WDPS31 PGTW 070900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07P (SEVEN) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.0S 156.6E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 442 NM NORTH-NORTHEAST OF BRISBANE, AUSTRALIA MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 15 KTS SIGNIFICANT WAVE HEIGHT: 19 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PERSISTENT AND SIZABLE CENTRAL DENSE COVER (CDC) MEASURING 200NM ACROSS. THIS FEATURE IS FULLY OBSCURING THE SOUTHERN EXTENT OF AN ELONGATED CIRCULATION THAT IS ALSO WELL OVER 100NM IN SIZE. A FORTUITOUS SUITE OF SSMIS MICROWAVE IMAGERY, SPECIFICALLY A 070604Z SSMIS 91GHZ IMAGE REVEALS THAT THE SOUTHERN EXTENT OF THE CIRCULATION IS TUCKED UNDER THE LARGE CDC WITH LOW LEVEL CLOUD LINES TRACING THE LARGE NORTHWESTERN EXTENT OF THE CIRCULATION. IT IS STILL FORECAST THAT THIS FULLY OBSCURED PORTION OF THE ELONGATION WILL EMERGE AS THE DOMINATE DOWNSTREAM CIRCULATION. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON MSI AND SSMIS IMAGERY. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A DISCREPANCY BETWEEN AGENCY DVORAK INTENSITY ESTIMATES AND AUTOMATED INTENSITY ESTIMATES WHICH INDICATE 35-55KTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHWEST PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS KNES: T2.5 - 35 KTS ABRF: T2.5 - 35 KTS CIMSS ADT: 55 KTS AT 070530Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 15-20 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD AND EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 07P (SEVEN) IS FORECAST TO CONTINUE TRACKING EAST-SOUTHEASTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE NORTHEAST. OVER THE NEXT 12 HOURS WHILE STILL IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES, STRONG DUAL CHANNEL OUTFLOW ALOFT AND RELATIVELY LOW VERTICAL WIND SHEAR (VWS), THE SYSTEM IS FORECAST TO REACH A PEAK INTENSITY OF 45 KNOTS. THROUGH TAU 24, TC 07P WILL EXPERIENCE INCREASING DRY AIR ENTRAINMENT FROM THE WEST AS WELL AS INCREASING VWS, THESE FACTORS WILL CONSPIRE TO WEAKEN THE SYSTEM AS IT PASSES SOUTH OF NEW CALEDONIA. AT THE SAME TIME, NEAR TAU 24 THE SYSTEM WILL CROSS POLEWARD OF THE 26C ISOTHERM AND MOVE UNDER THE SUBTROPICAL WESTERLIES ALOFT, THEREBY INITIATING SUBTROPICAL TRANSITION (STT). BY TAU 36 AND THROUGH TAU 48, TC 07P WILL ENGULF AND MERGE WITH INVEST 95P AS THE SYSTEM CONTINUES POLEWARD WEAKENING TO 35KTS AND EVENTUALLY COMPLETING STT. THE FORECASTED WEAKENING SEEN IN THE LATER TAUS AND BEYOND THE FORECAST PERIOD MAY BE BLUNTED BY STRONG BAROCLINIC FORCING AS THE SYSTEM TURNS SOUTH AND EVENTUALLY BECOMES EXTRATROPICAL. MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD WITH ALL MEMBERS INDICATING A SOUTH-SOUTHEASTERLY COURSE AND ONLY A 130NM SPREAD IN SOLUTIONS AT TAU 48. FOR THIS REASON THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE INDICATES A WIDE RANGE OF SOLUTIONS. GFS INDICATES AN UNREALISTIC AND UNCORROBORATED WEAKENING TREND THROUGH THE FORECAST PERIOD, WHILE THE BULK OF THE GUIDANCE INDICATES INITIAL INTENSIFICATION THROUGH TAU 12. AFTER WHICH, DECAY-SHIPS (BOTH NAVGEM AND GFS VERSIONS) HOLD THE SYSTEM UNREALISTICALLY ABOVE 45 KNOTS THROUGH TAU 48, WHILE THE MESOSCALE MODELS (HWRF AND COAMPS-TC) INDICATE A GRADUAL WEAKENING TREND THROUGH THE FORECAST PERIOD. FOR THIS REASON THE JTWC FORECAST INTENSITY GUIDANCE IS PLACED CLOSE TO THE HWRF SOLUTION WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM// NNNN