MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (TWELVE) WARNING NR 01// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 12W (TWELVE), LOCATED APPROXIMATELY 212 NM NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A WELL-DEFINED BUT PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH WEAK CONVECTIVE BANDING WRAPPING INTO THE CENTER. A 230421Z GPM 36GHZ MICROWAVE IMAGE DEPICTS IMPROVED TIGHTLY CURVED, BUT BROKEN, SHALLOW BANDING WRAPPING INTO THE LLCC. THE INITIAL POSITION IS BASED ON THE PARTIALLY EXPOSED LLCC IN MSI AND EXTRAPOLATED FROM THE GPM IMAGE WITH FAIR CONFIDENCE. THE INITIAL INTENSITY OF 25 KNOTS IS BASED ON AN ASSESSMENT OF AGENCY DVORAK INTENSITY ESTIMATES OF 25 KNOTS AND SUPPORTED BY A PREVIOUS ASCAT PASS SHOWING 25 KNOT WINDS. UPPER LEVEL ANALYSIS DEPICTS A MARGINAL ENVIRONMENT WITH STRONG NORTHEASTERLY FLOW ALOFT DISPLACING THE LIMITED CONVECTION TO THE WEST, OVER LAND, WITH WEAK EQUATORWARD OUTFLOW. IN ADDITION, WATER VAPOR IMAGERY AND THE AFOREMENTIONED MICROWAVE IMAGE SHOWS DRY AIR SURROUNDING THE EASTERN PERIPHERY OF THE SYSTEM. TD 12W IS TRACKING WITH THE STRONG SOUTHEASTERLY FLOW IN THE LOW TO MID-LEVEL CAUSED BY AN EXTENSION OF THE SUB-TROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING AND SETS THE FORECAST PHILOSOPHY. B. TD 12W WILL CONTINUE TO TRACK NORTH TO NORTHEASTWARD ALONG THE WESTERN EXTENSION OF THE STR. MARGINAL ENVIRONMENTAL CONDITIONS WILL PROHIBIT SIGNIFICANT DEVELOPMENT OF THE DEPRESSION AS IT GAINS LATITUDE. AFTER TAU 24, THE SYSTEM WILL BEGIN TO ACCELERATE TO THE NORTHEAST AS IT IS INFLUENCED BY TY 01C PASSING TO THE NORTH. THE OUTFLOW ASSOCIATED WITH TY 01C WILL CAUSE INCREASED SUBSIDENCE AND VERTICAL WIND SHEAR OVER TD 12W, CAUSING IT TO WEAKEN AND DISSIPATE BY THE END OF THE FORECAST PERIOD. LIMITED DYNAMIC MODEL GUIDANCE IS IN DECENT OVERALL AGREEMENT ON A NORTH-NORTHEASTWARD TRACK WITH MINIMAL, IF ANY, INTENSIFICATION FORECASTED. DUE TO THE LIMITED GUIDANCE AND THE EXPECTED INTERACTION BETWEEN TY 01C AND TD 12W, THERE IS LOW CONFIDENCE IN THE INITIAL JTWC FORECAST.// NNNN NNNN