MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (BOLAVEN) WARNING NR 09// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 01W (BOLAVEN), LOCATED APPROXIMATELY 305 NM EAST OF HO CHI MINH CITY, VIETNAM, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY DEPICTS FLARING CONVECTION TO THE NORTH OF A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC). A 031349Z 89GHZ AMSU MICROWAVE IMAGE SHOWS A SMALL AREA OF DEEP CONVECTION TO THE NORTHWEST OF THE LLCC. THE IMAGE ALSO DEPICTS WEAK BANDING FEATURES WRAPPING INTO THE LLCC FROM THE EASTERN SEMI-CIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON EXTRAPOLATION FROM THE AFOREMENTIONED MICROWAVE IMAGE AND THE PARTIALLY EXPOSED LLCC. THE INITIAL INTENSITY IS HEDGED ON THE UPPER END OF MUTLI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM T1.0 TO T2.0 (25-30 KNOTS) FROM PGTW AND RJTD RESPECTIVELY. ENVIRONMENTAL ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (15 TO 20 KNOTS) VERTICAL WIND SHEAR (VWS) AND WARM (26-27 CELSIUS) SEA SURFACE TEMPERATURES. UPPER LEVEL ANALYSIS REVEALS BROAD DIFFLUENCE ALOFT WITH NO DEFINED OUTFLOW CHANNELS. TD 01W IS TRACKING WESTWARD UNDER THE INFLUENCE OF AN EAST-WEST ORIENTED SUBTROPICAL STEERING RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 01W IS FORECAST TO TRACK WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF THE STR. THE SYSTEM WILL CONTINUE TO WEAKEN IN A MARGINALLY FAVORABLE ENVIRONMENT, EVENTUALLY MAKING LANDFALL NORTH OF HO CHI MINH CITY, VIETNAM AROUND TAU 12. AFTER LANDFALL, THE SYSTEM WILL DISSIPATE RAPIDLY AS IT TRACKS INLAND THROUGH THE RUGGED TERRAIN OF SOUTHERN VIETNAM. NUMERICAL MODEL GUIDANCE REMAINS IN FAIR AGREEMENT THROUGH TAU 12 WITH A GENERALLY WESTERN TRACK. AFTER TAU 12, THERE IS SIGNIFICANT SPREADING IN MODEL GUIDANCE WITH NAVGEM BEING THE PRINCIPLE OUTLIER, PRODUCING A NORTHWESTERN TRACK SOLUTION. OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST TRACK DUE TO THE LARGE SPREAD IN MODEL SOLUTIONS AFTER TAU 12.// NNNN NNNN