WDXS31 PGTW 121500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (FREDDY) WARNING NR 020// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.1S 98.9E INITIAL INTENSITY: 100 KTS GEOGRAPHIC REFERENCE: 210 NM SOUTHEAST OF THE COCOS ISLANDS MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 42 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL CYCLONE (TC) 11S HAS WEAKENED GRADUALLY OVER THE PAST 12 HOURS AND LOST ITS WELL-DEFINED EYE. HOWEVER, ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTIVE BANDING WRAPPING TIGHTLY INTO A PARTIALLY CLOUD-FILLED EYE. A 121322Z GMI 89GHZ MICROWAVE IMAGE REVEALS TIGHLY-CURVED BANDING WRAPPING INTO A SMALL MICROWAVE EYE FEATURE, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE. OVER THE PAST 12 HOURS, A SERIES OF WINDSPEED PRODUCTS AIDED IN ACCURATELY ASSESSING THE INTENSITY: FIRST, AN 112240Z RADARSAT-2 IMAGE INDICATED PEAK WINDS OF 97 KNOTS WITH AN INCIDENCE ANGLE OF 41-42 DEGREES SO LIKELY ON THE LOW SIDE. SECOND, A 120639Z AMSR2 WINDSPEED IMAGE SHOWED PEAK WINDS OF 101 KNOTS. THIS DATA SUPPORTS THE GRADUAL WEAKENING TREND FROM 110 KNOTS AT 120000Z TO 105 KNOTS AT 120600Z WITH DVORAK ESTIMATES SUPPORTING THE CURRENT INTENSITY OF 100 KNOTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T5.5 - 102 KTS KNES: T5.5 - 102 KTS DEMS: T5.5 - 102 KTS CIMSS ADT: 90 KTS AT 121130Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 20-25 KTS SST: 27-28 CELSIUS OUTFLOW: MODERATE WESTWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 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 THROUGH THE FORECAST PERIOD ALONG THE NORTHERN PERIPHERY OF THE STR. THE SYSTEM SHOULD WEAKEN STEADILY THROUGH TAU 48 DUE TO PERSISTENT MODERATE TO HIGH VERTICAL WIND SHEAR (20 TO 25 KNOTS). GRADUAL REINTENSIFICATION IS EXPECTED AFTER TAU 48 AS VWS RELAXES AGAIN WITH A PEAK OF 95 KNOTS BY TAU 96. AFTER TAU 96, SST IS EXPECTED TO DECREASE SLIGHTLY TO 26 TO 27C, WHICH SHOULD WEAKEN THE SYSTEM. MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A 145NM SPREAD IN SOLUTIONS AT TAU 72. AFTER TAU 72, MODEL GUIDANCE DIVERGES TO 210NM AT TAU 120 LENDING MEDIUM CONFIDENCE TO THE JTWC TRACK FORECAST. DUE TO THE COMPACT NATURE OF THE SYSTEM AND ITS TENDENCY FOR LARGE FLUCTUATIONS IN INTENSITY, THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST. RELIABLE INTENSITY GUIDANCE INDICATES GOOD AGREEMENT THROUGH TAU 48 SUPPORTING THE GRADUAL WEAKENING TREND. AFTER TAU 48, THERE IS A LARGE SPREAD IN INTENSITY GUIDANCE THROUGH TAU 120 LENDING LOW CONFIDENCE TO THE 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