MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT) WARNING NR 02// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 28W (TWENTYEIGHT), LOCATED APPROXIMATELY 284 NM NORTHEAST OF POHNPEI, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS A COMPLETE DISSIPATION OF THE DEEP CONVECTION ASSOCIATED WITH A WEAK LOW LEVEL CIRCULATION CENTER (LLCC). THE WEAK LLCC IS EVIDENT IN AN 110606Z GPM 89GHZ MICROWAVE IMAGE WHICH SUPPORTS THE CURRENT POSITION WITH GOOD CONFIDENCE. THE INTENSITY HAS BEEN HELD AT 30 KNOTS BASED ON THE DEFINED LLCC IN THE GPM IMAGE; HOWEVER, THE INTENSITY COULD BE LOWER. TD 28W IS LOCATED SOUTH OF THE UPPER LEVEL RIDGE UNDER STRONG EASTERLY FLOW. LIMITED DIVERGENCE ALOFT AND LOW TO MODERATE (10-15 KNOTS) VERTICAL WIND SHEAR (VWS) IS RESPONSIBLE FOR THE WANING CONVECTION. THE CYCLONE IS TRACKING WESTWARD WITH THE EASTERLY FLOW ASSOCIATED WITH THE DEEP-LAYERED SUB-TROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST TRACK PHILOSOPHY; HOWEVER, THE PEAK INTENSITY IN THE EXTENDED FORECAST HAS BEEN DECREASED. B. TD 28W IS EXPECTED TO TRACK WESTWARD UNDER THE INFLUENCE OF THE STR TO THE NORTH OVER THE NEXT 72 HOURS. THE UPPER-LEVEL ENVIRONMENT WILL REMAIN MOSTLY UNCHANGED WHICH WILL CAUSE THE CONVECTIVE STRUCTURE TO CONTINUE TO STRUGGLE WITH ONLY SLIGHT INTENSIFICATION POSSIBLE. C. IN THE EXTENDED FORECAST, THE STR WILL REMAIN THE DOMINANT STEERING MECHANISM FORCING THE CYCLONE ON A GENERALLY WEST- NORTHWESTWARD TRACK. ENVIRONMENTAL CONDITIONS WILL REMAIN MARGINAL THROUGH THE END OF THE FORECAST PERIOD KEEPING THE CYCLONE AT A WEAK TROPICAL STORM STRENGTH. DYNAMIC MODEL GUIDANCE IS IN DECENT AGREEMENT ON THE WEST-NORTHWESTWARD TRACK; HOWEVER, THERE ARE SOME DIFFERENCES IN THE FORWARD SPEED AND THE DEGREE OF THE NORTHWESTWARD COURSE. THE EARLY INSTABILITY IN THE MODEL GUIDANCE PROVIDES LOW CONFIDENCE IN THE JTWC FORECAST.// NNNN NNNN