MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 20W (HAGIBIS) WARNING NR 016// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 20W (HAGIBIS), LOCATED APPROXIMATELY 305 NM SOUTH OF IWO TO, HAS TRACKED NORTHWESTWARD AT 08 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A WELL-DEFINED, SYMMETRIC EYE WITH CONVECTIVE BANDING WRAPPING INTO THE CENTER. STY 20W HAS MAINTAINED A 20 NM DIAMETER EYE, SUPPORTING GOOD CONFIDENCE IN THE INITIAL POSITION. HOWEVER, THE IMMEDIATE EXTENT OF THE CIRRUS SHIELD HAS DECREASED IN THE PAST SIX HOURS. THE INITIAL INTENSITY IS SET AT 140 KTS WITH FAIR CONFIDENCE BASED ON DVORAK CURRENT INTENSITY (CI) ESTIMATES OF T7.0/140 KTS FROM PGTW/RJTD/RCTP ALONG WITH A 090033Z SATELLITE CONSENSUS OF 152 KTS AND A 090110Z ADVANCED DVORAK TECHNIQUE (ADT) ESTIMATE OF T6.9/137 KTS. UPPER-LEVEL ANALYSIS SHOWS EXCELLENT EQUATORWARD AND EASTWARD OUTFLOW WITH DEVELOPMENT OF A POLEWARD OUTFLOW CHANNEL AS A TROUGH PASSES TO THE NORTH. THE OVERALL ENVIRONMENT REMAINS FAVORABLE FOR BRIEF DEVELOPMENT WITH LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS) AND WARM (29-31 CELSIUS) SEA SURFACE TEMPERATURES (SST). TRACKING NORTH-NORTHWESTWARD, STY 20W IS BEING STEERED BY A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE LAST PROGNOSTIC REASONING MESSAGE. B. STY 20W WILL CONTINUE ALONG ITS NORTH-NORTHWESTWARD TRACK AS A PASSING MID-LATITUDE TROUGH TO THE NORTH CAUSES THE STR TO REORIENT. THE FAVORABLE ENVIRONMENT IS EXPECTED TO PERSIST WITH LOW VWS, WARM SST, AND STRONG UPPER-LEVEL OUTFLOW. THE OFFICIAL INTENSITY FORECAST REMAINS MORE AGGRESSIVE THAN MULTI-MODEL INTENSITY GUIDANCE DUE TO THE POSSIBILITY OF A BRIEF PERIOD OF ENHANCED POLEWARD OUTFLOW AS A RESULT OF INTERACTION WITH THE PASSING TROUGH. HOWEVER, AS THE OUTFLOW BEGINS TO BE SHEARED BY THE PASSING TROUGH, GRADUAL WEAKENING IS EXPECTED. THROUGH TAU 36, NUMERICAL MODELS REMAIN IN GOOD AGREEMENT. GFS AND THE GFS ENSEMBLE REMAIN THE EASTERNMOST OUTLIERS WITH NAVGEM AND AFUM AS THE WESTERNMOST OUTLIERS. AT TAU 72, THERE IS 190 NM OF CROSS-TRACK AND 200 NM OF ALONG-TRACK SPREAD AS THE MODEL SOLUTIONS DIFFER IN TIMING OF RECURVATURE. PLACED NEAR THE MULTI-MODEL CONSENSUS, THERE IS GOOD CONFIDENCE IN THE OFFICIAL JTWC FORECAST IN THIS PORTION OF THE TRACK. C. IN THE EXTENDED FORECAST PERIOD, STY 20W WILL BEGIN TO RECURVE AS A SHORTWAVE TROUGH PASSES OVER JAPAN, WEAKENING THE STR. AS VWS INCREASES AND SST COOL AFTER TAU 72, THE SYSTEM WILL CONTINUE TO SLOWLY WEAKEN AS IT APPROACHES HONSHU. AS STY 20W TRACKS OVER LAND, FRICTIONAL TERRAIN EFFECTS WILL ALSO BEGIN TO ERODE THE SYSTEM. STY 20W WILL BEGIN INTERACTING WITH THE TROUGH AROUND TAU 96, ACCELERATING NORTHEASTWARD AS EXTRATROPICAL TRANSITION OCCURS. BY TAU 120, THE SYSTEM WILL BE FULLY EXTRATROPICAL AND EMBEDDED IN THE MID-LATITUDE WESTERLIES. NUMERICAL MODELS ARE IN FAIR CROSS-TRACK AGREEMENT AFTER RECURVATURE OF STY 20W. HOWEVER, AS THE SYSTEM ACCELERATES, ALONG-TRACK SPREAD GREATLY INCREASES THROUGH TAU 120. THE JTWC FORECAST TRACK IS PLACED NEAR THE MULTI-MODEL CONSENSUS; BASED ON THE VARIATION IN MODEL TIMING OF THE RECURVE AND ALONG-TRACK SPEEDS, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST.// NNNN NNNN