WDPS31 PGTW 091500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (MAILA) WARNING NR 016// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 8.3S 154.4E INITIAL INTENSITY: 85 KTS GEOGRAPHIC REFERENCE: 721 NM NORTHEAST OF CAIRNS, AUSTRALIA MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 30 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A COMPACT SYSTEM RAPIDLY UNDERGOING CYCLOSIS AS IT CONTINUES TO MEANDER IN THE NORTHERN SOLOMON SEA. THE SYSTEM BRIEFLY MADE AN ATTEMPT AT REFORMING AN EYE AROUND THE 1200Z HOUR, WHICH QUICKLY FADED AWAY. ROBUST CONVECTIVE ACTIVITY CONTINUES TO DEVELOP ALONG THE NORTHERN FLANK OF THE LOW LEVEL CIRCULATION CENTER (LLCC), BUT PERSISTENT, STRONG, EASTERLY SHEAR IS INHIBITING CONVECTIVE ORGANIZATION. A 091213Z AWS 180.3GHZ MICROWAVE IMAGE REVEALED THAT THE UPPER-LEVEL EYE FEATURE REMAINS RELATIVELY INTACT, THOUGH SIGNIFICANTLY DEGRADED AS COMPARED TO EARLIER MICROWAVE IMAGERY. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY FIX POSITIONS AND ANIMATED EIR. THE INITIAL INTENSITY IS ASSESSED WITH LOW CONFIDENCE DUE TO THE RAPID WEAKENING, WIDE SPREAD IN THE AVAILABLE INTENSITY ESTIMATES AND A LACK OF RECENT WIND SPEED MEASUREMENTS. ENVIRONMENTAL CONDITIONS ARE CONTINUING TO DETERIORATE, PRIMARILY THE SHEAR WHICH CONTINUES TO REMAIN HIGH FROM THE EAST, AND THE VERY COOL SSTS AS THE SYSTEM MOVES OVER THE COLD UPWELLED POOL, WITH SSTS BETWEEN 22-24 (AN POTENTIALLY MUCH LOWER) AS ESTIMATED BY HWRF AND HAFS-A MODEL FIELDS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF AN EASTERN EXTENSION OF THE DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED OVER AUSTRALIA. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS KNES: T5.5 - 102 KTS ABRF: T5.0 - 90 KTS CIMSS ADT: 99 KTS AT 091130Z CIMSS AIDT: 93 KTS AT 091130Z CIMSS D-MINT: 84 KTS AT 091213Z CIMSS D-PRINT: 88 KTS AT 091240Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE VWS: 15-20 KTS SST: 22-24 CELSIUS OUTFLOW: STRONG WESTWARD OTHER FACTORS: POOL OF VERY COOL SSTS LOCATED JUST WEST OF THE CURRENT POSITION DUE TO UPWELLING EFFECTS DURING PREVIOUS TRACK THROUGH THIS AREA. ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: LOW INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE FORECAST NOW CALLS FOR RAPID WEAKENING AND A SLOWER TRACK WHICH ENDS NEAR THE TIP OF PAPUA NEW GUINEA. FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 30P (MAILA) CONTINUES MEANDERING ABOUT THE NORTHERN SOLOMON SEA, GENERALLY DRIFTING WESTWARD ALONG A WEAK STEERING GRADIENT ON THE NORTH SIDE OF AN EXTENSION OF THE STR OVER AUSTRALIA. IN THE NEAR-TERM, THE STR OVER EASTERN AUSTRALIA IS FORECAST TO CONTINUE BUILDING EASTWARD, ENABLING TC 30P TO CONTINUE DRIFTING WEST, THEN GRADUALLY TURNING SOUTHWESTWARD. BY TAU 48, THE SYSTEM IS FORECAST TO TRACK VERY NEAR, OR DIRECTLY OVER, WOODLARK ISLAND AS IT CONTINUES SOUTHWESTWARD. AT THIS POINT, WHILE THE FORECAST TRACK DOES NOT CHANGE SIGNIFICANTLY, THE STEERING INFLUENCE CHANGES ABRUPTLY AS A NEW DEEP-LAYER STR DEVELOPS THE VICINITY OF VANUATU. THE LARGER INFLUENCE ON THE TRACK WILL BE THE EVOLUTION OF THE VORTEX AS IT UNDERGOES RAPID WEAKENING AND SHALLOWS OUT. SO WHILE THE DIRECTION OF MOVEMENT IS NOT EXPECTED TO CHANGE, THE SPEED WILL REMAIN SLOW AS THE SYSTEM SHALLOWS OUT AND IS INFLUENCED BY A WEAKER STEERING GRADIENT. REGARDING INTENSITY, TC 30P HAS ALREADY BEGUN ITS RAPID WEAKENING PHASE AS IT BEGINS MOVING OVER VERY COOL WATERS UPWELLED TO THE SURFACE DUE TO ITS SLOW PASSAGE OF THE AREA DAYS AGO. SSTS ARE CURRENTLY ESTIMATED TO BE 22-24C, AND THE HAFS-A AND HWRF BOTH DEPICT SSTS DROPPING TO AS LOW AS 18C IN THE NEXT 24 HOURS AS TC 30P CROSSES OVER THE COOLEST PART OF THE COLD POOL. AS THE SYSTEM TRACKS OVER THIS COLD POOL, IT WILL ALSO CONTINUE TO FACE STRONG EASTERLY SHEAR, AND THE COMBINATION OF THESE FACTORS WILL RESULT IN 40-45 KNOTS OF WEAKENING OVER THE NEXT 48 HOURS. BEYOND TAU 48, THE ALREADY SHALLOW AND WEAK VORTEX WILL BE FURTHER DISRUPTED BY THE INFLOW OF DOWNSLOPE KATABATIC WINDS FLOWING OFF THE OWEN STANLEY RANGE, AND DIRECTLY INTO THE VORTEX. SOME MODELS SHOW COMPLETE DISSIPATION OF THE VORTEX WITHIN 72 HOURS DUE TO THE COMBINED EFFECTS OF THESE FACTORS. PROXIMITY TO THE SOUTHEASTERN TIP OF PAPUA NEW GUINEA WILL ULTIMATELY DETERMINE THE LIFESPAN OF THE SYSTEM. THE CURRENT FORECAST CALLS WEAKENING TO 35 KNOTS BY TAU 96 THEN MAINTENANCE AT THAT THRESHOLD THROUGH THE END OF THE FORECAST, THOUGH AN EARLIER DISSIPATION IS A POSSIBILITY. MODEL DISCUSSION: TRACK GUIDANCE IS EXTREMELY UNCERTAIN, WITH VERY HIGH MODEL SPREAD, PARTICULARLY IN THE LATER TAUS. THROUGH TAU 48, THE MODELS ARE ACTUALLY IN DECENT AGREEMENT ON AN OVERALL WEST, THEN SOUTHWESTWARD TRAJECTORY, WITH THE NOTABLE EXCEPTION OF THE EC-AIFS AND THE 2ND INTERPOLATION OF THE 0000Z ECMWF WHICH SHOW THE SYSTEM TRACKING OFF TO THE NORTH OR WEST RESPECTIVELY. THE GFS MEANWHILE RACES OFF THE SOUTHWEST, SHOWING A POSITION IN MILNE BAY AT TAU 48. THE REMAINDER OF THE CONSENSUS MEMBERS ARE FAIRLY CLOSELY PACKED NEAR WOODLARK ISLAND. BY TAU 72, THINGS BECOME HIGHLY UNCERTAIN; AIFS TRACKS TO NEAR THE SOUTHERN TIP OF NEW IRELAND, NAVGEM MOVES INTO THE CORAL SEA, GFS IS POSITIONED JUST SOUTHEAST OF PORT MORESBY AND THE ECMWF, AI CONSENSUS AND GALWEM INDICATE A WESTWARD TRACK TO THE TROBRIAND ISLANDS. THIS GENERAL TREND CONTINUES THROUGH TAU 120 WITH THE MODELS CONTINUING ALONG THE SAME TRENDLINES AS DESCRIBED ABOVE. ENSEMBLES ALSO SHOW A VERY LARGE AMOUNT OF UNCERTAINTY IN THE OVERALL FORECAST SCENARIO. THE JTWC FORECAST IS PLACED NEAR THE EXPERIMENTAL AI MODEL AND GENERALLY FOLLOWS THE GFS, BUT AT A MUCH SLOWER PACE. CONFIDENCE IS LOW, AND WOULD BE EXTREMELY LOW IF THAT WAS AN OPTION. INTENSITY GUIDANCE IS IN GOOD AGREEMENT, AND NEARLY ALL OF THE CONSENSUS MEMBERS INDICATE RAPID WEAKENING THROUGH TAU 48 FOLLOWED BY A GENERALLY FLAT TREND THROUGH TAU 120. FORECAST CONFIDENCE: TRACK 00-72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 00-72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN