WDXS31 PGTW 080900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 25S (KARIM) WARNING NR 003// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 10.3S 90.3E INITIAL INTENSITY: 55 KTS GEOGRAPHIC REFERENCE: 405 NM WEST-NORTHWEST OF THE COCOS ISLANDS MOVEMENT PAST 6 HOURS: SOUTHWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 20 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH AN IRREGULAR CENTRAL DENSE OVERCAST (CDO) OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 080729Z AMSR2 37GHZ COLOR COMPOSITE MICROWAVE IMAGE, WHICH REVEALS MULTIPLE CONVECTIVE BANDS WRAPPING TIGHTLY INTO A DEFINED, RAGGED LLCC. ENVIRONMENTAL CONDITIONS HAVE IMPROVED WITH LOW VERTICAL WIND SHEAR (VWS) AND MODERATE POLEWARD OUTFLOW. THE INITIAL INTENSITY OF 55 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW DVORAK ESTIMATE, WHICH IS CONSISTENT WITH THE OVERALL CONVECTIVE STRUCTURE. INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A NEAR-EQUATORIAL RIDGE (NER) POSITIONED TO THE EAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS APRF: T3.0 - 45 KTS CIMSS SATCON: 61 KTS AT 080345Z CIMSS ADT: 61 KTS AT 080615Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD 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: TC 25S WILL TRACK SLOWLY POLEWARD ALONG THE WESTERN PERIPHERY OF THE NER THROUGH TAU 48 WITH GRADUAL INTENSIFICATION TO A PEAK OF 65 KNOTS BY TAU 24. AFTER TAU 24, VWS WILL GRADUALLY INCREASE LEADING TO A STEADY WEAKENING TREND. AFTER TAU 48, THE SYSTEM WILL TRACK SOUTH-SOUTHEASTWARD AS IT TRACKS WITHIN THE ENHANCED FLOW BETWEEN A BROAD MIDLATITUDE TROUGH AND A SUBTROPICAL RIDGE TO THE EAST. RAPID WEAKENING WILL OCCUR AS THE SYSTEM ENCOUNTERS INCREASING VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT. NEAR TAU 96, THE SYSTEM WILL WEAKEN AND STALL AS IT ENCOUNTERS A STRONG HIGH BUILDING TO THE SOUTH EFFECTIVELY BLOCKING FURTHER POLEWARD MOTION. TC 25S SHOULD DISSIPATE BY TAU 96 WITH THE REMNANTS TRACKING BACK TOWARD THE EQUATOR UNDER THE LOW-LEVEL SOUTHEASTERLY FLOW ASSOCIATED WITH THE AFOREMENTIONED HIGH. MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH DRIVES THE SYSTEM THROUGH THE STRONG HIGH, NUMERICAL MODEL GUIDANCE SUPPORTS THE TRACK FORECAST WITH MEDIUM CONFIDENCE. THE 080000Z ECMWF ENSEMBLE (EPS) ALSO SUPPORTS THE JTWC FORECAST TRACK AND SHOWS THE BULK OF THE SOLUTIONS EITHER STALLING AND DISSIPATING TC 25S OR TRACKING THE REMNANTS WESTWARD UNDER THE LOW-LEVEL FLOW. RELIABLE INTENSITY GUIDANCE ALSO IS IN FAIR AGREEMENT WITH PEAK INTENSITIES RANGING FROM 60 TO 70 KNOTS. THE JTWC INTENSITY FORECAST IS IN CLOSE AGREEMENT WITH THE INTENSITY CONSENSUS (ICNW). FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN