WDPS31 PGTW 071500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 07P (SEVEN) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 21.6S 158.5E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 424 NM WEST OF NOUMEA, NEW CALEDONI MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 16 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A PERSISTENT CENTRAL DENSE COVER (CDC) MEASURING OVER 200NM ACROSS FULLY OBSCURING THE SOUTHERN EXTENT OF AN ELONGATED CIRCULATION. A RECENT 071057Z METOP-B ASCAT IMAGE REVEALS THE CIRCULATION IS ORIENTED NORTHWESTWARD TO SOUTHEASTWARD AND MORE THAN 230NM LONG. DETERMINISTIC MODEL RUNS HAVE BEEN CONSISTENTLY INDICATING THE SOUTHERN MOST EXTENT OF THE CIRCULATION EMERGES AS THE PRIMARY DOWNSTREAM CIRCULATION. OUR RECENT MICROWAVE HOT STREAK HAS ENDED, LEAVING US WITH A LOW RESOLUTION 071053Z METOP-B AMSU 89GHZ MICROWAVE IMAGE WHICH REVEALED A SECOND CONVECTIVE HOT TOWER HAS DEVELOPED EAST OF THE CIRCULATION WHILE THE LOW LEVEL CLOUD LINES ARE NEBULOUS AT BEST. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON EIR AND ASCAT IMAGERY. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH LOW CONFIDENCE BASED ON THE DISCREPANCY BETWEEN AGENCY DVORAK INTENSITY ESTIMATES AND AUTOMATED INTENSITY ESTIMATES WHICH INDICATE 30-59KTS. AT THE HIGH END OF THE SPECTRUM, CIMMS ADT IS USING A SCENE TYPE OF CURVE BAND WHICH AFTER INVESTIGATING EIR IMAGERY IS DECEPTIVE BECAUSE THE SYSTEM IS TAPPING INTO A VIGOROUS POLEWARD OUTFLOW CHANNEL GIVING THE APPEARANCE OF SPIRAL BANDING WHICH IS LIKELY A FACADE. WHILE LOW CONFIDENCE, THE TRUE INTENSITY OF 07P IS MOST LIKELY CLOSER TO THE MIDDLE OF THIS LARGE DISPARITY BETWEEN INTENSITY ESTIMATES. 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: T2.0 - 30 KTS CIMSS ADT: 59 KTS AT 071130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 27-28 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: LOW 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 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 MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES AND STRONG OUTFLOW ALOFT PARTIALLY HINDERED BY VERTICAL WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT, THE SYSTEM WILL MAINTAIN 45 KNOTS AND POTENTIALLY SLIGHTLY INTENSIFY. BY TAU 12 AND THROUGH TAU 24, TC 07P WILL EXPERIENCE INCREASING DRY AIR ENTRAINMENT FROM THE WEST AS WELL AS INCREASING VWS, THESE FACTORS WILL CONSPIRE TO FURTHER WEAKEN THE SYSTEM AS IT PASSES SOUTH OF NEW CALEDONIA. DURING THIS TIME THE SYSTEM WILL ALSO CROSS POLEWARD OF THE 26C ISOTHERM AND MOVE UNDER THE SUBTROPICAL WESTERLIES ALOFT, THEREBY INITIATING SUBTROPICAL TRANSITION (STT). BY TAU 24 AND THROUGH TAU 36, TC 07P WILL ENGULF AND MERGE WITH INVEST 95P AS THE SYSTEM CONTINUES POLEWARD, WEAKENING TO 40KTS AND EVENTUALLY COMPLETING STT. THE FORECASTED WEAKENING SEEN IN THE LATER TAUS AND BEYOND THE FORECAST PERIOD MAY BE BLUNTED OR EVEN OVERWHELMED 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 A 112NM SPREAD IN SOLUTIONS AT TAU 36. FOR THIS REASON THE JTWC TRACK FORECAST IS PLACED WITH HIGH CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE HAS IMPROVED OVER THE PAST 6 HOURS WITH GFS STILL A SIGNIFICANT OUTLIER AND THE ONLY MEMBER INDICATING AN IMMEDIATE AND TERMINAL WEAKENING TREND. THE BULK OF THE GUIDANCE GENERALLY FOLLOWS THE JTWC FORECAST INTENSITY, SHOWING STAGNATION OR MINOR INTENSIFICATION THROUGH TAU 12 AFTER WHICH ALL MEMBERS GRADUALLY WEAKEN THROUGH THE FORECAST PERIOD. FOR THESE REASONS THE JTWC FORECAST INTENSITY GUIDANCE IS PLACED WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM// NNNN