WDPN32 PGTW 250900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (HIGOS) WARNING NR 012// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 19.7N 135.5E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 589 NM SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 28 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL STORM 08W (HIGOS) WITH WARMING CLOUD TOPS, COLLAPSING DEEP CONVECTION, AND DRY AIR PRESENT SURROUNDING THE SYSTEM. A 250637Z SSMIS MICROWAVE IMAGE REVEALS LIMITED DEEP CONVECTION IN THE VICINITY OF THE LOW LEVEL CIRCULATION CENTER, WITH A SINGLE OVERSHOOTING TOP LOCATED IN THE SOUTHWEST QUADRANT. THE IMAGE ALSO REVEALS THAT 08W HAS ACCELERATED SIGNIFICANTLY, AND IS NOW TRAVELLING AT A FORWARD SPEED OF APPROXIMATELY 28 KTS. ENVIRONMENTAL ANALYSIS REVEALS A MARGINALLY FAVORABLE ENVIRONMENT, CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM (29-30 KTS) AND SEA SURFACE TEMPERATURES (SST), OFFSET BY THE WEAK DIVERGENCE ALOFT AND THE RELATIVELY DRY SURROUNDING ENVIRONMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED 250637Z SSMIS MICROWAVE IMAGE. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK FIXES AND CIMSS AUTOMATED INTENSITY ESTIMATES LISTED BELOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.5 - 35 KTS KNES: T3.0 - 45 KTS CIMSS SATCON: 45 KTS AT 250540Z CIMSS ADT: 55 KTS AT 250730Z CIMSS AIDT: 45 KTS AT 250730Z CIMSS D-MINT: 30 KTS AT 250637Z CIMSS D-PRINT: 28 KTS AT 250730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK EQUATORWARD 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 08W IS FORECASTED TO CONTINUE TRACKING TO THE NORTH-NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF THE STR POSITIONED TO THE NORTHEAST UNTIL ABOUT TAU 12. FOLLOWING TAU 12, THE SYSTEM IS EXPECTED TO TURN NORTHWARD AS IT RECURVES AROUND THE STR AXIS, BEFORE TRACKING NORTH-NORTHEASTWARD UNTIL TAU 36. BETWEEN TAU 24-36, THE INCREASINGLY HOSTILE ENVIRONMENT WITH VWS NEARING 30 KTS WILL INITIATE A SWIFT EXTRATROPICAL TRANSITION AS THE SYSTEM BECOMES FULLY ENVELOPED BY THE MID-LATITUDE WESTERLIES ALOFT. INCREASED UPPER-LEVEL SUPPORT WILL ASSIST IN SUSTAINING SURFACE INTENSITIES TOWARD 45 KTS BY TAU 36 AS TS 08W BECOMES A VERY SHALLOW, SYMMETRIC COLD-CORE LOW. THE POSSIBILITY FOR THE SURFACE CIRCULATION TO FILL INTO AN OPEN TROUGH PERSISTS; HOWEVER, ELEVATED SURFACE INTENSITIES ARE FORECASTED TO REMAIN UNTIL THE END OF THE FORECAST PERIOD REGARDLESS OF THE ULTIMATE FATE OF HIGOS. MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT FROM TAU 0-12, BUT IS IN POOR AGREEMENT THEREAFTER AND DISPLAYING SIGNIFICANT ALONG-TRACK AND CROSS-TRACK SPREAD AT TAU 36. A FEW SOLUTIONS CHARACTERIZE A SHALLOWING AND LOSS OF THE VORTEX PRIOR TO TAU 36, WHILE OTHERS ILLUSTRATE EXTRATROPICAL TRANSITION AND EVENTUAL FILLING INTO AN OPEN TROUGH BETWEEN TAU 24-36. THE JTWC TRACK FORECAST HAS BEEN PLACED WITH LOW CONFIDENCE DUE TO UNCERTAINTIES WITH THE EXPECTED QUICK EXTRATROPICAL TRANSITION OR COMPLETE DISSIPATION INTO AN OPEN TROUGH. RELIABLE INTENSITY GUIDANCE REMAINS IN MODERATE AGREEMENT, BUT GENERALLY, RELIABLE MODELS AGREE IN A SLIGHT INTENSIFICATION PHASE FOLLOWED BY TERMINAL WEAKENING. AS A RESULT, THE JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: LOW INTENSITY 00-72 HR: MEDIUM// NNNN