WDPN31 PGTW 171500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 02W (SURIGAE) WARNING NR 017// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 02W (SURIGAE), LOCATED APPROXIMATELY 324 NM EAST OF LEGAZPI, PHILIPPINES, HAS TRACKED NORTHWESTWARD AT 12 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A HIGHLY-SYMMETRICAL SYSTEM WITH A CENTRAL DENSE OVERCAST (CDO) THAT CONTINUED TO DEEPEN WHILE MAINTAINING A SHARPLY OUTLINED 16-NM EYE. FEEDER BANDS HAVE SHORTENED AND THINNED OUT AS THEY SPIRALED TIGHTER INTO THE CDO. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE OVER THE WELL-DEFINED EYE. THE INITIAL INTENSITY OF 15KTS IS BASED ON AN OVERALL ASSESSMENT OF AGENCY DVORAK ESTIMATES OF T7.0/140KTS (PGTW/RCTP), T7.5/155KTS (RJTD); AND THE OBJECTIVE ESTIMATES OF T7.9/167KTS (ADT) AND 152KTS (SATCON) THAT REFLECTS THE CONTINUED RAPID INTENSIFICATION OF THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES ROBUST EQUATORWARD AND POLEWARD OUTFLOW, LOW (5-10 KTS) VERTICAL WIND SHEAR, AND WARM (29-30C) SEA SURFACE TEMPERATURES IN THE PHILIPPINE SEA CONTRIBUTING TO AN OVERALL FAVORABLE ENVIRONMENT. STY 02W IS TRACKING TOWARD A BREAK IN THE RIDGE TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. STY 02W WILL CONTINUE ON ITS CURRENT NORTHWESTWARD TRACK. AFTER TAU 12, THE SPLIT SUBTROPICAL RIDGE (STR) TO THE NORTHEAST WILL BUILD, REORIENT AND TAKE OVER AS THE PRIMARY STEERING MECHANISM, DRIVING THE CYCLONE TO A SLOW NORTHWARD TRAJECTORY AS IT ENTERS A WEAK STEERING ENVIRONMENT. AS THE SYSTEM GAINS LATITUDE, DIVERGENCE ALOFT WILL DECREASE AND CAUSE THE SYSTEM TO SLOWLY WEAKEN, DOWN TO 110KTS BY TAU 72. NUMERICAL MODELS ARE IN FAIR AGREEMENT DURING THIS PORTION OF THE FORECAST WITH A GRADUAL AND EVEN CROSS-TRACK SPREAD TO 186NM BY TAU 72. THEREFORE, THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK WHICH IS LAID OVER BUT SLIGHTLY SLOWER THAN THE MULTI-MODEL CONSENSUS DURING THE SLOW PROGRESSION IN THE WEAK STEERING SEGMENT. C. AFTER TAU 72, STY SURIGAE WILL CONTINUE NORTHWARD ALONG THE WESTERN PERIPHERY OF THE STR, CREST THE AXIS, THEN ACCELERATE NORTHEASTWARD ON THE POLEWARD SIDE. AS IT MOVES FURTHER NORTH, THE ENVIRONMENT WILL SLOWLY BECOME LESS FAVORABLE AS UPPER LEVEL DIVERGENCE CONTINUES TO DECREASE LEADING TO GRADUAL WEAKENING, DOWN TO 85KTS BY TAU 120. NUMERICAL MODELS HAVE CLUSTERED CLOSER AND NO MEMBER TRACK TOWARD LUZON ANY LONGER. THE CROSS TRACK SPREAD IS NOW DOWN TO 442NM AT TAU 120, LENDING FAIR CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.// NNNN