WDPS33 PGTW 090900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 12P (TWELVE) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.9S 165.4E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 173 NM WEST-NORTHWEST OF PORT VILA, VANUATU MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 07 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL CYCLONE (TC) 12P (TWELVE) CONTINUES TO STRUGGLE AGAINST PERSISTENT NORTHWESTERLY SHEAR BUT MAINTAINS MINIMAL TC STRENGTH. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT THE LOW LEVEL CIRCULATION CENTER (LLCC) REMAINS HIGHLY ELONGATED, STRETCHED OUT ALONG A NORTHWEST-SOUTHEAST AXIS. THIS CONFIGURATION OF THE LLCC WAS CONFIRMED BY EARLIER ASCAT-B AND -C PASSES FROM 082151Z AND 082243Z RESPECTIVELY. BOTH SCATTEROMETER PASSES SHOWED A HIGHLY ASYMMETRIC LLCC WITH WINDS BARELY EXCEEDING 30 KNOTS. LATER SCATTEROMETER DATA FROM 090443Z SHOWS A SIMILAR WIND FIELD SETUP, BUT SHOWS A MORE DEFINED AND CONSOLIDATED CIRCULATION CENTER. THE LATEST ANIMATED MSI SHOWED HINTS OF THE LLCC STARTING TO CONSOLIDATE JUST EAST OF AN AREA OF EXPLOSIVE CONVECTIVE DEVELOPMENT, WHICH KICKED OFF AROUND 0500Z. IF THE LLCC CAN SUCCESSFULLY MOVE UNDER THIS CONVECTION, THEN THINGS WILL GET INTERESTING. IN THE MEANTIME, ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY FAVORABLE, WITH PERSISTENT, BUT WEAKENING NORTHWESTERLY SHEAR AND DRY MID-LEVEL AIR TO THE WEST OFFSETTING WARM SSTS AND STRONG POLEWARD OUTFLOW. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON TRACKING OF THE LLCC IN HIGH-RESOLUTION VISIBLE IMAGERY AND EXTRAPOLATION OF A LOW EMISSIVITY REGION IN A 090443Z SSMIS 37GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS SET WITH MEDIUM CONFIDENCE BASED ON THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES OUTLINED BELOW. INITIAL WIND RADII BASIS: PERSISTENCE WITH EARLIER SCATTEROMETER DATA. CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER NEAR EQUATORIAL RIDGE (NER) TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS KNES: T2.5 - 35 KTS PHFO: T2.5 - 35 KTS ABRF: T2.5 - 35 KTS CIMSS SATCON: 36 KTS AT 090700Z CIMSS ADT: 32 KTS AT 090530Z CIMSS DPRINT: 33 KTS AT 090600Z CIMSS DMINT: 33 KTS AT 090456Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: DRY MID-LEVEL AIR TO THE WEST AND MODERATE MID-LEVEL SHEAR ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 12P IS FORECAST TO CONTINUE TRACKING EAST-SOUTHEASTWARD THROUGH THE FIRST 48-60 HOURS OF THE FORECAST, ALONG THE SOUTHERN SIDE OF A STRONG NER TO THE NORTHEAST. AROUND TAU 48, THE RIDGE BEGINS TO BUILD SOUTHWARD AND EVENTUALLY PINCHES OFF INTO A SEPARATE SUBTROPICAL RIDGE (STR) CENTERED NEAR 20S 170W. THIS PROCESS OF STR DEVELOPMENT WILL EFFECTIVELY BLOCK TC 12P FROM TRAVELING FURTHER EAST AFTER TAU 72. THE FORECAST THUS CALLS FOR THE SYSTEM TO SLOW DOWN AFTER TAU 48 AND BECOME QUASI-STATIONARY AFTER TAU 72. IN TERMS OF INTENSITY, CURRENTLY THE SYSTEM CAN BARELY BE CATEGORIZED AS A MINIMAL TROPICAL CYCLONE. THE OVERALL ENVIRONMENT LOOKS SET TO IMPROVE SLIGHTLY OVER THE NEXT 12 HOURS, WITH A REDUCTION IN DEEP-LAYER SHEAR AND A SLIGHT MID-LEVEL MOISTENING ANTICIPATED. THIS SHOULD ALLOW THE SYSTEM TO CONSOLIDATE THE VORTEX A BIT AND THE FIRST HINTS OF THIS MAY BE BEING SEEN NOW. IF THIS PROCESS DOES IN FACT OCCUR AS EXPECTED, THEN A SLIGHT INTENSIFICATION UP TO 40 KNOTS IS FORECAST, WITH THIS INTENSITY PERSISTING THROUGH TAU 36 AS THE SYSTEM PASSES SOUTH OF PORT VILA, VANUATU. INCREASING SHEAR AND ESPECIALLY A SIGNIFICANT INFLUX OF DRY MID-LEVEL AIR EXPECTED AFTER TAU 48, WILL RAPIDLY SMOTHER WHAT REMAINS OF THE SYSTEM AND MARK THE ONSET OF RAPID WEAKENING AND DISSIPATION. DISSIPATION BELOW WARNING THRESHOLD IS FORECAST NO LATER THAN TAU 96 AND COULD PLAUSIBLY OCCUR AS EARLY AS TAU 72. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN MODEST AGREEMENT THROUGH TAU 48, WITH ALL OF THE CONSENSUS MEMBERS CONCURRING THAT THE SYSTEM WILL TRACK STEADILY EAST-SOUTHEASTWARD THROUGH THIS TIME PERIOD. CROSS-TRACK SPREAD IS MINIMAL THROUGH TAU 48, THOUGH ALONG-TRACK SPREAD BEGINS TO REAR ITS UGLY HEAD EVEN AT THIS EARLY POINT IN THE FORECAST, WITH THE NAVGEM PULLING AWAY AHEAD OF THE PACK WHILE THE GFS LAGS BEHIND. BY TAU 72, THE WHEELS FALL OFF THIS WAGON AND THE MODELS START TO WIDELY DIVERGE IN THEIR TRACK SOLUTIONS, WITH A TRIPLE OPTION SETTING UP. THE NAVGEM AND GALWEM PUSH THE SYSTEM STRAIGHT AHEAD TO A POSITION SOUTH OF FIJI, THE US MODELS TURN THE SYSTEM NORTH THEN NORTHWEST AND THE EUROPEAN MODELS TURN SOUTH THEN SOUTHWEST. THE RESULTING MODEL CONFIGURATION CAN BEST BE DESCRIBED AS A DRAWN BOW WITH THE ARROW POINTING STRAIGHT AHEAD, INTRODUCING SIGNIFICANT UNCERTAINTY AND LENDING LOW CONFIDENCE IN THE TRACK, ESPECIALLY AFTER TAU 48. INTENSITY GUIDANCE ALSO SHOWS A WIDE DISPARITY, WITH THE SHIPS GUIDANCE SHOWING STEADY INTENSIFICATION TO GREATER THAN 80 KNOTS WHILE THE HAFS-A SHOWS THE SYSTEM DISSIPATING IN THE NEXT 12 HOURS. THE COAMPS-TC (BOTH NAVGEM AND GFS) SEEM THE MOST REALISTIC, IN SHOWING A MARGINAL INTENSIFICATION IN THE FIRST 24 HOURS FOLLOWED BY A DISSIPATION BY THE END OF THE FORECAST. BUT WITH SUCH A LARGE SPREAD IN THE GUIDANCE, THE JTWC FORECAST IS SET WITH LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN