WDXS31 PGTW 200900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 13.9S 92.9E INITIAL INTENSITY: 110 KTS GEOGRAPHIC REFERENCE: 1270 NM EAST-SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 05 KTS SIGNIFICANT WAVE HEIGHT: 32 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A TIGHTLY WRAPPED TROPICAL CYCLONE WITH A WELL DEFINED 23NM EYE AND IMPROVED POLEWARD OUTFLOW. A 200602Z GMI 89GHZ MICROWAVE IMAGE REVEALS THAT 05S HAS A WELL DEFINED, SOLID EYEWALL AND A SERIES OF TIGHTLY WRAPPING DEEP CONVECTIVE BANDS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI AND GMI IMAGERY. THE INITIAL INTENSITY OF 110 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A MAJORITY OF THE AVAILABLE INTENSITY GUIDANCE INDICATING 110-115KTS WITH THE EXCEPTION OF ABOM WHO ESTIMATES CLOSER TO 90KTS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: IN TRANSITION TO THE INFLUENCE OF A SUBTROPICAL RIDGE (STR) TO THE SOUTH. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T6.0 - 115 KTS KNES: T6.0 - 115 KTS APRF: T5.0 - 90 KTS CIMSS ADT: 115 KTS AT 200600Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 26-27 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: OVER THE PAST 12 HOURS, TROPICAL CYCLONE 05S HAS RAPIDLY INTENSIFIED TO 110KTS IN A FAVORABLE ENVIRONMENT. THIS ENVIRONMENT IS CHARACTERIZED BY CONSISTENT, NEGLIGIBLE VERTICAL WIND SHEAR VALUES, WARM SEA SURFACE TEMPERATURES AND GOOD POLEWARD OUTFLOW. AS THE SYSTEM CONTINUES TO TRANSITION TO THE STEERING INFLUENCE OF THE STR CENTERED TO THE SOUTH, 05S WILL STEADY UP ON A GENERALLY WESTWARD COURSE ALONG THE 14TH PARALLEL. AS THE SYSTEM CONTINUES WESTWARD, INTENSITIES WILL GRADUALLY DECLINE AS 05S UPWELLS COOLER WATER, BY TAU 48 INTENSITIES ARE FORECAST TO FALL TO AROUND 75KTS. AFTER TAU 48, THE SYSTEM WILL ONCE AGAIN MIGRATE OVER WARMER WATERS, RESULTING IN RENEWED OPPORTUNITY FOR INTENSIFICATION. 05S IS FORECAST TO REACH ITS SECOND AND FINAL PEAK INTENSITY OF 90KTS NEAR TAU 96, AFTER WHICH DRY AIR BEGINS TO ERODE THE SYSTEMS CORE AND INTENSITIES ONCE AGAIN FALL THROUGH THE FORECAST PERIOD. MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT THAT 05S WILL TRANSIT THE 14TH PARALLEL WESTWARD WITH A 200NM SPREAD IN SOLUTIONS BY TAU 120. FOR THIS REASON THE JTWC TRACK IS PLACED INITIALLY WITH HIGH CONFIDENCE AND EVENTUALLY MEDIUM CONFIDENCE FOR THE EXTENDED TRACK FORECAST. RELIABLE MODEL INTENSITY GUIDANCE INDICATES AN OVERALL AGREEMENT ON THE GENERAL TREND THAT THE SYSTEM WILL TAKE THROUGH THE FORECAST PERIOD. WITH NOTABLE DIFFERENCES IN MAX AND MIN INTENSITIES A WEAKENING TREND APPEARS APPROXIMATELY THROUGH TAU 48, AFTER WHICH INTENSIFICATION AND EVENTUAL DECLINE NEAR TAU 96. THIS 15-20 KNOT VARIABILITY IN MODEL OUTPUT IS WHY THE JTWC FORECAST INTENSITY IS PLACED WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN