1WTNT43 KNHC 281442 2TCDAT3 3TROPICAL STORM HANNA DISCUSSION NUMBER 2 4NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 51100 AM EDT THU AUG 28 2008 6 7SATELLITE IMAGERY INDICATES THAT THE CLOUD PATTERN ASSOCIATED WITH 8THE CYCLONE HAS IMPROVED DURING THE LAST 6 HOURS AND LATEST DVORAK 9INTENSITY ESTIMATES INDICATE WINDS ARE NOW NEAR 35 KT. BASED ON 10THIS INFORMATION...THE DEPRESSION IS UPGRADED TO TROPICAL STORM 11HANNA. VISIBLE IMAGERY SHOWS THAT HANNA'S LOW LEVEL CIRCULATION IS 12PARTIALLY EXPOSED ON THE WESTERN EDGE OF THE DEEP CONVECTION 13INDICATING WESTERLY SHEAR...ASSOCIATED WITH AN UPPER-LEVEL LOW TO 14THE WEST IS IMPACTING THE SYSTEM. SINCE THE OCEAN IS PLENTY 15WARM...THE INTENSITY FORECAST IS PRIMARILY A FUNCTION OF HOW HANNA 16INTERACTS WITH THE UPPER-LEVEL LOW. GLOBAL MODELS FORECAST THE 17UPPER-LEVEL LOW TO MOVE WEST-SOUTHWEST OVER THE NEXT SEVERAL DAYS 18PLACING HANNA IN A LOW VERTICAL SHEAR ENVIRONMENT WITH AMPLE 19DIVERGENT FLOW ALOFT. SUCH AN ENVIRONMENT WOULD FAVOR 20INTENSIFICATION SHOULD IT MATERIALIZE. HOWEVER...AS IS OFTEN THE 21CASE...THERE IS A FINE LINE BETWEEN A FAVORABLE AND UNFAVORABLE 22ENVIRONMENT FOR STRENGTHENING. THE OFFICIAL FORECAST ASSUMES THERE 23WILL BE SUFFICIENT SPACING BETWEEN THE UPPER-LEVEL LOW AND HANNA TO 24PROMOTE STRENGTHENING. BY DAY 5...UPPER-LEVEL OUTFLOW FROM GUSTAV 25COULD IMPART NORTHERLY SHEAR OVER HANNA POSSIBLY AFFECTING THE 26INTENSITY. 27 28HANNA HAS BEEN MOVING TOWARD THE WEST-NORTHWEST...OR 300/10...DURING 29THE LAST 6 HOURS. HOWEVER...A MOTION TOWARD THE NORTHWEST IS 30EXPECTED OVER THE NEXT 2-3 DAYS AS HANNA MOVES AROUND THE 31SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE. THEREAFTER...THE 32TRACK BECOMES MUCH LESS CERTAIN AS IT REMAINS TO BE SEEN HOW HANNA 33WILL INTERACT WITH A MID-LATITUDE TROUGH FORECAST TO MOVE 34OFF THE U.S. EAST COAST. MOST OF THE DYNAMICAL MODELS SHOW HANNA 35BEING LEFT BEHIND IN AN AREA OF WEAK STEERING. HOWEVER...THE 36TRADITIONALLY GOOD PERFORMING GFS FORECASTS HANNA TO TURN 37NORTHEASTWARD AT DAYS 4 AND 5. THE OFFICIAL FORECAST ASSUMES THE 38FORMER OF THOSE SCENARIOS AND SHOWS A SLOW WESTWARD TRACK. 39 40FORECAST POSITIONS AND MAX WINDS 41 42INITIAL 28/1500Z 20.5N 59.2W 35 KT 4312HR VT 29/0000Z 21.4N 60.4W 40 KT 4424HR VT 29/1200Z 22.8N 61.9W 45 KT 4536HR VT 30/0000Z 24.4N 63.7W 55 KT 4648HR VT 30/1200Z 25.7N 65.6W 60 KT 4772HR VT 31/1200Z 27.0N 68.5W 70 KT 4896HR VT 01/1200Z 27.5N 70.0W 75 KT 49120HR VT 02/1200Z 27.5N 71.5W 70 KT 50 51$$ 52FORECASTER RHOME 53 54 55 56 57WTNT43 KNHC 282032 58TCDAT3 59TROPICAL STORM HANNA DISCUSSION NUMBER 3 60NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 61500 PM EDT THU AUG 28 2008 62 63AFTER LOOKING QUITE IMPRESSIVE IN SATELLITE IMAGERY THIS 64MORNING...VERTICAL SHEAR HAS TAKEN ITS TOLL ON HANNA AND THE 65LOW-LEVEL CIRCULATION HAS BECOME COMPLETELY EXPOSED. WHILE IT IS 66TEMPTING TO LOWER THE INTENSITY BASED ON THIS TREND...IT IS BEST TO 67KEEP HANNA AS A MINIMAL TROPICAL STORM FOR THIS ADVISORY. THE LACK 68OF ORGANIZATION NOTWITHSTANDING...THE OVERALL FORECAST PHILOSOPHY 69REMAINS UNCHANGED. DYNAMICAL MODELS INSISTS THAT THE UPPER-LEVEL 70LOW CURRENTLY IMPARTING WESTERLY SHEAR OVER HANNA WILL BEGIN TO MOVE 71WESTWARD ALLOWING A MORE FAVORABLE ENVIRONMENT FOR STRENGTHENING TO 72DEVELOP OVER THE CYCLONE. SIMILARLY...THE SHIPS AND LGEM MODELS 73ARE BASING THEIR FORECAST ON A LOW SHEAR ENVIRONMENT. ANALYSIS OF 74WATER VAPOR IMAGERY INDICATES THAT THE UPPER-LEVEL LOW HAS NOT 75BUDGED ALL DAY SO IT WOULD APPEAR THAT THE SHEAR WILL NOT RELAX IN 76THE SHORT-TERM. THIS IS THE BASIS FOR THE NEW OFFICIAL FORECAST 77WHICH IS BELOW THE INTENSITY MODEL CONSENSUS. IF THE UPPER-LOW 78DOES EVENTUALLY MOVE OUT OF HANNA'S WAY...ENVIRONMENTAL CONDITIONS 79WOULD FAVOR STRENGTHENING. BY DAY 5...UPPER-LEVEL OUTFLOW FROM 80GUSTAV COULD IMPART NORTHERLY SHEAR OVER HANNA POSSIBLY AFFECTING 81THE INTENSITY. 82 83HANNA CONTINUES MOVING WEST-NORTHWESTWARD...OR 300/10. HOWEVER...A 84MOTION TOWARD THE NORTHWEST IS FORECAST OVER THE NEXT 2-3 DAYS AS 85HANNA IS EXPECTED TO STRENGTHEN AND BECOMES A DEEPER SYSTEM. 86THEREAFTER...THE TRACK FORECAST IS RIDDLED WITH UNCERTAINTY AS IT 87IS UNCLEAR HOW HANNA WILL INTERACT WITH A MID-LATITUDE TROUGH 88FORECAST TO MOVE OFF THE U.S. EAST COAST. MOST OF THE DYNAMICAL 89MODELS SHOW THE TROUGH BYPASSING HANNA TO THE NORTH AND LEAVING IT 90BEHIND IN AN AREA OF WEAK STEERING. SUCH AN EVOLUTION WOULD RESULT 91IN ERRATIC OR LITTLE OVERALL MOTION. ACCORDINGLY...THE OFFICIAL 92FORECAST SHOWS A SLOW WESTWARD MOTION AT DAYS 4 AND 5. IT SHOULD BE 93ADDED THAT THERE IS LARGER THAN NORMAL UNCERTAINTY ASSOCIATED WITH 94BOTH THE TRACK AND INTENSITY FORECASTS OF HANNA. 95 96FORECAST POSITIONS AND MAX WINDS 97 98INITIAL 28/2100Z 20.7N 60.1W 35 KT 9912HR VT 29/0600Z 21.7N 61.4W 35 KT 10024HR VT 29/1800Z 23.4N 63.4W 40 KT 10136HR VT 30/0600Z 24.9N 65.3W 50 KT 10248HR VT 30/1800Z 25.9N 67.0W 60 KT 10372HR VT 31/1800Z 27.0N 69.0W 70 KT 10496HR VT 01/1800Z 27.5N 70.5W 70 KT 105120HR VT 02/1800Z 27.5N 71.5W 65 KT 106 107$$ 108FORECASTER RHOME 109 110 111 112 113WTNT43 KNHC 290259 114TCDAT3 115TROPICAL STORM HANNA DISCUSSION NUMBER 4 116NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1171100 PM EDT THU AUG 28 2008 118 119AFTER WESTERLY MID- TO UPPER-LEVEL SHEAR PRODUCED AN EXPOSED 120LOW-LEVEL CIRCULATION CENTER...CONVECTION HAS REDEVELOPED WITH A 121VENGEANCE OVER OR NEAR THE CENTER CONTAINING CLOUD TOPS AS COLD AS 122-83C. HOWEVER...THE CONVECTIVE DEVELOPMENT APPEARS TO BE A BURSTING 123PATTERN...WHICH IS USUALLY SHORT-LIVED. THE ADVISORY INTENSITY IS 12445 KT BASED ON A DVORAK T-NUMBER OF T3.0/45 KT FROM TAFB AND THE 125CONTINUED CONVECTIVE DEVELOPMENT SINCE THE 00Z SATELLITE FIX TIME. 126 127THE INITIAL MOTION ESTIMATE IS 290/06. HANNA HAD BEEN MOVING DUE 128WEST AT ABOUT 10 KT...BUT THE 24-HOUR MOTION OF THE PRESSURE 129ENVELOPE SURROUNDING THE CYCLONE CENTER HAS ONLY BEEN MOVING AT 130AROUND 5 KT. THE PRIMARY STEERING MECHANISMS FOR THE NEXT 3 DAYS 131WILL BE THE LARGE SUBTROPICAL HIGH TO THE NORTH OF HANNA AND THE 132MID- TO UPPER-LEVEL LOW LOCATED ABOUT 275 NMI WEST OF HANNA. ALL OF 133THE MODELS HAVE BEEN WEAKENING AND MOVING THE UPPER-LOW TO THE 134SOUTHWEST TOO QUICKLY...WHICH IS LIKELY DUE TO THE FAST OUTFLOW 135FROM GUSTAV GETTING ENTRAINED INTO THE LOW AND KEEPING IT STRONGER 136THAN THE MODEL FORECASTS. HOWEVER...OUTFLOW FROM GUSTAV IS NOW 137BEING SHUNTED SOUTHEASTWARD INTO THE EASTERN CARIBBEAN...SO A 138WEAKENING TREND AND SOUTHWESTWARD MOTION BY THE UPPER-LOW IS 139EXPECTED TO ENSUE WITHIN THE NEXT 24 HOURS. HANNA IS FORECAST TO 140MOVE AROUND THE UPPER-LOW THROUGH 72-96 HOURS BEFORE IT ENCOUNTERS 141STRONG MID- TO UPPER-LEVEL NORTHERLY WINDS BEHIND A POWERFUL 142MID-TROPOSPHERIC TROUGH...WHICH IS FORECAST TO MOVE OFF THE U.S. 143EAST COAST AT DAYS 4 AND 5. THAT DEVELOPING SCENARIO IS INDICATED 144BY ALMOST ALL OF THE MODELS TO VARYING DEGREES...BUT ENOUGH TO 145INDUCE SOME SOUTHWARD COMPONENT TO HANNA'S MOTION. MOST OF THE 146MODEL GUIDANCE HAS HAD A FAST AND RIGHT-OF-TRACK BIAS THE PAST 36 147HOURS...SO THE FORECAST TRACK FOR THIS ADVISORY WAS ADJUSTED TO THE 148LEFT OF THE PREVIOUS TRACK AND THE NHC MODEL CONSENSUS. 149 150MODERATE WESTERLY SHEAR HAS BEEN REPLACED BY LIGHT SOUTHERLY SHEAR 151DURING THE PAST 6 HOURS NOW THAT THE UPPER-LOW HAS SHOWN SIGNS OF 152WEAKENING AND MOVING FARTHER AWAY FROM HANNA. AS THE LOW CONTINUES 153TO WEAKEN AND MOVES TO A POSITION TO THE SOUTHWEST OF HANNA... 154UPPER-LEVEL OUTFLOW SHOULD IMPROVE TO THE NORTHWEST AIDING A STEADY 155INTENSIFICATION. ALTHOUGH NOT INDICATED AT ANY OF THE FORECAST 156TIMES... ATMOSPHERIC AND OCEANIC CONDITIONS ARE EXPECTED TO BECOME 157QUITE FAVORABLE FOR SIGNIFICANT STRENGTHENING BETWEEN 72 AND 96 158HOURS...AND HANNA COULD BECOME A MAJOR HURRICANE AS INDICATED BY 159THE GFDL MODEL. THE OFFICIAL FORECAST IS A BLEND OF THE SHIPS AND 160GFDL MODELS...AND IS SIMILAR TO THE LGEM MODEL. 161 162 163FORECAST POSITIONS AND MAX WINDS 164 165INITIAL 29/0300Z 21.1N 60.6W 45 KT 16612HR VT 29/1200Z 21.8N 62.0W 50 KT 16724HR VT 30/0000Z 23.2N 64.2W 55 KT 16836HR VT 30/1200Z 24.6N 66.3W 60 KT 16948HR VT 31/0000Z 25.7N 68.0W 70 KT 17072HR VT 01/0000Z 26.6N 70.0W 80 KT 17196HR VT 02/0000Z 26.5N 71.2W 80 KT 172120HR VT 03/0000Z 26.0N 71.6W 75 KT 173 174$$ 175FORECASTER STEWART/BEVEN 176 177 178 179 180WTNT43 KNHC 290853 181TCDAT3 182TROPICAL STORM HANNA DISCUSSION NUMBER 5 183NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 184500 AM EDT FRI AUG 29 2008 185 186ALTHOUGH THE UPPER-LOW TO THE NORTHWEST OF HANNA HAS BEGUN TO MOVE 187AWAY...IT IS STILL PRODUCING SHEAR OVER THE TROPICAL CYCLONE. ONCE 188AGAIN THE CENTER HAS MOVED AWAY FROM THE DEEP CONVECTION WHICH IS 189NOW CONFINED TO A CYCLONICALLY CURVED BAND IN THE EASTERN 190SEMICIRCLE. DVORAK T-NUMBERS STILL SUPPORT AN INITIAL INTENSITY OF 19145 KNOTS...BUT WITH THE CURRENT SHEARED PATTERN...THIS ESTIMATE 192COULD BE GENEROUS. THE EVOLUTION OF THE UPPER-LEVEL LOW APPEARS TO 193BE THE KEY PLAYER FOR BOTH THE INTENSITY AND TRACK OF HANNA FOR THE 194NEXT 24 TO 48 HOURS. IF THE LOW WEAKENS AND MOVES AWAY AS INDICATED 195BY GLOBAL MODELS...THE ENVIRONMENT BECOMES MORE FAVORABLE FOR 196STRENGTHENING. THE OFFICIAL FORECAST ASSUMES A GOOD SOLUTION FROM 197GLOBAL MODELS AND CALLS FOR A GRADUAL INTENSIFICATION FROM 24 TO 72 198HOURS. THE FORECAST IS SIMILAR TO THE SHIPS MODEL BUT DOES NOT 199SHOWS AS MUCH STRENGTHENING AS SUGGESTED BY THE GFDL AND HWRF. 200 201HANNA HAS BEEN MOVING AROUND THE EAST SIDE OF THE UPPER-LOW AND THE 202BEST ESTIMATE OF THE INITIAL MOTION IS 310 DEGREES AT 12 KNOTS. A 203GENERAL NORTHWEST TO WEST-NORTHWEST MOTION IS EXPECTED DURING THE 204NEXT 2 TO 3 DAYS WHILE THE CYCLONE IS EMBEDDED WITHIN THE FLOW 205BETWEEN THE UPPER LOW AND THE SUBTROPICAL RIDGE. BEYOND 3 206DAYS...MOST OF THE GLOBAL MODELS ARE CARVING A LARGE TROUGH OVER 207THE CENTRAL ATLANTIC AND DEVELOPING A LARGE RIDGE OVER THE EASTERN 208UNITED STATES. THIS PATTERN SHOULD FORCE HANNA ON A SLOW 209SOUTHWESTERLY TRACK BEYOND THREE DAYS...BUT AT THE SAME TIME THE 210UPPER-LEVEL WINDS SHOULD WEAKEN THE CYCLONE. THE OFFICIAL FORECAST 211SHOWS A LITTLE BIT OF THE SOUTHWESTERLY MOTION BUT DOES NOT GO AS 212FAR SOUTH AS SHOWN BY MOST OF THE MODELS. IN FACT...THE GFS HAS 213JOINED THE REST OF THE GLOBAL MODELS IN BRINGING THE CYCLONE 214SOUTHWESTWARD. I PREFER TO WAIT FOR MORE MODEL RUNS BEFORE FORECAST 215SUCH A RARE BUT NOT UNIQUE TRACK TOWARD THE SOUTHWEST. 216 217 218FORECAST POSITIONS AND MAX WINDS 219 220INITIAL 29/0900Z 21.7N 62.3W 45 KT 22112HR VT 29/1800Z 22.6N 64.0W 45 KT 22224HR VT 30/0600Z 24.0N 66.0W 50 KT 22336HR VT 30/1800Z 25.3N 68.3W 60 KT 22448HR VT 31/0600Z 26.0N 70.0W 70 KT 22572HR VT 01/0600Z 26.0N 71.5W 80 KT 22696HR VT 02/0600Z 25.5N 72.2W 80 KT 227120HR VT 03/0600Z 25.0N 73.0W 75 KT 228 229$$ 230FORECASTER AVILA 231 232 233 234 235WTNT43 KNHC 291453 236TCDAT3 237TROPICAL STORM HANNA DISCUSSION NUMBER 6 238NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2391100 AM EDT FRI AUG 29 2008 240 241A 1031 UTC QUIKSCAT OVERPASS WAS VERY HELPFUL IN LOCATING THE CENTER 242OF HANNA EARLY THIS MORNING. VISIBLE IMAGERY SHOWED THAT THE CENTER 243BRIEFLY BECAME EXPOSED...HOWEVER...NEW CONVECTION FORMED SINCE THAT 244TIME AND THE CENTER IS POSITIONED JUST BENEATH THE COLDER CLOUD 245TOPS. DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB CONTINUE TO 246SUPPORT 45 KT...SO THE INITIAL INTENSITY REMAINS UNCHANGED. IN THE 247NEAR TERM...THE DYNAMICAL MODELS SUGGEST THAT THE UPPER-LOW TO THE 248WEST-NORTHWEST OF HANNA WILL MOVE WESTWARD AND WEAKEN...WHICH 249SHOULD RELAX THE SOUTHWESTERLY SHEAR THAT IS CURRENTLY IMPINGING 250UPON THE CYCLONE. THE INTENSITY FORECAST FOLLOWS THIS SOLUTION 251AND CALLS FOR GRADUAL STRENGTHENING DURING THE NEXT 2 DAYS... 252BRINING HANNA TO HURRICANE STATUS. THEREAFTER THERE IS A LARGE 253AMOUNT OF UNCERTAINTY IN THE INTENSITY FORECAST. THE GLOBAL MODELS 254PREDICT STRONG NORTHWEST TO NORTH UPPER-LEVEL WINDS OVER 255HANNA...WHICH ONE WOULD THINK SHOULD HALT ADDITIONAL STRENGTHENING 256OR EVEN WEAKEN THE STORM. HOWEVER...NEARLY ALL OF THE INTENSITY 257GUIDANCE SHOW STRENGTHENING OR LITTLE INTENSITY CHANGE DURING THAT 258TIME. ASSUMING THAT THE SHEAR WILL PRODUCE A NEGATIVE AFFECT ON 259HANNA...THE NEW INTENSITY FORECAST FOLLOWS PERSISTENCE OF PREVIOUS 260ADVISORY AND IS A LITTLE BELOW MOST OF THE GUIDANCE. 261 262HANNA MOVED WEST-NORTHWESTWARD DURING THE PAST 12 HOURS AND THE 263INITIAL MOTION ESTIMATE IS 285/10. THE TRACK GUIDANCE IS 264IN GOOD AGREEMENT THROUGH 48 HOURS ON A WEST-NORTHWEST TO NORTHWEST 265MOTION. THEREAFTER...THE MODELS GENERALLY SHOW A WEST- 266SOUTHWESTWARD OR SOUTHWARD TURN..SOUTH OF A BUILDING RIDGE OVER 267THE EASTERN UNITED STATES. HOWEVER...THE SHARPNESS OF THE TURN 268AND SPEED OF MOTION VARIES GREATLY. THE NEW NHC TRACK HAS BEEN 269ADJUSTED SOUTHWARD DURING THE FIRST COUPLE OF DAYS...MAINLY DUE TO 270THE MORE WESTWARD INITIAL MOTION. THIS IS IN CLOSE AGREEMENT WITH 271THE MODEL CONSENSUS. AFTER 72 HOURS...THE NEW TRACK IS A LITTLE 272FASTER THAN THE PREVIOUS ADVISORY...BUT IS NOTICEABLY SLOWER THAN 273THE UKMET AND GFDL MODELS. THE HWRF...WHICH SHOWS A CYCLONIC LOOP 274NORTH OF THE BAHAMAS AND A NORTHEASTWARD MOTION AT DAY 5...IS 275CONSIDER AN OUTLIER AT THIS TIME. 276 277INTERESTS IN THE SOUTHWESTERN BAHAMAS AND TURKS AND CAICOS SHOULD 278MONITOR THE PROGRESS OF HANNA. IMPACTS IN THESE AREAS COULD OCCUR 279MUCH SOONER THAN INDICATED BY THE EXACT TRACK...ESPECIALLY IF THE 280MORE NORTHWESTWARD MOTION DOES NOT MATERIALIZED LATER TODAY OR ON 281SATURDAY. 282 283 284FORECAST POSITIONS AND MAX WINDS 285 286INITIAL 29/1500Z 21.3N 62.7W 45 KT 28712HR VT 30/0000Z 22.2N 64.5W 50 KT 28824HR VT 30/1200Z 23.6N 66.7W 55 KT 28936HR VT 31/0000Z 24.6N 68.6W 60 KT 29048HR VT 31/1200Z 25.1N 70.1W 70 KT 29172HR VT 01/1200Z 24.7N 71.6W 65 KT 29296HR VT 02/1200Z 24.0N 72.5W 65 KT 293120HR VT 03/1200Z 23.0N 73.5W 60 KT 294 295$$ 296FORECASTER BROWN 297 298 299 300 301WTNT43 KNHC 292054 302TCDAT3 303TROPICAL STORM HANNA DISCUSSION NUMBER 7 304NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 305500 PM EDT FRI AUG 29 2008 306 307THE CENTER OF HANNA REMAINS NEAR THE WESTERN EDGE OF THE RATHER 308SHAPELESS AREA OF DEEP CONVECTION SEEN IN SATELLITE IMAGERY. A 3091412 UTC ASCAT PASS FOUND WINDS OF 40 KT OVER THE NORTHEASTERN 310SEMICIRCLE. GIVEN THE LOW BIAS TYPICAL OF ASCAT WINDS IN THIS 311RANGE...IT SUPPORTS MAINTAINING THE INITIAL INTENSITY AT 45 KT. 312THIS INTENSITY IS ALSO SUPPORTED BY SATELLITE ESTIMATES FROM 313TAFB AND SAB WHICH REMAIN T3.0 OR 45 KT. 314 315WATER VAPOR IMAGERY SHOWS THAT THE UPPER-LEVEL LOW LOCATED A 316COUPLE HUNDRED MILES WEST-NORTHWEST OF HANNA HAS NOT BUDGED 317TODAY AND IT CONTINUES TO IMPART SOUTHWESTERLY SHEAR ON THE 318TROPICAL CYCLONE. THE DYNAMICAL MODELS REMAIN EMPHATIC 319SUGGESTING THAT THE UPPER-LOW WILL MOVE WEST OR WEST- 320SOUTHWESTWARD AND WEAKEN...ALLOWING HANNA TO GRADUALLY 321STRENGTHEN. THE NEW NHC INTENSITY FORECAST CONTINUES TO ALLOW FOR 322SOME STRENGTHENING DURING THE NEXT COUPLE DAYS BUT SHOWS A LOWER 323PEAK INTENSITY THAN WAS FORECAST IN THE PREVIOUS ADVISORY. IN 324ABOUT 3 DAYS...THE MODELS CONTINUE TO FORECAST STRONG NORTHWEST TO 325NORTH UPPER-LEVEL WINDS OVER THE WESTERN ATLANTIC. THESE WINDS ARE 326PARTIALLY THE RESULT OF OUTFLOW FROM GUSTAV. DESPITE THE HOSTILE 327UPPER-LEVEL WIND FORECAST...THE INTENSITY GUIDANCE DOES NOT PREDICT 328WEAKENING. OUR INTENSITY FORECAST REMAINS ON THE LOW SIDE OF THE 329GUIDANCE AND STILL ASSUMES THAT THE NORTHERLY SHEAR WILL HAVE A 330NEGATIVE IMPACT ON HANNA'S INTENSITY. 