BELOW TROPICAL STORM STRENGTH... 656AND BASED ON THESE DATA THE SYSTEM HAS BEEN DOWNGRADED TO A 30-KT 657TROPICAL DEPRESSION. LITTLE CHANGE IN STRENGTH IS EXPECTED DURING 658THE NEXT 24 HOURS AS THE CYCLONE REMAINS WITHIN AN AREA OF MODERATE 659WESTERLY WIND SHEAR AND DRY MID-LEVEL AIR. SOME INTENSIFICATION IS 660POSSIBLE AS GABRIELLE INTERACTS WITH A MID- TO UPPER-LEVEL TROUGH 661IN 36 TO 48 HOURS. THE TROUGH IS EXPECTED TO PROVIDE SOME 662BAROCLINIC FORCING AND SHOULD ALSO CAUSE THE CYCLONE TO BECOME 663EXTRATROPICAL IN ABOUT 2 DAYS. THE SYSTEM IS LIKELY TO BE ABSORBED 664BY A FRONT OVER NOVA SCOTIA SHORTLY THEREAFTER...HOWEVER A 72-HOUR 665POINT WAS PROVIDED ONCE AGAIN FOR FORECAST CONTINUITY. WITH THE 666LACK OF DEEP CONVECTION THIS EVENING...AN ALTERNATIVE SCENARIO IS 667THAT GABRIELLE COULD DEGENERATE INTO A REMNANT LOW ON THURSDAY OR 668BECOME AN OPEN TROUGH AS IT BEGINS TO ACCELERATE NORTH- 669NORTHEASTWARD IN A DAY OR SO. 670 671GABRIELLE CONTINUES MOVING SLOWLY WEST-NORTHWESTWARD. THE CYCLONE 672SHOULD TURN NORTHWARD ON THURSDAY AS IT IS STEERED AROUND THE 673WESTERN PORTION OF A LOW- TO MID-LEVEL RIDGE OVER THE WEST-CENTRAL 674ATLANTIC. AFTER 24 HOURS...GABRIELLE IS FORECAST TO ACCELERATE 675NORTH-NORTHEASTWARD AHEAD OF THE TROUGH MOVING INTO THE 676NORTHEASTERN UNITED STATES. THE TRACK GUIDANCE AGREES ON THIS 677SCENARIO AND THE UPDATED NHC TRACK IS ESSENTIALLY AN UPDATE OF THE 678PREVIOUS ADVISORY. 679 680FORECAST POSITIONS AND MAX WINDS 681 682INIT 12/0300Z 33.0N 67.0W 30 KT 35 MPH 683 12H 12/1200Z 33.7N 67.6W 30 KT 35 MPH 684 24H 13/0000Z 35.7N 67.6W 30 KT 35 MPH 685 36H 13/1200Z 39.4N 66.1W 35 KT 40 MPH 686 48H 14/0000Z 44.4N 62.8W 40 KT 45 MPH...POST-TROP/EXTRATROP 687 72H 15/0000Z 54.5N 50.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 688 96H 16/0000Z...ABSORBED BY FRONT 689 690$$ 691FORECASTER BROWN 692 693 694WTNT42 KNHC 120847 695TCDAT2 696 697TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER 16 698NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 699500 AM AST THU SEP 12 2013 700 701A NEW BURST OF CONVECTION HAS FORMED JUST EAST OF THE CENTER OF 702GABRIELLE DURING THE PAST FEW HOURS. THE SATELLITE INTENSITY 703ESTIMATE FROM TAFB IS 30 KT...AND AN EARLIER OSCAT OVERPASS SHOWED 70425-30 KT WINDS NORTHEAST OF THE CENTER. BASED ON THESE DATA...THE 705INITIAL INTENSITY REMAINS 30 KT. ALTHOUGH GABRIELLE REMAINS 706SHEARED...ANALYSES FROM CIMSS INDICATE THAT THE SHEAR HAS DECREASED 707TO 10-15 KT OVER THE PAST 24 HOURS. 708 709THE INITIAL MOTION IS NOW 305/6. WATER VAPOR IMAGERY AND SURFACE 710OBSERVATIONS SHOW A DEEP-LAYER TROUGH AND ASSOCIATED SURFACE COLD 711FRONT MOVING INTO THE NEW ENGLAND STATES. THE DYNAMICAL MODELS 712FORECAST A LOW TO FORM ON THE FRONT DURING THE NEXT 48 HOURS. THIS 713EVOLUTION SHOULD CREATE A BREAK IN THE SUBTROPICAL RIDGE OVER THE 714WESTERN ATLANTIC AND ALLOW GABRIELLE TO RECURVE INTO THE 715WESTERLIES. THE NEW FORECAST TRACK IS SIMILAR TO THE PREVIOUS 716TRACK...CALLING FOR A TURN TOWARD THE NORTH DURING THE NEXT 24 717HOURS FOLLOWED BY A NORTH-NORTHEASTWARD ACCELERATION TOWARD 718ATLANTIC CANADA. THE TRACK GUIDANCE CONTINUES TO AGREE ON THIS 719SCENARIO...AND THE NEW TRACK IS AGAIN AN UPDATE OF THE PREVIOUS 720ADVISORY. 721 722THE INTENSITY FORECAST IS A LITTLE TRICKY. ON ONE SIDE...THE 723DECREASED SHEAR...24 HOURS BEFORE CROSSING THE NORTH WALL OF THE 724GULF STREAM...AND POSSIBLE INTERACTION WITH A BAROCLINIC TROUGH 725SUGGEST SOME POTENTIAL FOR STRENGTHENING. ON THE OTHER HAND...THE 726CYCLONE IS LIKELY TO MERGE WITH THE NON-TROPICAL SYSTEM IN 36-48 727HOURS...AND THE DYNAMICAL MODELS ARE IN GOOD AGREEMENT IN THE 728CYCLONE DECAYING TO A TROUGH IN 36 HOURS OR LESS. ON THE PREMISE 729THAT THE PROS WILL OUTWEIGH THE CONS...THE INTENSITY FORECAST SHOWS 730MODEST STRENGTHENING BEFORE EXTRATROPICAL TRANSITION. THE 731ALTERNATIVE SCENARIO REMAINS THAT GABRIELLE COULD DECAY TO A 732REMNANT LOW OR TROUGH AT ANY TIME DURING THE NEXT 48 HOURS. AFTER 733EXTRATROPICAL TRANSITION...THE CYCLONE OR ITS REMNANTS WILL QUICKLY 734BE ABSORBED BY THE LARGER NON-TROPICAL LOW. 735 736 737FORECAST POSITIONS AND MAX WINDS 738 739INIT 12/0900Z 33.5N 67.7W 30 KT 35 MPH 740 12H 12/1800Z 34.4N 67.9W 30 KT 35 MPH 741 24H 13/0600Z 36.9N 67.5W 35 KT 40 MPH 742 36H 13/1800Z 41.2N 65.4W 35 KT 40 MPH 743 48H 14/0600Z 46.7N 61.8W 35 KT 40 MPH...POST-TROP/EXTRATROP 744 72H 15/0600Z...DISSIPATED 745 746$$ 747FORECASTER BEVEN 748 749 750WTNT42 KNHC 121432 751TCDAT2 752 753TROPICAL STORM GABRIELLE DISCUSSION NUMBER 17 754NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 7551100 AM AST THU SEP 12 2013 756 757DURING THE PAST SEVERAL HOURS...DEEP CONVECTION HAS RE-DEVELOPED 758NEAR THE CENTER OF GABRIELLE. GIVEN THE DISTANCE BETWEEN THE 759CENTER AND THE CONVECTION...AND THE PRESENCE OF A CURVED CONVECTIVE 760BAND TO THE EAST...IT IS ESTIMATED THAT THE WINDS ARE UP TO 35 761KNOTS. THE TROPICAL STORM IS EMBEDDED WITHIN A SHEARED 762ENVIRONMENT...AND CONVECTION COULD EASILY BE REMOVED AGAIN. ON THAT 763BASIS...GABRIELLE COULD EXPERIENCE SMALL FLUCTUATIONS IN INTENSITY 764DURING THE NEXT 24 HOURS OR SO BEFORE IT BECOMES EXTRATROPICAL. THE 765CYCLONE SHOULD THEN BECOME ABSORBED BY A LARGE MID-LATITUDE TROUGH 766AS IT MOVES NEAR ATLANTIC CANADA. 