MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 20W (HAGIBIS) WARNING NR 019// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUPER TYPHOON (STY) 20W (HAGIBIS), LOCATED APPROXIMATELY 798 NM SOUTH OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY REVEALS A 20 NAUTICAL MILE (NM) EYE, PROVIDING GOOD CONFIDENCE FOR THE INITIAL POSTION PLACEMENT. ADDITIONALLY, THE EYE IS SHOWING TROCHOIDAL MOTION OVER THE PAST 6 HRS. A 091619Z AMSR2 89GHZ IMAGE DISPLAYS CONCENTRIC EYEWALLS, HOWEVER THE CIMSS M- PERC PRODUCT IS NOT INDICATING A HIGH LIKELIHOOD OF AN EYEWALL REPLACEMENT CYCLE (ERC) OCCURRING AT THIS TIME. THE INITIAL INTENSITY IS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF 7.0 (140 KTS) BY PGTW AND RJTD. FURTHERMORE, THERE IS A 090835Z SMAP IMAGE (40 KM RESOLUTION) WITH MAX WIND SPEEDS OF 128 KTS (1-MINUTE AVERAGE) THAT SUPPORTS THE CURRENT INTENSITY ESTIMATE. STY 20W HAS STRONG RADIAL OUTFLOW; THE POLEWARD OUTFLOW IS BEING FURTHER ENHANCED BY A TROUGH TO THE NORTHWEST OF THE SYSTEM. FURTHERMORE, THE SYSTEM IS SITTING IN FAVORABLE ENVIRONMENTAL CONDITIONS WITH WARM SST (29C) AND LOW VERTICAL WIND SHEAR (VWS). STY 20W IS CURRENTLY WOBBLING TO THE NORTH-NORTHEAST AFTER A SHIFT FROM A NORTH- NORTHWESTWARD TRACK OVER THE PAST 6-12 HOURS. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE LAST PROGNOSTIC REASONING MESSAGE. WIND RADII HAVE BEEN ADJUSTED BASED ON RECENT ASCAT-C AND SMAP DATA--THIS DATA CONTINUES TO INDICATE AN EXPANSIVE GALE WIND FIELD. B. STY 20W WILL TRACK NORTH-NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) THROUGH TAU 36 WITH LOW VWS, WARM SST, AND STRONG UPPER-LEVEL OUTFLOW. STY 20W IS EXPECTED TO MAINTAIN INTENSITY FOR THE FIRST 12 HOURS DUE TO THE ENHANCED POLEWARD OUTFLOW. 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. AFTER TAU 36, A SHORTWAVE TROUGH WILL PASS OVER JAPAN, WEAKENING THE STR AND ALLOWING STY 20W TO BEGIN RECURVING. STY 20W WILL BEGIN EXTRA- TROPICAL TRANSITION (ETT) NEAR TAU 48. OVERALL, THERE IS GOOD CONFIDENCE IN THE OFFICIAL JTWC FORECAST IN THIS PORTION OF THE TRACK. C. AFTER TAU 72, VWS WILL INCREASE SIGNIFICANTLY, SSTS WILL DROP BELOW 24 DEGREES CELSIUS, FRICTIONAL EFFECTS FROM SKIRTING HONSHU WILL DISRUPT THE STRUCTURE, AND A LOW LEVEL NORTHEASTERLY COLD SURGE WILL BUILD IN TO THE WEST, ALL COMBINING TO CAUSE MORE RAPID WEAKENING. STY 20W WILL ACCELERATE NORTHEASTWARD AND COMPLETE ETT BY TAU 84 AS THE SYSTEM BECOMES EMBEDDED IN THE MIDLATITUDE WESTERLIES AND GAINS STRONG FRONTAL CHARACTERISTICS. 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 96. THE JTWC FORECAST TRACK IS PLACED NEAR BUT SLIGHTLY FASTER 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