WDPN31 PGTW 021500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 11W (HALONG) WARNING NR 21// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 11W (HALONG), LOCATED APPROXIMATELY 799 NM SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED WESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. STY 11W HAS RAPIDLY INTENSIFIED BY 75 KNOTS (60 TO 135 KNOTS) OVER THE PAST 24 HOURS. ANIMATED ENHANCED SATELLITE IMAGERY DEPICTS A 130-NM DIAMETER, SYMMETRIC EYEWALL WITH A 29-NM ROUND EYE, THEREFORE THERE IS GOOD CONFIDENCE IN THE CURRENT POSITION AND TRACK MOTION. A 021013Z SSMIS IMAGE DEPICTS IMPROVED CONVECTIVE BANDING OVER THE NORTHERN SEMI-CIRCLE WITH EXTENSIVE MULTIPLE CONVECTIVE BANDS OVER THE SOUTHERN SEMI-CIRCLE WRAPPING INTO THE EASTERN QUADRANT OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE CURRENT INTENSITY IS ASSESSED AT 135 KNOTS BASED ON DVORAK INTENSITY ESTIMATES RANGING FROM 127 KNOTS (T6.5) TO 140 KNOTS (T7.0). UPPER-LEVEL ANALYSIS INDICATES STRONG CONVERGENT FLOW OVER THE NORTHERN PERIPHERY OF THE SYSTEM, HOWEVER, STY 11W HAS MAINTAINED EXCELLENT EQUATORWARD OUTFLOW AS WELL AS POLEWARD OUTFLOW INTO THE TUTT POSITIONED TO THE NORTHEAST, WHICH HAS ALLOWED THE SYSTEM TO INSULATE THE CORE CONVECTION FROM PERSISTENT UPPER-LEVEL NORTHERLY FLOW. STY 11W IS CURRENTLY TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. THE RECENT 500MB ANALYSES DEPICT A NORTH-SOUTH ORIENTED STR POSITIONED SOUTH OF JAPAN WITH CONVERGENT SOUTHERLY FLOW EXTENDING FROM TAIWAN TO ABOUT 131E LONGITUDE. THIS SYNOPTIC STEERING ENVIRONMENT IS FORECAST TO MAINTAIN FOR THE NEXT THREE DAYS DUE TO THE POSITION OF TS 12W, WHICH SHOULD ALLOW STY 11W TO TRACK NORTH- NORTHWESTWARD TO NORTHWARD THROUGH TAU 72. WITH THE EXCEPTION OF UKMO, DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH A 165-NM SPREAD IN SOLUTIONS AT TAU 72, THEREFORE, THE JTWC FORECAST IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS. STY 11W IS FORECAST TO MAINTAIN SUPER TYPHOON STRENGTH THROUGH TAU 24 THEN WEAKEN SLIGHTLY AS IT TRACKS INTO INCREASING NORTHERLY VERTICAL WIND SHEAR. C. IN THE EXTENDED TAUS, THERE IS INCREASING UNCERTAINTY IN THE TRACK WITH GREATER SPREAD IN THE SOLUTIONS. AN APPROACHING MIDLATITUDE SHORTWAVE TROUGH IS FORECAST TO DIG OVER THE KOREAN PENINSULA AND WESTERN JAPAN, CREATING A BREAK IN THE STR, HOWEVER, THE DYNAMIC MODELS BUILD THE STR AHEAD OF THE TROUGH TO VARYING DEGREES. THE MOST LIKELY SCENARIO IS THAT THE SYSTEM TRACKS POLEWARD TOWARD KYUSHU DUE TO THE EXTENT OF THE TROUGH. DUE TO THE UNCERTAINTY IN TIMING OF THE POLEWARD TURN NEAR TAU 36 AND THE DEPICTION OF THE TROUGH AND STR IN THE EXTENDED TAUS, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST, WHICH IS POSITIONED CLOSE TO MULTI-MODEL CONSENSUS.// NNNN