MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 02W (SANBA) WARNING NR 25// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION 02W (SANBA), LOCATED APPROXIMATELY 447 NM SOUTH-SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WEST- NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED IMAGERY SHOWS A PARTIALLY EXPOSED AND ELONGATING LOW LEVEL CIRCULATION CENTER WITH FLARING CONVECTION IN THE NORTHWEST QUADRANT. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE INFRARED LOOP AND A 141801Z 37 GHZ GMI MICROWAVE IMAGE DEPICTING AN ELONGATED LLCC WITH WEAK, POORLY ORGANIZED BANDING. THE INITIAL INTENSITY OF 25 KNOTS IS BASED ON MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATE OF T1.5 (25 KNOTS) FROM PGTW AND KNES. ENVIRONMENTAL ANALYSIS REVEALS THE SYSTEM IS IN AN AREA OF MODERATE TO STRONG (20-25 KNOT) VERTICAL WIND SHEAR AND IS TRACKING THROUGH MARGINALLY FAVORABLE (27 CELSIUS) SEA SURFACE TEMPERATURES. UPPER LEVEL ANALYSIS REVEALS THAT THE MARGINALLY FAVORABLE ENVIRONMENT IS BEGIN OFFSET BY A STRONG POLEWARD OUTFLOW CHANNEL THAT IS ALLOWING THE SYSTEM TO MAINTAIN 25 KNOTS INTENSITY AND ENABLING FLARING CONVECTION. TD 02W IS CURRENTLY TRACKING WEST-NORTHWEST ALONG THE SOUTHERN PERIPHERY OF AN EXTENSION OF THE SUB TROPICAL RIDGE LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD SANBA IS FORECAST TO INITIALLY TRACK WEST-NORTHWEST THROUGH THE BALABAC STRAIT INTO THE SOUTH CHINA SEA. THE RIDGE EXTENSION IS FORECAST TO BUILD AS THE RIDGE SHIFTS TO THE WEST CAUSING THE SYSTEM TO TRACK MORE WESTWARD AND EVENTUALLY TO THE SOUTHWEST AFTER TAU 48. THOUGH THE SYSTEM HAS TRACKED AT A SLOW SPEED OVER THE LAST 18 HOURS TD SANBA IS FORECAST TO ACCELERATE AFTER ENTERING THE SOUTH CHINA SEA AS THE STEERING STR BUILDS IN FROM THE NORTHEAST. THE INTENSITY IS FORECAST TO PLATEAU AT 25 KTS, AS INCREASING VWS AND COOLING SSTS ARE OFFSET BY STRONG POLEWARD OUTFLOW. AFTER TAU 48, TD 02W WILL TRACK INTO INCREASINGLY COOLER (<26 CELSIUS) SSTS, CAUSING DISSIPATION BY TAU 72. AVAILABLE DYNAMIC MODEL GUIDANCE IS IN GENERAL AGREEMENT ON THE WESTWARD TRACK HOWEVER, VARY AS SEVERAL INITIALLY TRACK MORE TO THE WEST-NORTHWEST, AND OTHERS DIVERGE TO THE WEST. DUE TO THE LARGE SPREAD IN MODEL GUIDANCE, AND THE WEAK NATURE OF THE SYSTEM, THERE IS OVERALL A LOW CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN