MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 28W (TWENTYEIGHT) WARNING NR 03// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 28W (TWENTYEIGHT), LOCATED APPROXIMATELY 121 NM NORTHWEST OF ANDERSEN AFB, GUAM, HAS TRACKED NORTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS TS 28W CONTINUES TO IMPROVE IN STRUCTURE WITH EXCELLENT LOW LEVEL BANDING AND DEEP CONVECTION, MAINLY TO THE SOUTH AND EAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON A 210600Z HIMAWARI VISIBLE SATELLITE IMAGE. THE INITIAL INTENSITY OF 35 KNOTS IS BASED ON A DVORAK INTENSITY ESTIMATE OF T2.5 (35 KNOTS) FROM PGTW AND AN ADT ESTIMATE OF T2.4 (34 KNOTS). THIS IS HEDGED BETWEEN A DVORAK INTENSITY ESTIMATE OF T1.5 (25 KNOTS) FROM RJTD AND A 210337Z SATCON ESTIMATE OF 40 KNOTS. ENVIRONMENTAL ANALYSIS SHOWS TS 28W IS EXPERIENCING FAVORABLE VERTICAL WIND SHEAR (5 TO 10 KNOTS) ALONG WITH EXCELLENT RADIAL OUTFLOW. SEA SURFACE TEMPERATURES ARE ALSO FAVORABLE FOR CONTINUED DEVELOPMENT, BETWEEN 29 AND 30 DEGREES CELSIUS. TS 28W IS TRACKING NORTHWESTWARD UNDER THE INFLUENCE OF THE WEST TO EAST ORIENTATED SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 28W WILL CONTINUE TO TRACK TO THE NORTHWEST UNDER THE INFLUENCE OF THE AFOREMENTIONED STR. THE STR WILL BE THE PRIMARY STEERING FEATURE THROUGH TAU 72. VERTICAL WIND SHEAR, UPPER LEVEL, OUTFLOW, AND SEA SURFACE TEMPERATURES ARE ALL CONDUCIVE FOR RAPID INTENSIFICATION. THE POTENTIAL FOR RAPID INTENSIFICATION HAS BEEN CAPTURED BY MODEL GUIDANCE. AS A RESULT, TS 28W WILL QUICKLY REACH AN INTENSITY OF 70 KNOTS BY TAU 48 AND 105 KNOTS BY TAU 72. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT WITH A MODEL SPREAD OF 135 NM BY TAU 72. THEREFORE, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK. C. AFTER TAU 72, THE STR LOCATED TO THE NORTH WILL ERODE AS A RESULT OF AN APPROACHING MID-LATITUDE TROUGH. A STR TO THE WEST WILL ALSO BEGIN TO BUILD AT THIS TIME. THE POSITIONING OF THE STRS WILL ALLOW FOR TS 28W TO SLOW IN FORWARD SPEED. BY TAU 96, STRS TO THE NORTHEAST AND WEST WILL COMPETE TO BECOME THE DOMINANT STEERING FEATURE. THE PLACEMENT OF THE STRS MAY ALLOW TS 28W TO BECOME QUASI-STATIONARY BEGINNING NEAR TAU 108. VERTICAL WIND SHEAR AND SEA SURFACE TEMPERATURES WILL REMAIN FAVORABLE DURING THIS TIME PERIOD, ALLOWING TS 28W TO REACH AND INTENSITY OF 135 KNOTS BY TAU 96 AND UP TO 140 KNOTS BETWEEN TAU 96 AND 120. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT WITH A TRACK SPREAD OF 500 NM BY TAU 120. HWFI, CTCI, AND COTI ARE THE PRIMARY OUTLIERS, INDICATING A FASTER TRACK SPEED TO THE NORTH. THEREFORE, THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST T RACK WHICH IS PLACED NEAR THE MULTI-MODEL CONSENSUS AND THE GLOBAL MODEL GUIDANCE. THERE IS ALSO A LARGE SPREAD IN INTENSITY GUIDANCE. THE JTWC INTENSITY FORECAST IS PLACED ABOVE THE CONSENSUS BASED ON THE EXPECTED FAVORABLE VERTICAL WIND SHEAR AND SEA SURFACE TEMPERATURES.// NNNN NNNN