MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (BAILU) WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 12W (BAILU), LOCATED APPROXIMATELY 716 NM SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS THAT TD 12W HAS A BROAD AREA OF CONVECTION WHICH IS CONTINUING TO CONSOLIDATE AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON THE BROAD NATURE OF THE SYSTEM. THE POSITION IS BASED ON A PARTIAL 210503Z AMSR2 89GHZ MICROWAVE IMAGE WHICH SHOWS DEEP CONVECTION TO THE WEST OF THE LLCC WITH WEAKER BANDING CONVECTION TO THE NORTHWEST AND NORTH OF THE LLCC. THE INITIAL INTENSITY OF 25 KNOTS IS BASED ON A DVORAK CURRENT INTENSITY (CI) ESTIMATE OF T1.0 (25 KNOTS) FROM PGTW AND HEDGED SLIGHTLY BELOW THE CI OF T2.0 (30 KNOTS) FROM RJTD. ENVIRONMENTAL ANALYSIS SHOWS TD 12W IS EXPERIENCING FAVORABLE VERTICAL WIND SHEAR (5 TO 15 KNOTS). TD 12W HAS A STRONG EQUATORWARD OUTFLOW CHANNEL AND A DEVELOPING POLEWARD OUTFLOW CHANNEL WITH A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL BEGINNING TO ENHANCE THE OUTFLOW. SEA SURFACE TEMPERATURES ARE FAVORABLE FOR DEVELOPMENT, NEAR 30 DEGREES CELSIUS. TD 12W IS TRACKING NORTHWESTWARD WHILE UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THIS IS THE INITIAL PROGNOSTIC REASONING MESSAGE AND SETS THE FORECAST PHILOSOPHY FOR THIS SYSTEM. B. IN THE SHORT TERM, TD 12W WILL CONTINUE TO EXPERIENCE FAVORABLE VERTICAL WIND SHEAR AND REMAIN OVER WARM SEA SURFACE TEMPERATURES, WHICH WILL ALLOW FOR A STEADY INCREASE IN INTENSITY. THE AFOREMENTIONED TUTT CELL WILL CONTINUE TO ENHANCE UPPER LEVEL OUTFLOW IN THE SHORT TERM AND ALSO ALLOW FOR INTENSIFICATION. THE STR TO THE NORTHEAST WILL REMAIN IN PLACE THROUGH TAU 72 AND ALLOW TD 12W TO TRACK NORTHWESTWARD. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT, HOWEVER, DUE TO THE HIGH UNCERTAINTY IN THE INITIAL POSITION THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK. C. AFTER TAU 72, TD 12W WILL CONTINUE TO TRACK NORTHWESTWARD WHILE UNDER THE INFLUENCE OF THE STR. SHORTLY AFTER TAU 72, TD 12W WILL MAKE LANDFALL IN CENTRAL TAIWAN WHICH WILL LEAD TO A WEAKENING TREND. BY TAU 96, AN APPROACHING WEST TO EAST MOVING SHORTWAVE TROUGH WILL TEMPORARILY WEAKEN THE STR AND ALLOW TD 12W TO TRACK SLIGHTLY MORE NORTHWARD. LAND INTERACTION WITH CHINA WILL CAUSE TD 12W TO QUICKLY WEAKEN AFTER TAU 96 AND DISSIPATE BY TAU 120. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT DURING THIS PORTION OF THE TRACK. MODEL GUIDANCE HAS A SPREAD OF 860NM BY TAU 120. DUE TO THE MODEL SPREAD AND THE HIGH UNCERTAINTY IN THE INITIAL POSITION THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN