WDXS31 PGTW 082100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY) WARNING NR 011// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 16.3S 112.6E INITIAL INTENSITY: 75 KTS GEOGRAPHIC REFERENCE: 370 NM NORTH-NORTHWEST OF LEARMONTH, AUSTRALIA MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 06 KTS SIGNIFICANT WAVE HEIGHT: 30 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE LOW-LEVEL CIRCULATION CENTER (LLCC) REMAINS IN AN EMBEDDED CENTER. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE WITH A MICROWAVE EYE, AS SEEN IN A WELL-TIMED 081757Z AMSR2 36HZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 75 KTS IS HEDGED SLIGHTLY HIGHER BASED UPON MULTIPLE AGENCY FIX POSITIONS AND ADT AND AIDT ESTIMATES, WHICH HAVE BEEN DECREASING MORE RAPIDLY OVER TIME AS THE CLOUD TOPS HAVE WARMED CONSIDERABLY. ENVIRONMENTAL CONDITIONS HAVE DEGRADED WITH HIGH (25-30 KNOTS) EASTERLY VERTICAL WIND SHEAR, SLIGHTLY OFFSET BY MODERATE WESTWARD OUTFLOW. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTH OVER WESTERN AUSTRALIA. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.0 - 90 KTS KNES: T5.5 - 102 KTS DEMS: T5.0 - 90 KTS APRF: T5.0 - 90 KTS WIIX: T5.0 - 90 KTS CIMSS SATCON: 61 KTS AT 081741Z CIMSS ADT: 67 KTS AT 081730Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE VWS: 15-20 KTS SST: 30-31 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: TC 11S IS FORECAST TO TRACK WESTWARD ALONG THE NORTHERN PERIPHERY OF THE STR THROUGH THE FORECAST PERIOD. HIGH VWS IS EXPECTED TO PERSIST THROUGH TAU 36 AFTER THE SYSTEM MOVES INTO A REGION OF WEAKENED VWS ALLOWING THE SYSTEM A CHANCE TO RE-INTENSIFY. THE SYSTEM WILL CONTINUE TO MOVE ON A WESTERLY TRACK UNHINDERED FOR THE DURATION OF THE FORECAST PERIOD AS IT SLOWLY DECREASES IN INTENSITY BY TAU 120. MODEL DISCUSSION: NAVGEM REMAINS THE SOLE OUTLIER LEFT OF TRACK UNTIL TAU 72, WHILE THE BULK OF THE DETERMINISTIC GUIDANCE REMAINS IN TIGHT AGREEMENT WITH ONLY A 45 TO 75NM SPREAD IN SOLUTIONS FROM TAU 12 TO TAU 72. AFTER TAU 72 AND FOR THE REMAINING TRACK, THE MODEL GUIDANCE ONLY SPREADS TO 150NM UNTIL THE END OF THE FORECAST PERIOD. THERE IS HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM THEREAFTER AS THE SPREAD INCREASES. THERE IS SIGNIFICANT UNCERTAINTY IN THE JTWC INTENSITY FORECAST AS MODEL GUIDANCE HAS WANED ON THE SYSTEM OVER THE LAST COUPLE OF RUNS. HWRF CONTINUES TO INDICATE A SHARP WEAKENING TREND TO ABOUT 50 KNOTS, THEN A SHARP RE-INTENSIFICATION TO 105-110 KNOTS BY TAUS 72-96, LENDING OVERALL MEDIUM CONFIDENCE OUT TO 72 HOURS AND THEN LOW THEREAFTER FOR THE OVERALL JTWC INTENSITY FORECAST. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN