MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 20W (HAGIBIS) WARNING NR 017// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 20W (HAGIBIS), LOCATED APPROXIMATELY 258 NM SOUTH-SOUTHWEST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 10 KNOTS 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 30 NM DIAMETER EYE, SUPPORTING THE INITIAL POSITION WITH GOOD CONFIDENCE. THE CIRRUS SHIELD AND WIDTH OF THE DEEP CONVECTIVE EYEWALL HAVE CONTINUED TO THIN OVER THE PAST 6 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 AND RJTD, WHICH IS BETWEEN A 090540Z AUTOMATED DVORAK TECHNIQUE ESTIMATE OF 132 KTS AND A 090033Z SATCON ESTIMATE OF 154 KTS. UPPER-LEVEL ANALYSIS SHOWS EXCELLENT EQUATORWARD AND EASTWARD OUTFLOW, AND A POLEWARD OUTFLOW CHANNEL HAS DEVELOPED, TAPPING INTO A PASSING TROUGH 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). STY 20W IS TRACKING NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF 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. STY 20W IS EXPECTED TO MAINTAIN INTENSITY FOR THE FIRST 12 HOURS AS DIURNAL CONVECTIVE MINIMUM COMPETES WITH ENHANCED POLEWARD OUTFLOW DUE TO THE TROUGH PASSING TO THE NORTH. HOWEVER, STY 20W IS EXPECTED TO BEGIN A GRADUAL WEAKENING TREND AFTER TAU 12 AS THE TROUGH BEGINS TO INTERFERE WITH OUTFLOW. NUMERICAL MODELS REMAIN IN GOOD CROSS-TRACK AGREEMENT BUT POOR ALONG- TRACK SPEED AGREEMENT. GFS AND THE GFS ENSEMBLE REMAIN THE EASTERNMOST OUTLIERS WITH NAVGEM AS THE WESTERNMOST OUTLIER IN THE SHORT TERM. AT TAU 72, THERE IS 90 NM OF CROSS-TRACK AND 230 NM OF ALONG-TRACK SPREAD AS THE MODEL SOLUTIONS DIFFER IN TIMING OF RECURVATURE. PLACED NEAR THE MULTI-MODEL CONSENSUS AND MAIN MODEL GROUPING, 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 SSTS DROP BELOW 26 DEGREES CELSIUS AFTER TAU 72, THE SYSTEM WILL CONTINUE TO 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. ECMWF, NAVGEM, AND COAMPS-TC ARE SLOWER THAN THE MULTI-MODEL CONSENSUS AT LATER TAUS. THE JTWC FORECAST TRACK IS PLACED NEAR BUT SLIGHTLY SLOWER THAN THE MULTI-MODEL CONSENSUS AFTER TAU 72. 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