767 768GABRIELLE IS MOVING TOWARD THE NORTH OR 350 DEGREES AT 8 KNOTS AHEAD 769OF A DEVELOPING MID-LATITUDE TROUGH OVER THE EASTERN UNITED STATES. 770THIS PATTERN WILL FORCE GABRIELLE TO RECURVE AND TURN TO THE 771NORTH-NORTHEAST WITH AN INCREASE IN FORWARD SPEED. THE NHC FORECAST 772IS IN THE MIDDLE OF THE LATEST GUIDANCE ENVELOPE. 773 774 775FORECAST POSITIONS AND MAX WINDS 776 777INIT 12/1500Z 33.9N 67.7W 35 KT 40 MPH 778 12H 13/0000Z 35.0N 67.9W 35 KT 40 MPH 779 24H 13/1200Z 38.0N 67.0W 35 KT 40 MPH 780 36H 14/0000Z 43.0N 64.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 781 48H 14/1200Z...DISSIPATED 782 783$$ 784FORECASTER AVILA 785 786 787WTNT42 KNHC 130252 788TCDAT2 789 790TROPICAL STORM GABRIELLE DISCUSSION NUMBER 19 791NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 7921100 PM AST THU SEP 12 2013 793 794ONCE AGAIN DEEP CONVECTION HAS LARGELY DISAPPEARED NEAR THE CENTER 795OF GABRIELLE. THE INITIAL INTENSITY REMAINS 35 KT...BUT THIS COULD 796BE GENEROUS. WEAKENING IS FORECAST AS THE CYCLONE ACCELERATES 797NORTHEASTWARD AND IS ABSORBED BY A FRONTAL SYSTEM IN 36 HOURS OR 798PERHAPS A LITTLE SOONER. 799 800GABRIELLE IS NOW MOVING TOWARD THE NORTH-NORTHEAST OR 015 DEGREES AT 801ABOUT 9 KNOTS AHEAD OF A DEVELOPING MID-LATITUDE TROUGH OVER THE 802EASTERN UNITED STATES. GABRIELLE SHOULD CONTINUE TO ACCELERATE 803NORTH-NORTHEASTWARD ON FRIDAY...AND THE NHC TRACK IS IN GOOD 804AGREEMENT WITH THE MODEL GUIDANCE THROUGH DISSIPATION. 805 806FORECAST POSITIONS AND MAX WINDS 807 808INIT 13/0300Z 35.1N 67.7W 35 KT 40 MPH 809 12H 13/1200Z 38.0N 66.8W 30 KT 35 MPH 810 24H 14/0000Z 43.8N 64.3W 30 KT 35 MPH...POST-TROP/EXTRATROP 811 36H 14/1200Z...DISSIPATED 812 813$$ 814FORECASTER BRENNAN 815 816 817WTNT42 KNHC 130851 818TCDAT2 819 820TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER 20 821NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 822500 AM AST FRI SEP 13 2013 823 824ALTHOUGH DEEP CONVECTION HAS INCREASED TO THE NORTH OF THE CENTER OF 825GABRIELLE DURING THE LAST FEW HOURS...IT LACKS BANDING FEATURES. AN 826ASCAT OVERPASS AROUND 0200 UTC SHOWED MAXIMUM WINDS IN THE 25 TO 30 827KT RANGE...AND ALL OF THE SATELLITE INTENSITY ESTIMATES SUPPORT AN 828INTENSITY OF 30 KT OR LOWER. BASED ON THESE DATA...GABRIELLE IS 829ONCE AGAIN DOWNGRADED TO A 30-KT TROPICAL DEPRESSION. 830 831GABRIELLE IS MOVING A LITTLE FASTER THAN IT WAS EARLIER...WITH THE 832LATEST INITIAL MOTION ESTIMATE BEING 015/15. THE CYCLONE IS 833EXPECTED TO ACCELERATE TO THE NORTH-NORTHEAST LATER TODAY WHEN IT 834BECOMES MORE EMBEDDED IN THE STRONG FLOW ON THE EAST SIDE OF A 835DEEP-LAYER TROUGH OVER THE EASTERN UNITED STATES AND CANADA. 836GABRIELLE IS FORECAST TO DEGENERATE INTO A TROUGH IN 12 TO 24 HOURS 837BEFORE IT IS ABSORBED BY A COLD FRONT. SOME OF THE DYNAMICAL MODELS 838SHOW DISSIPATION OCCURRING EVEN SOONER THAN FORECAST. 839 840FORECAST POSITIONS AND MAX WINDS 841 842INIT 13/0900Z 36.5N 67.5W 30 KT 35 MPH 843 12H 13/1800Z 40.5N 65.8W 30 KT 35 MPH 844 24H 14/0600Z...DISSIPATED 845 846$$ 847FORECASTER CANGIALOSI 848 849 850WTNT42 KNHC 131440 851TCDAT2 852 853TROPICAL DEPRESSION GABRIELLE DISCUSSION NUMBER 21 854NWS NATIONAL HURRICANE CENTER MIAMI FL AL072013 8551100 AM AST FRI SEP 13 2013 856 857AMBIGUITIES FROM AN 0200 UTC ASCAT PASS SUGGEST THAT THERE ARE VERY 858LITTLE...IF ANY...NORTHERLY WINDS ON THE WEST SIDE OF THE 859CIRCULATION. GABRIELLE HAS ACCELERATED TOWARD THE NORTH-NORTHEAST 860SINCE THAT TIME...REDUCING THE LIKELIHOOD THAT NORTH WINDS ARE 861PRESENT. HOWEVER...A LARGE BURST OF CONVECTION DURING THE PAST 6 862HOURS AT LEAST MAKES IT PLAUSIBLE THAT THE CIRCULATION REMAINS 863CLOSED...AND SO GABRIELLE IS BEING HELD AS A 30 KT TROPICAL 864DEPRESSION FOR THIS ADVISORY. A SLIGHT INCREASE IN THE MAXIMUM 865WINDS IS POSSIBLE TODAY DUE TO BAROCLINIC PROCESSES. 866 867THE FORWARD SPEED OF GABRIELLE HAS INCREASED DURING THE PAST FEW 868HOURS...AND THE INITIAL MOTION ESTIMATE IS NOW 020/20. ALL OF THE 869DYNAMICAL MODELS SUGGEST THAT THE DEPRESSION WILL CONTINUE TO 870ACCELERATE TOWARD THE NORTH-NORTHEAST WHILE IT INTERACTS WITH A 871DEEP-LAYER TROUGH LOCATED OVER THE EASTERN UNITED STATES 872AND CANADA. THE GUIDANCE SUGGESTS THAT GABRIELLE WILL OPEN UP INTO 873A TROUGH LATER TODAY...ALTHOUGH THE OFFICIAL FORECAST 874CONSERVATIVELY SHOWS A 12-HOUR FORECAST POINT. AFTER 875THAT...GABRIELLE OR ITS REMNANTS SHOULD GET ABSORBED BY AN 876APPROACHING COLD FRONT. 877 878FORECAST POSITIONS AND MAX WINDS 879 880INIT 13/1500Z 39.1N 66.5W 30 KT 35 MPH 881 12H 14/0000Z 43.2N 64.6W 35 KT 40 MPH...POST-TROPICAL 882 24H 14/1200Z...DISSIPATED 883 884$$ 885FORECASTER FRANKLIN/ZELINSKY 886 887 888