WDPN31 PGTW 120900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (FIVE) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. 12JUN21. TROPICAL DEPRESSION (TD) 05W (FIVE), LOCATED APPROXIMATELY 203 NM SOUTHEAST OF HANOI, VIETNAM, HAS TRACKED NORTHWESTWARD AT 14 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE RAGGED AND PARTLY EXPOSED LOWEL CIRCULATION (LLC) TRACKED ACROSS SOUTHERN HAINAN WITH THE ASSOCIATED DISORGANIZED CONVECTION SHEARED WESTWARD AND SOUTHWESTWARD. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE LLC FEATURE IN THE MSI ANIMATION THAT COINCIDED WITH A WEAK CIRCULATION FEATURE IN A RADAR LOOP FROM CMA. THE INITIAL INTENSITY OF 25KTS IS EXTRAPOLATED FROM NEARBY OBSERVATIONS INCLUDING A SHIP REPORT (23KTS/999MB) 75NM TO THE NORTHWEST AND CONSISTENT WITH THE CONVECTIVE SIGNATURE. THE SYSTEM IS IN A MARGINAL ENVIRONMENT WITH GOOD WESTWARD AND EQUATORWARD OUTFLOW OFFSET BY MODERATE (15-20KTS) VERTICAL WIND SHEAR (VWS). THE SYSTEM IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE EAST- NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING BULLETIN. B. TD 05W WILL CONTINUE ON ITS CURRENT TRACK UNDER THE STR, CROSS THE GULF OF TONKIN, MAKE LANDFALL OVER NORTHERN VIETNAM AROUND TAU 18, THEN TRACK INLAND. THE ROBUST OUTFLOW AND THE WARM SST IN THE GULF WILL OFFSET THE VWS AND FUEL INTENSIFICATION TO A PEAK OF 45KTS BY TAU 12. AFTERWARD, LAND INTERACTION WITH THE RUGGED TERRAIN WILL RESULT IN A RAPID DECAY LEADING TO DISSIPATION BY TAU 36 AFTER IT PASSES JUST SOUTH OF HANOI. NUMERICAL MODELS ARE IN FAIR AGREEMENT WITH EVEN AND GRADUAL SPREADING TO 97NM AT TAU 24; AFTERWARD, ERRATIC DISPERSION AS THEY LOSE THE VORTEX OVER LAND. IN VIEW OF THIS, THERE IS FAIR CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN