MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (HAGIBIS) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 20W (HAGIBIS), LOCATED APPROXIMATELY 537 NM EAST OF ANDERSEN AFB, GUAM, HAS TRACKED WESTWARD AT 17 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THE SYSTEM HAS MAINTAINED TIGHTLY-CURVED DEEP CONVECTIVE BANDING WRAPPING INTO A FORMATIVE BANDING EYE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE FORMATIVE EYE, THE INITIAL INTENSITY OF 50KTS IS HEDGED HIGHER THAN AGENCY AND OBJECTIVE DVORAK ESTIMATES OF T4.0/45KTS TO INDICATE THE INTENSIFICATION AS EVIDENCED BY THE FORMATIVE EYE. UPPER-LEVEL ANALYSIS INDICATES NEAR-RADIAL OUTFLOW WITH LOW VERTICAL WIND SHEAR. SST VALUES OF 30-31C AND HIGH OCEAN HEAT CONTENT VALUES ALSO SUPPORT FURTHER INTENSIFICATION. THE CYCLONE IS TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 20W IS FORECAST TO TRACK WESTWARD TO WEST-NORTHWESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE STR. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN VERY FAVORABLE THROUGH THE FORECAST PERIOD WITH ROBUST OUTFLOW, WARM SST AND HIGH OCEAN HEAT CONTENT VALUES SUPPORTING RAPID INTENSIFICATION (RI), REACHING 80KTS IN 24HRS BEFORE THE SYSTEM HITS THE NORTHERN MARIANAS. AFTERWARD, TS 20W WILL CROSS INTO THE PHILIPPINE SEA AND CONTINUE WITH RI, REACHING 125KTS BY TAU 72. NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH A GRADUAL SPREAD TO 150NM BY TAU 72, LENDING FAIR CONFIDENCE IN THIS PORTION OF THE JTWC TRACK FORECAST. C. IN THE EXTENDED PERIOD, TS HAGIBIS WILL TRACK MORE NORTHWESTWARD TOWARD A BREAK IN THE STR ASSOCIATED WITH AN APPROACHING MIDLATITUDE TROUGH OVER WESTERN JAPAN. IMPROVED POLEWARD OUTFLOW ASSOCIATED WITH THIS SHORTWAVE TROUGH WILL AID IN BOOSTING THE INTENSITY TO SUPER TYPHOON STRENGTH. THERE IS INCREASING UNCERTAINTY AFTER TAU 96 AS THE NUMERICAL MODEL GUIDANCE DIVERGES WITH A 200 NM SPREAD IN SOLUTIONS AT TAU 120, THEREFORE, THERE IS LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC TRACK FORECAST.// NNNN NNNN