WDPN31 PGTW 072100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 02W (TWO) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 4.4N 146.3E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 564 NM SOUTH OF ANDERSEN AFB MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS SIGNIFICANT WAVE HEIGHT: 12 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TS 02W HAS CONTINUED TO STEADILY CONSOLIDATE AND INTENSIFY OVER THE PAST SIX HOURS, AND IS NOW ASSESSED TO HAVE REACHED TROPICAL STORM STRENGTH. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS CONVECTIVE HOT TOWERS FLARING UP TO THE SOUTH OF THE ASSESSED CENTER, WRAPPING UPSHEAR TO THE EASTERN SIDE WITH AN AREA OF MORE PERSISTENT CONVECTION FLARING UP DIRECTLY OVER THE CENTER. A TIMELY 071732Z GPM COLOR ENHANCED 37GHZ MICROWAVE IMAGE SHOWED FRAGMENTED CONVECTIVE BANDING, PARTICULARLY ENHANCED ON THE NORTHERN PERIPHERY, WRAPPING INTO A SMALL LOW LEVEL CIRCULATION CENTER, LENDING HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS INCREASED TO 35 KNOTS BASED ON THE T2.5 (35 KNOTS) DVORAK CURRENT INTENSITY ESTIMATES FROM PGTW AND KNES AND THE AIDT ESTIMATE OF 36 KNOTS, BUT REMAINING SLIGHTLY BELOW THE OBJECTIVE ADT AND SATCON ESTIMATES. ENVIRONMENTAL CONDITIONS REMAIN GENERALLY FAVORABLE FOR A SLOW TO MODERATE RATE OF INTENSIFICATION, WITH VERY WARM, HIGH OHC WATERS OFFSET SOMEWHAT BY MODERATE WESTERLY OUTFLOW AND MODERATE EASTERLY. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 40 KTS AT 071600Z CIMSS ADT: 43 KTS AT 071740Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 15-20 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: TS 02W CONTINUES SLIDING SLOWLY WEST-NORTHWESTWARD WHILE SLOWLY CONSOLIDATING. THE FORECAST CALLS FOR TRACK MOTION TO REMAIN RELATIVELY STEADY OVER THE NEXT 12 HOURS, BEFORE ASSUMING A SLIGHTLY MORE NORTHWESTWARD TRACK AFTER TAU 24. THE DOMINANT STEERING MECHANISM REMAINS THE STRONG DEEP-LAYER SUBTROPICAL RIDGE CURRENTLY CENTERED NEAR 22N 160E. OVER THE COURSE OF THE NEXT 96 HOURS THE STR IS EXPECTED TO SLIDE EAST THEN SOUTH, RE-CENTERING NEAR 12N 160E BY TAU 120, WITH RIDGING EXTENDING SOUTHWEST TO NEAR THE EQUATOR. THE SHIFT IN THE POSITIONING OF THE STR WILL ALLOW TS 02W TO TRACK NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE RIDGE THROUGH TAU 96 BEFORE SLOWLY TURNING MORE POLEWARD BY THE END OF THE FORECAST PERIOD. TS 02W IS FORECAST TO INTENSIFY AT NEAR THE CLIMATOLOGICAL RATE OF ONE T-NUMBER PER DAY IN THE FIRST 24-36 HOURS AS IT CONTINUES TO CONSOLIDATE AND REMAINS UNDER THE MODERATE EASTERLY FLOW ALOFT. AFTER TAU 36, THE UPPER-LEVEL ENVIRONMENT IS FORECAST TO CHANGE, WITH A POINT SOURCE DEVELOPING OVER TOP OF THE SYSTEM WHICH WILL PROVIDE ENHANCED OUTFLOW ALOFT, IN ADDITION TO DEVELOPMENT OF A POLEWARD OUTFLOW CHANNEL. THE SYSTEM IS FORECAST TO MORE RAPIDLY INTENSIFY AFTER TAU 48, REACHING A PEAK OF 105 KNOTS BY THE END OF THE FORECAST. SOME OF THE GUIDANCE IS DEPICTING AN OUTLIER SCENARIO OF RAPID INTENSIFICATION (RI) IN A MODERATE EASTERLY SHEAR ENVIRONMENT, WITH RI FROM 35 KNOTS TO 100 KNOTS WITHIN THE NEXT 72 HOURS. THIS IS CONSIDERED A SIGNIFICANT OUTLIER, BUT NOT OUTSIDE THE REALM OF POSSIBILITY AT THIS POINT. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE SHOWS NOW SIGNIFICANT CHANGE FROM THE PREVIOUS MODEL RUN, WITH THE GFS AND HWRF TRACKERS REMAINING ON THE EASTERN EDGE OF THE ENVELOPE, AND THE ECMWF ON THE FAR WESTERN EDGE, WITH SPREAD DRAMATICALLY INCREASING FROM 215NM AT TAU 72 TO OVER 750NM BY TAU 120. HOWEVER, THE ENSEMBLE GUIDANCE HAS COME INTO BETTER AGREEMENT, WITH LESS SPREAD THAT THE PREVIOUS RUN, AND THE ENSEMBLE MEANS (GFS AND ECMWF) NOW SEPARATED BY LESS THAN 250NM AT TAU 120. ANALYSIS OF THE ENSEMBLE MEAN AND DETERMINISTIC TRACKERS REVEALS THAT THE DETERMINISTIC TRACKERS THEMSELVES ARE OUTLIERS AMONGST THE ENSEMBLE MEMBERS. WITH THIS INFORMATION AT HAND, THE EXTREME GFS AND ECMWRF OUTLIERS ARE CONSIDERED IMPROBABLE AND DISCARDED, AND THUS THE OVERALL GUIDANCE ENVELOPE IS SMALLER, AND PROVIDES HIGHER CONFIDENCE TO THE JTWC FORECAST TRACK, WHICH LIES JUST WEST OF THE MULTI-MODEL CONSENSUS MEAN. INTENSITY GUIDANCE IS MIXED, WITH THE MESOSCALE MODELS INCLUDING HWRF AND COAMPS-TC, INDICATING SLOW BUT STEADY INTENSIFICATION THROUGH THE FORECAST PERIOD, PEAKING NEAR 70 KNOTS THOUGH HWRF RAPIDLY INTENSIFIES AFTER TAU 120. THE GLOBAL DECAY SHIPS ON THE OTHER HAND INDICATE NEAR-RAPID INTENSIFICATION, WITH A PEAK OF 90 KNOTS AT TAU 96 FOLLOWED BY WEAKENING. IN ADDITION, THE RI25, RI45 AND RIPA RI AIDS HAVE BEEN TRIGGERED FOR THE FIRST TIME ON THIS RUN. AS DISCUSSED IN THE FORECAST DISCUSSION, WHILE THE RI AIDS ARE TRIGGERING, THE SYNOPTIC ENVIRONMENT IS NOT OPTIMUM FOR RI AT THIS TIME. HENCE THE JTWC FORECAST LIES NEAR THE CONSENSUS MEAN THROUGH TAU 24, THEN CLOSER TO THE DECAY-SHIPS, ABOVE THE MEAN BUT BELOW THE RIPA, THROUGH THE REMAINDER OF THE FORECAST. CONFIDENCE IS MEDIUM THROUGH THE FORECAST PERIOD. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN