1WTNT42 KNHC 062050 2TCDAT2 3SUBTROPICAL STORM OTTO DISCUSSION NUMBER 3 4NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 5500 PM AST WED OCT 06 2010 6 7SATELLITE IMAGERY AND DATA FROM AN AIR FORCE RESERVE RECONNAISSANCE 8UNIT AIRCRAFT INDICATE THAT THE SUBTROPICAL DEPRESSION HAS 9CONTINUED TO BECOME BETTER ORGANIZED AND HAS STRENGTHEN INTO 10SUBTROPICAL STORM OTTO. CONVECTIVE BANDING NOW WRAPS ABOUT 75 11PERCENT AROUND THE BROAD INNER CORE WIND FIELD. MAXIMUM 1500-FT 12FLIGHT-LEVEL WINDS OBSERVED HAVE BEEN 63 KT IN THE SOUTHWESTERN 13QUADRANT...WHICH CORRESPONDS TO ABOUT 50 KT AT THE SURFACE. THIS 14VALUE IS CLOSE TO THE 48 KT CREDIBLE SFMR WINDS OBSERVED IN THE 15SAME AREA...SO THE INITIAL INTENSITY IS SET AT 50 KT. VISIBLE AND 16WATER VAPOR SATELLITE IMAGERY INDICATE THAT A SMALL UPPER-LEVEL 17COLD LOW...LOCATED PREVIOUSLY IN THE SOUTHEAST QUADRANT...HAS MOVED 18CYCLONICALLY AROUND THE LOW-LEVEL CIRCULATION AND IS NOW SITUATED 19ABOUT 30 NMI WEST OF THE LOW-LEVEL CENTER. THIS SUGGESTS THAT OTTO 20IS STILL A SUBTROPICAL CYCLONE...BUT THAT IT IS ALSO GRADUALLY 21ACQUIRING TROPICAL CHARACTERISTICS. 22 23THE INITIAL MOTION ESTIMATE IS 360/4. THERE ARE NO SIGNIFICANT 24CHANGES TO THE PREVIOUS FORECAST TRACK OR REASONING. OTTO IS MOVING 25NORTHWARD THROUGH A BROAD WEAKNESS IN A DEEP-LAYER RIDGE WHERE 26STEERING CURRENTS ARE WEAK. HOWEVER...A STRONG MID-TROPOSPHERIC 27TROUGH LOCATED OVER THE EASTERN U.S. IS FORECAST TO MOVE EASTWARD 28AND GRADUALLY NUDGE OTTO ON A NORTHEASTWARD TRACK DURING THE NEXT 2924 HOURS...AND THEN RAPIDLY ACCELERATE THE CYCLONE TO THE 30EAST-NORTHEAST AHEAD OF A STRONG COLD FRONT BY 36 HOURS. BETWEEN 72 31AND 96 HOURS...OTTO IS EXPECTED TO MERGE WITH THE COLD FRONT AND 32BECOME A STRONG EXTRATROPICAL LOW PRESSURE SYSTEM THAT MAY POSE A 33THREAT TO THE AZORES ISLANDS BY 120 HOURS. THE FORECAST TRACK IS 34JUST AN UPDATE OF THE PREVIOUS ADVISORY TRACK AND IS DOWN THE 35MIDDLE OF THE TIGHTLY PACKED NHC MODEL GUIDANCE. 36 37OTTO IS EXPECTED TO TRANSITION INTO A TROPICAL CYCLONE WITHIN THE 38NEXT 12 HOURS OR SO DUE TO A COMBINATION OF LIGHT VERTICAL WIND 39SHEAR...WARM SSTS OF AT LEAST 28C...AND THE EXPECTED DISSIPATION OF 40THE SMALL UPPER-LEVEL LOW. THE OFFICIAL INTENSITY FORECAST NOW 41CALLS FOR OTTO TO REACH HURRICANE STRENGTH BY 36 HOURS...AND THEN 42GRADUALLY WEAKEN AS THE WIND SHEAR INCREASES AHEAD OF THE 43AFOREMENTIONED STRONG UPPER-LEVEL TROUGH. BY 96 HOURS...OTTO IS 44EXPECTED TO TRANSITION INTO AN EXTRATROPICAL LOW. THE OFFICIAL 45INTENSITY FORECAST IS A COMPROMISE OF THE STRONGER SHIPS/LGEM 46MODELS AND THE WEAKER GFDL/HWRF MODELS. 47 48 49FORECAST POSITIONS AND MAX WINDS 50 51INITIAL 06/2100Z 23.2N 68.3W 50 KT 52 12HR VT 07/0600Z 23.8N 68.5W 55 KT 53 24HR VT 07/1800Z 24.5N 67.9W 60 KT 54 36HR VT 08/0600Z 25.5N 66.4W 65 KT 55 48HR VT 08/1800Z 26.8N 63.7W 65 KT 56 72HR VT 09/1800Z 30.3N 55.8W 55 KT 57 96HR VT 10/1800Z 34.5N 44.5W 40 KT...POST-TROP/EXTRATROP 58120HR VT 11/1800Z 39.0N 31.0W 35 KT...POST-TROP/EXTRATROP 59 60$$ 61FORECASTER STEWART 62 63 64WTNT42 KNHC 070235 65TCDAT2 66SUBTROPICAL STORM OTTO DISCUSSION NUMBER 4 67NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 681100 PM AST WED OCT 06 2010 69 70AFTER THE LAST ADVISORY WAS ISSUED...THE HURRICANE HUNTER AIRCRAFT 71MADE ONE MORE PASS THROUGH THE CENTER OF OTTO AND MEASURED A PEAK 721500-FT FLIGHT-LEVEL WIND OF 68 KT IN THE SOUTHEASTERN QUADRANT... 73CORRESPONDING TO ABOUT 54 KT AT THE SURFACE. AN SFMR WIND OF 55 KT 74WAS ALSO REPORTED EARLIER IN THE MISSION...AND THAT WILL BE THE 75INITIAL INTENSITY IN THIS ADVISORY. WATER VAPOR AND INFRARED 76IMAGERY SHOW THAT THE SURFACE AND UPPER-LEVEL LOW ARE ALMOST 77COLLOCATED...BUT RECENT AMSU DATA INDICATE THAT THE WARM CORE IN 78THE MID-LEVELS OF THE CIRCULATION IS STRENGTHENING. ALTHOUGH OTTO 79STILL LOOKS LIKE A CLASSIC SUBTROPICAL CYCLONE IN SATELLITE 80IMAGERY...IT APPEARS TO BE SLOWLY GAINING TROPICAL CHARACTERISTICS. 81 82VERTICAL SHEAR IS EXPECTED TO BE LIGHT FOR THE NEXT 48 HOURS OR 83SO...AND THE CYCLONE HAS AN OPPORTUNITY TO STRENGTHEN DURING THAT 84PERIOD. THE STATISTICAL INTENSITY GUIDANCE SHOWS THE MOST 85STRENGTHENING AND BRINGS OTTO TO AN 80-KT HURRICANE...BUT THESE 86MODELS PROBABLY DO NOT HANDLE TRANSITIONING SUBTROPICAL CYCLONES AS 87WELL AS PURE TROPICAL CYCLONES. THE OFFICIAL FORECAST LEANS CLOSER 88TO THE DYNAMICAL HURRICANE AND GLOBAL MODELS AND SHOWS OTTO 89REACHING 65 KT FROM 24 TO 48 HOURS BEFORE THE SHEAR INCREASES. 90GRADUAL WEAKENING IS EXPECTED THEREAFTER WITH OTTO BECOMING AN 91EXTRATROPICAL CYCLONE BY 96 HOURS...IF NOT SOONER. 92 93THE INITIAL MOTION IS 360/3. THE TRACK GUIDANCE REMAINS IN 94GENERALLY GOOD AGREEMENT...AND LITTLE CHANGE WAS REQUIRED TO THE 95PREVIOUS FORECAST TRACK. OTTO SHOULD MOVE LITTLE FOR THE NEXT 12 96HOURS OR SO BEFORE ACCELERATING NORTHEASTWARD BETWEEN A MID-LEVEL 97HIGH OVER THE CENTRAL ATLANTIC AND A MID/UPPER-LEVEL TROUGH OVER 98THE WESTERN ATLANTIC. 99 100FORECAST POSITIONS AND MAX WINDS 101 102INITIAL 07/0300Z 23.5N 68.2W 55 KT 103 12HR VT 07/1200Z 23.9N 68.1W 60 KT 104 24HR VT 08/0000Z 24.7N 66.9W 65 KT 105 36HR VT 08/1200Z 26.0N 64.8W 65 KT 106 48HR VT 09/0000Z 27.8N 61.6W 65 KT 107 72HR VT 10/0000Z 32.0N 52.0W 60 KT 108 96HR VT 11/0000Z 37.0N 38.5W 45 KT...POST-TROP/EXTRATROP 109120HR VT 12/0000Z 42.0N 27.0W 40 KT...POST-TROP/EXTRATROP 110 111$$ 112FORECASTER BERG 113 114 115WTNT42 KNHC 070842 116TCDAT2 117SUBTROPICAL STORM OTTO DISCUSSION NUMBER 5 118NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 119500 AM AST THU OCT 07 2010 120 121OTTO HAS BEEN STRUGGLING TO PRODUCE MUCH CONVECTION DURING THE 122OVERNIGHT HOURS. A CURVED OUTER BAND PERSISTS IN THE SOUTHERN 123SEMICIRCLE OF THE STORM...WITH A SMALL AMOUNT OF CONVECTION NEAR 124THE CENTER. SINCE THE CLOUD PATTERN HAS DETERIORATED A LITTLE 125BIT...THE MAXIMUM WINDS ARE REDUCED TO 50 KT...IN AGREEMENT WITH 126VARIOUS SATELLITE INTENSITY ESTIMATES FROM 35 TO 50 KT. IF THE 127CONVECTION NEAR THE CENTER CONTINUES...THEN OTTO WILL LIKELY 128TRANSITION INTO A TROPICAL STORM LATER TODAY. THE SYSTEM STILL HAS 129DAY OR TWO OF LIGHT SHEAR CONDITIONS AND WARM WATER TO INTENSIFY. 130IN FACT...ALL OF THE GUIDANCE SHOW OTTO BECOMING A HURRICANE...AND 131THE NHC FORECAST WILL GO ALONG WITH THAT SCENARIO. HOWEVER...OTTO 132PROBABLY NEEDS TO SHED ITS SUBTROPICAL CHARACTERISTICS TO TAKE 133ADVANTAGE OF THE FAVORABLE ENVIRONMENT. SINCE THE SYSTEM IS STILL 134RETAINING SOME SUBTROPICAL FEATURES...THE NHC FORECAST REMAINS 135BELOW THE MODEL CONSENSUS. GLOBAL MODELS SHOW OTTO BECOMING 136EMBEDDED WITHIN A FRONTAL ZONE BY 72 HR...SO EXTRATROPICAL STATUS 137IS INDICATED IN THE OFFICIAL FORECAST AT THAT TIME. 138 139THE STORM HAS NOT BEEN MOVING MUCH DURING THE PAST FEW HOURS AND IS 140ONLY DRIFTING NORTHWARD. INITIALLY...OTTO IS IN AN AREA OF LIGHT 141STEERING CURRENTS BETWEEN A DISTANT RIDGE OVER THE EAST-CENTRAL 142ATLANTIC OCEAN AND A MID-LATITUDE TROUGH OVER THE WESTERN ATLANTIC. 143THE TROUGH IS EXPECTED TO DIG SOUTHEASTWARD TODAY...WHICH SHOULD 144STEER OTTO MORE TO THE NORTHEAST AND CAUSE A FASTER FORWARD SPEED 145AS THE STORM MOVES IN FASTER FLOW BETWEEN THE RIDGE AND THE TROUGH. 146WHILE THE MODEL GUIDANCE REMAINS WELL CLUSTERED ON THIS SYNOPTIC 147PATTERN...THERE ARE SOME NOTABLE SPEED DIFFERENCES...AS THE 148GFDL/HWRF ARE MUCH FASTER THAN THE REST OF THE GUIDANCE. FOR NOW 149THE TRACK FORECAST WILL STAY CLOSER TO THE GLOBAL MODELS...SHOWING 150A SLOWER FORWARD MOTION...AND THE PREVIOUS NHC FORECAST. THE 15196 AND 120 HR POSITIONS OF OTTO MAY HAVE TO BE ADJUSTED SOUTHWARD 152LATER TODAY DUE TO THE POSSIBILITY THAT THE CYCLONE GETS CAUGHT UP 153IN NORTHWESTERLY FLOW FROM A TROUGH EAST OF THE AZORES...RATHER 154THAN MID-LATITUDE SOUTHWESTERLY FLOW AS EARLIER MODEL RUNS WERE 155INDICATING. 156 157 158FORECAST POSITIONS AND MAX WINDS 159 160INITIAL 07/0900Z 23.6N 68.2W 50 KT 161 12HR VT 07/1800Z 24.0N 67.7W 55 KT 162 24HR VT 08/0600Z 25.1N 66.0W 60 KT 163 36HR VT 08/1800Z 26.8N 63.3W 65 KT 164 48HR VT 09/0600Z 28.8N 59.7W 60 KT 165 72HR VT 10/0600Z 33.5N 48.5W 55 KT...POST-TROP/EXTRATROP 166 96HR VT 11/0600Z 38.5N 35.0W 45 KT...POST-TROP/EXTRATROP 167120HR VT 12/0600Z 41.0N 25.0W 35 KT...POST-TROP/EXTRATROP 168 169$$ 170FORECASTER BLAKE 171 172 173WTNT42 KNHC 071442 174TCDAT2 175TROPICAL STORM OTTO DISCUSSION NUMBER 6 176NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 1771100 AM AST THU OCT 07 2010 178 179OTTO HAS FINALLY TRANSITIONED INTO A TROPICAL CYCLONE BASED ON A 18007/0935Z AMSU VERTICAL TEMPERATURE ANALYSIS PROFILE FROM UW-CIMSS 181THAT INDICATED THE WARM CORE HAD MOVED UPWARD FROM THE MID-LEVELS 182TO THE UPPER-LEVELS OF THE CYCLONE. A RECENT BURST OF DEEP 183CONVECTION WITH CLOUD TOP TEMPERATURES NEAR -80C THAT HAS DEVELOPED 184OVER THE CENTER ALSO SUPPORTS A TRANSITION TO TROPICAL CYCLONE 185STATUS. SATELLITE INTENSITY ESTIMATES ARE RUNNING BETWEEN T2.0/30 186KT AND T2.5/35 KT FROM TAFB...SAB...AND UW-CIMSS USING A CURVED 187BAND PATTERN. HOWEVER...USING A SHEAR PATTERN WITH THE RECENT BURST 188OF CENTRAL CONVECTION YIELDS A VALUE OF T3.5/55 KT. SINCE THE 189CONVECTION HAS ONLY PERSISTED FOR ABOUT 3-4 HOURS...THE INITIAL 190INTENSITY WILL BE MAINTAINED AT 50 KT FOR THIS ADVISORY...BUT THE 19150-KT WIND RADII DISTANCE HAS BEEN REDUCED FROM 45 NMI TO 15 NMI. 192 193OTTO HAS ESSENTIALLY BEEN STATIONARY FOR THE PAST 6 HOURS...BUT A 194SLOW DRIFT TO THE NORTHEAST...OR 325/02...IS EXPECTED TO BEGIN SOON 195AND THAT IS THE MOTION USED FOR THIS ADVISORY. OTHERWISE...THERE 196REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACKS OR 197PHILOSOPHIES FOR THE PAST 24 HOURS. A LARGE DEEP-LAYER TROUGH ALONG 198THE U.S. EAST COAST IS EXPECTED TO CONTINUE ITS EASTWARD TREK AND 199GRADUALLY NUDGE OTTO TO THE NORTHEAST DURING THE NEXT 24 HOURS. BY 20036-48 HOURS...HOWEVER...THE LARGE TROUGH IS FORECAST TO CAPTURE 201OTTO AND ACCELERATE IT TO THE NORTHEAST AHEAD OF A STRONG COLD 202FRONT. OTTO IS EXPECTED TO MERGE WITH THE FRONTAL SYSTEM BY 72 203HOURS AND BECOME A SIGNIFICANT EXTRATROPICAL CYCLONE THAT COULD 204AFFECT THE AZORES ISLANDS IN 96 TO 120 HOURS. THE OFFICIAL FORECAST 205TRACK IS BASICALLY JUST AN UPDATE OF THE PREVIOUS TRACK AND IS 206CLOSE TO THE CONSENSUS MODEL...TVCN. 207 208NOW THAT OTTO HAS TRANSITIONED INTO A TROPICAL CYCLONE...THE STORM 209HAS A BETTER CHANCE OF REACHING HURRICANE STATUS AS FORECAST BY THE 210GFDL AND HWRF MODELS. THE VERTICAL SHEAR IS EXPECTED TO REMAIN 211AROUND 10 KT OR LESS FOR THE NEXT 24 HOURS WHILE OTTO WILL BE OVER 21228C OR WARMER SSTS. THE MUCH SMALLER INNER CORE WIND FIELD ALSO 213SHOULD ALLOW FOR A MORE RAPID RESPONSE TO DEEP CONVECTION THAT 214DEVELOPS NEAR THE CENTER. IN THE LATER FORECAST PERIODS...THE 215INTENSITY HAS BEEN HELD A LITTLE HIGHER THAN WHAT WOULD TYPICALLY 216BE EXPECTED FOR A CYCLONE EXPERIENCING SHEAR CONDITIONS OF 40-50 KT 217DUE TO EXTRATROPICAL TRANSITION AND AN EXPECTED INFUSION OF 218BAROCLINIC ENERGY THAT SHOULD HELP TO SUSTAIN THE CIRCULATION. THE 219OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND 220IS A BLEND OF THE NHC OBJECTIVE INTENSITY GUIDANCE. 221 222 223FORECAST POSITIONS AND MAX WINDS 224 225INITIAL 07/1500Z 23.8N 68.0W 50 KT 226 12HR VT 08/0000Z 24.3N 67.1W 55 KT 227 24HR VT 08/1200Z 25.7N 65.0W 60 KT 228 36HR VT 09/0000Z 27.6N 61.8W 65 KT 229 48HR VT 09/1200Z 29.8N 57.2W 60 KT 230 72HR VT 10/1200Z 34.7N 45.2W 55 KT...POST-TROP/EXTRATROP 231 96HR VT 11/1200Z 39.0N 32.5W 45 KT...POST-TROP/EXTRATROP 232120HR VT 12/1200Z 39.0N 25.0W 35 KT...POST-TROP/EXTRATROP 233 234$$ 235FORECASTER STEWART 236 237 238WTNT42 KNHC 072035 239TCDAT2 240TROPICAL STORM OTTO DISCUSSION NUMBER 7 241NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 242500 PM AST THU OCT 07 2010 243 244BURSTS OF DEEP CONVECTION WITH CLOUD TOP TEMPERATURES OF -70C TO 245-80C HAVE CONTINUED TO DEVELOP OVER AND EAST OF THE LOW-LEVEL 246CENTER DURING THE PAST 6 HOURS. SHEAR PATTERN SATELLITE INTENSITY 247ESTIMATES HAVE BEEN VARYING BETWEEN T3.0/45 KT AND T3.5/55 KT. 248THEREFORE...THE INITIAL INTENSITY WILL REMAIN AT 50 KT. ALTHOUGH 249A SMALL UPPER-LEVEL ANTICYCLONE HAS DEVELOPED OVER THE CENTER OF 250OTTO...LOWER CIRRUS CLOUD ELEMENTS CAN BE SEEN UNDERCUTTING THE 251FAVORABLE OUTFLOW LAYER IN VISIBLE AND WATER VAPOR IMAGERY...WHICH 252IS CREATING SOME MODEST UPPER-LEVEL SHEAR CONDITIONS ON THE CYCLONE. 253 254THE INITIAL MOTION ESTIMATE IS 050/05. OTTO IS COMING UNDER THE 255INCREASING INFLUENCE OF A LARGE DEEP-LAYER TROUGH THAT HAS MOVED 256EASTWARD OFF THE U.S. EAST COAST. THE TROUGH IS FORECAST BY ALL OF 257THE MODELS TO CONTINUE MOVING EASTWARD AND STEADILY ACCELERATE OTTO 258TO THE NORTHEAST DURING THE NEXT 48 HOURS. BY 72 HOURS...OTTO IS 259EXPECTED TO MERGE WITH A FRONTAL SYSTEM AND BECOME AN EXTRATROPICAL 260CYCLONE AND GALE AREA THAT COULD AFFECT THE AZORES ISLANDS IN 96 TO 261120 HOURS. THE OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS 262ADVISORY TRACK AND IS CLOSE TO THE CONSENSUS MODEL...TVCN. 263 264SLOW STRENGTHENING IS EXPECTED DURING THE NEXT 24 HOURS OR SO WHILE 265OTTO REMAINS OVER WARM SSTS AND ALSO MOVES INTO AN AREA OF 266INCREASING INSTABILITY LOCATED IN THE EASTERN SEMICIRCLE. VERTICAL 267WIND SHEAR IS EXPECTED TO DECREASE SLIGHTLY BETWEEN 24 AND 36 268HOURS...AND THAT IS WHEN OTTO COULD POSSIBLY REACH HURRICANE 269STRENGTH AS SUGGESTED BY THE GFDL/HWRF MODELS. HOWEVER...THIS WOULD 270LIKELY BE SHORT-LIVED DUE TO INCREASING WESTERLY SHEAR. BY 72 271HOURS...OTTO IS EXPECTED TO ENCOUNTER STRONGER SHEAR OF 35-40 272KT...WHICH SHOULD HASTEN THE WEAKENING PROCESS. HOWEVER...OTTO IS 273EXPECTED TO BE AN EXTRATROPICAL GALE AREA BY THAT TIME...AND THE 274INFUSION OF BAROCLINIC ENERGY SHOULD HELP MAINTAIN THE CYCLONE. THE 275OFFICIAL OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS 276ADVISORY AND IS A BLEND OF THE NHC OBJECTIVE INTENSITY GUIDANCE. 277 278 279FORECAST POSITIONS AND MAX WINDS 280 281INITIAL 07/2100Z 24.0N 67.6W 50 KT 282 12HR VT 08/0600Z 24.7N 66.3W 55 KT 283 24HR VT 08/1800Z 26.1N 63.8W 60 KT 284 36HR VT 09/0600Z 28.4N 59.7W 60 KT 285 48HR VT 09/1800Z 30.8N 54.5W 55 KT 286 72HR VT 10/1800Z 35.7N 42.3W 50 KT...POST-TROP/EXTRATROP 287 96HR VT 11/1800Z 39.0N 29.0W 40 KT...POST-TROP/EXTRATROP 288120HR VT 12/1800Z 37.0N 23.5W 35 KT...POST-TROP/EXTRATROP 289 290$$ 291FORECASTER STEWART 292 293 294WTNT42 KNHC 080241 295TCDAT2 296TROPICAL STORM OTTO DISCUSSION NUMBER 8 297NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 2981100 PM AST THU OCT 07 2010 299 300A LITTLE BIT OF WESTERLY SHEAR IS AFFECTING OTTO...AND THE LOW-LEVEL 301CENTER IS EMBEDDED BENEATH THE WESTERN SIDE OF A NEARLY CIRCULAR 302AREA OF DEEP CONVECTION. SATELLITE INTENSITY ESTIMATES ARE T3.5/55 303KT AND T3.0/45 KT FROM TAFB AND SAB...RESPECTIVELY...AND THE 304INITIAL INTENSITY WILL BE MAINTAINED AT 50 KT. STRENGTHENING IS 305STILL POSSIBLE DURING THE NEXT 48 HOURS SINCE THE VERTICAL SHEAR IS 306EXPECTED TO BE RELATIVELY LIGHT. THE ONE BIG CHANGE IN THE 307INTENSITY GUIDANCE IS THAT MOST OF THE MODELS NOW SHOW A PEAK IN 308INTENSITY OCCURRING AROUND 48 HOURS...WHICH IS ABOUT 12 HOURS LATER 309THAN INDICATED IN THE PREVIOUS ADVISORY. THE NEW FORECAST... 310THEREFORE...DOES NOT SHOW WEAKENING COMMENCING UNTIL AFTER 48 311HOURS. THIS SOLUTION IS CLOSE TO THE STATISTICAL AND GLOBAL 312GUIDANCE BUT TENDS TO DISREGARD THE HWRF AND GFDL SINCE THOSE 313MODELS APPEAR TO DISSIPATE OTTO TOO SOON. 314 315THE INITIAL MOTION IS 070/8. THE CYCLONE IS BEING PICKED UP BY A 316LARGE MID/UPPER-LEVEL TROUGH OVER THE WESTERN ATLANTIC AND IS 317EXPECTED TO BECOME EMBEDDED WITHIN FAST MID-LATITUDE WESTERLIES 318OVER THE NEXT 24-48 HOURS. BY THE END OF THE FORECAST...MODEL 319GUIDANCE SUGGESTS THAT THE FLOW WILL SPLIT WITH THE POST-TROPICAL 320CYCLONE TAKING THE SOUTHERN ROUTE AND SLOWING DOWN AS IT NEARS THE 321AZORES. THE OFFICIAL FORECAST IS NOT MUCH DIFFERENT FROM THE 322PREVIOUS ONE AND GENERALLY LIES BETWEEN THE FASTER ECMWF AND SLOWER 323GFS. 324 325THE FSU PHASE SPACE DIAGRAMS SHOW THAT OTTO SHOULD BEGIN 326EXTRATROPICAL TRANSITION IN THE NEXT 24-36 HOURS...BUT THEY ALSO 327SUGGEST THAT IT WILL NOT BECOME A DEEP COLD-CORE SYSTEM WITHIN THE 3285-DAY FORECAST PERIOD. AS SUCH...CONFIDENCE IS NOT HIGH THAT OTTO 329WILL BECOME COMPLETELY EXTRATROPICAL BY 72 HOURS. 330 331FORECAST POSITIONS AND MAX WINDS 332 333INITIAL 08/0300Z 24.1N 66.6W 50 KT 334 12HR VT 08/1200Z 24.9N 65.1W 55 KT 335 24HR VT 09/0000Z 26.7N 62.0W 55 KT 336 36HR VT 09/1200Z 29.0N 57.6W 60 KT 337 48HR VT 10/0000Z 31.4N 52.1W 60 KT 338 72HR VT 11/0000Z 36.5N 38.5W 50 KT...POST-TROP/EXTRATROP 339 96HR VT 12/0000Z 39.0N 27.0W 45 KT...POST-TROP/EXTRATROP 340120HR VT 13/0000Z 36.5N 23.0W 35 KT...POST-TROP/EXTRATROP 341 342$$ 343FORECASTER BERG 344 345 346WTNT42 KNHC 080842 347TCDAT2 348TROPICAL STORM OTTO DISCUSSION NUMBER 9 349NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 350500 AM AST FRI OCT 08 2010 351 352SATELLITE IMAGES INDICATE THAT DEEP AND SYMMETRIC CONVECTION HAS 353INTENSIFIED NEAR THE CENTER OF OTTO DURING THE PAST SEVERAL HOURS 354WITH AN OCCASIONAL HINT OF A WARM SPOT IN THE INFRARED CHANNEL. 355UNFORTUNATELY THERE HAVE BEEN NO RECENT MICROWAVE OVERPASSES TO 356HELP LOCATE THE CENTER...WHICH HANDICAPS THE INTENSITY ESTIMATE. 357DVORAK NUMBERS FROM TAFB/SAB ARE 65/55 KT...AND A BLEND OF THESE 358DATA GIVE AN INITIAL WIND SPEED OF 60 KT. THE SHIPS MODEL SUGGESTS 359THAT SOUTHWESTERLY SHEAR WILL RELAX NEAR OTTO DURING THE NEXT 24 360HOURS...WHICH SHOULD ALLOW THE STORM TO BECOME A HURRICANE. 361GUIDANCE IS NOW IN AGREEMENT ON OTTO ATTAINING HURRICANE STRENGTH 362LATER TODAY. SINCE ANY SUBTROPICAL CHARACTERISTICS ARE NOW 363GONE...I DO NOT SEE A GOOD REASON TO DISCOUNT THE GUIDANCE...AND 364THE OFFICIAL FORECAST IS RAISED FROM THE PREVIOUS ONE...JUST BELOW 365THE MODEL CONSENSUS. WEAKENING SEEMS LIKELY IN A COUPLE OF DAYS 366DUE TO WATERS COOLING BELOW 26C AND INCREASING SOUTHWESTERLY SHEAR. 367 368BASED PRIMARILY ON CONTINUITY FROM THE PREVIOUS FORECAST TRACK...THE 369INITIAL MOTION IS 060/12. OTTO IS BEING ACCELERATED GENERALLY 370NORTHEASTWARD BY A LARGE MID-LATITUDE TROUGH OVER THE WESTERN 371ATLANTIC OCEAN. THE TROPICAL CYCLONE SHOULD BECOME EMBEDDED WITHIN 372FAST SOUTHWESTERLY FLOW FOR THE NEXT TWO TO THREE DAYS...AND MODEL 373GUIDANCE IS IN GOOD AGREEMENT ON THE TRACK DURING THAT TIME. 374HOWEVER...LARGE DISAGREEMENTS OCCUR IN THE LONG RANGE AS IT IS NOT 375CLEAR WHETHER OTTO WILL REMAIN WITHIN THE MID-LATITUDE FLOW OR TURN 376MORE TO THE EAST AND SOUTHEAST AROUND THE WEST SIDE OF A TROUGH 377OVER THE FAR NORTHEASTERN ATLANTIC OCEAN. THE MOST RELIABLE 378GUIDANCE SHOW THE LATTER SOLUTION...AND THE OFFICIAL FORECAST WILL 379STAY WITH THAT SCENARIO. 380 381EXTRATROPICAL TRANSITION WILL PROBABLY BEGIN AFTER THE CYCLONE 382CROSSES 30N AS THE CYCLONE MOVES OVER COOLER WATERS AND INTO HIGHER 383SHEAR. FSU PHASE SPACE DIAGRAMS...HOWEVER...SUGGEST THAT OTTO WILL 384RETAIN ITS WARM CORE FOR SEVERAL DAYS. THE MODEL THICKNESS FIELDS 385DO SHOW THE CYCLONE DEVELOPING FRONTAL FEATURES IN ABOUT THREE 386DAYS... THUS EXTRATROPICAL STATUS IS SHOWN AT THAT TIME. 387 388 389FORECAST POSITIONS AND MAX WINDS 390 391INITIAL 08/0900Z 24.8N 65.5W 60 KT 392 12HR VT 08/1800Z 25.9N 63.6W 65 KT 393 24HR VT 09/0600Z 28.0N 60.1W 70 KT 394 36HR VT 09/1800Z 30.3N 55.2W 75 KT 395 48HR VT 10/0600Z 33.2N 49.0W 70 KT 396 72HR VT 11/0600Z 38.5N 34.0W 55 KT...POST-TROP/EXTRATROP 397 96HR VT 12/0600Z 39.0N 25.5W 45 KT...POST-TROP/EXTRATROP 398120HR VT 13/0600Z 36.5N 21.5W 35 KT...POST-TROP/EXTRATROP 399 400$$ 401FORECASTER BLAKE 402 403 404WTNT42 KNHC 081431 405TCDAT2 406HURRICANE OTTO DISCUSSION NUMBER 10 407NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 4081100 AM AST FRI OCT 08 2010 409 410SATELLITE IMAGES INDICATE THAT OTTO IS STEADILY INCREASING IN 411ORGANIZATION. THE CYCLONE HAS DEVELOPED A WELL DEFINED AND LARGE 412CENTRAL DENSE OVERCAST DURING THE LAST 6-12 HOURS...WITH A CURVED 413BAND OVER THE SOUTHEAST QUADRANT ATTACHED TO THE MAIN CONVECTIVE 414MASS. A 1059 UTC SSMIS OVERPASS SHOWED THE DEVELOPMENT OF A 415MID-LEVEL EYEWALL...ALTHOUGH THE LOW-LEVEL CENTER APPEARS TO BE A 416BIT TO THE WEST OF THAT FEATURE. DVORAK T-NUMBERS ARE AT 4.0 FROM 417TAFB AND SAB...AND OTTO IS UPGRADED TO A HURRICANE BASED UPON THESE 418DATA AND THE EARLIER MICROWAVE OVERPASS. THE SHIPS MODEL OUTPUT 419INDICATES THAT OTTO SHOULD REMAIN IN A GENERALLY LIGHT SHEAR 420ENVIRONMENT DURING THE NEXT 24 HOURS AND OVER MARGINALLY WARM 421WATERS...BOTH OF WHICH SHOULD LEAD TO SOME ADDITIONAL 422INTENSIFICATION. AFTER THAT...WEAKENING SHOULD OCCUR AS OTTO 423ENCOUNTERS A RAPID INCREASE IN SOUTHWESTERLY SHEAR AND MOVES OVER 424PROGRESSIVELY COOLER WATERS. THE OFFICIAL INTENSITY FORECAST IS 425SIMILAR TO THE PREVIOUS ONE AND CLOSE TO THE SHIPS/LGEM INTENSITY 426GUIDANCE. 427 428OTTO HAS CONTINUED TO ACCELERATE EAST-NORTHEASTWARD...AND THE LATEST 429FIXES SUGGEST AN INITIAL MOTION OF 060/15. THE TRACK GUIDANCE IS 430IN GOOD AGREEMENT THAT OTTO SHOULD ACCELERATE FURTHER ON A 431GENERALLY NORTHEASTWARD COURSE DURING THE NEXT 2-3 DAYS...EMBEDDED 432IN A SWIFT SOUTHWESTERLY FLOW ASSOCIATED WITH A DEEP LAYER TROUGH 433COVERING THE NORTHWEST ATLANTIC. BEYOND ABOUT 72 HOURS...OTTO IS 434EXPECTED TO SEPARATE FROM THE MID-LATITUDE SOUTHWESTERLY FLOW AND 435TURN EASTWARD AND THEN SOUTHEASTWARD ON THE WEST SIDE OF A TROUGH 436OVER THE NORTHEAST ATLANTIC AND WESTERN EUROPE. ALTHOUGH THIS 437SOLUTION IS GENERALLY FAVORED BY GLOBAL MODELS...THERE REMAINS SOME 438SPREAD IN THE GUIDANCE AS TO WHERE AND WHEN THE EXPECTED TURN 439TOWARD THE EAST SHOULD OCCUR. THE OFFICIAL FORECAST TRACK IS CLOSE 440TO THE PREVIOUS ONE THROUGH 48 HOURS AND IS ADJUSTED A BIT TO THE 441LEFT BEYOND THAT TIME...FOLLOWING THE TREND IN THE GUIDANCE. 442 443EXTRATROPICAL TRANSITION WILL LIKELY BEGIN IN ABOUT 48 HOURS ONCE 444OTTO BECOMES MORE DEEPLY INVOLVED WITH THE FAST-PACED...MID- 445LATITUDE FLOW TO THE NORTH. THERE IS STILL A FAIR AMOUNT OF 446UNCERTAINTY REGARDING THE COMPLETION OF THIS PROCESS AS OTTO IS 447FORECAST TO REMAIN TO THE SOUTH OF THE MAIN BAROCLINIC ZONE OVER 448THE NORTH ATLANTIC. 449 450 451FORECAST POSITIONS AND MAX WINDS 452 453INITIAL 08/1500Z 25.9N 64.0W 65 KT 454 12HR VT 09/0000Z 27.3N 61.7W 70 KT 455 24HR VT 09/1200Z 29.7N 57.5W 75 KT 456 36HR VT 10/0000Z 32.4N 51.9W 70 KT 457 48HR VT 10/1200Z 35.5N 45.0W 65 KT 458 72HR VT 11/1200Z 40.0N 31.0W 50 KT...POST-TROP/EXTRATROP 459 96HR VT 12/1200Z 40.0N 24.0W 40 KT...POST-TROP/EXTRATROP 460120HR VT 13/1200Z 37.0N 22.0W 35 KT...POST-TROP/EXTRATROP 461 462$$ 463FORECASTER KIMBERLAIN 464 465 466WTNT42 KNHC 082038 467TCDAT2 468HURRICANE OTTO DISCUSSION NUMBER 11 469NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 470500 PM AST FRI OCT 08 2010 471 472OTTO CONTINUES TO MAINTAIN A CENTRAL DENSE OVERCAST WITH CLOUD TOPS 473COLDER THAN -80C NEAR THE CENTER...ALONG WITH AN AREA OF OUTER 474BANDING OVER THE EASTERN SEMICIRCLE. SATELLITE INTENSITY ESTIMATES 475ARE 77 KT FROM SAB AND 65 KT FROM TAFB...AND THERE IS A RECENT 476CIMSS AMSU INTENSITY ESTIMATE OF 63 KT. THE INITIAL INTENSITY IS 477INCREASED TO 70 KT AS A BLEND OF THESE DATA. THE CIRRUS OUTFLOW IS 478GOOD IN THE NORTHEASTERN SEMICIRCLE AND FAIR/POOR ELSEWHERE. 479 480THE INITIAL MOTION IS NOW 055/18. THERE IS LITTLE CHANGE IN THE 481FORECAST PHILOSOPHY...GUIDANCE...OR FORECAST TRACK DURING THE FIRST 48272 HR OF THE FORECAST. OTTO IS BECOMING EMBEDDED IN THE STRONG 483SOUTHWESTERLY FLOW OVER THE CENTRAL ATLANTIC...AND IT SHOULD MOVE 484RAPIDLY NORTHEASTWARD FOR THE NEXT THREE DAYS OR SO. AFTER 72 485HR...THE GUIDANCE HAS BECOME DIVERGENT. WHILE THE GFS...GFS 486ENSEMBLE MEAN...AND HWRF STILL SHOW A TURN TOWARD THE SOUTHEAST... 487THE UKMET...CANADIAN...NOGAPS...AND GFDL NOW SHOW A CONTINUED 488NORTHEASTWARD MOTION. THE ECMWF IS IN BETWEEN THESE CAMPS... 489FORECASTING OTTO TO MOVE NORTHEASTWARD FOR 84-96 HR BEFORE SHARPLY 490TURNING IT DUE SOUTH. THE NEW FORECAST TRACK GENERALLY FOLLOWS THE 491GFS SCENARIO...BUT IS SHIFTED TO THE NORTH OUT OF RESPECT FOR THE 492OTHER MODELS. HOWEVER...THIS PART OF THE FORECAST TRACK STILL LIES 493WELL TO THE RIGHT OF THE CENTER OF THE GUIDANCE ENVELOPE...AND MORE 494NORTHWARD ADJUSTMENT OF THE TRACK COULD BE NEEDED LATER. 495 496OTTO WILL SPEND 12-24 HR IN A LIGHT VERTICAL WIND SHEAR/WARM SEA 497SURFACE TEMPERATURE ENVIRONMENT...AND THE INTENSITY FORECAST THUS 498SHOWS A LITTLE MORE STRENGTHENING DURING THAT TIME. AFTER 24 HR... 499INCREASING SHEAR AND DECREASING SEA SURFACE TEMPERATURES SHOULD 500START A WEAKENING TREND. EXTRATROPICAL TRANSITION IS EXPECTED TO 501BEGIN AT ABOUT 48 HR AND BE COMPLETE BY 72 HR. HOWEVER...THERE IS 502STILL A FAIR AMOUNT OF UNCERTAINTY REGARDING THE COMPLETION OF THIS 503PROCESS DUE TO DISAGREEMENT IN THE DYNAMICAL MODELS ON HOW CLOSE 504OTTO WILL BE TO THE MAIN BAROCLINIC ZONE OVER THE NORTH ATLANTIC. 505 506FORECAST POSITIONS AND MAX WINDS 507 508INITIAL 08/2100Z 26.8N 62.3W 70 KT 509 12HR VT 09/0600Z 28.7N 59.5W 75 KT 510 24HR VT 09/1800Z 31.3N 54.6W 75 KT 511 36HR VT 10/0600Z 34.3N 48.2W 70 KT 512 48HR VT 10/1800Z 38.2N 40.6W 65 KT 513 72HR VT 11/1800Z 42.0N 30.0W 50 KT...POST-TROP/EXTRATROP 514 96HR VT 12/1800Z 41.0N 25.0W 40 KT...POST-TROP/EXTRATROP 515120HR VT 13/1800Z 39.0N 20.0W 40 KT...POST-TROP/EXTRATROP 516 517$$ 518FORECASTER BEVEN 519 520 521WTNT42 KNHC 090232 522TCDAT2 523HURRICANE OTTO DISCUSSION NUMBER 12 524NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 5251100 PM AST FRI OCT 08 2010 526 527ALTHOUGH THE CENTRAL DENSE OVERCAST FEATURE HAS DECREASED IN AREAL 528COVERAGE...CLOUD TOP TEMPERATURES COLDER THAN -80C HAVE PERSISTED 529NEAR THE UPPER-LEVEL CENTER. A 08/2217Z SSMIS MICROWAVE OVERPASS 530INDICATED THE EYE IS TILTED SIGNIFICANTLY DOWNSTREAM TO THE 531NORTHEAST BY AT LEAST 35 NMI BETWEEN THE LOW- AND MID-LEVEL 532CIRCULATIONS. SUBJECTIVE SATELLITE INTENSITY ESTIMATES ARE T5.0/90 533KT FROM TAFB AND T4.5/77 KT FROM SAB...AND AROUND 67 KT FROM THE 534UW-CIMSS ADT PROGRAM. THEREFORE...THE INITIAL INTENSITY IS BEING 535INCREASED TO 75 KT...AND OTTO HAS LIKELY PEAKED IN STRENGTH GIVEN 536THE EYEWALL WAS OPEN AT ALL LEVELS IN THE AFOREMENTIONED SSMIS 537MICROWAVE IMAGES. 538 539THE INITIAL MOTION IS 060/18. WATER VAPOR IMAGERY INDICATES OTTO IS 540NOW EMBEDDED WITHIN A DEEP-LAYER WEST-SOUTHWESTERLY FLOW ON THE 541EAST SIDE OF A MASSIVE MID-LATITUDE TROUGH THAT EXTENDS SOUTHWARD 542FROM THE CANADIAN MARITIME PROVINCES TO THE NORTHERN BAHAMAS. THIS 543FLOW REGIME SHOULD CONTINUE TO ACCELERATE OTTO TO THE NORTHEAST OR 544EAST-NORTHEAST FOR THE NEXT 72 HOURS OR SO...WHICH IS CONSISTENT 545WITH ALL OF THE NHC MODEL GUIDANCE. AFTER THAT...HOWEVER...THE 546GUIDANCE REMAINS DIVERGENT ON WHETHER OTTO WILL CONTINUE TO MOVE TO 547THE NORTHEAST OR SLOW DOWN AND TURN SOUTHEASTWARD TOWARD THE AZORES 548ISLANDS. THERE IS MUCH LESS SPREAD IN THE MODEL SOLUTIONS FOR THIS 549RUN COMPARED TO THE PREVIOUS ADVISORY...SO THE FORECAST TRACK HAS 550BEEN SHIFTED SLIGHTLY NORTHWARD WITH A NOTED DECREASE IN FORWARD 551SPEED. OVERALL...THE OFFICIAL FORECAST IS SIMILAR TO THE CONSENSUS 552MODEL...TVCN...THROUGH 72 HOURS...AND THEN A LITTLE SOUTH OF THAT 553MODEL AT 96 AND 120 HOURS. 554 555CONVENTIONAL INFRARED SATELLITE POSITION ESTIMATES INDICATE THAT THE 556UPPER-LEVEL CIRCULATION IS OUTRUNNING THE LOW-LEVEL CENTER NOTED IN 557MICROWAVE DATA BY MORE THAN 60 NMI...SO GRADUAL WEAKENING IS 558FORECAST SINCE OTTO WILL BE MOVING OVER PROGRESSIVELY COOLER SSTS 559AND EXPERIENCING INCREASING SOUTHWESTERLY VERTICAL SHEAR. TIMING 560POSSIBLE DECOUPLING OF THE LOWER- AND UPPER-LEVEL CIRCULATIONS IS 561TRICKY. HOWEVER...SINCE OTTO WILL BE MOVING OVER SUB-23C SSTS...BE 562UNDERNEATH VERTICAL SHEAR CONDITIONS EXCEEDING 40 KT...AND POSSIBLY 563MERGE WITH A FRONTAL ZONE BY 48 HOURS...OTTO IS EXPECTED TO BEGIN 564EXTRATROPICAL TRANSITION BETWEEN 36-48 HOURS. THE INTENSITY 565FORECAST IS SIMILAR TO BUT SLIGHTLY LOWER THAN A BLEND OF THE NHC 566INTENSITY GUIDANCE...DUE IN PART TO THE TILTED VORTEX STRUCTURE. 567 568FORECAST POSITIONS AND MAX WINDS 569 570INITIAL 09/0300Z 27.8N 60.8W 75 KT 571 12HR VT 09/1200Z 29.7N 57.4W 70 KT 572 24HR VT 10/0000Z 32.6N 51.7W 70 KT 573 36HR VT 10/1200Z 36.1N 44.4W 65 KT 574 48HR VT 11/0000Z 40.0N 36.4W 60 KT...POST-TROP/EXTRATROP 575 72HR VT 12/0000Z 43.0N 28.0W 50 KT...POST-TROP/EXTRATROP 576 96HR VT 13/0000Z 43.0N 23.5W 40 KT...POST-TROP/EXTRATROP 577120HR VT 14/0000Z 40.0N 20.0W 40 KT...POST-TROP/EXTRATROP 578 579$$ 580FORECASTER STEWART 581 582 583WTNT42 KNHC 090834 584TCDAT2 585HURRICANE OTTO DISCUSSION NUMBER 13 586NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 587500 AM AST SAT OCT 09 2010 588 589OTTO CONTINUES TO PRODUCE DEEP CONVECTION IN A CDO WITH CLOUD TOPS 590COLDER THAN -80C...HOWEVER THE CLOUD PATTERN IS BECOMING 591INCREASINGLY DISTORTED DUE TO 20 TO 25 KT OF SOUTHWESTERLY SHEAR. 592THIS SHEAR IS ALSO TILTING THE VORTEX NORTHEASTWARD WITH HEIGHT AS 593SEEN IN A 0021 UTC SSMIS PASS. THE INITIAL INTENSITY OF 75 KT IS 594BASED ON A BLEND OF DVORAK FINAL-T AND CI NUMBERS OF 4.0 TO 5.0 595FROM TAFB AND SAB. SLOW WEAKENING IS EXPECTED OVER THE NEXT DAY OR 596SO WHILE OTTO REMAINS A TROPICAL CYCLONE DUE TO SHEAR AND 597DECREASING SEA SURFACE TEMPERATURES. GRADUAL WEAKENING SHOULD 598CONTINUE BEYOND THAT TIME AS OTTO UNDERGOES EXTRATROPICAL 599TRANSITION. 600 601THE INITIAL MOTION ESTIMATE OF 055/21 IS UNCERTAIN DUE TO A LACK OF 602RECENT MICROWAVE IMAGERY...AND IS BASED ON THE ASSUMPTION THAT THE 603LOW-LEVEL CENTER CONTINUES TO LAG BEHIND THE COLDEST CLOUD TOPS. 604OTTO WILL CONTINUE ACCELERATING NORTHEASTWARD OVER THE NEXT COUPLE 605OF DAYS BETWEEN A LARGE DEEP-LAYER TROUGH OFF THE COAST OF NORTH 606AMERICA AND A SUBTROPICAL RIDGE OVER THE EASTERN TROPICAL ATLANTIC. 607THE OFFICIAL FORECAST IS A BLEND OF THE PREVIOUS PACKAGE AND THE 608TVCN MULTI-MODEL CONSENSUS THROUGH 48 HOURS. BEYOND THAT TIME... 609MOST OF THE GLOBAL MODELS AND THE GFS ENSEMBLE MEAN SUGGEST THAT 610POST-TROPICAL OTTO WILL MOVE AROUND THE TOP OF A SHORTWAVE RIDGE 611AND TURN SOUTHEASTWARD IN THE VICINITY OF THE AZORES. HOWEVER... 612THERE ARE DIFFERENCES IN BOTH THE SHARPNESS OF THE SOUTHEASTWARD 613TURN AND THE FORWARD SPEED. THE OFFICIAL FORECAST HAS BEEN ADJUSTED 614SOUTHWARD AND WESTWARD AT DAYS 4 AND 5 TOWARD A BLEND OF THE UKMET 615AND GFS MODELS...BUT CONFIDENCE IS LOWER THAN NORMAL AT THESE TIMES 616DUE TO THE LARGE SPREAD IN THE GUIDANCE. 617 618THE INITIAL 34-KT WIND RADII WERE ADJUSTED BASED ON A 0052 UTC ASCAT 619PASS. 620 621FORECAST POSITIONS AND MAX WINDS 622 623INITIAL 09/0900Z 29.2N 58.5W 75 KT 624 12HR VT 09/1800Z 31.1N 54.8W 70 KT 625 24HR VT 10/0600Z 34.3N 48.3W 70 KT 626 36HR VT 10/1800Z 37.7N 40.8W 65 KT 627 48HR VT 11/0600Z 41.3N 33.4W 55 KT...POST-TROP/EXTRATROP 628 72HR VT 12/0600Z 43.0N 27.0W 45 KT...POST-TROP/EXTRATROP 629 96HR VT 13/0600Z 40.5N 24.5W 40 KT...POST-TROP/EXTRATROP 630120HR VT 14/0600Z 37.0N 22.0W 40 KT...POST-TROP/EXTRATROP 631 632$$ 633FORECASTER BRENNAN 634 635 636WTNT42 KNHC 091435 637TCDAT2 638HURRICANE OTTO DISCUSSION NUMBER 14 639NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 6401100 AM AST SAT OCT 09 2010 641 642THE CLOUD PATTERN ASSOCIATED WITH OTTO HAS GRADUALLY BEEN DECREASING 643IN ORGANIZATION DURING THE LAST SEVERAL HOURS. THE CENTRAL DENSE 644OVERCAST THAT THE CYCLONE HAD BEEN MAINTAINING HAS BECOME 645INCREASINGLY DISTORTED...AND CONVECTIVE CLOUD TOPS HAVE WARMED. A 646SERIES OF MICROWAVE OVERPASSES SUGGEST THAT THE CENTER IS LOCATED 647ON THE SOUTHWEST SIDE OF THE DEEPEST CONVECTION...AND GIVE EVIDENCE 648OF A PRONOUNCED TILT OF THE VORTEX DUE TO THE EFFECT OF MODERATE 649SOUTHWESTERLY SHEAR. THE INITIAL INTENSITY IS LOWERED TO 65 KT 650BASED UPON DVORAK T-NUMBERS OF 3.5 AND 4.0 FROM SAB AND TAFB... 651RESPECTIVELY. FURTHER WEAKENING IS LIKELY OVER THE NEXT SEVERAL 652DAYS AS OTTO ENTERS A STRONGLY SHEARED ENVIRONMENT AND MOVES OVER 653PROGRESSIVELY COOLER WATERS. GLOBAL MODELS SUGGEST THAT 654EXTRATROPICAL TRANSITION MAY HAVE ALREADY BEGUN...AND THE COMPLETION 655OF THIS PROCESS...ALTHOUGH STILL A BIT UNCERTAIN...IS FORECAST BY 656ABOUT 48 HOURS. THE OFFICIAL INTENSITY FORECAST IS ADJUSTED 657DOWNWARD BASED UPON RECENT TRENDS AND IS IN GOOD AGREEMENT 658WITH THE STATISTICAL-DYNAMICAL GUIDANCE. 659 660THE MICROWAVE FIXES WERE HELPFUL IN FINDING THE CENTER OF OTTO AND 661SUGGEST THAT THE HURRICANE HAS CONTINUED TO ACCELERATE...WITH AN 662INITIAL MOTION ESTIMATE OF 055/25. OTTO IS FORECAST TO ACCELERATE 663FURTHER ON A GENERALLY NORTHEASTWARD COURSE DURING THE NEXT 24-36 664HOURS IN BETWEEN A LARGE DEEP-LAYER TROUGH OVER THE NORTHWEST 665ATLANTIC AND A SUBTROPICAL RIDGE TO ITS EAST. ONCE POST- 666TROPICAL...OTTO IS EXPECTED TO ABRUPTLY DECELERATE AND TURN 667EASTWARD AND SOUTHEASTWARD AS IT ROUNDS THE TOP OF A SHORTWAVE 668RIDGE AND DIVES INTO THE WEST SIDE OF A TROUGH OVER THE NORTHEAST 669ATLANTIC. ALTHOUGH THE MODEL GUIDANCE CONTINUES TO HAVE DIFFICULTY 670IN PREDICTING THE SHARPNESS OF THIS TURN...THE SPREAD IN THE MODEL 671SOLUTIONS HAS DECREASED SOME SINCE THE LAST CYCLE. THE OFFICIAL 672TRACK FORECAST IS BASICALLY AN UPDATE OF THE PREVIOUS ONE AND IS 673CLOSE TO THE MULTI-MODEL CONSENSUS. 674 675 676FORECAST POSITIONS AND MAX WINDS 677 678INITIAL 09/1500Z 30.7N 55.7W 65 KT 679 12HR VT 10/0000Z 32.9N 51.4W 60 KT 680 24HR VT 10/1200Z 36.2N 44.2W 55 KT 681 36HR VT 11/0000Z 39.7N 36.7W 50 KT 682 48HR VT 11/1200Z 42.5N 31.0W 45 KT...POST-TROP/EXTRATROP 683 72HR VT 12/1200Z 43.0N 26.0W 35 KT...POST-TROP/EXTRATROP 684 96HR VT 13/1200Z 39.6N 24.0W 30 KT...POST-TROP/EXTRATROP 685120HR VT 14/1200Z 36.5N 21.5W 30 KT...POST-TROP/EXTRATROP 686 687$$ 688FORECASTER KIMBERLAIN 689 690 691WTNT42 KNHC 092031 692TCDAT2 693HURRICANE OTTO DISCUSSION NUMBER 15 694NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 695500 PM AST SAT OCT 09 2010 696 697SATELLITE IMAGES INDICATE THAT OTTO IS GRADUALLY WEAKENING. WARMING 698CLOUD TOPS ARE PRIMARILY LOCATED NORTH OF THE CIRCULATION CENTER AS 699A CONSEQUENCE OF CONTINUED MODERATE SOUTHWESTERLY SHEAR. HOWEVER... 700SATELLITE CLASSIFICATIONS SUPPORT MAINTAINING OTTO AS A HURRICANE 701FOR THIS ADVISORY. FURTHER WEAKENING IS FORECAST AS OTTO ENCOUNTERS 702A HIGH SHEAR ENVIRONMENT AND PASSES OVER PROGRESSIVELY COOLER 703WATERS DURING THE NEXT FEW DAYS. EXTRATROPICAL TRANSITION APPEARS 704TO BE UNDERWAY AS EVIDENCED BY CURRENT CONVECTIVE TRENDS AND 705COLDER...DRIER AIR IMPINGING ON THE CIRCULATION FROM THE WEST. 706GLOBAL MODELS INDICATE THAT THIS PROCESS SHOULD BE COMPLETE BY 36 707HOURS...ALTHOUGH IT COULD FINISH EARLIER. THE OFFICIAL NHC 708INTENSITY FORECAST IS ABOUT THE SAME AS THE PREVIOUS ONE AND IS IN 709LINE WITH THE SHIPS/LGEM GUIDANCE. 710 711OTTO IS STILL ACCELERATING...AND THE INITIAL MOTION ESTIMATE IS 712055/28. SOME FURTHER ACCELERATION TOWARD THE NORTHEAST IS LIKELY 713DURING THE NEXT 12-24 HOURS AS THE CYCLONE IS EMBEDDED IN A DEEP 714LAYER OF STRONG SOUTHWESTERLY FLOW AHEAD OF A LARGE MID-LATITUDE 715TROUGH OVER THE WESTERN ATLANTIC. AFTER 36 HOURS....OTTO SHOULD 716ABRUPTLY DECELERATE AND TURN EASTWARD AND THEN SOUTHEASTWARD AS IT 717STEERED AROUND THE CIRCULATION OF A DEEP LAYER CYCLONE OVER THE 718NORTHEAST ATLANTIC. THE MODEL GUIDANCE...EXCEPT FOR THE NOGAPS AND 719THE CANADIAN...IS IN GOOD AGREEMENT ON THIS SCENARIO...AND THE 720OFFICIAL TRACK FORECAST IS CLOSE TO THE PREVIOUS ONE AND THE 721MULTI-MODEL CONSENSUS. 722 723 724FORECAST POSITIONS AND MAX WINDS 725 726INITIAL 09/2100Z 32.4N 52.6W 65 KT 727 12HR VT 10/0600Z 34.7N 47.6W 60 KT 728 24HR VT 10/1800Z 38.0N 40.3W 55 KT 729 36HR VT 11/0600Z 41.3N 33.6W 50 KT...POST-TROP/EXTRATROP 730 48HR VT 11/1800Z 43.4N 29.4W 45 KT...POST-TROP/EXTRATROP 731 72HR VT 12/1800Z 43.0N 25.5W 35 KT...POST-TROP/EXTRATROP 732 96HR VT 13/1800Z 39.0N 24.0W 30 KT...POST-TROP/EXTRATROP 733120HR VT 14/1800Z 37.0N 22.0W 30 KT...POST-TROP/EXTRATROP 734 735$$ 736FORECASTER KIMBERLAIN 737 738 739WTNT42 KNHC 100235 740TCDAT2 741TROPICAL STORM OTTO DISCUSSION NUMBER 16 742NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 7431100 PM AST SAT OCT 09 2010 744 745CONVENTIONAL AND MICROWAVE SATELLITE IMAGERY INDICATE OTTO IS 746QUICKLY COMING UNRAVELED. CLOUD TOPS HAVE WARMED SIGNIFICANTLY AND 747THE OVERALL CONVECTIVE PATTERN HAS BECOME RATHER DISHEVELED 748LOOKING. THE INITIAL INTENSITY OF 60 KT IS BASED ON A BLEND OF 749SATELLITE CURRENT INTENSITY ESTIMATES OF T4.0/65 KT FROM TAFB AND 750T3.5/55 KT FROM SAB...AND OTTO IS NOW A TROPICAL STORM. THE CENTRAL 751PRESSURE IS BASED ON A PRESSURE REPORT OF 989.1 MB AT 23Z FROM 752DRIFTING BUOY 62905 THAT OTTO PASSED OVER OR VERY CLOSE TO. 753 754THE INITIAL MOTION ESTIMATE IS 060/33. OTTO CONTINUES TO ACCELERATE 755AHEAD OF A SHARP DEEP-LAYERED TROUGH MOVING ACROSS THE CENTRAL 756ATLANTIC. HOWEVER...ACCELERATION SHOULD LIKELY CEASE DURING THE 757NEXT 12 HOURS OR SO AS THE LOW- AND UPPER-LEVEL CIRCULATIONS 758DECOUPLE DUE TO VERTICAL SHEAR INCREASING TO MORE THAN 40 KT AND 759SSTS COOLING TO BELOW 23C. BY 36 HOURS....OTTO SHOULD BE STEERED BY 760THE WEAKER WESTERLY LOW-LEVEL FLOW AND SLOW DOWN AND TURN 761EASTWARD...FOLLOWED BY A SOUTHEASTWARD TURN AS THE CYCLONE ROUNDS 762THE TOP OF A MID-LEVEL RIDGE LOCATED WEST OF THE AZORES ISLANDS. 763THE NHC TRACK GUIDANCE IS IN GOOD AGREEMENT ON THIS SCENARIO AND 764THERE IS LESS SPREAD IN THE MODELS FOR THIS ADVISORY PACKAGE. THE 765OFFICIAL FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY...AND 766REMAINS SOUTH OF THE MODEL CONSENSUS AFTER 48 HOURS. 767 768INCREASING VERTICAL SHEAR...COMBINED WITH DECREASING SSTS AND DRY 769AIR ENTRAINMENT FROM THE WEST...SHOULD HASTEN THE WEAKENING PROCESS 770AND OTTO SHOULD TRANSITION TO AN EXTRATROPICAL CYCLONE IN 24 HOURS 771OR LESS. THE NHC INTENSITY FORECAST IS SIMILAR TO THE SHIPS/LGEM 772INTENSITY GUIDANCE. 773 774FORECAST POSITIONS AND MAX WINDS 775 776INITIAL 10/0300Z 33.9N 48.7W 60 KT 777 12HR VT 10/1200Z 36.3N 43.4W 50 KT 778 24HR VT 11/0000Z 39.7N 36.5W 45 KT...POST-TROP/EXTRATROP 779 36HR VT 11/1200Z 42.0N 31.4W 40 KT...POST-TROP/EXTRATROP 780 48HR VT 12/0000Z 43.5N 28.0W 40 KT...POST-TROP/EXTRATROP 781 72HR VT 13/0000Z 42.0N 25.0W 35 KT...POST-TROP/EXTRATROP 782 96HR VT 14/0000Z 39.0N 23.0W 30 KT...POST-TROP/EXTRATROP 783120HR VT 15/0000Z 37.0N 21.5W 30 KT...POST-TROP/EXTRATROP 784 785$$ 786FORECASTER STEWART 787 788 789WTNT42 KNHC 100850 790TCDAT2 791TROPICAL STORM OTTO DISCUSSION NUMBER 17 792NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 793500 AM AST SUN OCT 10 2010 794 795THE SATELLITE PRESENTATION OF OTTO CONTINUES TO DETERIORATE. THE 796LOW-LEVEL CENTER IS NOW COMPLETELY EXPOSED TO THE SOUTH OF A LARGE 797SHIELD OF CIRRUS AND A FEW BURSTS OF CONVECTION...AND THE CYCLONE IS 798LOOKING INCREASINGLY EXTRATROPICAL. THE INTENSITY IS SET AT 55 KT 799BASED ON A DVORAK ESTIMATE OF T3.0/4.0 FROM TAFB. STRONG VERTICAL 800SHEAR AND COLDER WATERS ARE EXPECTED TO CONTINUE WEAKENING 801OTTO...AND THE NHC INTENSITY FORECAST IS BASED ON A BLEND OF THE 802GFS...GFDL...AND HWRF MODELS. THESE MODELS PROBABLY HAVE A BETTER 803HANDLE ON THE MID-LATITUDE ENVIRONMENT THAN THE SHIPS/LGEM 804MODELS...WHICH APPEAR TO WEAKEN THE CYCLONE TOO FAST. IT SHOULD BE 805NOTED THAT THE GFS AND ECMWF RE-ENERGIZE OTTO BY THE END OF THE 806FORECAST PERIOD...SO THE OFFICIAL FORECAST COULD BE A LITTLE LOW ON 807DAYS 4 AND 5. 808 809OTTO IS EMBEDDED WITHIN STRONG FLOW TO THE SOUTH OF A MID/ 810UPPER-LEVEL TROUGH AND IS MOVING 65 DEGREES AT 34 KT. THE FLOW 811AHEAD OF OTTO IS EXPECTED TO SPLIT IN THE NEXT 24-36 HOURS...AND 812THIS SHOULD CAUSE THE CYCLONE TO DECELERATE AND TURN 813SOUTHEASTWARD...MOVING AROUND THE APEX OF A MID-LEVEL RIDGE 814EXTENDING ACROSS THE AZORES. THE EXTRATROPICAL LOW IS THEN 815EXPECTED TO BECOME EMBEDDED WITHIN A LARGE CYCLONIC GYRE CURRENTLY 816NEAR WESTERN EUROPE ON DAYS 3 THROUGH 5. BASED ON THE NEW MODEL 817GUIDANCE...THE OFFICIAL TRACK FORECAST IS A LITTLE FASTER THAN THE 818PREVIOUS ONE FOR THE FIRST 36 HOURS OR SO. THE ENTIRE FORECAST 819TRACK IS MIRRORED MAINLY ON A CONSENSUS OF THE GFS...ECMWF... 820UKMET...AND GFDL. 821 822FORECAST POSITIONS AND MAX WINDS 823 824INITIAL 10/0900Z 35.3N 45.0W 55 KT 825 12HR VT 10/1800Z 38.1N 39.2W 50 KT...POST-TROP/EXTRATROP 826 24HR VT 11/0600Z 41.5N 32.4W 45 KT...POST-TROP/EXTRATROP 827 36HR VT 11/1800Z 43.4N 27.5W 45 KT...POST-TROP/EXTRATROP 828 48HR VT 12/0600Z 42.4N 25.1W 40 KT...POST-TROP/EXTRATROP 829 72HR VT 13/0600Z 39.5N 23.5W 35 KT...POST-TROP/EXTRATROP 830 96HR VT 14/0600Z 37.0N 21.5W 30 KT...POST-TROP/EXTRATROP 831120HR VT 15/0600Z 36.5N 19.0W 30 KT...POST-TROP/EXTRATROP 832 833$$ 834FORECASTER BERG 835 836 837WTNT42 KNHC 101435 838TCDAT2 839TROPICAL STORM OTTO DISCUSSION NUMBER 18 840NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 8411100 AM AST SUN OCT 10 2010 842 843RECENT SATELLITE IMAGERY SHOWS THE DEVELOPMENT OF FRONTAL CLOUD 844BANDS AND ALSO INDICATES THAT COOL DRY AIR HAS WRAPPED AROUND THE 845SOUTHERN SEMICIRCLE OF OTTO AND INTO THE CENTER. THE REMAINING 846CONVECTION IS NOW NORTH AND WEST OF THE CENTER AND AMSU TEMPERATURE 847PROFILES SHOW THAT THE UPPER-LEVEL WARM CORE HAS WEAKENED. BASED ON 848ALL OF THIS...OTTO IS NOW A POST-TROPICAL EXTRATROPICAL CYCLONE... 849AND THIS WILL BE THE LAST NHC ADVISORY. THE INITIAL INTENSITY IS 850HELD AT 55 KT...AND SLOW WEAKENING SHOULD BEGIN LATER TODAY AS OTTO 851MOVES AWAY FROM THE BEST BAROCLINIC DYNAMICS. GRADUAL WEAKENING IS 852EXPECTED TO CONTINUE FOR THE REST OF THE PERIOD. HOWEVER...IT IS 853WORTH NOTING THAT THE GFS AND ECMWF STRENGTHEN OTTO A LITTLE AT THE 854END OF THE PERIOD...SO THE OFFICIAL FORECAST COULD BE A LITTLE LOW 855ON DAYS 4 AND 5. 856 857OTTO IS RACING TOWARD THE NORTHEAST AT 35 TO 40 KNOTS...EMBEDDED 858WITHIN DEEP-LAYER SOUTHWESTERLY FLOW TO THE SOUTHEAST OF A LARGE 859MID/UPPER-LEVEL TROUGH CENTERED BETWEEN 55W AND 60W. THE GLOBAL 860MODELS ARE IN GENERALLY GOOD AGREEMENT IN SHOWING POST-TROPICAL OTTO 861ESCAPING THE WESTERN ATLANTIC TROUGH AND TURNING EASTWARD AND THEN 862SOUTHEASTWARD WITHIN 48 HOURS AS IT COMES UNDER THE INFLUENCE OF A 863DEEP-LAYER LOW CENTERED OVER THE IBERIAN PENINSULA AND WESTERN 864MEDITERRANEAN SEA. LATE IN THE PERIOD THE DEEP-LAYER LOW MOVES 865EAST...LEAVING OTTO BEHIND TO MOVE SLOWLY EASTWARD OR NORTHEASTWARD 866BY DAY 5. THE OFFICIAL FORECAST IS BASED ON A CONSENSUS OF THE GFS 867...UKMET...ECMWF...AND CANADIAN GLOBAL MODELS. 868 869FUTURE INFORMATION ON POST-TROPICAL OTTO CAN BE FOUND IN HIGH SEAS 870FORECASTS ISSUED BY THE NATIONAL WEATHER SERVICE UNDER AWIPS HEADER 871NFDHSFAT1 AND WMO HEADER FZNT01 KWBC...AND BY METEO-FRANCE UNDER WMO 872HEADER FQNT50 LFPW. 873 874FORECAST POSITIONS AND MAX WINDS 875 876INITIAL 10/1500Z 37.3N 41.1W 55 KT...POST-TROP/EXTRATROP 877 12HR VT 11/0000Z 40.0N 35.6W 50 KT...POST-TROP/EXTRATROP 878 24HR VT 11/1200Z 42.6N 29.7W 45 KT...POST-TROP/EXTRATROP 879 36HR VT 12/0000Z 43.0N 26.3W 45 KT...POST-TROP/EXTRATROP 880 48HR VT 12/1200Z 41.5N 24.1W 40 KT...POST-TROP/EXTRATROP 881 72HR VT 13/1200Z 37.0N 22.0W 35 KT...POST-TROP/EXTRATROP 882 96HR VT 14/1200Z 36.0N 20.5W 30 KT...POST-TROP/EXTRATROP 883120HR VT 15/1200Z 37.0N 19.5W 30 KT...POST-TROP/EXTRATROP 884 885$$ 886FORECASTER BRENNAN 887 888 889