331 332HANNA CONTINUES MOVING WEST-NORTHWESTWARD OR 295/9. IN 333GENERAL...THE FORECAST GUIDANCE HAS COME INTO A LITTLE BETTER 334AGREEMENT ON THE FUTURE TRACK OF HANNA. THE TROPICAL STORM IS 335FORECAST TO CONTINUE WEST-NORTHWESTWARD DURING THE NEXT 2 336DAYS...FOLLOWED BY A TURN TOWARD THE WEST-SOUTHWEST. THE HWRF 337CONTINUES TO BE AN OUTLIER SHOWING A CYCLONIC LOOP NORTH OF THE 338SOUTHEASTERN BAHAMAS. THE NEW TRACK FORECAST IS VERY SIMILAR TO 339THE PREVIOUS FORECAST THROUGH 48 HOURS...BUT IS A LITTLE FASTER 340AND FARTHER WEST THEREAFTER. 341 342FORECAST POSITIONS AND MAX WINDS 343 344INITIAL 29/2100Z 21.8N 63.8W 45 KT 34512HR VT 30/0600Z 22.8N 65.4W 50 KT 34624HR VT 30/1800Z 24.0N 67.7W 55 KT 34736HR VT 31/0600Z 24.8N 69.8W 60 KT 34848HR VT 31/1800Z 25.0N 71.1W 65 KT 34972HR VT 01/1800Z 24.5N 72.5W 65 KT 35096HR VT 02/1800Z 23.7N 73.7W 60 KT 351120HR VT 03/1800Z 23.0N 75.0W 60 KT 352 353$$ 354FORECASTER BROWN 355 356 357 358 359WTNT43 KNHC 300259 360TCDAT3 361TROPICAL STORM HANNA DISCUSSION NUMBER 8 362NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 3631100 PM EDT FRI AUG 29 2008 364 365CONVENTIONAL SATELLITE IMAGERY SUGGESTS THAT HANNA REMAINS WITHIN A 366VERY HARSH VERTICAL WIND SHEAR ENVIRONMENT. THE SURFACE 367CIRCULATION...EXPOSED WELL WEST OF THE REMAINING CONVECTIVE 368BAND...PASSED ABOUT 60 MILES NORTH OF BUOY 41043 WHICH RECORDED A 369SEA LEVEL PRESSURE OF 1004 MB. CONSEQUENTLY...HANNA'S CENTRAL 370PRESSURE IS INCREASED SLIGHTLY TO 1002 MB BASED ON THIS DATA. A 371QUIKSCAT OVERPASS JUST CAME IN A FEW MINUTES AGO AND INDICATED THAT 372THE CIRCULATION MAY BE JUST A BIT SOUTH OF THE ADVISORY POSITION AS 373WELL AS ALSO REVEALING A FEW BELIEVABLE 40-45 KT WINDS OVER THE 374NORTHEAST QUADRANT. THEREFORE...THE INITIAL INTENSITY IS HELD AT 37545 KT. THE GLOBAL MODELS CONTINUE TO INDICATE THAT THE UPPER-LEVEL 376LOW LOCATED A FEW HUNDRED MILES WEST-NORTHWEST OF CYCLONE WILL 377EITHER INCREASE IN DISTANCE BETWEEN THE TWO FEATURES WITH TIME OR 378WEAKEN AND OPEN UP INTO A TROUGH. THE SHIPS MODEL FOLLOWS SUIT BY 379SUGGESTING THAT THE SHEAR WILL DECREASE IN 12 TO 24 HOURS...WHICH 380IS REFLECTED IN THE INTENSITY FORECAST WITH GRADUAL STRENGTHENING 381THROUGH THE 72 HOUR PERIOD. THROUGH THE REMAINING PORTION OF THE 382FORECAST...THE LARGE-SCALE MODELS SHOW STRONG NORTH TO 383NORTHWESTERLY UPPER-LEVEL WINDS SETTING UP OVER THE WESTERN 384ATLANTIC...WHICH COULD ALSO BE INFLUENCED BY HURRICANE GUSTAV'S 385OUTFLOW PATTERN. SINCE THERE IS A CONSENSUS IN THE DEVELOPMENT OF 386AN INHIBITING SYNOPTIC UPPER-LEVEL PATTERN...A WEAKENING IS 387INDICATED THROUGH DAY 5. 388 389INITIAL MOTION IS ESTIMATED AT 295/12...WITHIN THE DEEP LAYER 390EAST-SOUTHEASTERLY FLOW OF THE SUBTROPICAL RIDGE TO THE NORTH OF 391THE CYCLONE. THE FORECAST PHILOSOPHY REMAINS INTACT FROM THE 392PREVIOUS ADVISORY...WHICH FOLLOWS CLOSELY TO THE DYNAMICAL MODEL 393BLEND THROUGH 72 HOURS. BEYOND THE DAY 3 PERIOD...THE OFFICIAL 394FORECAST IS NUDGED TOWARD THE PREVIOUS TRACK AND A BLEND OF THE GFS 395AND UKMET MODELS WHICH APPEAR TO BE DEPICTING THE SHEARED VERTICAL 396STRUCTURE OF THE SYSTEM MORE ACCURATELY. 397 398FORECAST POSITIONS AND MAX WINDS 399 400INITIAL 30/0300Z 22.1N 65.3W 45 KT 40112HR VT 30/1200Z 22.9N 67.0W 50 KT 40224HR VT 31/0000Z 23.9N 69.2W 55 KT 40336HR VT 31/1200Z 24.5N 70.8W 60 KT 40448HR VT 01/0000Z 24.6N 72.1W 65 KT 40572HR VT 02/0000Z 24.4N 73.4W 65 KT 40696HR VT 03/0000Z 23.6N 75.0W 60 KT 407120HR VT 04/0000Z 23.0N 76.3W 55 KT 408 409$$ 410FORECASTER ROBERTS 411 412 413 414 415WTNT43 KNHC 300857 416TCDAT3 417TROPICAL STORM HANNA DISCUSSION NUMBER 9 418NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 419500 AM EDT SAT AUG 30 2008 420 421THERE HAS BEEN NO SIGNIFICANT CHANGE IN THE CLOUD PATTERN OF HANNA. 422THE CENTER CONTINUES TO RUN AWAY FROM THE CONVECTION AND NEW 423THUNDERSTORM ACTIVITY REDEVELOPS OVER IT. THIS MEANS THAT THE SHEAR 424HAS NOT RELAXED YET. A NOAA BUOY...41043...HAS BEEN EXTREMELY USEFUL 425IN TRACKING THE CYCLONE. IT HAS DEPICTED THE WELL-DEFINED SURFACE 426CIRCULATION ASSOCIATED WITH HANNA AND HAS RECENTLY 427REPORTED A MINIMUM PRESSURE OF NEAR 1002 MB. AS LONG AS THE 428MODERATE SHEAR PREVAILS...CAUSED BY THE RESILIENT UPPER-LOW...HANNA 429MOST LIKELY WILL NOT STRENGTHEN. THE OFFICIAL FORECAST CALLS FOR NO 430CHANGE 431IN INTENSITY DURING THE NEXT 12 HOURS OR SO. GLOBAL MODELS INSIST 432ON WEAKENING THE UPPER-LOW...CREATING A MORE FAVORABLE ENVIRONMENT 433FOR HANNA TO STRENGTHEN IN THE PERIOD BETWEEN 12 AND 48 HOURS. 434THEREAFTER...THE SHEAR IS FORECAST TO INCREASE AND THIS IS 435REFLECTED IN THE OFFICIAL FORECAST BY SHOWING SOME SLIGHT 436WEAKENING. MOST OF THE MODELS CONTINUE TO INTENSIFY HANNA...SOME OF 437THEM QUITE SIGNIFICANTLY...DESPITE THE SHEAR. I DO NOT HAVE AN 438EXPLANATION FOR IT. 439 440THE CENTER IS VERY DIFFICULT TO LOCATE ON IR IMAGES BUT SATELLITE 441FIXES AND DATA FROM THE NOAA BUOY SUGGEST THAT HANNA HAS BEEN 442MOVING WESTWARD OR 280 DEGREES AT 10 KNOTS. FOR ABOUT 12 TO 24 443HOURS...A WEST-NORTHWEST MOTION AROUND THE UPPER-LOW IS 444ANTICIPATED. THEREAFTER...A STRONG SUBTROPICAL HIGH WHICH IS 445FORECAST TO BUILD TO THE NORTH OF HANNA WILL THEN PROVIDE THE 446DOMINANT STEERING FLOW. THIS SHOULD FORCE THE CYCLONE ON A 447WESTWARD AND THEN AN EVEN SLOWER WEST-SOUTHWESTWARD TRACK. I TRIED 448VERY HARD NOT TO FORECAST THE WEST-SOUTHWEST TURN SINCE THIS IS NOT 449A VERY COMMON TROPICAL CYCLONE TRACK BUT RELIABLE DYNAMICAL 450GUIDANCE HAS FORCED ME TO DO SO. THE OFFICIAL FORECAST IS 451PRACTICALLY ON TOP OF THE MODEL CONSENSUS. I ALWAYS WONDERED HOW 452TODAY'S SOPHISTICATED DYNAMICAL MODELS WOULD HAVE FORECAST 453HURRICANE BETSY BACK IN 1965. THIS HURRICANE MOVED SOUTHWESTWARD 454OVER THE BAHAMAS. 455 456 457FORECAST POSITIONS AND MAX WINDS 458 459INITIAL 30/0900Z 21.9N 66.3W 45 KT 46012HR VT 30/1800Z 22.6N 68.0W 45 KT 46124HR VT 31/0600Z 23.3N 70.0W 50 KT 46236HR VT 31/1800Z 23.5N 71.5W 60 KT 46348HR VT 01/0600Z 23.5N 72.5W 65 KT 46472HR VT 02/0600Z 23.5N 74.0W 65 KT 46596HR VT 03/0600Z 23.0N 75.5W 60 KT 466120HR VT 04/0600Z 22.5N 77.0W 55 KT 467 468$$ 469FORECASTER AVILA 470 471 472 473000 474 475WTNT43 KNHC 301447 476TCDAT3 477TROPICAL STORM HANNA DISCUSSION NUMBER 10 478NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 4791100 AM EDT SAT AUG 30 2008 480 481HANNA CONTINUES TO PRODUCE A LARGE AREA OF DEEP CONVECTION WITH 482CLOUD TOP TEMPERATURES BELOW -80 DEGREES C. HOWEVER...THE CENTER OF 483THE TROPICAL CYCLONE IS LOCATED NEAR THE SOUTHWESTERN EDGE OF THIS 484CONVECTION. THE EXACT CENTER HAS BEEN DIFFICULT TO LOCATE AS A 485COUPLE OF SMALL VORTICES HAVE BEEN SEEN ROTATING AROUND THE LARGER 486CIRCULATION THIS MORNING. SATELLITE INTENSITY ESTIMATES REMAIN 487T3.0 OR 45 KT AND AN EARLIER QUIKSCAT PASS SUGGEST MAXIMUM WINDS 488WERE NEAR THAT VALUE. THERE WERE SOME STRONGER WINDS SEEN IN THE 489QUIKSCAT DATA...BUT THESE WINDS WERE WELL REMOVED FROM THE CENTER 490AND APPEAR TO HAVE BEEN RAIN-INFLATED. 491 492THE SOMEWHAT UNCERTAIN INITIAL MOTION ESTIMATE IS 275/7. HANNA HAS 493CONTINUED TO MOVE MORE WESTWARD DURING THE PAST 12-24 HOURS...WHICH 494HAS REQUIRED A LITTLE SOUTHWARD ADJUSTMENT TO THE TRACK FORECAST IN 495THE SHORT-TERM. THE TRACK GUIDANCE PREDICTS A GENERAL WEST TO 496WEST-NORTHWEST MOTION DURING THE NEXT 24-36 HOURS. THEREAFTER... 497THERE IS A GREAT DEAL OF SPREAD AMONG THE MODELS...AS A STRONG HIGH 498PRESSURE RIDGE BUILDS OVER THE EASTERN UNITED STATES. THE GFDL AND 499HWRF RESPOND BY SHOWING A VERY SLOW AND ERRATIC MOTION IN ABOUT 3 500DAYS...WHILE THE UKMET TURNS HANNA SOUTHWESTWARD TOWARDS EASTERN 501CUBA. VERY LATE IN THE PERIOD...THE HIGH OVER THE EASTERN U.S. IS 502FORECAST TO MOVE OFF THE EAST COAST INTO THE WESTERN ATLANTIC AND 503SEVERAL OF THE FORECAST MODELS NOW INDICATE A WEST-NORTHWESTWARD 504AROUND DAY 5. THE NEW FORECAST WHICH IS VERY SIMILAR TO THE 505PREVIOUS ADVISORY...BUT SMOOTHS THROUGH THESE POSSIBLE UNDULATIONS 506AND SHOWS A SLOW WESTWARD MOTION BETWEEN 72-120 HOURS. THE NEW 507TRACK IS GENERALLY ALONG OR JUST SOUTH OF THE MODEL CONSENSUS. 508 509THE MUCH DISCUSSED UPPER-LOW JUST WEST OF THE STORM APPEARS TO HAVE 510WEAKENED A LITTLE THIS MORNING. THE SHIPS GUIDANCE SUGGESTS THE 511WESTERLY SHEAR MAY RELAX JUST A LITTLE OVER THE NEXT 24 HOURS. 512GIVEN THE RESILIENCE OF HANNA...THE OFFICIAL FORECAST SHOWS A 513LITTLE STRENGTHENING DURING THE NEXT DAY OR SO. 514THEREAFTER...STRONG NORTHWEST TO NORTH UPPER-LEVEL WINDS ARE 515FORECAST...SO THE OFFICIAL INTENSITY FORECAST NOW KEEPS HANNA JUST 516BELOW HURRICANE STRENGTH. IT SHOULD BE NOTED ONCE AGAIN...THAT THE 517NHC INTENSITY FORECAST REMAINS BELOW ALL OF THE RELIABLE GUIDANCE. 518 519BASED ON THE NEW FORECAST TRACK...THE GOVERNMENT OF THE BAHAMAS HAS 520ISSUED A TROPICAL STORM WATCH FOR THE SOUTHEASTERN BAHAMAS AND 521TURKS AND CAICOS ISLANDS. 522 523FORECAST POSITIONS AND MAX WINDS 524 525INITIAL 30/1500Z 21.9N 66.4W 45 KT 52612HR VT 31/0000Z 22.4N 67.9W 50 KT 52724HR VT 31/1200Z 22.9N 69.6W 55 KT 52836HR VT 01/0000Z 23.2N 71.0W 60 KT 52948HR VT 01/1200Z 23.2N 72.1W 60 KT 53072HR VT 02/1200Z 23.0N 73.5W 55 KT 53196HR VT 03/1200Z 23.0N 75.0W 55 KT 532120HR VT 04/1200Z 23.0N 76.5W 55 KT 533 534$$ 535FORECASTER BROWN 536 537 538 539 540WTNT43 KNHC 302048 541TCDAT3 542TROPICAL STORM HANNA DISCUSSION NUMBER 11 543NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 544500 PM EDT SAT AUG 30 2008 545 546THE CLOUD PATTERN OF HANNA HAS CHANGED QUITE A BIT DURING THE DAY 547TODAY. THE TROPICAL STORM HAS BECOME INVOLVED WITH THE UPPER-LEVEL 548LOW THAT WAS LOCATED TO ITS WEST...AND HANNA NOW HAS SOME 549RESEMBLANCE OF A SUB-TROPICAL CYCLONE. EVEN THOUGH THE CENTER IS 550LOCATED WELL SOUTHWEST OF THE THUNDERSTORM ACTIVITY...BANDING OVER 551THE NORTHEASTERN SEMICIRCLE STILL YIELD INTENSITY ESTIMATES OF T3.0 552OR 45 KT FROM BOTH AGENCIES. 553 554HANNA HAS BEEN MOVING BETWEEN THE WEST AND WEST-NORTHWEST AT 555ABOUT 7 KT TODAY. A SIMILAR MOTION IS FORECAST BY THE NUMERICAL 556MODEL GUIDANCE FOR THE NEXT 24-36 HOURS...SO VERY LITTLE CHANGE WAS 557NEEDED TO THE PREVIOUS FORECAST DURING THAT TIME. THEREAFTER...THE 558MODEL SPREAD HAS BECOME EXTREMELY LARGE AS A STRONG HIGH PRESSURE 559RIDGE BUILDS OVER THE EASTERN UNITED STATES. THE TRACK GUIDANCE NOW 560PREDICTS A SLOW AND ERRATIC MOTION OF HANNA DURING THE 48 TO ABOUT 56196 HOUR TIME FRAME. THE GFDL AND HWRF BOTH PREDICT HANNA TO MAKE A 562CYCLONIC LOOP NEAR THE SOUTHEASTERN BAHAMAS. MEANWHILE...THE ECMWF 563AND UKMET SHOW A SOUTHWESTWARD MOTION...WITH THE LATTER MODEL 564FORECASTING HANNA TO BE OVER EASTERN CUBA. BEYOND 96 HOURS... 565NEARLY ALL OF THE GUIDANCE...EXCEPT THE UKMET...NOW FORECAST A 566WEST-NORTHWESTWARD OR NORTHWESTWARD MOTION TO RESUME AS THE RIDGE 567OVER THE EASTERN UNITED STATES WEAKENS. WITH ALL OF THAT SAID... 568THERE IS VERY LOW CONFIDENCE IN THE TRACK FORECAST. THE NEW TRACK 569SLOWS DOWN THE STORM CONSIDERABLY...AND NOW PREDICTS A SLOW 570WEST-NORTHWESTWARD MOTION LATE IN THE PERIOD. THE NHC TRACK IS A 571LITTLE SOUTH OF THE CONSENSUS...ESPECIALLY AT DAY 5...BUT IS IN 572GENERAL AGREEMENT WITH THE 12Z ECMWF. 573 574GIVEN ALL THE UNCERTAINTIES IN THE TRACK FORECAST...THE INTENSITY 575FORECAST SEEMS JUST AS DIFFICULT. THE DYNAMICAL MODELS AND SHIPS 576GUIDANCE SUGGEST THAT WEST TO NORTHWESTERLY SHEAR WILL CONTINUE 577DURING THE NEXT 24-36 HOURS...FOLLOWED BY AN INCREASE IN NORTHERLY 578SHEAR. GIVEN THE UNCERTAINTIES AS TO HOW HANNA WILL RESPOND TO THE 579SHEAR...THE INTENSITY FORECAST ALLOWS FOR SOME STRENGTHENING IN THE 580SHORT-TERM...BUT LEVELS OFF THE INTENSITY BETWEEN 36-96 HOURS. 581THERE ARE SOME INDICATIONS THAT THE UPPER-LEVEL ENVIRONMENT COULD 582BECOME MORE CONDUCIVE VERY LATE IN THE PERIOD...SO SLIGHT 583STRENGTHENING IS INDICATE AT DAY 5. THE NHC FORECAST REMAINS BELOW 584ALL OF THE RELIABLE INTENSITY GUIDANCE. 585 586THE 12-FT SEA RADII WERE ADJUSTED OUTWARD OVER THE NORTHWESTERN 587SEMICIRCLE BASED ON REPORTS FROM NOAA BUOY 41046. 588 589FORECAST POSITIONS AND MAX WINDS 590 591INITIAL 30/2100Z 22.4N 67.2W 45 KT 59212HR VT 31/0600Z 22.8N 68.6W 45 KT 59324HR VT 31/1800Z 23.3N 70.2W 50 KT 59436HR VT 01/0600Z 23.5N 71.4W 55 KT 59548HR VT 01/1800Z 23.5N 72.1W 55 KT 59672HR VT 02/1800Z 23.5N 72.8W 55 KT 59796HR VT 03/1800Z 24.0N 74.0W 55 KT 598120HR VT 04/1800Z 25.0N 76.5W 60 KT 599 600$$ 601FORECASTER BROWN 602 603 604 605000 606 607WTNT43 KNHC 310244 608TCDAT3 609TROPICAL STORM HANNA DISCUSSION NUMBER 12 610NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 6111100 PM EDT SAT AUG 30 2008 612 613ENHANCED INFRARED IMAGERY AND MICROWAVE OVERPASSES DEPICT A 614CONVECTIVELY CHALLENGED TROPICAL CYCLONE. THE VERTICAL STRUCTURE 615OF THE HANNA HAS TRANSFORMED INTO A SYSTEM SIMILAR TO A SUBTROPICAL 616CYCLONE...WITH A SLIGHT TILT TO THE WEST WITH HEIGHT. THE CYCLONE 617HAS BEEN STRUGGLING TO MAINTAIN DEEP CONVECTION NEAR THE PARTLY 618EXPOSED CENTER...PARTICULARLY OVER THE WEST AND SOUTH QUADRANTS. 619THERE APPEARS TO BE SOME MODERATE SUBSIDENCE SPREADING OVER THE 620AREA PRODUCED BY CONVERGING UPPER-LEVEL WINDS BETWEEN THE UPPER LOW 621NOW ASSOCIATED WITH HANNA AND GUSTAV'S OUTFLOW PATTERN...WITH THIS 622DRYER MORE STABLE AIR BEING ENTRAINED INTO THE SYSTEM'S CORE. THE 623INITIAL INTENSITY IS HELD AT 45 KT BASED ON DVORAK AND 624HEBERT/POTEAT INTENSITY TECHNIQUES...AS WELL AS A QUIKSCAT PASS 625THAT SUPPORTED THIS INTENSITY. 626 627THE INTENSITY MODELS CONTINUE TO INDICATE AN INCREASE IN NORTHERLY 628SHEAR AROUND THE 24 HOUR PERIOD...THEN TRANSITIONING TO A MORE 629SOUTH TO SOUTHWESTERLY COMPONENT AFTERWARD. THE SHIPS AND THE LGEM 630AGREE WITH GRADUAL STRENGTHENING UNTIL THE STRONG NORTHERLY SHEAR 631APPEARS...THEN THE MODELS AGREE WITH LITTLE CHANGE THROUGH THE 72 632HOUR PERIOD. BEYOND DAY 3...THE DYNAMICAL MODELS INDICATE A HINT 633OF A MORE FAVORABLE UPPER WIND ENVIRONMENT...WHICH THE 634AFOREMENTIONED MODELS ALSO DEPICT. THE OFFICIAL FORECAST FOLLOWS 635THIS PHILOSOPHY AND INDICATES SLIGHT INTENSIFICATION AT THE 120 636HOUR PERIOD. 637 638THE INITIAL MOTION IS ESTIMATED AT 300/7. DYNAMICAL MODELS SUGGEST 639THAT AN ANCHORED SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE 640SHOULD INFLUENCE A GENERAL WEST-NORTHWESTWARD MOTION DURING THE 641NEXT 48 HOURS. AFTERWARD...A DEEP MID-LATITUDE LOW AND ASSOCIATED 642TROUGH IS EXPECTED TO MOVE OVER THE WESTERN ATLANTIC AND WEAKEN A 643PORTION OF THE RIDGE LOCATED OVER SOUTHEAST U.S. AND THE BAHAMAS 644WHILE A HIGH AMPLITUDE BLOCKING HIGH SETS UP OVER THE EASTERN 645SEABOARD. THIS PARTICULAR PATTERN IS EXPECTED TO CAUSE HANNA TO 646TEMPORARILY SLOW ITS FORWARD SPEED THROUGH THE 72 HOUR PERIOD WHILE 647MAINTAINING A WEST-NORTHWESTWARD TRACK. THROUGH THE REMAINDER OF 648THE FORECAST...A MID-LEVEL RIDGE IS FORECAST TO BUILD NORTHEAST OF 649HANNA IN RESPONSE TO THE AFOREMENTIONED MID-LATITUDE LOW LIFTING OUT 650AND MOVING AWAY FROM THE NORTHEAST COAST. THE MODEL SPREAD REMAINS 651RATHER LARGE...HOWEVER...THE MAJORITY ARE SHOWING A TURN TOWARD THE 652NORTHWEST OVER OR EAST OF THE BAHAMAS BEYOND 72 HOURS...WHILE THE 653UKMET IS STILL PREDICTING THE SUBTROPICAL RIDGE TO REMAIN INTACT 654TO THE NORTH. THE OFFICIAL FORECAST FOLLOWS THE MODEL CONSENSUS 655AND IS SIMILAR TO THE PREVIOUS ADVISORY BUT INDICATES A MORE 656NORTHWESTWARD MOTION BEYOND DAY 3. 657 658FORECAST POSITIONS AND MAX WINDS 659 660INITIAL 31/0300Z 22.9N 67.8W 45 KT 66112HR VT 31/1200Z 23.3N 69.0W 45 KT 66224HR VT 01/0000Z 23.6N 70.4W 50 KT 66336HR VT 01/1200Z 23.6N 71.4W 55 KT 66448HR VT 02/0000Z 23.6N 72.2W 55 KT 66572HR VT 03/0000Z 23.8N 73.1W 55 KT 66696HR VT 04/0000Z 24.5N 74.5W 55 KT 667120HR VT 05/0000Z 26.5N 76.5W 60 KT 668 669$$ 670FORECASTER ROBERTS/BEVEN 671 672 673 674 675WTNT43 KNHC 310855 676TCDAT3 677TROPICAL STORM HANNA DISCUSSION NUMBER 13 678NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 679500 AM EDT SUN AUG 31 2008 680 681HANNA HAS BEEN GOING THROUGH SOME STRUCTURAL CHANGES THAT HAVE 682RESEMBLED A SUBTROPICAL CYCLONE AT TIMES AS AN UPPER-LEVEL COLD LOW 683AND DRY AIR HAVE BECOME ENTANGLED WITH THE INNER-CORE CIRCULATION. 684HOWEVER...DURING THE PAST 6 HOURS WATER VAPOR IMAGERY HAS INDICATED 685THAT THE UPPER-LOW HAS BEGUN TO DROP SOUTHWARD TOWARD HISPANIOLA 686...WHICH MAY ALLOW HANNA TO TRANSITION BACK INTO A FULL WARM CORE 687TROPICAL CYCLONE LATER TODAY. THE INTENSITY WAS INCREASED TO 50 KT 688AND THE WIND RADII WERE EXPANDED SIGNIFICANTLY IN THE NORTHERN 689SEMICIRCLE BASED ON A 30/2231Z QUIKSCAT OVERPASS THAT WAS NOT 690AVAILABLE FOR THE PREVIOUS ADVISORY. SATELLITE ESTIMATES FROM TAFB 691AND SAB ARE ST3.0/45 KT. 692 693THE INITIAL MOTION ESTIMATE AT 290/10. ALL OF THE NHC MODEL GUIDANCE 694NOW INDICATES SOME SOUTHWARD COMPONENT TO HANNA'S TRACK BY 48 HOURS 695AS STRONG NORTHERLY FLOW IMPINGES ON THE CYCLONE BEHIND A DIGGING 696TROUGH OFF THE U.S. EAST COAST COMBINED WITH OUTFLOW FROM HURRICANE 697GUSTAV LOCATED WELL TO THE WEST OF HANNA. THE SHIPS MODEL INDICATES 698AT LEAST 30 KT OF NORTHERLY SHEAR ACROSS HANNA AT 48 HOURS...WHICH 699SHOULD ACT TO DISPLACE ANY DEEP CONVECTION INTO THE SOUTHERN 700SEMICIRCLE AND ALSO HELP TO FORCE THE CYCLONE SOUTHWARD. SHOULD 701HANNA BE STRIPPED OF ALL CONVECTION AROUND THAT TIME PERIOD...THE 702SHALLOW BAM MODEL ALSO INDICATES A SOUTHWARD COMPONENT OF MOTION 703...INCLUDING A CYCLONIC LOOP. HOWEVER...BY 96 HOURS... NEARLY ALL OF 704THE MODELS FORECAST THE STRONG UPPER-TROUGH TO LIFT OUT TO THE 705NORTHEAST AND BE REPLACED BY A LARGE RIDGE TO THE NORTH AND EAST OF 706HANNA. THE LATTER FEATURE IS EXPECTED TO GRADUALLY INDUCE A 707NORTHWESTWARD COMPONENT OF MOTION BY DAYS 4 AND 5. THE KEY TO THE 708FORECAST TRACK AT THOSE FORECAST TIMES WILL BE JUST HOW FAR SOUTH 709AND WEST HANNA MOVES BEFORE IT BEGINS TO MOVE NORTHWESTWARD. MOST 710OF THE MODEL GUIDANCE KEEPS HANNA OVER OR JUST EAST OF THE 711BAHAMAS...THE EXCEPTION BEING THE UKMET AND ECMWF MODELS...WHICH 712BRING HANNA NEAR THE NORTH-CENTRAL COAST OF CUBA BY DAY 4 AND INTO 713THE FLORIDA STRAITS BY DAY 5. AT THIS TIME...THE SPECIFICS OF THOSE 714TWO TRACKS ARE CONSIDERED TO BE OUTLIERS...BUT THEY HAVE NOT BEEN 715ENTIRELY DISCOUNTED. THE OFFICIAL TRACK IS CLOSE TO THE PREVIOUS 716FORECAST TRACK AND THE NHC MODEL CONSENSUS. 717 718THE INTENSITY FORECAST IS SOMEWHAT TRICKY. WITH MORE THAN 30 KT OF 719SHEAR FORECAST TO AFFECT HANNA BY 48 HOURS...THE CYCLONE COULD 720EASILY BE SHEARED APART. HOWEVER...WHILE THE SHEAR WILL BE 721STRONG...ITS NEGATIVE EFFECTS MAY BE OFFSET BY THE STRONG 722UPPER-LEVEL DIFLUENT PATTERN THAT IS ALSO FORECAST TO EXIST ACROSS 723HANNA AT THAT TIME. BY 72-96 HOURS...ALL OF THE MODELS AGREE ON 724ANTICYCLONIC OUTFLOW REPLACING THE STRONG NORTHERLY SHEAR 725PATTERN...INCLUDING OUTFLOW JETS DEVELOPING TO THE NORTH AND 726SOUTH...WHICH WOULD FAVOR SIGNIFICANT STRENGTHENING OVER 29-30C 727SSTS BENEATH THE CYCLONE. HOWEVER...THE INTENSITY FORECAST HAS BEEN 728HELD BELOW ALL OF THE AVAILABLE MODEL GUIDANCE DUE TO THE 729UNCERTAINTY OF WHAT THE EXACT STRUCTURE OF HANNA WILL BE AFTER THE 730UPCOMING STRONG SHEAR PATTERN ABATES IN AROUND 72 HOURS. 731 732FORECAST POSITIONS AND MAX WINDS 733 734INITIAL 31/0900Z 23.2N 69.0W 50 KT 73512HR VT 31/1800Z 23.6N 70.2W 50 KT 73624HR VT 01/0600Z 23.7N 71.4W 50 KT 73736HR VT 01/1800Z 23.7N 72.5W 50 KT 73848HR VT 02/0600Z 23.3N 73.1W 50 KT 73972HR VT 03/0600Z 23.6N 73.9W 55 KT 74096HR VT 04/0600Z 25.1N 75.4W 60 KT 741120HR VT 05/0600Z 28.0N 78.0W 70 KT 742 743$$ 744FORECASTER STEWART 745 746 747 748000 749 750WTNT43 KNHC 311446 751TCDAT3 752TROPICAL STORM HANNA DISCUSSION NUMBER 14 753NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 7541100 AM EDT SUN AUG 31 2008 755 756HANNA'S OVERALL SATELLITE APPEARANCE REMAINS RATHER RAGGED AND DEEP 757CONVECTION IS LIMITED NEAR THE LOW-LEVEL CIRCULATION. THE INITIAL 758INTENSITY IS LOWERED TO 45 KT BASED ON LATEST SATELLITE INTENSITY 759ESTIMATES AND NEARBY BUOY 41046. HANNA WILL ENCOUNTER A RATHER 760COMPLICATED ATMOSPHERIC ENVIRONMENT DURING THE NEXT COUPLE OF DAYS 761MAKING THE INTENSITY FORECAST PROBLEMATIC. WHILE MOST OF THE 762DYNAMICAL GUIDANCE SUGGEST THAT THE UPPER-LEVEL LOW CURRENTLY OVER 763HANNA WILL GRADUALLY WEAKEN...THEY HAVE NOT NECESSARILY HAD THE 764BEST TRACK RECORD FORECASTING THIS FEATURE. EVEN IF THE UPPER-LOW 765DOES WEAKEN AS SHOWN BY THE GLOBAL MODELS...GUSTAV'S OUTFLOW COULD 766PRODUCE STRONG NORTHERLY SHEAR OVER HANNA. INDEED WATER VAPOR 767IMAGERY CURRENTLY SHOWS A DEFORMATION AXIS FORMING NORTH OF HANNA 768AS A RESULT OF GUSTAV'S OUTFLOW INTERACTING WITH CYCLONIC FLOW 769AROUND THE UPPER-LEVEL LOW. BOTTOM LINE...THE ATMOSPHERE LOOKS 770RATHER HOSTILE FOR THE NEXT COUPLE OF DAYS AND SHOULD LIMIT THE 771POTENTIAL FOR SIGNIFICANT INTENSIFICATION. DYNAMICAL MODELS DO 772INDICATE SOME IMPROVEMENT IN THE ATMOSPHERIC ENVIRONMENT TOWARD THE 773END OF THE FORECAST AS A SECOND UPPER-LEVEL LOW OR CYCLONIC SHEAR 774AXIS FORMS TO THE WEST OF HANNA. HOWEVER...ACCURATELY PREDICTING 775THE ENVIRONMENT IN WHICH HANNA WILL BE LOCATED AT DAYS 4 AND 5 IS 776DIFFICULT...AND THE NEW OFFICIAL FORECAST IS LITTLE CHANGED FROM 777THE PREVIOUS ADVISORY. 778 779HANNA IS CURRENTLY SITUATED SOUTH OF A MID-LEVEL RIDGE OVER THE 780WESTERN ATLANTIC RESULTING IN A MOTION TOWARD THE WEST OR 280/09. 781GLOBAL MODELS INDICATE THIS RIDGE WILL WEAKEN DURING THE NEXT DAY 782OR SO AS A LARGE DEEP-LAYERED TROUGH AMPLIFIES SOUTHWARD OVER THE 783WESTERN ATLANTIC. SUCH AN EVOLUTION IN THE LARGE-SCALE PATTERN IS 784EXPECTED TO CAUSE THE STEERING CURRENTS TO COLLAPSE RESULTING IN A 785REDUCTION IN HANNA'S FORWARD SPEED AND POSSIBLY SOME ERRATIC 786MOTION. BY DAYS 4 AND 5...THE DEEP-LAYERED TROUGH BEGINS TO LIFT 787NORTHEASTWARD AND THE SUBTROPICAL RIDGE BUILDS BACK WESTWARD IN ITS 788WAKE. MOST OF THE TRACK MODELS RESPOND BY TURNING HANNA NORTHWEST 789WITH AN INCREASE IN FORWARD SPEED. HOWEVER...THE UKMET MODEL 790ACTUALLY SHOWS THE RIDGE AXIS BUILDING SUFFICIENTLY FAR WEST...AND 791TO THE NORTH OF HANNA...TO RESULT IN MORE WESTWARD TRACK. SINCE 792THIS IS A NORMALLY GOOD PERFORMING MODEL...IT CANNOT COMPLETELY BE 793IGNORED AND THE NEW OFFICIAL FORECAST LIES SOUTH OF THE DYNAMICAL 794MODEL CONSENSUS. 795 796GIVEN THE HIGH SPREAD AMONG THE VARIOUS MODELS...THERE IS 797CONSIDERABLE UNCERTAINTY REGARDING HANNA'S EVENTUAL TRACK AND 798INTENSITY. 799 800FORECAST POSITIONS AND MAX WINDS 801 802INITIAL 31/1500Z 23.3N 70.0W 45 KT 80312HR VT 01/0000Z 23.4N 71.1W 45 KT 80424HR VT 01/1200Z 23.5N 72.1W 45 KT 80536HR VT 02/0000Z 23.3N 72.9W 50 KT 80648HR VT 02/1200Z 23.0N 73.4W 55 KT 80772HR VT 03/1200Z 23.5N 74.5W 60 KT 80896HR VT 04/1200Z 26.0N 76.0W 65 KT 809120HR VT 05/1200Z 29.5N 79.0W 70 KT 810 811$$ 812FORECASTER RHOME 813 814 815 816000 817 818WTNT43 KNHC 312038 819TCDAT3 820TROPICAL STORM HANNA DISCUSSION NUMBER 15 821NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 822500 PM EDT SUN AUG 31 2008 823 824AN AIR FORCE RECONNAISSANCE AIRCRAFT INVESTIGATING HANNA DURING THE 825LAST SEVERAL HOURS FOUND A PEAK FLIGHT LEVEL WIND OF 48 KT WHICH 826REDUCES TO APPROXIMATELY 40 KT AT THE SURFACE. WHILE THERE WERE A 827FEW HIGHER VALUES FROM THE SFMR...THESE WERE LIKELY RAIN INFLATED. 828THE OVERALL INTENSITY FORECAST REASONING IS ESSENTIALLY UNCHANGED. 829HANNA IS CURRENTLY EXPERIENCING STRONG NORTHERLY SHEAR ASSOCIATED 830WITH AN UPPER-LEVEL LOW TO ITS SOUTHEAST. GLOBAL MODELS DO 831FORECAST THIS UPPER-LEVEL LOW TO WEAKEN OVER THE NEXT DAY OR SO. 832HOWEVER...STRONG NORTHERLY FLOW ASSOCIATED WITH GUSTAV'S 833UPPER-LEVEL OUTFLOW SHOULD KEEP NORTHERLY SHEAR OVER HANNA THROUGH 834DAY 3. BY DAYS 4 AND 5...DYNAMICAL MODELS FORECAST A SOMEWHAT 835IMPROVED ENVIRONMENT AS A SECOND UPPER-LEVEL LOW OR CYCLONIC SHEAR 836AXIS FORMS TO THE WEST OF HANNA. THIS WOULD PUT HANNA IN A MORE 837FAVORABLE ENVIRONMENT FOR STRENGTHENING. HOWEVER...ACCURATELY 838PREDICTING HANNA'S PROXIMITY TO LARGE-SCALE ATMOSPHERIC FEATURES AT 839DAYS 4 AND 5 IS DIFFICULT...TO SAY THE LEAST. GIVEN THE 840UNCERTAINTY...THE OFFICIAL FORECAST SHOWS SLOW STRENGTHENING...BUT 841IS BELOW THE INTENSITY MODEL CONSENSUS. 842 843HANNA CONTINUES TO BE STEERED BY A MID-LEVEL RIDGE OVER THE WESTERN 844ATLANTIC...RESULTING IN A MOTION TOWARD THE WEST OR 280/09. GLOBAL 845MODELS INDICATE THIS RIDGE WILL WEAKEN DURING THE NEXT DAY OR SO AS 846A LARGE DEEP-LAYER TROUGH AMPLIFIES SOUTHWARD OVER THE WESTERN 847ATLANTIC. SUCH AN EVOLUTION IN THE LARGE-SCALE PATTERN SHOULD CAUSE 848THE STEERING CURRENTS TO COLLAPSE RESULTING IN A DECREASE IN 849HANNA'S FORWARD SPEED. IN FACT...SOME OF THE MODELS SHOW HANNA 850MEANDERING OVER OR JUST NORTHEAST OF THE CENTRAL BAHAMAS. BY DAY 8513...THE DEEP-LAYER TROUGH IS FORECAST TO LIFT NORTHEASTWARD 852ALLOWING THE SUBTROPICAL RIDGE TO BUILD BACK WESTWARD IN ITS WAKE. 853THERE REMAINS CONSIDERABLE SPREAD AMONG THE DYNAMICAL MODELS AT THE 854EXTENDED RANGE. THE GFS...GFDL...AND THE HWRF MODELS LIE ALONG THE 855RIGHT SIDE OF THE MODEL ENVELOPE AND SHOW HANNA LIFTING QUICKLY 856NORTHWESTWARD AROUND THE WESTERN PERIPHERY OF THE RIDGE. 857CONVERSELY...THE UKMET MODEL SHOWS THE RIDGE NOSING WESTWARD TO THE 858NORTH OF HANNA...PRODUCING A TRACK ALONG THE LEFT...OR 859SOUTHWEST...SIDE OF THE MODEL ENVELOPE. SINCE THERE IS NO CLEAR 860REASON TO FAVOR ONE SCENARIO OVER THE OTHER AT THIS TIME...I'VE 861ELECTED TO LEAVE THE OFFICIAL FORECAST ESSENTIALLY UNCHANGED BEYOND 86272 HOURS. 863 864FORECAST POSITIONS AND MAX WINDS 865 866INITIAL 31/2100Z 23.5N 71.4W 40 KT 86712HR VT 01/0600Z 23.5N 72.3W 40 KT 86824HR VT 01/1800Z 23.3N 73.1W 45 KT 86936HR VT 02/0600Z 23.3N 73.7W 50 KT 87048HR VT 02/1800Z 23.5N 74.1W 55 KT 87172HR VT 03/1800Z 24.5N 75.0W 60 KT 87296HR VT 04/1800Z 27.5N 77.5W 65 KT 873120HR VT 05/1800Z 31.5N 81.0W 65 KT 874 875$$ 876FORECASTER RHOME 877 878 879 880000 881 882WTNT43 KNHC 010258 883TCDAT3 884TROPICAL STORM HANNA DISCUSSION NUMBER 16 885NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 8861100 PM EDT SUN AUG 31 2008 887 888SINCE THE RECONNAISSANCE AIRCRAFT DEPARTED HANNA THIS AFTERNOON... 889DEEP CONVECTION HAS BECOME A LITTLE MORE CONCENTRATED JUST 890SOUTHEAST OF THE CENTER. SEVERAL MICROWAVE IMAGES FROM BETWEEN 2200 891AND 0000 UTC HAVE BEEN VERY HELPFUL IN LOCATING THE CENTER. DVORAK 892INTENSITY ESTIMATES HAVE INCREASED AGAIN TO T3.0 OR 45 KT... AND 893NOAA BUOY 41046 RECENTLY REPORTED A PEAK ONE-MINUTE WIND SPEED OF 89439 KT VERY NEAR THE AREA OF DEEP CONVECTION. THESE DATA SUPPORT 895INCREASING THE INTENSITY TO 45 KT. 896 897BOTH THE SHIPS MODEL AND UW-CIMSS DIAGNOSE ABOUT 20 KT OF 898NORTHWESTERLY SHEAR OVER HANNA AT THIS TIME. THE SHIPS GUIDANCE AND 899THE GLOBAL MODELS PREDICT SIMILAR OR SLIGHTLY HIGHER SHEAR VALUES 900DURING THE NEXT 2-3 DAYS. GIVEN THIS SHEAR...IT IS TEMPTING TO NOT 901FORECAST ANY STRENGTHENING DURING THIS TIME...BUT MOST OF THE 902GUIDANCE SHOWS SOME INTENSIFICATION. LATE IN THE FORECAST 903PERIOD...THERE ARE SOME INDICATIONS THAT THE UPPER-LEVEL 904ENVIRONMENT COULD BECOME SOMEWHAT MORE CONDUCIVE FOR 905STRENGTHENING...HOWEVER IT WILL DEPEND ON EXACTLY WHERE HANNA IS 906LOCATED. THE LGEM MODEL IS AT THE LOW END OF THE SPECTRUM AND 907FORECASTS VERY LITTLE INTENSITY CHANGE DURING THE NEXT 5 DAYS. THE 908NEW INTENSITY FORECAST IS VERY SIMILAR TO PREVIOUS ADVISORY THROUGH 90936 HOURS...BUT IS A LITTLE MORE CONSERVATIVE THEREAFTER AND USES A 910BLEND OF THE SHIPS AND LGEM MODELS AT 3 DAYS AND BEYOND. 911 912HANNA HAS BEEN MOVING WESTWARD OR 280/7 KT. THE BUILDING DEEP-LAYER 913RIDGE OVER THE EASTERN UNITED STATES IS FORECAST TO BLOCK HANNA'S 914FORWARD MOTION VERY SOON...AND THE TRACK GUIDANCE SHOWS VERY SLOW 915AND ERRATIC MOTION OVER THE NEXT COUPLE OF DAYS. AFTER 48 916HOURS...THE RIDGE BEGINS TO WEAKEN OVER THE U.S. WHILE ANOTHER 917RIDGE BUILDS OVER THE ATLANTIC TO THE NORTHEAST OF HANNA. THE 918ATLANTIC RIDGE IS EXPECTED TO STEER THE STORM NORTHWESTWARD BY THAT 919TIME. THE TRACK GUIDANCE GENERALLY AGREES ON THIS SCENARIO...BUT 920THE SPREAD OF THE GUIDANCE REMAINS QUITE LARGE AT DAYS 4 AND 5. THE 921UKMET REMAINS THE SOUTHERN OUTLIER WITH A TRACK NEAR CUBA AND 922SOUTHERN FLORIDA...WHILE THE GFS...HWRF...AND GFDL ARE ON THE 923EASTERN EDGE OF THE GUIDANCE ENVELOPE WITH A TRACK TOWARDS THE 924CAROLINAS. THE OFFICIAL FORECAST REMAINS VERY CLOSE TO THE PREVIOUS 925ADVISORY AND CLOSE TO THE MODEL CONSENSUS WHICH HAS SHIFTED EVER SO 926SLIGHTLY WESTWARD. 927 928 929FORECAST POSITIONS AND MAX WINDS 930 931INITIAL 01/0300Z 23.7N 72.2W 45 KT 93212HR VT 01/1200Z 23.5N 72.9W 45 KT 93324HR VT 02/0000Z 23.4N 73.5W 45 KT 93436HR VT 02/1200Z 23.4N 73.7W 50 KT 93548HR VT 03/0000Z 23.7N 74.2W 50 KT 93672HR VT 04/0000Z 25.4N 75.8W 55 KT 93796HR VT 05/0000Z 29.0N 79.0W 60 KT 938120HR VT 06/0000Z 33.5N 82.0W 45 KT...INLAND 939 940$$ 941FORECASTER BROWN 942 943 944 945 946WTNT43 KNHC 010848 947TCDAT3 948TROPICAL STORM HANNA DISCUSSION NUMBER 17 949NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 950500 AM EDT MON SEP 01 2008 951 952DURING THE PAST 6 HOURS...A LARGE MASS OF INTENSE CONVECTION WITH 953CLOUD TOP TEMPERATURES AS COLD AS -87C HAS DEVELOPED IN THE 954SOUTHEASTERN SEMICIRCLE OF HANNA. NOAA BUOY 41046 JUST EAST OF THE 955ALLEGED CENTER HAS REPORTED 1-MINUTE SUSTAINED WINDS OF 43 KT... 956WHICH EASILY SUPPORTS AN INITIAL INTENSITY OF 45 KT...AND HANNA 957COULD EVEN BE A LITTLE STRONGER BASED ON AN EARLIER PRESSURE OF 958997.1 MB FROM THE SAME BUOY. A RECON AIRCRAFT WILL INVESTIGATE 959HANNA LATER TODAY AND PROVIDE A BETTER ESTIMATE OF INTENSITY. 960 961THE INITIAL MOTION IS AN UNCERTAIN 260/02...DUE MAINLY TO SOME 962UNCERTAINTY IN THE EXACT LOCATION OF THE CENTER. A 01/0224Z ASCAT 963OVERPASS SUGGESTED THE CENTER OF HANNA WAS FARTHER SOUTHEAST AND 964EMBEDDED IN THE DEEP CONVECTION. IF THAT IS THE CASE...HANNA WOULD 965EASILY BE A 55-KT OR STRONGER TROPICAL STORM. HOWEVER...EARLIER 966PASSIVE MICROWAVE IMAGERY...THE MOST RECENT NIGHTTIME VISIBLE 967IMAGERY...AND THE CURRENT NORTHWESTERLY SHEAR PATTERN ALL SUGGEST 968THAT THE CENTER SHOULD BE LOCATED NEAR THE NORTHWESTERN EDGE OF THE 969DEEP CONVECTION RATHER THAN EMBEDDED WITHIN IT. IN CONTRAST TO THE 970UNCERTAINTY ASSOCIATED WITH THE LOCATION OF HANNA...ALL OF THE 971GLOBAL MODELS HAVE NEARLY IDENTICAL FORECAST SCENARIOS OF THE MID- 972TO UPPER-LEVEL FLOW PATTERNS. THE BERMUDA HIGH IS FORECAST TO 973EXTEND WESTWARD ACROSS THE ATLANTIC AND INTO THE TENNESSEE VALLEY 974BY DAYS 3-5...WHILE AN UPPER-LEVEL TROUGH DIGS SOUTHWARD OFF THE 975U.S. EAST COAST AND SPLITS...WITH THE SOUTHERN PORTION DIGGING 976SOUTH OF HANNA AND THE NORTHERN PORTION LIFTING OUT AND ALLOWING 977RIDGING TO FILL IN BEHIND THE TROUGH TO THE NORTH OF HANNA. THIS 978COMBINED FLOW PATTERN IS EXPECTED TO ACCELERATE HANNA TOWARD THE 979SOUTHEASTERN U.S. COAST BY 72-96 HOURS/DAYS 3-4. THE PRIMARY 980DIFFERENCE IN THE MODELS IS HOW THEY HANDLE THE SIZE OF HANNA 981BETWEEN NOW AND 72 HOURS. THE ECMWF AND UKMET KEEP HANNA ABOUT 100 982NMI IN DIAMETER SMALLER AT 500 MB THAN THE OTHER MODELS DO...WHICH 983RESULTS IN MORE RIDGING TO EXIST ON THE EAST SIDE OF HANNA...AND 984WHICH FORCES THE CYCLONE CLOSER TO THE FLORIDA EAST COAST. THE 985OFFICIAL FORECAST TRACK IS ALMOST IDENTICAL TO THE PREVIOUS TRACK 986AND IS VERY CLOSE TO THE MODEL CONSENSUS AND LEANS A LITTLE TOWARD 987THE ECMWF-UKMET SCENARIOS BASED ON HANNA'S CURRENT SIZE. 988 989LITTLE...IF ANY...STRENGTHENING IS EXPECTED DURING THE NEXT 48 HOURS 990DUE TO HOSTILE NORTHERLY SHEAR CONDITIONS. HOWEVER...BY 96 HOURS... 991ALL OF THE MODELS HAVE ALMOST IDENTICAL 200 MB FLOW PATTERNS 992INDICATING THE DEVELOPMENT OF BOTH POLEWARD AND EQUATORWARD OUTFLOW 993REGIMES SURROUNDING HANNA. THIS TYPE OF DUAL JET PATTERN WOULD 994FAVOR SIGNIFICANT INTENSIFICATION...AND HANNA COULD EASILY BE A 995HURRICANE BEFORE IT MAKES LANDFALL ALONG THE SOUTHEASTERN U.S. 996COAST. THE OFFICIAL INTENSITY IS SIMILAR TO THE SHIPS MODEL...BUT 997REMAINS BELOW ALL OF THE AVAILABLE NHC INTENSITY GUIDANCE. 998 999ALL INTERESTS IN FLORIDA SHOULD CLOSELY MONITOR THE FORECASTS FOR 1000HANNA SINCE ONLY A SLIGHT DEVIATION TO THE WEST OF THE OFFICIAL 1001TRACK COULD BRING THE CENTER OF HANNA MUCH CLOSER TO THE FLORIDA 1002EAST COAST AND THE BAHAMAS THAN CURRENTLY INDICATED. 1003 1004FORECAST POSITIONS AND MAX WINDS 1005 1006INITIAL 01/0900Z 23.6N 72.4W 45 KT 100712HR VT 01/1800Z 23.4N 73.0W 50 KT 100824HR VT 02/0600Z 23.4N 73.5W 50 KT 100936HR VT 02/1800Z 23.7N 74.0W 50 KT 101048HR VT 03/0600Z 24.2N 74.5W 55 KT 101172HR VT 04/0600Z 26.2N 76.5W 60 KT 101296HR VT 05/0600Z 30.0N 80.0W 65 KT 1013120HR VT 06/0600Z 35.0N 82.5W 30 KT...INLAND 1014 1015$$ 1016FORECASTER STEWART 1017 1018 1019 1020 1021WTNT43 KNHC 011452 1022TCDAT3 1023TROPICAL STORM HANNA DISCUSSION NUMBER 18 1024NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 10251100 AM EDT MON SEP 01 2008 1026 1027HANNA'S OVERALL SATELLITE PRESENTATION HAS BEEN IMPROVING THIS 1028MORNING WITH AN IMPRESSIVE CDO FEATURE NOW COVERING THE LOW-LEVEL 1029CIRCULATION. DVORAK SATELLITE INTENSITY ESTIMATES HAVE INCREASED 1030AND SUGGEST MAX WINDS NEAR 55 KT. I'M GOING TO CONSERVATIVELY SET 1031THE INITIAL INTENSITY TO 50 KT SINCE AN AIR FORCE RECONNAISSANCE 1032AIRCRAFT IS ON ITS WAY. HAVING SAID THAT...A RECENT QUIKSCAT PASS 1033SUGGEST THAT THE LOW-LEVEL CIRCULATION COULD BE LOCATED A LITTLE 1034FARTHER INTO THE DEEP CONVECTION. THIS SUGGEST THAT HANNA COULD BE 1035STRONGER THAN ESTIMATED. THE INTENSITY FORECAST REMAINS TRICKY. 1036WATER VAPOR IMAGERY SUGGESTS THAT THE UPPER-LEVEL LOW WHICH HAD 1037PREVIOUSLY INHIBITED DEVELOPMENT HAS DISSIPATED...AND HANNA NOW 1038FINDS ITSELF IN A VERY SMALL AREA OF LOW SHEAR. HOWEVER...WATER 1039VAPOR IMAGERY ALSO SHOWS STRONG NORTHERLY FLOW ASSOCIATED WITH 1040GUSTAV'S UPPER-LEVEL OUTFLOW JUST NORTH OF HANNA...AND GLOBAL MODELS 1041FORECAST MODERATE TO STRONG NORTHERLY SHEAR PERSISTING DURING THE 1042NEXT DAY OR SO. GIVEN THE UNCERTAINTY...THE OFFICIAL INTENSITY 1043FORECAST IS CLOSE TO THE MODEL CONSENSUS AND SHOWS HANNA BECOMING A 1044HURRICANE A LITTLE SOONER THAN THE PREVIOUS ADVISORY. BY 72 1045HOURS...GLOBAL MODELS SUGGEST THE SHEAR COULD WEAKEN...AND HANNA 1046COULD FIND ITSELF IN A MORE FAVORABLE ENVIRONMENT FOR 1047STRENGTHENING. STILL...PREDICTING THE ATMOSPHERIC ENVIRONMENT... 1048AND TROPICAL CYCLONE INTENSITY...AT DAYS 3-5 IS VERY DIFFICULT. 1049 1050WHILE THE CENTER IS DIFFICULT TO LOCATE...HANNA APPEARS TO BE MOVING 1051MORE TOWARD THE WEST-SOUTHWEST OR 250/4. A VERY SLOW WEST- 1052SOUTHWEST OR SOUTHWEST MOTION IS EXPECTED DURING THE NEXT 36 HOURS. 1053IN 2 TO 3 DAYS...THE SUBTROPICAL RIDGE IS EXPECTED TO BUILD 1054WESTWARD OVER THE CENTRAL ATLANTIC CAUSING HANNA TO MOVE 1055NORTHWESTWARD WITH AN INCREASE IN FORWARD SPEED. THE NEW OFFICIAL 1056TRACK FORECAST IS ADJUSTED A LITTLE TO THE SOUTH THROUGH 36 HOURS 1057BASED ON THE LATEST MOTION. TRACK GUIDANCE HAS NOT CHANGED 1058SIGNIFICANTLY AT THE EXTENDED RANGES AND NEITHER HAS THE OFFICIAL 1059FORECAST. 1060 1061FORECAST POSITIONS AND MAX WINDS 1062 1063INITIAL 01/1500Z 23.0N 72.9W 50 KT 106412HR VT 02/0000Z 22.8N 73.3W 55 KT 106524HR VT 02/1200Z 22.7N 73.7W 55 KT 106636HR VT 03/0000Z 22.9N 74.1W 60 KT 106748HR VT 03/1200Z 23.7N 74.9W 65 KT 106872HR VT 04/1200Z 26.5N 77.5W 70 KT 106996HR VT 05/1200Z 30.5N 80.5W 70 KT 1070120HR VT 06/1200Z 36.5N 82.0W 35 KT...INLAND 1071 1072$$ 1073FORECASTER RHOME/AVILA 1074 1075 1076 1077000 1078 1079WTNT43 KNHC 011732 1080TCDAT3 1081HURRICANE HANNA SPECIAL DISCUSSION NUMBER 19 1082NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1083130 PM EDT MON SEP 01 2008 1084 1085THIS SPECIAL ADVISORY IS TO UPDATE THE INTENSITY OF HANNA. DATA 1086FROM THE AIR FORCE RECONNAISSANCE AIRCRAFT INDICATE THAT HANNA IS 1087NOW A HURRICANE WITH 65 KT WINDS. THE INTENSITY HAS BEEN ADJUSTED 1088UPWARD AT ALL FORECAST TIMES. THE TRACK HAS ALSO BEEN SLIGHTLY 1089ADJUSTED BASED ON THE LATEST FIX. THIS SPECIAL ADVISORY SUPERSEDES 1090THE INTERMEDIATE ADVISORY. 1091 1092 1093FORECAST POSITIONS AND MAX WINDS 1094 1095INITIAL 01/1730Z 22.4N 72.6W 65 KT 109612HR VT 02/0000Z 22.4N 73.3W 70 KT 109724HR VT 02/1200Z 22.5N 73.7W 70 KT 109836HR VT 03/0000Z 22.8N 74.2W 70 KT 109948HR VT 03/1200Z 23.7N 74.9W 75 KT 110072HR VT 04/1200Z 26.5N 77.5W 80 KT 110196HR VT 05/1200Z 30.5N 80.5W 80 KT 1102120HR VT 06/1200Z 36.5N 82.0W 30 KT...INLAND 1103 1104$$ 1105FORECASTER RHOME/AVILA 1106 1107 1108 1109 1110WTNT43 KNHC 012050 1111TCDAT3 1112HURRICANE HANNA DISCUSSION NUMBER 20 1113NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1114500 PM EDT MON SEP 01 2008 1115 1116THE AIR FORCE RECONNAISSANCE AIRCRAFT RECENTLY FOUND A CENTRAL 1117PRESSURE OF 983 MB AND A PEAK FLIGHT LEVEL WIND OF 89 KT. THESE 1118NUMBERS INDICATE HANNA HAS CONTINUED TO STRENGTHEN IN THE FACE OF 1119WHAT APPEARS TO BE STRONG NORTHERLY SHEAR...AND THE INITIAL 1120INTENSITY IS INCREASED TO 70 KT. THE INTENSITY FORECAST REMAINS 1121DIFFICULT SINCE GLOBAL MODES SHOW THE SHEAR REMAINING STRONG OR 1122POSSIBLY INCREASING DURING THE NEXT COUPLE OF DAYS. GIVEN HANNA'S 1123TENACITY THUS FAR...THE OFFICIAL FORECAST PRESUMES THAT HANNA WILL 1124BE ABLE TO FIGHT OFF THE SHEAR. AT DAY 5...HANNA IS FORECAST TO BE 1125INLAND SO WEAKENING IS SHOWN. 1126 1127THE LAST FEW FIXES FROM THE AIRCRAFT INDICATE THAT HANNA HAS BEEN 1128MEANDERING. HOWEVER...A 12-HOUR AVERAGE MOTION IS SOUTH- 1129SOUTHWESTWARD AT ABOUT 4 KT AND THIS WILL BE THE INITIAL MOTION 1130ESTIMATE. WITH THE SUBTROPICAL RIDGE NORTH OF HANNA NOW 1131DISSIPATED...THE CYCLONE'S MOTION DURING THE NEXT COUPLE OF DAYS IS 1132EXPECTED TO BE SLOW AND POSSIBLY ERRATIC. AFTER THAT...GLOBAL 1133MODELS SHOW THE SUBTROPICAL RIDGE BUILDING BACK OVER THE 1134WEST-CENTRAL ATLANTIC...AND THIS SHOULD CAUSE HANNA TO TURN 1135NORTHWEST WITH AN INCREASE IN FORWARD SPEED. THERE IS STILL SOME 1136SPREAD AMONG THE VARIOUS TRACK MODELS WITH POTENTIAL AREAS OF 1137IMPACT RANGING FROM SOUTH FLORIDA THROUGH THE CAROLINAS. UNTIL 1138HANNA TAKES A MORE DEFINITIVE MOTION...IT WILL BE DIFFICULT TO BE 1139MORE SPECIFIC ABOUT THE POTENTIAL THREAT AREA. ALL INTERESTS ALONG 1140THE SOUTHEASTERN UNITED STATES COASTS SHOULD MONITOR THE PROGRESS 1141OF THIS SYSTEM. 1142 1143FORECAST POSITIONS AND MAX WINDS 1144 1145INITIAL 01/2100Z 22.2N 72.6W 70 KT 114612HR VT 02/0600Z 21.9N 72.9W 75 KT 114724HR VT 02/1800Z 21.8N 73.5W 75 KT 114836HR VT 03/0600Z 22.1N 73.9W 75 KT 114948HR VT 03/1800Z 23.1N 74.5W 75 KT 115072HR VT 04/1800Z 27.0N 78.0W 85 KT 115196HR VT 05/1800Z 31.5N 81.0W 85 KT 1152120HR VT 06/1800Z 39.0N 80.5W 25 KT...INLAND 1153 1154$$ 1155FORECASTER RHOME/AVILA 1156 1157 1158 1159000 1160 1161WTNT43 KNHC 020257 1162TCDAT3 1163HURRICANE HANNA DISCUSSION NUMBER 21 1164NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 11651100 PM EDT MON SEP 01 2008 1166 1167WHILE THE AREAL COVERAGE OF DEEP CONVECTION HAS DECREASED OVER THE 1168PAST COUPLE OF HOURS...WHAT'S LEFT SHOWS GOOD BANDING IN AGREEMENT 1169WITH RECENT MICROWAVE IMAGERY. THE PINE CAY SURFACE STATION IN THE 1170CAICOS ISLAND SUGGESTS THAT THE PRESSURE HAS FALLEN TO ABOUT 978 1171MB. THE NORTHERLY FLOW ALOFT...ASSOCIATED WITH THE OUTFLOW FROM 1172GUSTAV...IS CLEARLY NOT MAKING IT INTO THE CENTER OF THE TROPICAL 1173CYCLONE. EVEN SO...ONLY MODEST CHANGES IN INTENSITY ARE 1174ANTICIPATED OVER THE NEXT 24-36 HOURS UNTIL THE UPPER FLOW BEGINS 1175TO REVERSE WHEN MID- TO UPPER-LEVEL RIDGING BUILDS IN OVER THE 1176WESTERN ATLANTIC. THERE IS GOOD AGREEMENT AMONG THE GLOBAL MODELS 1177ON THIS EVOLUTION...WHICH SHOULD CREATE A MORE FAVORABLE PATTERN 1178FOR INTENSIFICATION. THE OFFICIAL INTENSITY FORECAST LIES A LITTLE 1179ABOVE THE PREVIOUS ONE...AND IS CLOSE TO A BLEND OF THE 1180GFDL/HWRF/SHIPS/LGEM GUIDANCE...WITH THE DYNAMICAL MODELS A LITTLE 1181HIGHER AND THE STATISTICAL MODELS A LITTLE LOWER. ONE SHOULD NOT 1182INTERPOLATE A PRESUMED LANDFALL INTENSITY FROM THE 72 AND 96 HOUR 1183FORECAST POINTS...AS SOME ADDITIONAL STRENGTHENING COULD OCCUR 1184BETWEEN 72 HOURS AND LANDFALL. 1185 1186THERE HAS BEEN NO AIRCRAFT RECONNAISSANCE THIS EVENING AND PRECISE 1187LOCATION OF THE CENTER IS DIFFICULT. IT APPEARS THAT THE CENTER 1188HAS BEEN MEANDERING...FIRST APPROACHING THE STATION AT PINE CAY BUT 1189IN RECENT HOURS MOVING AWAY AS THE WINDS AT THAT STATION HAVE 1190INCREASED TO 58 MPH IN THE LAST HOUR. WITH NO DEFINITIVE TREND YET 1191ESTABLISHED...THE INITIAL MOTION IS ESTIMATED TO BE STATIONARY. 1192HANNA IS CURRENTLY BLOCKED BY HIGH PRESSURE EXTENDING SOUTHWARD 1193FROM THE GREAT LAKES...BUT THIS FEATURE IS FORECAST BY THE GLOBAL 1194MODELS TO WEAKEN AND SHIFT EASTWARD. AS HIGH PRESSURE DEVELOPS 1195OVER THE WESTERN ATLANTIC OVER THE NEXT 2 TO 3 DAYS...A 1196NORTHWESTWARD TRACK FOR HANNA IS EXPECTED TO DEVELOP. WITH THE 1197EXCEPTION OF THE UKMET...THE MODEL GUIDANCE IS REMARKABLY WELL 1198CLUSTERED. THE OFFICIAL FORECAST IS ADJUSTED SLIGHTLY TO THE EAST 1199OF THE PREVIOUS ADVISORY AND IS ONLY SLIGHTLY TO THE LEFT OF THE 1200GFS...GFDL...AND HWRF. THE UKMET STILL IS THE LEFT-MOST 1201OUTLIER...SHOWING MORE OF A SOUTHWESTWARD MOTION INITIALLY AND A 1202TRACK CLOSER TO THE FLORIDA PENINSULA...ALTHOUGH IT IS WORTH NOTING 1203THAT THE 18Z UKMET SHOWS LESS OF THIS INITIAL SOUTHWESTWARD JUMP 1204THAN THE FULL RUN FROM 12Z. 1205 1206 1207FORECAST POSITIONS AND MAX WINDS 1208 1209INITIAL 02/0300Z 21.8N 72.5W 70 KT 121012HR VT 02/1200Z 21.8N 72.8W 75 KT 121124HR VT 03/0000Z 22.0N 73.3W 75 KT 121236HR VT 03/1200Z 22.8N 74.0W 80 KT 121348HR VT 04/0000Z 24.0N 75.0W 85 KT 121472HR VT 05/0000Z 28.0N 78.0W 90 KT 121596HR VT 06/0000Z 34.0N 80.5W 65 KT...INLAND 1216120HR VT 07/0000Z 41.5N 77.0W 30 KT...REMNANT LOW 1217 1218$$ 1219FORECASTER FRANKLIN 1220 1221 1222 1223 1224WTNT43 KNHC 020859 1225TCDAT3 1226HURRICANE HANNA DISCUSSION NUMBER 22 1227NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1228500 AM EDT TUE SEP 02 2008 1229 1230CONVENTIONAL AND PASSIVE MICROWAVE SATELLITE IMAGERY INDICATE HANNA 1231HAS MOVED SOUTHWARD OVER THE PAST 6 HOURS WHILE MAINTAINING A 1232PRONOUNCED EYE FEATURE IN A 02/203Z AMSU OVERPASS. SATELLITE 1233INTENSITY ESTIMATES ARE T4.0/65 KT AND T4.5/77 KT FROM TAFB AND 1234SAB...RESPECTIVELY. THEREFORE...THE INITIAL INTENSITY REMAINS 1235UNCHANGED AT 70 KT FOR THIS ADVISORY. 1236 1237THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 270/02 KT. LATEST 1238SATELLITE POSITION ESTIMATES SUGGEST THAT HANNA COULD STILL BE 1239MOVING SOUTHWARD. HOWEVER...ALL OF THE GLOBAL MODELS ARE NOW IN 1240EXCELLENT AGREEMENT THAT AN UPPER-LEVEL LOW WILL PINCH OFF TO THE 1241SOUTH AND WEST OF HANNA DURING THE NEXT 24-36 HOURS...WHICH IS 1242EXPECTED TO INDUCE A SLOW NORTH AND THEN NORTHWESTWARD MOTION 1243ACROSS THE SOUTHEASTERN BAHAMAS. BY 48-72 HOURS...THE SUBTROPICAL 1244RIDGE TO THE NORTHEAST OF HANNA IS FORECAST TO GRADUALLY BUILD 1245WESTWARD THROUGH 96 HOURS...WHICH SHOULD INDUCE A FASTER FORWARD 1246NORTHWESTWARD MOTION TOWARD THE SOUTHEASTERN UNITED STATES. THE 1247RIDGE AXIS IS FORECAST BY ALL THE MODELS TO GENERALLY EXTEND 1248EAST-WEST BETWEEN 32-24N LATITUDE...AND THE EXACT TRACK OF HANNA 1249WILL DEPEND HEAVILY ON HOW FAR SOUTH AND WEST THE CYCLONE MOVES 1250DURING THE NEXT 36 HOURS...AND ALSO HOW STRONG THE WESTERN PORTION 1251OF THE RIDGE WILL BE. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE 1252PREVIOUS ADVISORY AND IS DOWN THE MIDDLE OF THE TIGHTLY CLUSTERED 1253NHC MODEL GUIDANCE SUITE. HANNA IS FORECAST TO MOVE NORTHWESTWARD 1254UNTIL IT REACHES THE COAST OF SOUTH CAROLINA...AFTER WHICH IT IS 1255EXPECTED TO GRADUALLY RECURVE TO THE NORTHEAST. AN APPROXIMATE 125684-HOUR POSITION WOULD BE NEAR 31.3N 80.2W. 1257 1258HANNA HAS MAINTAINED A WELL-DEFINED INNER-CORE STRUCTURE BASED ON 1259THE 0202Z AMSU OVERPASS...AND ANOTHER CDO FEATURE WITH CLOUD TOPS 1260AS COLD OF -80C TO -87C HAS REDEVELOPED OVER THE CENTER SIMILAR TO 1261THE THIS TIME LAST NIGHT. THE CURRENT 30-KT NORTHERLY SHEAR PATTERN 1262IS FORECAST BY ALL THE MODELS TO BEGIN TO WEAKEN TODAY AND CONTINUE 1263TO WEAKEN DURING THE NEXT 48 HOURS...AND GRADUALLY SWITCH TO A 1264SOUTHEASTERLY COMPONENT WITH LESS THAN 15 KT OF SHEAR AT 72-96 1265HOURS. GIVEN THE DEVELOPMENT OF A FAVORABLE UPPER-LEVEL OUTFLOW 1266PATTERN AND SSTS OF AT LEAST 28C ALONG THE FORECAST TRACK UNTIL 1267LANDFALL...STEADY INTENSIFICATION SEEMS QUITE REASONABLE. THE 1268OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY 1269...AND IS SIMILAR TO THE SHIPS MODEL. IT IS IMPORTANT TO NOTE THAT 1270HANNA IS EXPECTED TO CONTINUE TO INTENSIFY...OR AT LEAST REMAIN 1271STEADY...UNTIL LANDFALL OCCURS BETWEEN 84 AND 96 HOURS...RATHER 1272THAN APPEAR TO BE WEAKENING LIKE SOME AUTOMATIC INTENSITY PLOTTING 1273SOFTWARE MAY SHOW. IN FACT...BY 84 HOURS HANNA COULD BE A MAJOR 1274HURRICANE. 1275 1276FORECAST POSITIONS AND MAX WINDS 1277 1278INITIAL 02/0900Z 21.3N 72.7W 70 KT 127912HR VT 02/1800Z 21.4N 73.1W 70 KT 128024HR VT 03/0600Z 22.0N 73.5W 75 KT 128136HR VT 03/1800Z 23.0N 74.3W 80 KT 128248HR VT 04/0600Z 24.4N 75.5W 85 KT 128372HR VT 05/0600Z 28.7N 79.0W 90 KT 128496HR VT 06/0600Z 34.7N 80.7W 55 KT...INLAND 1285120HR VT 07/0600Z 42.5N 74.0W 35 KT...EXTRATROPICAL INLAND 1286 1287$$ 1288FORECASTER STEWART 1289 1290 1291 1292 1293WTNT43 KNHC 021455 1294TCDAT3 1295TROPICAL STORM HANNA DISCUSSION NUMBER 23 1296NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 12971100 AM EDT TUE SEP 02 2008 1298 1299HANNA HAS FINALLY SUCCUMBED TO THE STRONG VERTICAL SHEAR WITH 1300VISIBLE SATELLITE IMAGERY SHOWING A PARTIALLY EXPOSED LOW-LEVEL 1301CIRCULATION AND A SHRINKING CDO FEATURE. THE INITIAL INTENSITY IS 1302SET AT 60 KT...BUT GIVEN THE CURRENT SATELLITE PRESENTATION...THIS 1303MIGHT BE A BIT GENEROUS. AN AIR FORCE RECONNAISSANCE AIRCRAFT WILL 1304INVESTIGATE HANNA THIS AFTERNOON AND PROVIDE A BETTER INTENSITY 1305ESTIMATE. WATER VAPOR IMAGERY SHOWS A SHARP EDGE OR DEFORMATION 1306AXIS ON THE NORTH SIDE OF THE CIRRUS CANOPY SUGGESTING THAT THE 1307SHEAR WILL PERSIST IN THE SHORT-TERM...AND SOME ADDITIONAL 1308WEAKENING IS POSSIBLE TODAY AND TONIGHT. IN ABOUT 24 1309HOURS...GLOBAL MODELS SHOW THE SHEAR WEAKENING AND THIS COULD ALLOW 1310HANNA TO RESTRENGTHEN. HOWEVER...GIVEN THE PRESENT LACK OF 1311ORGANIZATION...IT IS DIFFICULT TO KNOW HOW MUCH STRENGTHENING IS 1312POSSIBLE. THE NEW OFFICIAL FORECAST IS LOWER THAN THE PREVIOUS 1313ADVISORY BUT SHOWS HANNA BECOMING A CATEGORY ONE HURRICANE IN ABOUT 131436 HOURS. IT SHOULD BE NOTED THAT THIS IS A LOW CONFIDENCE 1315FORECAST. IN FACT...IF ONE CONSULTS THE WIND SPEED PROBABILITY 1316PRODUCT INCLUDED IN THIS PACKAGE...IT CAN BE SEEN THAT THERE IS 1317NEARLY AN EQUAL PROBABILITY OF HANNA BEING A TROPICAL STORM OR 1318HURRICANE AT DAY 3. 1319 1320HANNA CONTINUES TO MEANDER BUT THE BEST ESTIMATE OF AN INITIAL 1321MOTION IS 250/05. SLOW AND ERRATIC MOTION IS EXPECTED TODAY BUT 1322HANNA SHOULD START MOVING NORTHWESTWARD TONIGHT OR TOMORROW AS A 1323LARGE MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC LIFTS NORTHWARD 1324AND THE SUBTROPICAL RIDGE BUILDS BACK IN. HANNA SHOULD ACCELERATE 1325NORTHWESTWARD AT DAYS 2 TO 3 AS THE RIDGE STRENGTHENS. DYNAMICAL 1326TRACK MODELS HAVE SHIFTED A LITTLE TO THE WEST AND THE NEW OFFICIAL 1327FORECAST FOLLOWS SUIT. ON THE FORECAST TRACK...HANNA IS EXPECTED TO 1328APPROACH THE EAST COAST OF FLORIDA... GEORGIA...OR SOUTH CAROLINA 1329IN 2 TO 3 DAYS. IT SHOULD BE STRESSED THAT THE EXPECTED ANGLE OF 1330APPROACH AND TRACK UNCERTAINTY MAKE IT IMPOSSIBLE TO NARROW DOWN 1331THE POTENTIAL IMPACT AREA. INTERESTS IN THE NORTHWESTERN BAHAMAS 1332AND ALONG THE ENTIRE SOUTHEASTERN UNITED STATES COAST SHOULD 1333CLOSELY MONITOR THE PROGRESS OF THIS SYSTEM. 1334 1335FORECAST POSITIONS AND MAX WINDS 1336 1337INITIAL 02/1500Z 21.0N 73.5W 60 KT 133812HR VT 03/0000Z 21.4N 73.7W 55 KT 133924HR VT 03/1200Z 22.3N 74.2W 60 KT 134036HR VT 04/0000Z 23.6N 75.3W 65 KT 134148HR VT 04/1200Z 25.1N 76.8W 70 KT 134272HR VT 05/1200Z 29.5N 80.5W 75 KT 134396HR VT 06/1200Z 36.5N 80.0W 35 KT...INLAND 1344120HR VT 07/1200Z 45.5N 70.0W 25 KT...INLAND REMNANT LOW 1345 1346$$ 1347FORECASTER RHOME/KNABB 1348 1349 1350 1351000 1352 1353WTNT43 KNHC 022056 1354TCDAT3 1355TROPICAL STORM HANNA DISCUSSION NUMBER 24 1356NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1357500 PM EDT TUE SEP 02 2008 1358 1359AN AIR FORCE RECONNAISSANCE AIRCRAFT CURRENTLY INVESTIGATING HANNA 1360CONFIRMS THAT THE SYSTEM HAS WEAKENED. THE PEAK FLIGHT-LEVEL WIND 1361AT 850 MB WAS 66 KT WHICH CORRESPONDS TO ABOUT 55 KT AT THE 1362SURFACE. HANNA WILL CONTINUE TO ENCOUNTER STRONG SHEAR FOR ANOTHER 136312-24 HOURS WHICH SHOULD LIMIT STRENGTHENING IN THE SHORT TERM. BY 1364TOMORROW...GLOBAL MODELS FORECAST AN UPPER-LEVEL LOW TO CUT OFF 1365JUST WEST OF HANNA AND THEN DROP SOUTHWARD DURING THE NEXT FEW 1366DAYS. IF THIS EVOLUTION MATERIALIZES...AND ASSUMING HANNA IS ABLE 1367TO FIGHT OFF THE SHEAR...THE ENVIRONMENT WOULD GRADUALLY BECOME 1368MORE FAVORABLE FOR STRENGTHENING. THE OFFICIAL INTENSITY FORECAST 1369CALLS FOR HANNA TO REGAIN HURRICANE STRENGTH IN A DAY OR SO...IN 1370LINE WITH NEARLY ALL OF THE AVAILABLE INTENSITY MODELS. 1371HOWEVER...THE EVOLUTION OF THE LARGE-SCALE ENVIRONMENT OVER THE 1372NEXT DAY OR SO IS COMPLEX...WHICH RESULTS IN LOWER THAN NORMAL 1373CONFIDENCE IN THE INTENSITY FORECAST. 1374 1375THE LAST FEW AIRCRAFT FIXES INDICATE THAT HANNA CONTINUES TO DRIFT 1376SOUTHEASTWARD WITH AN INITIAL MOTION ESTIMATE OF 150/02. TRACK 1377MODELS INSIST THAT HANNA WILL START ITS MUCH-ANTICIPATED TURN 1378TOWARD THE NORTHWEST SOON...AS A LARGE MID-LATITUDE TROUGH OVER THE 1379WESTERN ATLANTIC LIFTS NORTHWARD AND THE SUBTROPICAL RIDGE BUILDS 1380BACK IN. SUCH A TRACK WOULD TAKE THE CYCLONE NORTHWESTWARD THROUGH 1381THE CENTRAL AND NORTHWESTERN BAHAMAS DURING THE NEXT TWO DAYS. 1382HANNA IS THEN EXPECTED TO ACCELERATE AS IT MAKES ITS APPROACH TO 1383THE SOUTHEASTERN UNITED STATES. HOWEVER...UNTIL HANNA BEGINS A 1384MORE DEFINITIVE MOTION...IT WILL BE DIFFICULT TO NARROW THE 1385POTENTIAL IMPACT AREA. IN ADDITION...THE ANTICIPATED ANGLE OF 1386APPROACH TO THE SOUTHEAST UNITED STATES COAST MEANS THAN ONLY A 1387SMALL DEVIATION LEFT OR RIGHT OF THE TRACK WILL HAVE LARGE 1388IMPLICATIONS IN BOTH TIME AND LOCATION OF LANDFALL. IN FACT...THE 1389WIND SPEED PROBABILITY PRODUCT INCLUDED WITH THIS ADVISORY PACKAGE 1390SHOWS THAT THE CHANCES OF HURRICANE-FORCE WINDS ARE ABOUT EQUAL AT 1391EACH SPECIFIC LOCATION ALONG THE COAST FROM FLORIDA THROUGH THE 1392CAROLINAS. 1393 1394FORECAST POSITIONS AND MAX WINDS 1395 1396INITIAL 02/2100Z 20.4N 72.7W 55 KT 139712HR VT 03/0600Z 20.9N 73.1W 55 KT 139824HR VT 03/1800Z 22.2N 74.0W 60 KT 139936HR VT 04/0600Z 23.5N 75.5W 65 KT 140048HR VT 04/1800Z 25.4N 77.2W 70 KT 140172HR VT 05/1800Z 30.5N 80.5W 70 KT 140296HR VT 06/1800Z 38.0N 78.0W 30 KT...INLAND 1403120HR VT 07/1800Z 47.0N 66.0W 25 KT...REMNANT LOW 1404 1405$$ 1406FORECASTER RHOME/KNABB 1407 1408 1409 1410 1411WTNT43 KNHC 030256 1412TCDAT3 1413TROPICAL STORM HANNA DISCUSSION NUMBER 25 1414NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 14151100 PM EDT TUE SEP 02 2008 1416 1417THE LAST COUPLE OF FIXES FROM THE RECONNAISSANCE AIRCRAFT 1418INDICATED THAT HANNA WAS MOVING SLOWLY EASTWARD. IT SEEMS THAT 1419HANNA IS MAKING A SMALL COUNTER-CLOCKWISE LOOP BETWEEN HISPANIOLA 1420AND THE SOUTHEASTERN BAHAMAS. I HAVE TO GIVE SOME CREDIT TO THE 1421GFDL AND HWRF MODELS WHICH PREDICTED THIS LOOP A FEW DAYS AGO... 1422HOWEVER THEY INDICATED THAT HANNA WOULD BE A LITTLE FURTHER NORTH 1423WHEN IT OCCURRED. SINCE THE AIRCRAFT DEPARTED HANNA THE CLOUD 1424PATTERN HAS CONTINUED TO DEGRADE...AND IT IS POSSIBLE THAT HANNA 1425HAS WEAKENED EVEN MORE. HOWEVER...WE WILL KEEP THE INITIAL 1426INTENSITY AT 55 KT SINCE ANOTHER AIRCRAFT IS SCHEDULED TO 1427INVESTIGATE THE STORM AROUND 0600 UTC. 1428 1429STRONG NORTHWESTERLY UPPER-LEVEL WINDS CONTINUE TO SHEAR HANNA. 1430BUT...THE GLOBAL MODELS FORECAST AN UPPER-LEVEL LOW TO CUT-OFF TO 1431THE NORTHWEST OF HANNA VERY SOON...AND THERE IS SOME EVIDENCE IN 1432WATER VAPOR IMAGERY THAT THIS IS BEGINNING TO OCCUR. AS THE 1433UPPER-LOW CUTS-OFF IT IS FORECAST TO DROP SOUTHWARD WHICH SHOULD 1434TURN THE UPPER-FLOW OVER THE STORM FROM THE SOUTH AND SOUTHEAST... 1435WHICH WOULD BE MORE FAVORABLE FOR STRENGTHENING DURING THE NEXT 1436COUPLE OF DAYS. THE NEW INTENSITY FORECAST IS SIMILAR TO THE 1437PREVIOUS ADVISORY AND IS CLOSE TO THE CONSENSUS OF THE GUIDANCE. AT 143896 HOURS...HANNA WAS MAINTAINED AS A TROPICAL STORM...BECAUSE IT IS 1439PREDICTED TO BE FAIRLY CLOSE TO THE COAST OF THE NORTHEAST UNITED 1440STATES AND THERE COULD STILL BE TROPICAL STORM FORCE WINDS OVER 1441WATER AT THAT TIME. 1442 1443THE TRACK MODELS SUGGEST THAT HANNA WILL BEGIN MOVING NORTHWESTWARD 1444VERY SOON AS THE LARGE UPPER-LEVEL TROUGH OFF THE NORTHEAST UNITED 1445STATES COAST LIFTS NORTHWARD...ALLOWING THE SUBTROPICAL RIDGE OVER 1446THE ATLANTIC TO BUILD WESTWARD. THIS PATTERN IS FORECAST TO STEER 1447HANNA ON A GENERAL NORTHWESTWARD MOTION WITH SOME INCREASE IN 1448FORWARD SPEED OVER THE NEXT COUPLE OF DAYS. SOME OF THE TRACK 1449MODELS HAVE SHIFTED A LITTLE EASTWARD...BUT NOT ENOUGH TO WARRANT A 1450CHANGE TO THE OFFICIAL FORECAST. THE NEW TRACK HAS BEEN ADJUSTED 1451EASTWARD DURING THE FIRST 24-36 HOURS DUE TO THE MORE EASTWARD 1452INITIAL LOCATION...BUT THEREAFTER IT REMAINS VERY CLOSE TO THE 1453PREVIOUS ADVISORY. AS A REMINDER...ONE SHOULD NOT FOCUS ON THE 1454EXACT TRACK AS SMALL DEVIATIONS LEFT OR RIGHT WOULD HAVE LARGE 1455IMPLICATIONS ON BOTH THE TIME AND LOCATION OF LANDFALL. A G-IV 1456MISSION WAS FLOWN THIS EVENING AND THE DATA GATHERED BY THIS 1457AIRCRAFT SHOULD GET ASSIMILATED INTO THE 0000 UTC MODEL GUIDANCE. 1458 1459FORECAST POSITIONS AND MAX WINDS 1460 1461INITIAL 03/0300Z 20.5N 72.4W 55 KT 146212HR VT 03/1200Z 21.3N 72.3W 55 KT 146324HR VT 04/0000Z 22.8N 73.6W 60 KT 146436HR VT 04/1200Z 24.4N 75.5W 65 KT 146548HR VT 05/0000Z 26.4N 77.4W 70 KT 146672HR VT 06/0000Z 32.5N 80.5W 75 KT...INLAND 146796HR VT 07/0000Z 41.0N 75.5W 35 KT...INLAND 1468120HR VT 08/0000Z 50.0N 60.0W 35 KT...EXTRATROPICAL 1469 1470$$ 1471FORECASTER BROWN/AVILA 1472 1473 1474 1475 1476WTNT43 KNHC 030843 1477TCDAT3 1478TROPICAL STORM HANNA DISCUSSION NUMBER 26 1479NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1480500 AM EDT WED SEP 03 2008 1481 1482FIXES FROM AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT 1483INDICATE HANNA HAS ALMOST COMPLETED A TIGHT CYCLONIC LOOP AND IS 1484NOW POSSIBLY TURNING SLOWLY NORTHWARD. THE INITIAL INTENSITY WAS 1485DECREASED TO COME MORE IN LINE WITH THE CENTRAL PRESSURE...WHICH IS 1486ESTIMATED TO BE 993 MB BASED ON A DROPSONDE REPORT THAT ALSO 1487MEASURED 25-KT SURFACE WINDS. 1488 1489THE INITIAL MOTION ESTIMATE IS 360/02. THERE IS NO SIGNIFICANT 1490CHANGE TO THE PREVIOUS TRACK OR INTENSITY FORECAST REASONINGS. 1491HANNA IS EXPECTED TO GRADUALLY ACCELERATE NORTHWESTWARD OVER THE 1492NEXT 72 HOURS AND MAKE LANDFALL OVER THE SOUTHEASTERN UNITED STATES 1493...POSSIBLY IN THE SOUTH CAROLINA AREA. IT IS WORTH MENTIONING THAT 1494THE 00Z MODEL RUNS CONTAINED UPPER-AIR DATA FROM DROPSONDES 1495RELEASED AROUND HANNAFROM THE NOAA GULFSTREAM-IV JET AIRCRAFT... 1496WHICH USUALLY PRODUCES BETTER TRACK FORECASTS. THE OFFICIAL 1497FORECAST IS SIMILAR TO THE PREVIOUS TRACK AND IS CLOSE TO THE NHC 1498MODEL CONSENSUS. 1499 1500THE INTENSITY FORECAST BASICALLY REMAINS UNCHANGED AND FOLLOWS THE 1501SHIPS INTENSITY MODEL...WITH HANNA EXPECTED TO REGAIN HURRICANE 1502STATUS BY 36 HOURS AND CONTINUE TO INTENSIFY UNTIL LANDFALL OCCURS. 1503 1504FORECAST POSITIONS AND MAX WINDS 1505 1506INITIAL 03/0900Z 20.2N 72.2W 50 KT 150712HR VT 03/1800Z 21.5N 72.8W 55 KT 150824HR VT 04/0600Z 23.2N 74.1W 60 KT 150936HR VT 04/1800Z 24.8N 76.0W 65 KT 151048HR VT 05/0600Z 27.2N 78.1W 75 KT 151172HR VT 06/0600Z 33.7N 80.0W 70 KT...INLAND 151296HR VT 07/0600Z 42.5N 71.5W 35 KT...EXTRATROPICAL INLAND 1513120HR VT 08/0600Z 51.0N 55.0W 35 KT...EXTRATROPICAL INLAND 1514 1515$$ 1516FORECASTER STEWART 1517 1518 1519 1520 1521WTNT43 KNHC 031500 1522TCDAT3 1523TROPICAL STORM HANNA DISCUSSION NUMBER 27 1524NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 15251100 AM EDT WED SEP 03 2008 1526 1527THERE HAVE BEEN SOME STRUCTURAL CHANGES WITH HANNA TODAY AS IT 1528INTERACTS WITH THE UPPER-LEVEL LOW MOVING THROUGH THE NORTHWESTERN 1529BAHAMAS. THE WIND FIELD HAS EXPANDED IN THE NORTHERN SEMICIRCLE 1530AND THE LOW-LEVEL CIRCULATION CENTER HAS BECOME LESS WELL DEFINED. 1531VISIBLE IMAGERY SUGGESTS MULTIPLE LOW-LEVEL SWIRLS COMING OUT OF 1532THE DEEP CONVECTION TO THE NORTH OF A MEAN CENTER...AND THE 1533SYSTEM'S CONVECTIVE BANDS ARE WELL REMOVED FROM THE CORE. THE 1534RECONNAISSANCE MISSION THAT ENDED AROUND 12Z REPORTED SOME SFMR 1535WINDS OF UP TO 45 KT ABOUT 70 NM FROM THE CENTER...AND THE INITIAL 1536INTENSITY ESTIMATE REMAINS 50 KT. 1537 1538BECAUSE THE CENTER IS NOT WELL DEFINED...THE INTIAL MOTION IS HARD 1539TO GAUGE. MY BEST ESTIMATE IS 360/5...AND THIS COULD BE THE START 1540OF THE EXPECTED NORTHWESTWARD TURN. THE STEERING FLOW SHOULD 1541BECOME BETTER DEFINED OVER THE NEXT 24-48 HOURS AS THE UPPER LOW 1542MOVES WEST-SOUTHWESTWARD AND MID-LEVEL RIDGING BUILDS IN BEHIND THE 1543LARGE DEEP-LAYER LOW OFF THE UPPER U.S. EAST COAST. MODEL GUIDANCE 1544RESPONDS TO THIS PATTERN WITH A NORTHWESTWARD ACCELERATION WITH A 1545RECURVATURE AROUND THE MID-LEVEL RIDGE IN ABOUT THREE DAYS. THE 1546GUIDANCE HAS BEEN TOO FAST WITH THIS SCENARIO OVER THE PAST COUPLE 1547OF DAYS...AND GIVEN THE POOR CORE STRUCTURE OF HANNA I AM INCLINED 1548TO THINK THAT SUBSEQUENT INTERACTION WITH THE UPPER STEERING MAY BE 1549A LITTLE OVERDONE...AT LEAST INITIALLY. THE OFFICIAL FORECAST IS 1550IN BEST AGREEMENT WITH THE ECMWF AND UKMET IN TERMS OF SPEED...WITH 1551THE GFS/HWRF/GFDL SHOWING A MORE VERTICAL SYSTEM MOVING MORE 1552RAPIDLY. THE GUIDANCE HAS ALSO BEEN TRENDING EASTWARD OVER THE 1553PAST FEW CYCLES...AND I HAVE SHIFTED THE TRACK SLIGHTLY IN THAT 1554DIRECTION. 1555 1556WESTERLY SHEAR AND DRY AIR ASSOCIATED WITH THE UPPER LOW WILL 1557INHIBIT DEVELOPMENT IN THE SHORT TERM BUT SHOULD DIMINISH OVER THE 1558NEXT COUPLE OF DAYS...TO BE REPLACED WITH MODERATE SOUTHEASTERLY 1559SHEAR. THIS PATTERN WOULD PERMIT SOME RE-INTENSIFICATION...BUT 1560HANNA WILL NEED TO RECREATE AN INNER CORE IN ORDER TO INTENSIFY 1561SUBSTANTIALLY. THE AVAILABLE GUIDANCE STILL BRINGS HANNA TO 1562MINIMAL HURRICANE INTENSITY AND THE OFFICIAL FORECAST IS JUST ABOVE 1563THIS GUIDANCE. 1564 1565 1566FORECAST POSITIONS AND MAX WINDS 1567 1568INITIAL 03/1500Z 20.6N 71.8W 50 KT 156912HR VT 04/0000Z 21.5N 72.0W 50 KT 157024HR VT 04/1200Z 23.4N 73.3W 55 KT 157136HR VT 05/0000Z 25.2N 75.2W 60 KT 157248HR VT 05/1200Z 27.3N 77.1W 65 KT 157372HR VT 06/1200Z 33.0N 79.0W 70 KT 157496HR VT 07/1200Z 42.0N 71.0W 35 KT...INLAND EXTRATROPICAL 1575120HR VT 08/1200Z 47.0N 60.0W 35 KT...EXTRATROPICAL 1576 1577$$ 1578FORECASTER FRANKLIN 1579 1580 1581 1582000 1583 1584WTNT43 KNHC 032059 1585TCDAT3 1586TROPICAL STORM HANNA DISCUSSION NUMBER 28 1587NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1588500 PM EDT WED SEP 03 2008 1589 1590AN ASCAT PASS FROM 14Z REVEALED THAT THE LOW-LEVEL CIRCULATION OF 1591HANNA WAS BECOMING ELONGATED IN RESPONSE TO THE ASYMMETRIC 1592DISTRIBUTION OF CONVECTION. IN SPITE OF THIS...DATA FROM THE 1593RECONNAISSANCE AIRCRAFT INDICATE THAT HANNA IS BECOMING A LITTLE 1594BETTER ORGANIZED. TROPICAL STORM FORCE WINDS HAVE RETURNED TO THE 1595SOUTHWEST QUADRANT AND THE PRESSURE HAS FALLEN TO 989 MB. THE 1596AIRCRAFT DATA CONTINUE TO SUGGEST THAT THE MAXIMUM WINDS ARE ABOUT 159750 KT. 1598 1599A MORE DEFINITIVE NORTHWARD MOTION HAS COMMENCED...WITH THE INITIAL 1600ESTIMATE BEING 360/10. THE UPPER LOW OFF OF NEW ENGLAND IS 1601BEGINNING TO MOVE OUT...AND AS IT DOES SO MID-LEVEL RIDGING WILL 1602BUILD IN BEHIND IT. HANNA SEEMS TO BE FOLLOWING THE CONVECTION 1603FAIRLY WELL...AND I'VE HAD TO SPEED UP MY PREVIOUS FORECAST A 1604LITTLE BIT. THE OFFICIAL FORECAST IS IN BEST AGREEMENT WITH A 1605BLEND OF THE ECMWF AND THE GFS. THE HWRF AND GFDL CONTINUE TO BE 1606FASTER THAN THE OFFICIAL FORECAST...AND IF HANNA DEVELOPS FASTER 1607THAN SHOWN BELOW ADDITIONAL TIMING ADJUSTMENTS MAY NEED TO BE MADE. 1608IT'S WORTH NOTING THAT CONNECTING THE 48 AND 72 HOUR FORECAST POINTS 1609WITH A STRAIGHT LINE GIVES A MISLEADING UNDERESTIMATE OF THE 1610THREAT TO THE GEORGIA AND SOUTH CAROLINA COASTS. ONLY A GRADUAL 1611RIGHT TURN IS EXPECTED AFTER 48 HOURS. 1612 1613AS THE UPPER LOW IN THE BAHAMAS AND HANNA SEPARATE...THE SOUTHERLY 1614SHEAR OVER THE CYCLONE WILL TURN SOUTHEASTERLY AND LESSEN. THIS IS 1615EXPECTED TO PROVIDE A MORE FAVORABLE ENVIRONMENT FOR 1616STRENGTHENING...ALTHOUGH NONE OF THE OBJECTIVE AIDS SHOWS VERY 1617MUCH. THE SHIPS AND LGEM BRING THE SYSTEM ONLY TO 60 KT...AND THE 1618HWRF NOT QUITE THAT HIGH. THE OFFICIAL FORECAST IS IN GOOD 1619AGREEMENT WITH THE GFDL WHICH BRINGS HANNA TO 70 KT PRIOR TO 1620LANDFALL. 1621 1622 1623FORECAST POSITIONS AND MAX WINDS 1624 1625INITIAL 03/2100Z 21.9N 71.9W 50 KT 162612HR VT 04/0600Z 23.2N 72.7W 55 KT 162724HR VT 04/1800Z 25.2N 74.5W 60 KT 162836HR VT 05/0600Z 27.4N 76.6W 65 KT 162948HR VT 05/1800Z 30.0N 78.5W 70 KT 163072HR VT 06/1800Z 36.8N 76.9W 50 KT...INLAND 163196HR VT 07/1800Z 44.5N 67.0W 35 KT...EXTRATROPICAL 1632120HR VT 08/1800Z 48.0N 55.0W 35 KT...EXTRATROPICAL 1633 1634$$ 1635FORECASTER FRANKLIN 1636 1637 1638 1639 1640WTNT43 KNHC 040254 1641TCDAT3 1642TROPICAL STORM HANNA DISCUSSION NUMBER 29 1643NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 16441100 PM EDT WED SEP 03 2008 1645 1646HANNA HAS BEEN A TENACIOUS TROPICAL CYCLONE. SINCE ITS FORMATION IT 1647HAS FOUGHT TWO UPPER-LEVEL LOWS...STRONG NORTHERLY SHEAR AND THE 1648EFFECTS OF LAND. FURTHERMORE...AT TIMES HANNA HAS RESEMBLED A 1649SUBTROPICAL CYCLONE. SURFACE AND AIRCRAFT OBSERVATIONS TONIGHT 1650CONTINUE TO SHOW THAT HANNA HAS A LARGE CIRCULATION AND SATELLITE 1651IMAGES SUGGEST THAT THE SHEAR IS DECREASING AND HANNA IS DEVELOPING 1652UPPER-LEVEL OUTFLOW. THESE CHANGES IN THE UPPER FLOW OVER HANNA 1653HAVE BEEN ACCURATELY FORECAST BY MOST OF THE NUMERICAL WEATHER 1654PREDICTION MODELS. THE INITIAL INTENSITY IS 55 KNOTS...AND IS 1655BASED ON A 68 KT FLIGHT-LEVEL WIND MEASURED AS THE PLANE DEPARTED 1656THE CYCLONE. WITH THE MORE FAVORABLE UPPER-LEVEL ENVIRONMENT...SOME 1657INTENSIFICATION IS INDICATED IN THE OFFICIAL FORECAST. HANNA IS 1658FORECAST TO REGAIN HURRICANE STATUS IN A DAY OR TWO BUT IT COULD 1659OCCUR EARLIER. NONE OF THE GUIDANCE INTENSIFIES HANNA BEYOND 70 1660KNOTS. 1661 1662THE CENTER HAS BEEN ROTATING AROUND A LARGE CYCLONIC GYRE AND FIXES 1663FROM THE RECONNAISSANCE PLANE AND DATA FROM A NOAA BUOY SUGGEST 1664THAT THE INITIAL MOTION IS 335/11. SOME OF THIS MOTION COULD HAVE 1665RESULTED FROM REFORMATION OF THE CENTER. SINCE THE SUBTROPICAL RIDGE 1666IS EXPANDING TO THE NORTHEAST OF HANNA...A NORTHWEST MOTION SHOULD 1667CONTINUE DURING THE NEXT DAY OR TWO WITH A GRADUAL TURN TO THE 1668NORTH AROUND THE WESTERN EDGE OF THE HIGH. THE TRACK 1669MODELS ARE NOT TIGHTLY CLUSTERED AND THE CONFIDENCE IN THE TRACK 1670FORECAST IS NOT VERY HIGH. HOWEVER...THE MIDDLE OF THE GUIDANCE 1671ENVELOPE HAS HANNA MOVING OVER OR VERY CLOSE TO THE COAST OF THE 1672CAROLINAS. BECAUSE HANNA IS A LARGE CYCLONE...A HURRICANE WATCH 1673WILL LIKELY BE REQUIRED FOR A PORTION OF THE SOUTHEASTERN UNITED 1674STATES COAST EARLY THURSDAY. 1675 1676A NOAA JET HAS SAMPLED THE ENVIRONMENT TONIGHT AND THE DATA IS BEING 1677USED TO INITIALIZE THE 00Z GLOBAL MODEL RUNS. 1678 1679 1680FORECAST POSITIONS AND MAX WINDS 1681 1682INITIAL 04/0300Z 23.2N 72.1W 55 KT 168312HR VT 04/1200Z 24.7N 73.1W 55 KT 168424HR VT 05/0000Z 26.9N 75.0W 60 KT 168536HR VT 05/1200Z 29.3N 77.3W 65 KT 168648HR VT 06/0000Z 32.0N 79.0W 70 KT 168772HR VT 07/0000Z 39.5N 74.0W 50 KT...INLAND 168896HR VT 08/0000Z 46.5N 63.0W 35 KT...EXTRATROPICAL 1689120HR VT 09/0000Z 49.0N 47.0W 35 KT...EXTRATROPICAL 1690 1691$$ 1692FORECASTER AVILA 1693 1694 1695 1696000 1697 1698WTNT43 KNHC 040900 1699TCDAT3 1700TROPICAL STORM HANNA DISCUSSION NUMBER 30 1701NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1702500 AM EDT THU SEP 04 2008 1703 1704LOOKS CAN CERTAINLY BE DECEIVING. HANNA HAS NOT BEEN PRODUCING VERY 1705MUCH DEEP CONVECTION SINCE AN EARLIER STRONG BURST DIED AFTER ABOUT 170604Z...AS THE UPPER-LEVEL LOW TO ITS WEST CONTINUES TO IMPOSE STRONG 1707SOUTHERLY SHEAR. NEVERTHELESS...HANNA HAS A LARGE AND ROBUST 1708CIRCULATION...AND A NOAA RECONNAISSANCE AIRCRAFT HAS RECENTLY 1709REPORTED A MINIMUM CENTRAL PRESSURE OF 990 MB. FLIGHT-LEVEL WINDS 1710AT 850 MB HAVE BEEN AS STRONG AS 65 KT...AND NUMEROUS SFMR VALUES 1711OF 55-60 KT HAVE BEEN RETRIEVED. I HAVE NO GOOD REASON TO DISCOUNT 1712THE SFMR WINDS...SO THE INITIAL INTENSITY IS INCREASED TO 60 KT. 1713GIVEN THAT THE SOUTHERLY SHEAR IS FORECAST BY THE DYNAMICAL MODELS 1714TO PERSIST OVER HANNA EVEN AS IT GAINS LATITUDE DURING THE NEXT 1715COUPLE OF DAYS...STRENGTHENING WOULD AT FIRST GLANCE SEEM UNLIKELY. 1716CONSISTENT WITH THAT THINKING...THE GFDL AND HWRF SHOW LITTLE 1717CHANGE IN STRENGTH OR EVEN SOME WEAKENING...EXCEPT MUCH LATER WHEN 1718HANNA BECOMES AN EXTRATROPICAL CYCLONE. ON THE OTHER HAND...THE 1719SHIPS AND LGEM...DESPITE DIAGNOSING LITTLE CHANGE IN 1720SHEAR...FORECAST A LITTLE STRENGTHENING TO HURRICANE STATUS. A 1721CONSENSUS OF THESE VARIOUS MODELS WOULD YIELD A FLAT 60 KT 1722INTENSITY FORECAST UNTIL HANNA PASSES NEAR OR OVER THE 1723CAROLINAS...BUT FOR CONTINUITY AND SINCE HANNA IS ALREADY PRODUCING 1724WINDS JUST SHY OF HURRICANE STRENGTH....65 KT IS STILL SHOWN 1725EXPLICITLY IN THE FORECAST. GRADUAL WEAKENING IS THEN FORECAST AS 1726HANNA ACCELERATES NORTHEASTWARD AND BECOMES EXTRATROPICAL. 1727 1728DESPITE HAVING AIRCRAFT FIXES...THE INITIAL MOTION IS HARD TO 1729GAGE...PROBABLY DUE TO THE SPRAWLING NATURE OF THE 1730CIRCULATION...BUT THE INITIAL MOTION ESTIMATE IS 320/10. HANNA 1731SHOULD ROUND THE BUILDING WESTERN ATLANTIC RIDGE AND ROUGHLY HUG 1732THE EAST COAST OF THE UNITED STATES...BUT PASSING NEAR OR OVER THE 1733COAST OF THE CAROLINAS ALONG THE WAY. PERHAPS DUE IN PART TO THE 1734BENEFIT OF DATA FROM THE NOAA G-IV JET MISSION LAST NIGHT...THE 1735LATEST MODEL TRACKS HAVE COME INTO A LITTLE TIGHTER AGREEMENT...AND 1736IN GENERAL THEY HAVE SHIFTED SLIGHTLY TO THE LEFT. THE NEW TRACK 1737FORECAST IS SHIFTED JUST SLIGHTLY LEFT OF THE PREVIOUS ONE...TO BE 1738CLOSER TO THE CONSENSUS. AS ALWAYS...ONE SHOULD NOT FOCUS ON THE 1739EXACT FORECAST OF THE CENTER...ESPECIALLY SINCE MUCH OF THE WEATHER 1740ASSOCIATED WITH HANNA IS WELL-REMOVED FROM THE CENTER. 1741 1742 1743FORECAST POSITIONS AND MAX WINDS 1744 1745INITIAL 04/0900Z 24.0N 72.8W 60 KT 174612HR VT 04/1800Z 25.3N 74.1W 60 KT 174724HR VT 05/0600Z 27.5N 76.6W 60 KT 174836HR VT 05/1800Z 30.3N 78.4W 65 KT 174948HR VT 06/0600Z 33.5N 78.4W 65 KT 175072HR VT 07/0600Z 41.0N 72.5W 50 KT...INLAND 175196HR VT 08/0600Z 48.5N 59.0W 45 KT...EXTRATROPICAL 1752120HR VT 09/0600Z 51.5N 41.0W 45 KT...EXTRATROPICAL 1753 1754$$ 1755FORECASTER KNABB 1756 1757 1758 1759 1760WTNT43 KNHC 041450 1761TCDAT3 1762TROPICAL STORM HANNA DISCUSSION NUMBER 31 1763NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 17641100 AM EDT THU SEP 04 2008 1765 1766VERY DRY AIR ASSOCIATED WITH THE UPPER-LEVEL LOW OVER THE 1767NORTHWESTERN BAHAMAS IS CHOKING OFF CONVECTION NEAR THE CORE OF 1768HANNA...AND THE CYCLONE HAS A VERY SUBTROPICAL APPEARANCE. 1769CONVECTION HAS DIMINISHED SUBSTANTIALLY OVER THE PAST 6-12 HOURS 1770AND THE HIGHEST FLIGHT-LEVEL AND SFMR WINDS HAVE COME DOWN AS WELL. 1771BASED ON SOME 52 KT SFMR WINDS AROUND 11Z...THE INITIAL INTENSITY 1772IS LOWERED TO 55 KT. 1773 1774CONDITIONS ARE NOT CONDUCIVE TO STRENGTHENING RIGHT NOW...WITH 1775MODERATE SOUTHERLY SHEAR AND POOR THERMODYNAMICS. THE GFS SUGGESTS 1776THAT DRY AIR IS LIKELY TO CONTINUE TO BE AN ISSUE UP TO LANDFALL. 1777HOWEVER...AS HANNA AND THE UPPER LOW BEGIN TO SEPARATE SOME OF THE 1778GLOBAL MODELS...INCLUDING THE GFS...SUGGEST THAT THE SHEAR WILL 1779LESSEN SOMEWHAT. THIS WOULD ALLOW FOR SOME INTENSIFICATION...AND 1780SO THE OFFICIAL FORECAST CONTINUES TO SHOW HANNA ATTAINING 1781HURRICANE STRENGTH. THIS IS IN GOOD AGREEMENT WITH THE 1782HWRF...ALTHOUGH THE GFDL AND SHIPS GUIDANCE IS LOWER. 1783 1784THE INITIAL MOTION IS 315/10. THE FORECAST SCENARIO IS UNCHANGED 1785FROM PREVIOUS ADVISORIES. MID-LEVEL HIGH PRESSURE IS BUILDING OVER 1786THE WESTERN ATLANTIC AS A DEEP LAYER LOW MOVES AWAY FROM NEW 1787ENGLAND. HANNA IS EXPECTED TO RECURVE AROUND THE PERIPHERY OF THE 1788HIGH AHEAD OF A MID-LATITUDE SHORT WAVE TROUGH IN THE WESTERLIES. 1789MODEL GUIDANCE REMAINS IN FAIRLY GOOD AGREEMENT AND LITTLE CHANGE 1790TO THE FORECAST TRACK IS REQUIRED. THE OFFICIAL FORECAST IS 1791SLIGHTLY TO THE RIGHT OF THE MODEL CONSENSUS BECAUSE THE BETTER 1792PERFORMING MODELS THIS YEAR...NAMELY THE GFS AND GFDL...ARE ON THE 1793RIGHT SIDE OF THE GUIDANCE ENVELOPE. BECAUSE OF THE LARGE... 1794SPRAWLING NATURE OF THE CIRCULATION...THE EXACT TRAJECTORY OF THE 1795CENTER IS RELATIVELY UNIMPORTANT. 1796 1797 1798FORECAST POSITIONS AND MAX WINDS 1799 1800INITIAL 04/1500Z 24.5N 73.5W 55 KT 180112HR VT 05/0000Z 26.2N 75.2W 55 KT 180224HR VT 05/1200Z 28.7N 77.2W 60 KT 180336HR VT 06/0000Z 31.7N 78.2W 65 KT 180448HR VT 06/1200Z 35.4N 77.4W 55 KT 180572HR VT 07/1200Z 43.0N 69.5W 40 KT...INLAND 180696HR VT 08/1200Z 50.0N 54.0W 40 KT...EXTRATROPICAL 1807120HR VT 09/1200Z 51.5N 37.5W 45 KT...EXTRATROPICAL 1808 1809$$ 1810FORECASTER FRANKLIN 1811 1812 1813 1814 1815WTNT43 KNHC 041514 1816TCDAT3 1817TROPICAL STORM HANNA DISCUSSION NUMBER 31...CORRECTED 1818NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 18191100 AM EDT THU SEP 04 2008 1820 1821...CORRECT STATUS AT 48 AND 72 HR... 1822 1823VERY DRY AIR ASSOCIATED WITH THE UPPER-LEVEL LOW OVER THE 1824NORTHWESTERN BAHAMAS IS CHOKING OFF CONVECTION NEAR THE CORE OF 1825HANNA...AND THE CYCLONE HAS A VERY SUBTROPICAL APPEARANCE. 1826CONVECTION HAS DIMINISHED SUBSTANTIALLY OVER THE PAST 6-12 HOURS 1827AND THE HIGHEST FLIGHT-LEVEL AND SFMR WINDS HAVE COME DOWN AS WELL. 1828BASED ON SOME 52 KT SFMR WINDS AROUND 11Z...THE INITIAL INTENSITY 1829IS LOWERED TO 55 KT. 1830 1831CONDITIONS ARE NOT CONDUCIVE TO STRENGTHENING RIGHT NOW...WITH 1832MODERATE SOUTHERLY SHEAR AND POOR THERMODYNAMICS. THE GFS SUGGESTS 1833THAT DRY AIR IS LIKELY TO CONTINUE TO BE AN ISSUE UP TO LANDFALL. 1834HOWEVER...AS HANNA AND THE UPPER LOW BEGIN TO SEPARATE SOME OF THE 1835GLOBAL MODELS...INCLUDING THE GFS...SUGGEST THAT THE SHEAR WILL 1836LESSEN SOMEWHAT. THIS WOULD ALLOW FOR SOME INTENSIFICATION...AND 1837SO THE OFFICIAL FORECAST CONTINUES TO SHOW HANNA ATTAINING 1838HURRICANE STRENGTH. THIS IS IN GOOD AGREEMENT WITH THE 1839HWRF...ALTHOUGH THE GFDL AND SHIPS GUIDANCE IS LOWER. 1840 1841THE INITIAL MOTION IS 315/10. THE FORECAST SCENARIO IS UNCHANGED 1842FROM PREVIOUS ADVISORIES. MID-LEVEL HIGH PRESSURE IS BUILDING OVER 1843THE WESTERN ATLANTIC AS A DEEP LAYER LOW MOVES AWAY FROM NEW 1844ENGLAND. HANNA IS EXPECTED TO RECURVE AROUND THE PERIPHERY OF THE 1845HIGH AHEAD OF A MID-LATITUDE SHORT WAVE TROUGH IN THE WESTERLIES. 1846MODEL GUIDANCE REMAINS IN FAIRLY GOOD AGREEMENT AND LITTLE CHANGE 1847TO THE FORECAST TRACK IS REQUIRED. THE OFFICIAL FORECAST IS 1848SLIGHTLY TO THE RIGHT OF THE MODEL CONSENSUS BECAUSE THE BETTER 1849PERFORMING MODELS THIS YEAR...NAMELY THE GFS AND GFDL...ARE ON THE 1850RIGHT SIDE OF THE GUIDANCE ENVELOPE. BECAUSE OF THE LARGE... 1851SPRAWLING NATURE OF THE CIRCULATION...THE EXACT TRAJECTORY OF THE 1852CENTER IS RELATIVELY UNIMPORTANT. 1853 1854 1855FORECAST POSITIONS AND MAX WINDS 1856 1857INITIAL 04/1500Z 24.5N 73.5W 55 KT 185812HR VT 05/0000Z 26.2N 75.2W 55 KT 185924HR VT 05/1200Z 28.7N 77.2W 60 KT 186036HR VT 06/0000Z 31.7N 78.2W 65 KT 186148HR VT 06/1200Z 35.4N 77.4W 55 KT...INLAND 186272HR VT 07/1200Z 43.0N 69.5W 40 KT...EXTRATROPICAL 186396HR VT 08/1200Z 50.0N 54.0W 40 KT...EXTRATROPICAL 1864120HR VT 09/1200Z 51.5N 37.5W 45 KT...EXTRATROPICAL 1865 1866$$ 1867FORECASTER FRANKLIN 1868 1869 1870 1871 1872WTNT43 KNHC 042101 1873TCDAT3 1874TROPICAL STORM HANNA DISCUSSION NUMBER 32 1875NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1876500 PM EDT THU SEP 04 2008 1877 1878THE RECONNAISSANCE AIRCRAFT INVESTIGATING HANNA IS FINDING THE 1879CIRCULATION CENTER AT 850 MB DISPLACED TO THE NORTHWEST OF THE MEAN 1880CENTER OF ROTATION APPARENT IN THE LOW CLOUD LINES. THERE ARE ALSO 1881MULTIPLE SWIRLS...BUT IT DOES APPEAR THAT THE LOW-LEVEL CENTER HAS 1882JUMPED A LITTLE BIT TO THE WEST IN RESPONSE TO THE CONVECTIVE 1883ASYMMETRY. ALTHOUGH A COUPLE MORE SHIFTS ARE POSSIBLE...THE 1884ORIENTATION OF THE SHEAR SHOULD TURN MORE SOUTHERLY WITH 1885TIME...THAT IS...MORE ALONG THE TRACK...AND THEN HAVE LESS OF AN 1886IMPACT ON THE TRACK. THE BASIC FORECAST PHILOSOPHY IS UNCHANGED. 1887THE NEW TRACK FORECAST IS VERY CLOSE TO THE PREVIOUS ONE WITH ONLY 1888A SLIGHT LEFTWARD SHIFT...AND IS NEAR THE MODEL CONSENSUS. 1889 1890RECONNAISSANCE DATA THUS FAR DO NOT SUPPORT ANY INCREASE IN THE 1891INTENSITY ESTIMATE. WATER VAPOR IMAGERY CONTINUES TO SHOW VERY DRY 1892AIR IMPINGING ON HANNA FROM THE SOUTHEAST...AND THIS IS EXPECTED TO 1893CONTINUE. WHILE THE VERTICAL SHEAR IS FORECAST TO DIMINISH A 1894LITTLE PRIOR TO LANDFALL...NONE OF THE OBJECTIVE GUIDANCE MODELS 1895NOW MAKE HANNA A HURRICANE AND THE OFFICIAL INTENSITY FORECAST NOW 1896TOPS OUT AT 60 KT. HURRICANE WATCHES WILL REMAIN IN EFFECT FOR THE 1897POSSIBILITY THAT HANNA BECOMES A LITTLE STRONGER THAN 1898FORECAST...AND PEOPLE ARE REMINDED THAT THERE IS VERY LITTLE 1899DIFFERENCE BETWEEN A STRONG TROPICAL STORM AND A MINIMAL HURRICANE. 1900 1901 1902FORECAST POSITIONS AND MAX WINDS 1903 1904INITIAL 04/2100Z 25.5N 75.0W 55 KT 190512HR VT 05/0600Z 27.2N 76.4W 55 KT 190624HR VT 05/1800Z 30.3N 78.0W 60 KT 190736HR VT 06/0600Z 33.9N 78.3W 60 KT...ON THE COAST 190848HR VT 06/1800Z 37.5N 76.5W 50 KT...INLAND 190972HR VT 07/1800Z 46.0N 65.5W 40 KT...EXTRATROPICAL 191096HR VT 08/1800Z 51.0N 50.0W 40 KT...EXTRATROPICAL 1911120HR VT 09/1800Z 52.5N 32.5W 45 KT...EXTRATROPICAL 1912 1913$$ 1914FORECASTER FRANKLIN 1915 1916 1917 1918 1919WTNT43 KNHC 050246 1920TCDAT3 1921TROPICAL STORM HANNA DISCUSSION NUMBER 33 1922NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 19231100 PM EDT THU SEP 04 2008 1924 1925A RECONNAISSANCE AIRCRAFT MEASURED A MINIMUM PRESSURE OF 987 MB AND 192660 KNOTS AT FLIGHT LEVEL ON ITS WAY HOME A FEW HOURS AGO. SINCE 1927THEN SATELLITE IMAGES HAVE SHOWN AN INCREASE IN THUNDERSTORM 1928ACTIVITY AND THERE ARE SOME INDICATIONS THAT THE CENTER COULD BE 1929UNDER THE CONVECTION OR VERY NEAR THE SOUTHERN EDGE. THE CLOUD 1930PATTERN ON IR IMAGES INDICATE THAT HANNA LOOKS A LITTLE MORE 1931TROPICAL THAN EARLIER TODAY BUT THE CYCLONE STILL HAS A LARGE WIND 1932FIELD AND LACKS AN INNER CORE. INITIAL INTENSITY IS KEPT AT 55 1933KNOTS AND ANOTHER PLANE WILL BE IN THE AREA IN A FEW HOURS TO CHECK 1934IF THE WINDS HAVE INCREASED. NONE OF THE GUIDANCE INDICATE 1935SIGNIFICANT STRENGTHENING AND THE OFFICIAL FORECAST BRINGS HANNA TO 193660 KNOTS BEFORE IT REACHES THE UNITED STATES COAST. PEOPLE ARE 1937REMINDED THAT THERE IS VERY LITTLE DIFFERENCE BETWEEN A STRONG 1938TROPICAL STORM AND A MINIMAL HURRICANE...ONLY A FIVE KNOT 1939DIFFERENCE. 1940 1941SURFACE DATA AND EXTRAPOLATION FROM EARLIER RECONNAISSANCE FIXES 1942INDICATE THAT HANNA IS MOVING TOWARD THE NORTHWEST OR 320 DEGREES 1943AT 12 KNOTS...STEERED BY STRONG SUBTROPICAL RIDGE OVER THE WESTERN 1944ATLANTIC. THE WESTERN EDGE OF THE RIDGE IS FORECAST TO BE ERODED BY 1945AN APPROACHING SHORT WAVE. THIS PATTERN SHOULD FORCE HANNA TO MOVE 1946ON A MORE NORTHERLY TRACK DURING THE NEXT 24 TO 48 HOURS WITH AN 1947INCREASE IN FORWARD SPEED. THEREAFTER...HANNA IS EXPECTED TO BE 1948FULLY EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES AND RACE TO THE 1949NORTHEAST WHILE BECOMING EXTRATROPICAL. THIS IS BASICALLY THE 1950SOLUTION PROVIDED BY MOST OF THE GUIDANCE. 1951 1952IF HANNA BECOMES MORE TROPICAL AS SUGGESTED BY THE INCREASE IN 1953CONVECTION...THE WIND FIELD MOST LIKELY WILL CONTRACT A LITTLE BIT. 1954 1955 1956FORECAST POSITIONS AND MAX WINDS 1957 1958INITIAL 05/0300Z 26.5N 76.3W 55 KT 195912HR VT 05/1200Z 28.5N 77.7W 55 KT 196024HR VT 06/0000Z 31.5N 78.5W 60 KT 196136HR VT 06/1200Z 35.0N 78.0W 50 KT...INLAND 196248HR VT 07/0000Z 39.0N 75.0W 40 KT...INLAND 196372HR VT 08/0000Z 46.0N 62.0W 40 KT...EXTRATROPICAL 196496HR VT 09/0000Z 50.5N 44.5W 40 KT...EXTRATROPICAL 1965120HR VT 10/0000Z 51.2N 27.0W 40 KT...EXTRATROPICAL 1966 1967$$ 1968FORECASTER AVILA 1969 1970 1971 1972000 1973 1974WTNT43 KNHC 050900 1975TCDAT3 1976TROPICAL STORM HANNA DISCUSSION NUMBER 34 1977NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1978500 AM EDT FRI SEP 05 2008 1979 1980A RECONNAISSANCE AIRCRAFT CURRENTLY SAMPLING HANNA RECENTLY FOUND 1981PEAK FLIGHT-LEVEL WINDS OF 73 KT. THIS WOULD NORMALLY CORRESPOND 1982TO SURFACE WINDS OF ABOUT 60 KT USING THE STANDARD REDUCTION. 1983HOWEVER...THE WINDS WERE FOUND IN AN AREA ABSENT OF DEEP CONVECTION 1984AND THE SFMR INSTRUMENT ONLY SHOWED ABOUT 51 KT IN THE SAME AREA. 1985IN ADDITION...A DROPSONDE RELEASED IN THE AREA HAD A SURFACE WIND 1986OF 57 KT. THESE DATA SUGGEST THE INTENSITY REMAINS NEAR 55 KT. 1987HANNA HAS BEEN STRUGGLING TO GENERATE PERSISTENT DEEP CONVECTION 1988NEAR THE CENTER DUE TO SHEAR AND DRY AIR...ALTHOUGH THERE HAS BEEN 1989A RECENT BURST WITHIN THE LAST COUPLE OF HOURS. WHILE THERE IS 1990SOME POTENTIAL FOR A LITTLE ADDITIONAL STRENGTHENING...ALL BUT ONE 1991OF THE INTENSITY MODELS KEEP HANNA JUST BELOW HURRICANE STRENGTH. 1992STILL...THERE IS LITTLE DIFFERENCE BETWEEN A STRONG TROPICAL STORM 1993AND A CATEGORY ONE HURRICANE...AND HANNA COULD REACH HURRICANE 1994STRENGTH BEFORE MOVING INLAND OVER THE SOUTHEASTERN UNITED STATES 1995IN ABOUT 24 HOURS. 1996 1997HANNA IS BEING STEERED BY THE SUBTROPICAL RIDGE OVER THE WESTERN 1998ATLANTIC RESULTING IN A MOTION TOWARD THE NORTHWEST OR 320/17. 1999HANNA IS EXPECTED TO TURN TOWARD THE NORTH TODAY THEN NORTHEASTWARD 2000TONIGHT AND TOMORROW AS IT ROUNDS THE WESTERN PERIPHERY OF THE 2001RIDGE. THEREAFTER...HANNA IS EXPECTED TO RACE NORTHEASTWARD AND 2002BECOME EXTRATROPICAL IN ABOUT 3 DAYS. TRACK MODELS HAVE BEEN 2003TRENDING TOWARD THE WEST AND THE OFFICIAL FORECAST IS SHIFTED TO 2004THE LEFT THROUGH 36 HOURS. HOWEVER...GIVEN HANNA'S LARGE 2005SIZE...ONE SHOULD NOT FOCUS ON THE EXACT TRACK AS THE INCLEMENT 2006WEATHER EXTENDS WELL BEYOND THE CENTER. 2007 2008FORECAST POSITIONS AND MAX WINDS 2009 2010INITIAL 05/0900Z 28.0N 78.0W 55 KT 201112HR VT 05/1800Z 30.0N 78.8W 60 KT 201224HR VT 06/0600Z 33.2N 79.1W 60 KT 201336HR VT 06/1800Z 36.7N 77.2W 45 KT...INLAND 201448HR VT 07/0600Z 40.6N 72.9W 40 KT...INLAND 201572HR VT 08/0600Z 48.0N 58.0W 40 KT...EXTRATROPICAL 201696HR VT 09/0600Z 50.5N 40.0W 40 KT...EXTRATROPICAL 2017120HR VT 10/0600Z 51.5N 23.5W 40 KT...EXTRATROPICAL 2018 2019$$ 2020FORECASTER RHOME 2021 2022 2023 2024 2025WTNT43 KNHC 051452 2026TCDAT3 2027TROPICAL STORM HANNA DISCUSSION NUMBER 35 2028NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 20291100 AM EDT FRI SEP 05 2008 2030 2031SATELLITE IMAGERY AND RADAR DATA FROM THE MELBOURNE WSR-88D INDICATE 2032THAT HANNA HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING...AS 2033THE LATEST CONVECTIVE BURST HAS PRODUCED AN INNER WIND CORE. 2034HOWEVER...THE RADAR-OBSERVED VELOCITIES DO NOT YET SUGGEST 2035INTENSIFICATION. THE INITIAL INTENSITY REMAINS 55 KT. 2036 2037THE CENTER OF HANNA JOGGED WESTWARD BETWEEN 06-12Z. HOWEVER...THE 2038MELBOURNE RADAR SUGGEST THE CENTER HAS RESUMED A MORE NORTHWARD 2039MOTIONS...WITH THE INITIAL MOTION ESTIMATED AT 325/17. HANNA IS 2040MOVING AROUND THE WESTERN END OF THE SUBTROPICAL RIDGE OVER THE 2041WESTERN ATLANTIC AND SHOULD ENTER THE WESTERLIES IN 24-48 HR. THIS 2042SHOULD RESULT IN RECURVATURE TO THE NORTHEAST AND ACCELERATION. 2043ALL GUIDANCE AGREES WITH THIS SCENARIO...AND THERE ARE NO 2044SIGNIFICANT OUTLIERS AMONGST THE DYNAMICAL MODELS. THE NEW 2045FORECAST TRACK IS ADJUSTED A LITTLE TO THE LEFT FOR THE FIRST 36 HR 2046TO ACCOUNT FOR THE INITIAL POSITION...AND IS CLOSE TO THE PREVIOUS 2047FORECAST TRACK THEREAFTER. 2048 2049WHILE VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT ARE STILL 2050ISSUES...THE INCREASED ORGANIZATION SUGGESTS THE POSSIBILITY OF 2051STRENGTHENING BEFORE LANDFALL. THUS...THE INTENSITY FORECAST CALLS 2052FOR A PEAK INTENSITY OF 60 KT NEAR LANDFALL. NONE OF THE GUIDANCE 2053INDICATES THAT HANNA WILL REACH HURRICANE STRENGTH PRIOR TO 2054LANDFALL...ALTHOUGH THIS CANNOT BE RULED OUT. THE CYCLONE SHOULD 2055WEAKEN AFTER LANDFALL AND BECOME EXTRATROPICAL IN ABOUT 48 HR. THE 2056GFS AND UKMET SUGGEST THE POSSIBILITY OF DEEPENING AS AN 2057EXTRATROPICAL SYSTEM LATE IN THE PERIOD...AND THIS IS REFLECTED IN 2058THE 96 AND 120 HR FORECASTS. 2059 2060 2061FORECAST POSITIONS AND MAX WINDS 2062 2063INITIAL 05/1500Z 28.9N 79.2W 55 KT 206412HR VT 06/0000Z 31.2N 79.7W 60 KT 206524HR VT 06/1200Z 34.5N 79.1W 55 KT...INLAND 206636HR VT 07/0000Z 38.2N 76.1W 45 KT...INLAND 206748HR VT 07/1200Z 42.5N 70.1W 40 KT...EXTRATROPICAL 206872HR VT 08/1200Z 49.0N 52.5W 40 KT...EXTRATROPICAL 206996HR VT 09/1200Z 50.5N 35.0W 45 KT...EXTRATROPICAL 2070120HR VT 10/1200Z 51.0N 18.5W 45 KT...EXTRATROPICAL 2071 2072$$ 2073FORECASTER BEVEN 2074 2075 2076 2077 2078WTNT43 KNHC 052038 2079TCDAT3 2080TROPICAL STORM HANNA DISCUSSION NUMBER 36 2081NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2082500 PM EDT FRI SEP 05 2008 2083 2084REPORTS FROM AN AIR FORCE RESERVE HURRICANE HURRICANE HUNTER 2085AIRCRAFT INDICATE THAT HANNA IS JUST BELOW HURRICANE STRENGTH. THE 2086STEPPED FREQUENCY MICROWAVE REPORTED TWO AREAS OF WIND OF ABOUT 65 2087KT. HOWEVER...DROPSONDE DATA SUGGESTS THAT THE SFMR ESTIMATES WERE 2088A LITTLE TOO HIGH. THE MAXIMUM 850 MB FLIGHT-LEVEL WINDS WERE 75 2089KT ABOUT 75 N MI EAST OF THE CENTER. THE LAST REPORTED CENTRAL 2090PRESSURE WAS 984 MB...UP A LITTLE FROM THIS MORNING. BASED ON ALL 2091THIS...THE INITIAL INTENSITY IS SET AT 60 KT. IT SHOULD BE NOTED 2092THAT THERE IS NOT MUCH DIFFERENCE METEOROLOGICALLY BETWEEN A 60-KT 2093TROPICAL STORM AND A 65-KT HURRICANE. 2094 2095THE MOTION IS A SOMEWHAT WOBBLY 360/17...WITH A RE-ANALYSIS OF 2096AIRCRAFT DATA SUGGESTING THIS MOTION BEGAN JUST AFTER THE 11Z 2097AIRCRAFT FIX. HANNA IS MOVING AROUND THE WESTERN END OF THE 2098SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC AND SHOULD ENTER THE 2099WESTERLIES IN 24-36 HR. THIS SHOULD RESULT IN RECURVATURE TO THE 2100NORTHEAST AND ACCELERATION. ALL GUIDANCE AGREES WITH THIS 2101SCENARIO...AND THERE ARE NO SIGNIFICANT OUTLIERS AMONGST THE 2102DYNAMICAL MODELS. THE NEW FORECAST TRACK IS ADJUSTED A LITTLE TO 2103THE RIGHT OF THE PREVIOUS TRACK AND LIES DOWN THE MIDDLE OF THE 2104GUIDANCE ENVELOPE. 2105 2106VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT ARE STILL ISSUES FOR 2107HANNA...AND SIGNIFICANT STRENGTHENING APPEARS UNLIKELY BEFORE 2108LANDFALL. HOWEVER...THERE IS A POSSIBILITY THAT A CONVECTIVE BURST 2109COULD CAUSE THE STORM TO REACH HURRICANE STRENGTH. THE CYCLONE 2110SHOULD WEAKEN AFTER LANDFALL AND BECOME EXTRATROPICAL IN ABOUT 36 2111HR. THE GFS AND UKMET CONTINUE TO SUGGEST THE POSSIBILITY OF 2112DEEPENING AS AN EXTRATROPICAL SYSTEM LATE IN THE FORECAST 2113PERIOD...AND THIS IS REFLECTED IN THE 96 AND 120 HR FORECASTS. 2114 2115FORECAST POSITIONS AND MAX WINDS 2116 2117INITIAL 05/2100Z 30.8N 78.7W 60 KT 2118 12HR VT 06/0600Z 33.2N 78.5W 60 KT 2119 24HR VT 06/1800Z 36.7N 76.8W 50 KT...INLAND 2120 36HR VT 07/0600Z 40.7N 72.4W 45 KT...EXTRATROPICAL 2121 48HR VT 07/1800Z 44.5N 65.6W 40 KT...INLAND EXTRATROPICAL 2122 72HR VT 08/1800Z 50.0N 47.5W 40 KT...EXTRATROPICAL 2123 96HR VT 09/1800Z 51.0N 30.0W 45 KT...EXTRATROPICAL 2124120HR VT 10/1800Z 52.5N 14.0W 45 KT...EXTRATROPICAL 2125 2126$$ 2127FORECASTER BEVEN 2128 2129 2130WTNT43 KNHC 060255 2131TCDAT3 2132TROPICAL STORM HANNA DISCUSSION NUMBER 37 2133NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 21341100 PM EDT FRI SEP 05 2008 2135 2136DATA FROM A RECONNAISSACE PLANE INDICATE THAT THE SURFACE PRESSURE 2137HAS DROPPED TO 978 MB BUT WINDS HAVE NOT INCREASED. INITIAL 2138INTENSITY IS KEPT AT 60 KNOTS. THE AREA OF STRONG WINDS HAS BEEN 2139SHRINKING SINCE HANNA APPEARS TO BE MORE TROPICAL AND THERE IS A 2140PERSISTENT AND LARGE AREA OF DEEP CONVECTION NEAR THE CENTER. HANNA 2141COULD REACH THE COAST IN LESS THAN 12 HOURS AS A HURRICANE SINCE IT 2142ONLY NEEDS FIVE KNOTS TO BE ONE. HOWEVER...THERE IS NOT MUCH 2143DIFFERENCE BETWEEN A 60-KT TROPICAL STORM AND A 65-KT HURRICANE. 2144 2145RADAR AND RECONNAISSANCE FIXES INDICATE THAT HANNA IS MOVING 2146NORTHWARD AT 17 KNOTS. THE CYCLONE IS ALREADY EMBEDDED IN A STRONG 2147SOUTHERLY AND SOUTHWESTERLY FLOW...AND SOON HANNA SHOULD BEGIN TO 2148TURN TO THE NORTHEAST WITH AN INCREASE IN FORWARD SPEED. AFTER 2149LANDFALL...AS HANNA BECOMES FULLY INVOLVED WITH THE MID-LATITUDE 2150FLOW...IT SHOULD BECOME EXTRATROPICAL IN ABOUT 24 TO 36 HOURS. 2151DURING THIS PERIOD...HANNA WILL BE MOVING VERY CLOSE TO OR OVER THE 2152NORTHEAST COAST OF THE UNITED STATES. 2153 2154 2155FORECAST POSITIONS AND MAX WINDS 2156 2157INITIAL 06/0300Z 32.4N 79.1W 60 KT 2158 12HR VT 06/1200Z 34.9N 78.6W 50 KT...INLAND 2159 24HR VT 07/0000Z 39.0N 75.0W 45 KT...INLAND 2160 36HR VT 07/1200Z 42.5N 69.5W 40 KT...EXTRATROPICAL 2161 48HR VT 08/0000Z 46.5N 60.0W 40 KT...EXTRATROPICAL 2162 72HR VT 09/0000Z 50.0N 42.0W 40 KT...EXTRATROPICAL 2163 96HR VT 10/0000Z 51.5N 27.5W 45 KT...EXTRATROPICAL 2164120HR VT 11/0000Z 55.0N 13.0W 45 KT...EXTRATROPICAL 2165 2166$$ 2167FORECASTER AVILA 2168 2169 2170WTNT43 KNHC 060856 2171TCDAT3 2172TROPICAL STORM HANNA DISCUSSION NUMBER 38 2173NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2174500 AM EDT SAT SEP 06 2008 2175 2176NATIONAL WEATHER SERVICE WSR-88D RADAR DATA...AND SURFACE 2177OBSERVATIONS...SHOW THAT THE CENTER OF HANNA CAME ASHORE AT ABOUT 21780720 UTC NEAR THE BORDER BETWEEN SOUTH CAROLINA AND NORTH CAROLINA. 2179PRIOR TO LANDFALL...AN AIR FORCE RECONNAISSANCE AIRCRAFT MEASURED A 2180CENTRAL PRESSURE OF 983 MB...BUT FLIGHT-LEVEL AND SFMR DATA DID NOT 2181REVEAL ANY INCREASE IN THE WINDS...NOR DID WSR-88D RADAR 2182VELOCITIES. THE INTENSITY APPEARED TO BE 55 TO 60 KT WHILE THE 2183CENTER WAS STILL OVER WATER...BUT NOW THAT IT IS INLAND THE MAXIMUM 2184WINDS HAVE PROBABLY COME DOWN TO ABOUT 50 KT. SLIGHT WEAKENING IS 2185FORECAST AS HANNA WILL BE MOVING ROUGHLY PARALLEL TO THE EAST COAST 2186OF THE UNITED STATES DURING THE NEXT DAY OR SO. LITTLE CHANGE IN 2187STRENGTH IS ANTICIPATED THEREAFTER AS HANNA BECOMES AN 2188EXTRATROPICAL CYCLONE NEAR OR OVER SOUTHEASTERN CANADA. 2189 2190HANNA IS ROUNDING THE MID-LEVEL RIDGE OVER THE WESTERN 2191ATLANTIC...TURNING RIGHT AND ACCELERATING. THE INITIAL MOTION 2192ESTIMATE IS ABOUT 020/19...BUT HANNA SHOULD TURN NORTHEASTWARD 2193WITHIN THE NEXT 24 HOURS AS IT ENTERS THE MID-LATITUDE WESTERLIES. 2194THE NEW OFFICIAL FORECAST TRACK IS ADJUSTED SLIGHTLY TO THE LEFT OF 2195THE PREVIOUS ONE...AND IS NOW CLOSE TO A CONSENSUS OF THE 2196TIGHTLY-CLUSTERED MODEL SOLUTIONS. 2197 2198 2199 2200FORECAST POSITIONS AND MAX WINDS 2201 2202INITIAL 06/0900Z 34.4N 78.3W 50 KT 2203 12HR VT 06/1800Z 37.3N 76.7W 50 KT...INLAND 2204 24HR VT 07/0600Z 41.2N 72.2W 45 KT...NEAR COAST 2205 36HR VT 07/1800Z 45.0N 64.8W 45 KT...INLAND EXTRATROPICAL 2206 48HR VT 08/0600Z 48.2N 56.2W 45 KT...INLAND EXTRATROPICAL 2207 72HR VT 09/0600Z 50.5N 38.5W 45 KT...EXTRATROPICAL 2208 96HR VT 10/0600Z 54.5N 20.5W 45 KT...EXTRATROPICAL 2209120HR VT 11/0600Z 58.5N 11.5W 45 KT...EXTRATROPICAL 2210 2211$$ 2212FORECASTER KNABB 2213 2214 2215WTNT43 KNHC 061435 2216TCDAT3 2217TROPICAL STORM HANNA DISCUSSION NUMBER 39 2218NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 22191100 AM EDT SAT SEP 06 2008 2220 2221THE CENTER OF HANNA IS MOVING INTO SOUTHEASTERN VIRGINA...WITH 2222SATELLITE IMAGERY SHOWING A CONVECTIVE OVERCAST JUST NORTH OF THE 2223CENTER...AND RADAR DATA SHOWING WIDESPREAD RAINBANDS OVER THE 2224NORTHERN SEMICIRCLE. WHILE THERE ARE NO RECENT OBSERVATIONS OF 2225SUSTAINED TROPICAL STORM-FORCE WINDS...IT IS ESTIMATED THAT THE 2226MAXIMUM WINDS REMAIN 45 KT IN THE EASTERN SEMICIRCLE IN AREAS NOT 2227CURRENTLY SAMPLED. WHILE LITTLE CHANGE IN STRENGTH IS LIKELY 2228THROUGH THE FORECAST PERIOD...HANNA IS EXPECTED TO LOSE TROPICAL 2229CHARACTERISTICS IN ABOUT 24 HOURS. 2230 2231THE INITIAL MOTION IS NOW 025/22. HANNA IS ROUNDING THE END OF THE 2232WESTERN ATLANTIC RIDGE AND SHOULD ACCELERATE NORTHEASTWARD INTO THE 2233WESTERLIES DURING THE NEXT 24-48 HR. AFTER THAT...THE SYSTEM 2234SHOULD MOVE GENERALLY EAST-NORTHEASTWARD FOR THE REMAINDER OF THE 2235FORECAST PERIOD. THE MODEL GUIDANCE IS TIGHTLY CLUSTERED AROUND 2236THIS SCENARIO...AND NEW FORECAST TRACK IS ESSENTIALLY AN UPDATE OF 2237THE PREVIOUS TRACK. 2238 2239FORECAST POSITIONS AND MAX WINDS 2240 2241INITIAL 06/1500Z 36.6N 77.4W 45 KT 2242 12HR VT 07/0000Z 39.7N 74.7W 45 KT...INLAND 2243 24HR VT 07/1200Z 43.5N 68.4W 45 KT...INLAND EXTRATROPICAL 2244 36HR VT 08/0000Z 46.8N 60.1W 45 KT...EXTRATROPICAL 2245 48HR VT 08/1200Z 49.0N 51.6W 45 KT...EXTRATROPICAL 2246 72HR VT 09/1200Z 51.0N 34.0W 45 KT...EXTRATROPICAL 2247 96HR VT 10/1200Z 55.0N 19.0W 45 KT...EXTRATROPICAL 2248120HR VT 11/1200Z 59.0N 10.5W 45 KT...EXTRATROPICAL 2249 2250$$ 2251FORECASTER BEVEN 2252 2253 2254WTNT43 KNHC 062032 2255TCDAT3 2256TROPICAL STORM HANNA DISCUSSION NUMBER 40 2257NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2258500 PM EDT SAT SEP 06 2008 2259 2260THE CENTER OF HANNA IS MOVING OVER THE DELMARVA PENINSULA... 2261WITH RADAR DATA CONTINUING TO SHOW WIDESPREAD RAINBANDS OVER THE 2262NORTHERN SEMICIRCLE. HOWEVER...THE CENTRAL CONVECTION IS 2263DECREASING...AND THE CENTRAL PRESSURE HAS RISEN TO 994 MB. 2264RECENT SURFACE OBSERVATIONS HAVE SHOWN 35-40 KT SUSTAINED WINDS. 2265SO...THE MAXIMUM INTENSITY IS MAINTAINED AT 45 KT ON THE PREMISE 2266THAT THE MAXIMUM WINDS WERE NOT SAMPLED. AS BEFORE...WHILE LITTLE 2267CHANGE IN STRENGTH IS LIKELY THROUGH THE FORECAST PERIOD...HANNA IS 2268EXPECTED TO LOSE TROPICAL CHARACTERISTICS IN 12-24 HOURS. 2269 2270THE INITIAL MOTION IS NOW 040/23. HANNA IS ENTERING THE WESTERLIES 2271AND SHOULD ACCELERATE NORTHEASTWARD FOR THE NEXT 24-36 HR..FOLLOWED 2272BY A RAPID EASTWARD MOTION. A TURN TOWARD THE NORTHEAST WITH SOME 2273DECELERATION IS POSSIBLE AFTER 96 HR. THE MODEL GUIDANCE IS FAIRLY 2274WELL CLUSTERED AROUND THIS SCENARIO...AND THE NEW FORECAST TRACK IS 2275ESSENTIALLY AN UPDATE OF THE PREVIOUS TRACK. 2276 2277FORECAST POSITIONS AND MAX WINDS 2278 2279INITIAL 06/2100Z 38.5N 75.8W 45 KT...INLAND 2280 12HR VT 07/0600Z 41.7N 71.8W 45 KT...INLAND 2281 24HR VT 07/1800Z 45.3N 64.6W 45 KT...EXTRATROPICAL 2282 36HR VT 08/0600Z 48.3N 56.0W 45 KT...INLAND EXTRATROPICAL 2283 48HR VT 08/1800Z 49.6N 47.2W 45 KT...EXTRATROPICAL 2284 72HR VT 09/1800Z 51.5N 31.0W 45 KT...EXTRATROPICAL 2285 96HR VT 10/1800Z 56.0N 17.5W 45 KT...EXTRATROPICAL 2286120HR VT 11/1800Z 60.0N 10.0W 45 KT...EXTRATROPICAL 2287 2288$$ 2289FORECASTER BEVEN 2290 2291 2292WTNT43 KNHC 070250 2293TCDAT3 2294TROPICAL STORM HANNA DISCUSSION NUMBER 41 2295NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 22961100 PM EDT SAT SEP 06 2008 2297 2298THE CENTER OF HANNA IS MOVING OVER THE WEST-CENTRAL PORTION OF LONG 2299ISLAND. THE INITIAL MOTION ESTIMATE IS 050/26...AND HANNA IS RIGHT 2300ON TRACK. GRADUAL ACCELERATION IS FORECAST DURING THE NEXT 48 HOURS 2301AS HANNA GETS CAUGHT UP IN THE FAST UPPER-LEVEL WESTERLIE...AND THE 2302NEW NHC MODEL GUIDANCE IS TIGHTLY CLUSTERED ABOUT THE PREVIOUS 2303FORECAST TRACK. THEREFORE...NO SIGNIFICANT CHANGES HAVE BEEN MADE 2304AND HANNA IS EXPECTED TO CLEAR THE U.S. COASTLINE AROUND CAPE COD 2305MASSACHUSETTS BY 07/0900Z. 2306 2307HANNA'S FAST FORWARD MOTION HAS LIKELY CONTRIBUTED TO SOME OF 2308INCREASE IN OBSERVED SURFACE WINDS OBTAINED FROM SHIPS AND BUOYS 2309SOUTH OF LONG ISLAND. TWO UNCONFIRMED SHIP REPORTS OF 64 KT AND 60 2310KT HAVE BEEN RECEIVED DURING THE PAST COUPLE OF HOURS...ONE OF 2311WHICH OCCURRED IN A RAIN BAND. HOWEVER...THESE COULD HAVE BEEN 2312ISOLATED GUSTS AND THE RAIN BANDS HAVE SINCE DISSIPATED. 2313THEREFORE...THE INITIAL INTENSITY WILL BE 50 KT FOR THIS ADVISORY 2314BASED ON EARLIER DOPPLER VELOCITY VALUES OF 70 KT AT 5000 TO 7000 2315FT THAT COVERED A SIGNIFICANT PORTION OF THE SOUTHEASTERN QUADRANT 2316OF HANNA IN SEVERAL RAIN BANDS. LITTLE CHANGE IN STRENGTH IS 2317EXPECTED THROUGHOUT THE FORECAST PERIOD...AND HANNA COULD EASILY BE 2318AN EXTRATROPICAL STORM WITH 50-KT SUSTAINED WINDS AT ANY OF THE 2319FORECAST TIMES. 2320 2321FORECAST POSITIONS AND MAX WINDS 2322 2323INITIAL 07/0300Z 40.5N 73.4W 50 KT...BECOMING EXTRATROPICAL 2324 12HR VT 07/1200Z 43.0N 68.8W 50 KT...EXTRATROPICAL 2325 24HR VT 08/0000Z 46.4N 61.1W 45 KT...EXTRATROPICAL 2326 36HR VT 08/1200Z 48.8N 53.2W 45 KT...EXTRATROPICAL 2327 48HR VT 09/0000Z 50.0N 45.0W 45 KT...EXTRATROPICAL 2328 72HR VT 10/0000Z 52.5N 28.3W 45 KT...EXTRATROPICAL 2329 96HR VT 11/0000Z 56.5N 15.5W 45 KT...EXTRATROPICAL 2330120HR VT 12/0000Z 61.5N 11.5W 45 KT...EXTRATROPICAL 2331 2332$$ 2333FORECASTER STEWART 2334 2335 2336WTNT43 KNHC 070857 2337TCDAT3 2338TROPICAL STORM HANNA DISCUSSION NUMBER 42 2339NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2340500 AM EDT SUN SEP 07 2008 2341 2342THE CLOUD PATTERN ASSOCIATED WITH HANNA IS SPREADING OUT WELL AHEAD 2343OF THE SURFACE CENTER...WITH THE CLOSEST DEEP CONVECTION NOW 2344DISPLACED ABOUT 125 NMI TO THE NORTH AND NORTHEAST. THE 2345CIRCULATION IS ALSO CLOSE TO...BUT NOT QUITE ENTANGLED WITH...A 2346FRONTAL BOUNDARY. BASED ON THE LOSS OF CONVECTION NEAR THE 2347CORE...HANNA IS NO LONGER CONSIDERED TO BE A TROPICAL CYCLONE AND 2348THIS WILL BE THE LAST ADVISORY. 2349 2350MAXIMUM WINDS ARE ESTIMATED TO BE 45 KT BASED ON SHIP REPORTS...AND 2351HANNA IS EXPECTED TO REMAIN A VIGOROUS EXTRATROPICAL CYCLONE DURING 2352ITS PASSAGE OVER THE NORTH ATLANTIC. THE OFFICIAL FORECAST IS IN 2353GOOD AGREEMENT WITH THE GFS. 2354 2355FUTURE INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS 2356FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE OCEAN PREDICTION 2357CENTER...UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC. 2358 2359 2360FORECAST POSITIONS AND MAX WINDS 2361 2362INITIAL 07/0900Z 42.6N 70.0W 45 KT...EXTRATROPICAL 2363 12HR VT 07/1800Z 45.4N 64.5W 45 KT...EXTRATROPICAL 2364 24HR VT 08/0600Z 48.4N 57.1W 45 KT...EXTRATROPICAL 2365 36HR VT 08/1800Z 50.0N 50.0W 45 KT...EXTRATROPICAL 2366 48HR VT 09/0600Z 51.0N 43.0W 45 KT...EXTRATROPICAL 2367 72HR VT 10/0600Z 53.5N 27.0W 45 KT...EXTRATROPICAL 2368 96HR VT 11/0600Z 58.0N 16.0W 40 KT...EXTRATROPICAL 2369120HR VT 12/0600Z...ABSORBED WITHIN EXTRATROPICAL LOW 2370 2371$$ 2372FORECASTER FRANKLIN 2373 2374 2375WTNT43 KNHC 052038 2376TCDAT3 2377TROPICAL STORM HANNA DISCUSSION NUMBER 36 2378NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2379500 PM EDT FRI SEP 05 2008 2380 2381REPORTS FROM AN AIR FORCE RESERVE HURRICANE HURRICANE HUNTER 2382AIRCRAFT INDICATE THAT HANNA IS JUST BELOW HURRICANE STRENGTH. THE 2383STEPPED FREQUENCY MICROWAVE REPORTED TWO AREAS OF WIND OF ABOUT 65 2384KT. HOWEVER...DROPSONDE DATA SUGGESTS THAT THE SFMR ESTIMATES WERE 2385A LITTLE TOO HIGH. THE MAXIMUM 850 MB FLIGHT-LEVEL WINDS WERE 75 2386KT ABOUT 75 N MI EAST OF THE CENTER. THE LAST REPORTED CENTRAL 2387PRESSURE WAS 984 MB...UP A LITTLE FROM THIS MORNING. BASED ON ALL 2388THIS...THE INITIAL INTENSITY IS SET AT 60 KT. IT SHOULD BE NOTED 2389THAT THERE IS NOT MUCH DIFFERENCE METEOROLOGICALLY BETWEEN A 60-KT 2390TROPICAL STORM AND A 65-KT HURRICANE. 2391 2392THE MOTION IS A SOMEWHAT WOBBLY 360/17...WITH A RE-ANALYSIS OF 2393AIRCRAFT DATA SUGGESTING THIS MOTION BEGAN JUST AFTER THE 11Z 2394AIRCRAFT FIX. HANNA IS MOVING AROUND THE WESTERN END OF THE 2395SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC AND SHOULD ENTER THE 2396WESTERLIES IN 24-36 HR. THIS SHOULD RESULT IN RECURVATURE TO THE 2397NORTHEAST AND ACCELERATION. ALL GUIDANCE AGREES WITH THIS 2398SCENARIO...AND THERE ARE NO SIGNIFICANT OUTLIERS AMONGST THE 2399DYNAMICAL MODELS. THE NEW FORECAST TRACK IS ADJUSTED A LITTLE TO 2400THE RIGHT OF THE PREVIOUS TRACK AND LIES DOWN THE MIDDLE OF THE 2401GUIDANCE ENVELOPE. 2402 2403VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT ARE STILL ISSUES FOR 2404HANNA...AND SIGNIFICANT STRENGTHENING APPEARS UNLIKELY BEFORE 2405LANDFALL. HOWEVER...THERE IS A POSSIBILITY THAT A CONVECTIVE BURST 2406COULD CAUSE THE STORM TO REACH HURRICANE STRENGTH. THE CYCLONE 2407SHOULD WEAKEN AFTER LANDFALL AND BECOME EXTRATROPICAL IN ABOUT 36 2408HR. THE GFS AND UKMET CONTINUE TO SUGGEST THE POSSIBILITY OF 2409DEEPENING AS AN EXTRATROPICAL SYSTEM LATE IN THE FORECAST 2410PERIOD...AND THIS IS REFLECTED IN THE 96 AND 120 HR FORECASTS. 2411 2412FORECAST POSITIONS AND MAX WINDS 2413 2414INITIAL 05/2100Z 30.8N 78.7W 60 KT 241512HR VT 06/0600Z 33.2N 78.5W 60 KT 241624HR VT 06/1800Z 36.7N 76.8W 50 KT...INLAND 241736HR VT 07/0600Z 40.7N 72.4W 45 KT...EXTRATROPICAL 241848HR VT 07/1800Z 44.5N 65.6W 40 KT...INLAND EXTRATROPICAL 241972HR VT 08/1800Z 50.0N 47.5W 40 KT...EXTRATROPICAL 242096HR VT 09/1800Z 51.0N 30.0W 45 KT...EXTRATROPICAL 2421120HR VT 10/1800Z 52.5N 14.0W 45 KT...EXTRATROPICAL 2422 2423$$ 2424FORECASTER BEVEN 2425 2426 2427 2428000 2429 2430WTNT43 KNHC 060255 2431TCDAT3 2432TROPICAL STORM HANNA DISCUSSION NUMBER 37 2433NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 24341100 PM EDT FRI SEP 05 2008 2435 2436DATA FROM A RECONNAISSACE PLANE INDICATE THAT THE SURFACE PRESSURE 2437HAS DROPPED TO 978 MB BUT WINDS HAVE NOT INCREASED. INITIAL 2438INTENSITY IS KEPT AT 60 KNOTS. THE AREA OF STRONG WINDS HAS BEEN 2439SHRINKING SINCE HANNA APPEARS TO BE MORE TROPICAL AND THERE IS A 2440PERSISTENT AND LARGE AREA OF DEEP CONVECTION NEAR THE CENTER. HANNA 2441COULD REACH THE COAST IN LESS THAN 12 HOURS AS A HURRICANE SINCE IT 2442ONLY NEEDS FIVE KNOTS TO BE ONE. HOWEVER...THERE IS NOT MUCH 2443DIFFERENCE BETWEEN A 60-KT TROPICAL STORM AND A 65-KT HURRICANE. 2444 2445RADAR AND RECONNAISSANCE FIXES INDICATE THAT HANNA IS MOVING 2446NORTHWARD AT 17 KNOTS. THE CYCLONE IS ALREADY EMBEDDED IN A STRONG 2447SOUTHERLY AND SOUTHWESTERLY FLOW...AND SOON HANNA SHOULD BEGIN TO 2448TURN TO THE NORTHEAST WITH AN INCREASE IN FORWARD SPEED. AFTER 2449LANDFALL...AS HANNA BECOMES FULLY INVOLVED WITH THE MID-LATITUDE 2450FLOW...IT SHOULD BECOME EXTRATROPICAL IN ABOUT 24 TO 36 HOURS. 2451DURING THIS PERIOD...HANNA WILL BE MOVING VERY CLOSE TO OR OVER THE 2452NORTHEAST COAST OF THE UNITED STATES. 2453 2454 2455FORECAST POSITIONS AND MAX WINDS 2456 2457INITIAL 06/0300Z 32.4N 79.1W 60 KT 245812HR VT 06/1200Z 34.9N 78.6W 50 KT...INLAND 245924HR VT 07/0000Z 39.0N 75.0W 45 KT...INLAND 246036HR VT 07/1200Z 42.5N 69.5W 40 KT...EXTRATROPICAL 246148HR VT 08/0000Z 46.5N 60.0W 40 KT...EXTRATROPICAL 246272HR VT 09/0000Z 50.0N 42.0W 40 KT...EXTRATROPICAL 246396HR VT 10/0000Z 51.5N 27.5W 45 KT...EXTRATROPICAL 2464120HR VT 11/0000Z 55.0N 13.0W 45 KT...EXTRATROPICAL 2465 2466$$ 2467FORECASTER AVILA 2468 2469 2470 2471000 2472 2473WTNT43 KNHC 060856 2474TCDAT3 2475TROPICAL STORM HANNA DISCUSSION NUMBER 38 2476NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2477500 AM EDT SAT SEP 06 2008 2478 2479NATIONAL WEATHER SERVICE WSR-88D RADAR DATA...AND SURFACE 2480OBSERVATIONS...SHOW THAT THE CENTER OF HANNA CAME ASHORE AT ABOUT 24810720 UTC NEAR THE BORDER BETWEEN SOUTH CAROLINA AND NORTH CAROLINA. 2482PRIOR TO LANDFALL...AN AIR FORCE RECONNAISSANCE AIRCRAFT MEASURED A 2483CENTRAL PRESSURE OF 983 MB...BUT FLIGHT-LEVEL AND SFMR DATA DID NOT 2484REVEAL ANY INCREASE IN THE WINDS...NOR DID WSR-88D RADAR 2485VELOCITIES. THE INTENSITY APPEARED TO BE 55 TO 60 KT WHILE THE 2486CENTER WAS STILL OVER WATER...BUT NOW THAT IT IS INLAND THE MAXIMUM 2487WINDS HAVE PROBABLY COME DOWN TO ABOUT 50 KT. SLIGHT WEAKENING IS 2488FORECAST AS HANNA WILL BE MOVING ROUGHLY PARALLEL TO THE EAST COAST 2489OF THE UNITED STATES DURING THE NEXT DAY OR SO. LITTLE CHANGE IN 2490STRENGTH IS ANTICIPATED THEREAFTER AS HANNA BECOMES AN 2491EXTRATROPICAL CYCLONE NEAR OR OVER SOUTHEASTERN CANADA. 2492 2493HANNA IS ROUNDING THE MID-LEVEL RIDGE OVER THE WESTERN 2494ATLANTIC...TURNING RIGHT AND ACCELERATING. THE INITIAL MOTION 2495ESTIMATE IS ABOUT 020/19...BUT HANNA SHOULD TURN NORTHEASTWARD 2496WITHIN THE NEXT 24 HOURS AS IT ENTERS THE MID-LATITUDE WESTERLIES. 2497THE NEW OFFICIAL FORECAST TRACK IS ADJUSTED SLIGHTLY TO THE LEFT OF 2498THE PREVIOUS ONE...AND IS NOW CLOSE TO A CONSENSUS OF THE 2499TIGHTLY-CLUSTERED MODEL SOLUTIONS. 2500 2501 2502 2503FORECAST POSITIONS AND MAX WINDS 2504 2505INITIAL 06/0900Z 34.4N 78.3W 50 KT 250612HR VT 06/1800Z 37.3N 76.7W 50 KT...INLAND 250724HR VT 07/0600Z 41.2N 72.2W 45 KT...NEAR COAST 250836HR VT 07/1800Z 45.0N 64.8W 45 KT...INLAND EXTRATROPICAL 250948HR VT 08/0600Z 48.2N 56.2W 45 KT...INLAND EXTRATROPICAL 251072HR VT 09/0600Z 50.5N 38.5W 45 KT...EXTRATROPICAL 251196HR VT 10/0600Z 54.5N 20.5W 45 KT...EXTRATROPICAL 2512120HR VT 11/0600Z 58.5N 11.5W 45 KT...EXTRATROPICAL 2513 2514$$ 2515FORECASTER KNABB 2516 2517 2518 2519 2520WTNT43 KNHC 061435 2521TCDAT3 2522TROPICAL STORM HANNA DISCUSSION NUMBER 39 2523NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 25241100 AM EDT SAT SEP 06 2008 2525 2526THE CENTER OF HANNA IS MOVING INTO SOUTHEASTERN VIRGINA...WITH 2527SATELLITE IMAGERY SHOWING A CONVECTIVE OVERCAST JUST NORTH OF THE 2528CENTER...AND RADAR DATA SHOWING WIDESPREAD RAINBANDS OVER THE 2529NORTHERN SEMICIRCLE. WHILE THERE ARE NO RECENT OBSERVATIONS OF 2530SUSTAINED TROPICAL STORM-FORCE WINDS...IT IS ESTIMATED THAT THE 2531MAXIMUM WINDS REMAIN 45 KT IN THE EASTERN SEMICIRCLE IN AREAS NOT 2532CURRENTLY SAMPLED. WHILE LITTLE CHANGE IN STRENGTH IS LIKELY 2533THROUGH THE FORECAST PERIOD...HANNA IS EXPECTED TO LOSE TROPICAL 2534CHARACTERISTICS IN ABOUT 24 HOURS. 2535 2536THE INITIAL MOTION IS NOW 025/22. HANNA IS ROUNDING THE END OF THE 2537WESTERN ATLANTIC RIDGE AND SHOULD ACCELERATE NORTHEASTWARD INTO THE 2538WESTERLIES DURING THE NEXT 24-48 HR. AFTER THAT...THE SYSTEM 2539SHOULD MOVE GENERALLY EAST-NORTHEASTWARD FOR THE REMAINDER OF THE 2540FORECAST PERIOD. THE MODEL GUIDANCE IS TIGHTLY CLUSTERED AROUND 2541THIS SCENARIO...AND NEW FORECAST TRACK IS ESSENTIALLY AN UPDATE OF 2542THE PREVIOUS TRACK. 2543 2544FORECAST POSITIONS AND MAX WINDS 2545 2546INITIAL 06/1500Z 36.6N 77.4W 45 KT 254712HR VT 07/0000Z 39.7N 74.7W 45 KT...INLAND 254824HR VT 07/1200Z 43.5N 68.4W 45 KT...INLAND EXTRATROPICAL 254936HR VT 08/0000Z 46.8N 60.1W 45 KT...EXTRATROPICAL 255048HR VT 08/1200Z 49.0N 51.6W 45 KT...EXTRATROPICAL 255172HR VT 09/1200Z 51.0N 34.0W 45 KT...EXTRATROPICAL 255296HR VT 10/1200Z 55.0N 19.0W 45 KT...EXTRATROPICAL 2553120HR VT 11/1200Z 59.0N 10.5W 45 KT...EXTRATROPICAL 2554 2555$$ 2556FORECASTER BEVEN 2557 2558 2559 2560000 2561 2562WTNT43 KNHC 062032 2563TCDAT3 2564TROPICAL STORM HANNA DISCUSSION NUMBER 40 2565NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2566500 PM EDT SAT SEP 06 2008 2567 2568THE CENTER OF HANNA IS MOVING OVER THE DELMARVA PENINSULA... 2569WITH RADAR DATA CONTINUING TO SHOW WIDESPREAD RAINBANDS OVER THE 2570NORTHERN SEMICIRCLE. HOWEVER...THE CENTRAL CONVECTION IS 2571DECREASING...AND THE CENTRAL PRESSURE HAS RISEN TO 994 MB. 2572RECENT SURFACE OBSERVATIONS HAVE SHOWN 35-40 KT SUSTAINED WINDS. 2573SO...THE MAXIMUM INTENSITY IS MAINTAINED AT 45 KT ON THE PREMISE 2574THAT THE MAXIMUM WINDS WERE NOT SAMPLED. AS BEFORE...WHILE LITTLE 2575CHANGE IN STRENGTH IS LIKELY THROUGH THE FORECAST PERIOD...HANNA IS 2576EXPECTED TO LOSE TROPICAL CHARACTERISTICS IN 12-24 HOURS. 2577 2578THE INITIAL MOTION IS NOW 040/23. HANNA IS ENTERING THE WESTERLIES 2579AND SHOULD ACCELERATE NORTHEASTWARD FOR THE NEXT 24-36 HR..FOLLOWED 2580BY A RAPID EASTWARD MOTION. A TURN TOWARD THE NORTHEAST WITH SOME 2581DECELERATION IS POSSIBLE AFTER 96 HR. THE MODEL GUIDANCE IS FAIRLY 2582WELL CLUSTERED AROUND THIS SCENARIO...AND THE NEW FORECAST TRACK IS 2583ESSENTIALLY AN UPDATE OF THE PREVIOUS TRACK. 2584 2585FORECAST POSITIONS AND MAX WINDS 2586 2587INITIAL 06/2100Z 38.5N 75.8W 45 KT...INLAND 258812HR VT 07/0600Z 41.7N 71.8W 45 KT...INLAND 258924HR VT 07/1800Z 45.3N 64.6W 45 KT...EXTRATROPICAL 259036HR VT 08/0600Z 48.3N 56.0W 45 KT...INLAND EXTRATROPICAL 259148HR VT 08/1800Z 49.6N 47.2W 45 KT...EXTRATROPICAL 259272HR VT 09/1800Z 51.5N 31.0W 45 KT...EXTRATROPICAL 259396HR VT 10/1800Z 56.0N 17.5W 45 KT...EXTRATROPICAL 2594120HR VT 11/1800Z 60.0N 10.0W 45 KT...EXTRATROPICAL 2595 2596$$ 2597FORECASTER BEVEN 2598 2599 2600 2601000 2602 2603WTNT43 KNHC 070250 2604TCDAT3 2605TROPICAL STORM HANNA DISCUSSION NUMBER 41 2606NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 26071100 PM EDT SAT SEP 06 2008 2608 2609THE CENTER OF HANNA IS MOVING OVER THE WEST-CENTRAL PORTION OF LONG 2610ISLAND. THE INITIAL MOTION ESTIMATE IS 050/26...AND HANNA IS RIGHT 2611ON TRACK. GRADUAL ACCELERATION IS FORECAST DURING THE NEXT 48 HOURS 2612AS HANNA GETS CAUGHT UP IN THE FAST UPPER-LEVEL WESTERLIE...AND THE 2613NEW NHC MODEL GUIDANCE IS TIGHTLY CLUSTERED ABOUT THE PREVIOUS 2614FORECAST TRACK. THEREFORE...NO SIGNIFICANT CHANGES HAVE BEEN MADE 2615AND HANNA IS EXPECTED TO CLEAR THE U.S. COASTLINE AROUND CAPE COD 2616MASSACHUSETTS BY 07/0900Z. 2617 2618HANNA'S FAST FORWARD MOTION HAS LIKELY CONTRIBUTED TO SOME OF 2619INCREASE IN OBSERVED SURFACE WINDS OBTAINED FROM SHIPS AND BUOYS 2620SOUTH OF LONG ISLAND. TWO UNCONFIRMED SHIP REPORTS OF 64 KT AND 60 2621KT HAVE BEEN RECEIVED DURING THE PAST COUPLE OF HOURS...ONE OF 2622WHICH OCCURRED IN A RAIN BAND. HOWEVER...THESE COULD HAVE BEEN 2623ISOLATED GUSTS AND THE RAIN BANDS HAVE SINCE DISSIPATED. 2624THEREFORE...THE INITIAL INTENSITY WILL BE 50 KT FOR THIS ADVISORY 2625BASED ON EARLIER DOPPLER VELOCITY VALUES OF 70 KT AT 5000 TO 7000 2626FT THAT COVERED A SIGNIFICANT PORTION OF THE SOUTHEASTERN QUADRANT 2627OF HANNA IN SEVERAL RAIN BANDS. LITTLE CHANGE IN STRENGTH IS 2628EXPECTED THROUGHOUT THE FORECAST PERIOD...AND HANNA COULD EASILY BE 2629AN EXTRATROPICAL STORM WITH 50-KT SUSTAINED WINDS AT ANY OF THE 2630FORECAST TIMES. 2631 2632FORECAST POSITIONS AND MAX WINDS 2633 2634INITIAL 07/0300Z 40.5N 73.4W 50 KT...BECOMING EXTRATROPICAL 263512HR VT 07/1200Z 43.0N 68.8W 50 KT...EXTRATROPICAL 263624HR VT 08/0000Z 46.4N 61.1W 45 KT...EXTRATROPICAL 263736HR VT 08/1200Z 48.8N 53.2W 45 KT...EXTRATROPICAL 263848HR VT 09/0000Z 50.0N 45.0W 45 KT...EXTRATROPICAL 263972HR VT 10/0000Z 52.5N 28.3W 45 KT...EXTRATROPICAL 264096HR VT 11/0000Z 56.5N 15.5W 45 KT...EXTRATROPICAL 2641120HR VT 12/0000Z 61.5N 11.5W 45 KT...EXTRATROPICAL 2642 2643$$ 2644FORECASTER STEWART 2645 2646 2647 2648 2649WTNT43 KNHC 070857 2650TCDAT3 2651TROPICAL STORM HANNA DISCUSSION NUMBER 42 2652NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 2653500 AM EDT SUN SEP 07 2008 2654 2655THE CLOUD PATTERN ASSOCIATED WITH HANNA IS SPREADING OUT WELL AHEAD 2656OF THE SURFACE CENTER...WITH THE CLOSEST DEEP CONVECTION NOW 2657DISPLACED ABOUT 125 NMI TO THE NORTH AND NORTHEAST. THE 2658CIRCULATION IS ALSO CLOSE TO...BUT NOT QUITE ENTANGLED WITH...A 2659FRONTAL BOUNDARY. BASED ON THE LOSS OF CONVECTION NEAR THE 2660CORE...HANNA IS NO LONGER CONSIDERED TO BE A TROPICAL CYCLONE AND 2661THIS WILL BE THE LAST ADVISORY. 2662 2663MAXIMUM WINDS ARE ESTIMATED TO BE 45 KT BASED ON SHIP REPORTS...AND 2664HANNA IS EXPECTED TO REMAIN A VIGOROUS EXTRATROPICAL CYCLONE DURING 2665ITS PASSAGE OVER THE NORTH ATLANTIC. THE OFFICIAL FORECAST IS IN 2666GOOD AGREEMENT WITH THE GFS. 2667 2668FUTURE INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS 2669FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE OCEAN PREDICTION 2670CENTER...UNDER AWIPS HEADER NFDHSFAT1 AND WMO HEADER FZNT01 KWBC. 2671 2672 2673FORECAST POSITIONS AND MAX WINDS 2674 2675INITIAL 07/0900Z 42.6N 70.0W 45 KT...EXTRATROPICAL 267612HR VT 07/1800Z 45.4N 64.5W 45 KT...EXTRATROPICAL 267724HR VT 08/0600Z 48.4N 57.1W 45 KT...EXTRATROPICAL 267836HR VT 08/1800Z 50.0N 50.0W 45 KT...EXTRATROPICAL 267948HR VT 09/0600Z 51.0N 43.0W 45 KT...EXTRATROPICAL 268072HR VT 10/0600Z 53.5N 27.0W 45 KT...EXTRATROPICAL 268196HR VT 11/0600Z 58.0N 16.0W 40 KT...EXTRATROPICAL 2682120HR VT 12/0600Z...ABSORBED WITHIN EXTRATROPICAL LOW 2683 2684$$ 2685FORECASTER FRANKLIN 2686 2687 2688 2689 2690