WDPN31 PGTW 250900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (MALOU) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 18.3N 138.4E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 416 NM WEST OF AGRIHAN MOVEMENT PAST 6 HOURS: NORTHWARD AT 16 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD, ASYMMETRIC CIRCULATION WITH A PARTIALLY EXPOSED CENTER AND DEEP CONVECTIVE BANDS TO THE EAST. THESE BANDS CAN ALSO BE SEEN IN A 250350Z 89GHZ AMSR2 IMAGE. THE INITIAL INTENSITY IS BASED ON THE ASSOCIATED AMSR2 WINDSPEED PRODUCT WHICH SHOWS 38-44 KNOT WINDS ABOUT 100 NM FROM THE CENTER IN THE NORTHEASTERN QUADRANT OF THE CIRCULATION. THE INITIAL POSITION IS BASED ON THE PARTIALLY EXPOSED CENTER IN MSI. TROPICAL STORM 25W HAS TRACKED NORTHWARD OVER THE PAST SIX HOURS, DEVIATING SOONER THAN FORECASTED FROM ITS ORIGINAL NORTH-NORTHWESTWARD TRACK. INITIAL WIND RADII BASIS: 250350Z AMSR2 WINDSPEED PRODUCT CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A BUILDING SUBTROPICAL RIDGE POSITIONED TO THE EAST-NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 42 KTS AT 250350Z CIMSS ADT: 43 KTS AT 250540Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE CURRENT JTWC FORECAST TRACK DIFFERS FROM PREVIOUS TRACK BY 60 NM AT TAU 12 DUE REPOSITIONING OF 00Z POSITION AND THE STORM MOTION CHANGING TO A MORE NORTHERLY DIRECTION. FORECAST DISCUSSION: TROPICAL STORM 25W WILL CONTINUE TO TRACK NORTHWARD UNTIL ABOUT TAU 36, AT WHICH POINT IT WILL BEGIN TO ROUND THE SUBTROPICAL RIDGE AXIS AND ACCELERATE TO THE NORTHEAST IN THE WAKE OF A MIDLATITUDE LOW PRESSURE SYSTEM. TS 25W WILL REMAIN IN A FAVORABLE ENVIRONMENT UNTIL ABOUT TAU 72, ALLOWING FOR A PEAK INTENSITY OF 80 KTS AT THAT TIME. AFTERWARDS, COOLING SEA SURFACE TEMPERATURES AND INCREASING VERTICAL WIND SHEAR WILL BEGIN TO WEAKEN THE SYSTEM AS IT BEGINS EXTRATROPICAL TRANSITION (ETT) BY TAU 96. IT IS EXPECTED TO COMPLETE ETT BY TAU 120 AS IT BECOMES FURTHER EMBEDDED IN THE BAROCLINIC ZONE AND WEAKENS TO 55 KTS. MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT IN REGARDS TO FORECAST TRACK WITH ALL MODELS DEPICTING A NORTHWARD TRACK FOLLOWED BY A TURN TO THE NORTHEAST AROUND TAU 36. HOWEVER, THE MODELS ARE IN DISAGREEMENT IN REGARDS TO ALONG TRACK SPEED AND DON'T SEEM TO BE HANDLING THE STORM CURRENT TRACK SPEED VERY WELL, RESULTING IN THE CURRENT BEST TRACK POSITION TO BE ABOUT SIX HOURS AHEAD ON TRACK FROM THE PREVIOUS FORECAST. THIS DIFFERENCE IN ALONG TRACK PLACEMENT FURTHER INCREASES IN LATER TAUS. NUMERICAL MODELS ARE IN GOOD AGREEMENT IN REGARDS TO THE INTENSITY GUIDANCE WITH ALL MODELS SHOWING A STEADY INTENSIFICATION PERIOD PEAKING AROUND TAU 72 AT ABOUT 70-85 KTS. THE RAPID INTENSIFICATION PREDICTION AID (RIPA) THAT WAS TRIGGERED AT 30 PERCENT LAST WARNING CYCLE, IS NOW AT 23 PERCENT AND NOW OTHER MODELS ARE INDICATING ANY RAPID INTENSIFICATION IN THE NEXT 24 HOURS, INCLUDING THE ENSEMBLES. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN