WDPN32 PGTW 180900 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (TWELVE) WARNING NR 03// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 12W (TWELVE), LOCATED APPROXIMATELY 439 NM SOUTH OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED EAST- NORTHEASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS TD 12W IS CONTINUING TO CONSOLIDATE WITH THE MAJORITY OF THE CONVECTION LOCATED TO THE SOUTH OF THE ELONGATED CIRCULATION. THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON AN 180600Z HIMAWARI VISIBLE SATELLITE IMAGE. THE INITIAL INTENSITY OF 30 KNOTS IS HEDGED BETWEEN A RJTD DVORAK INTENSITY ESTIMATE OF T1.5 (25 KNOTS) AND AN ADT ESTIMATE OF T2.3 (33 KNOTS). ENVIRONMENTAL CONDITIONS SHOW TD 12W IS EXPERIENCING FAVORABLE VERTICAL WIND SHEAR (10 TO 15 KNOTS). UPPER LEVEL WINDS CONTINUE TO IMPROVE IN STRUCTURE WITH MODERATE EQUATORWARD OUTFLOW. POLEWARD OUTFLOW ALSO CONTINUES TO IMPROVE AS IT TAPS INTO THE TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL LOCATED TO THE NORTHEAST. SEA SURFACE TEMPERATURES ARE FAVORABLE FOR ADDITIONAL DEVELOPMENT, BETWEEN 29 AND 30 DEGREES CELSIUS. TD 12W IS POSITIONED BETWEEN THE SUBTROPICAL RIDGE (STR) TO THE NORTH AND THE NEAR EQUATORIAL RIDGE (NER) TO THE SOUTH. THE NER IS CURRENTLY THE DOMINANT FEATURE, CAUSING TD 12W TO TRACK SLOWLY EAST- NORTHEASTWARD. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. HOWEVER, THE INITIAL POSITION HAS SHIFTED 52NM TO THE NORTHEAST SINCE THE PREVIOUS WARNING DUE TO THE BROAD NATURE OF THE CIRCULATION AND LOW CONFIDENCE IN THE INITIAL POSITION. THIS POSITIONAL ADJUSTMENT HAS CAUSED THE FORECAST TRACK TO ALSO SHIFT TO THE NORTHEAST. B. A WEST TO EAST MOVING TROUGH, CURRENTLY LOCATED OVER ASIA, WILL CONTINUE TO ERODE THE AFOREMENTIONED STR, ALLOWING THE NER TO REMAIN THE DOMINANT STEERING FEATURE IN THE SHORT TERM. THIS WILL ALLOW TD 12W TO TRACK TOWARD THE NORTHEAST TROUGH TAU 24. FAVORABLE SEA SURFACE TEMPERATURES AND ENHANCED POLEWARD OUTFLOW AS A RESULT OF THE TUTT TO THE NORTHEAST WILL ALLOW TD 12W TO REACH AN INTENSITY OF 40 KNOTS BY TAU 24. AFTER TAU 24, THE STR WILL BEGIN TO BUILD TO THE NORTHEAST OF TD 12W. THIS REORIENTATION OF THE STR WILL ALLOW FOR TD 12W TO TRACK NORTHWARD AND THEN NORTHWESTWARD. FAVORABLE ENVIRONMENTAL CONDITIONS WILL PERSIST THROUGH TAU 72 AS TD 12W TRACKS NORTHWESTWARD, REACHING AN INTENSITY OF 55 KNOTS BY TAU 72. THE LOW CONFIDENCE IN THE INITIAL POSITION ALONG WITH A WIDE SPREAD IN DYNAMIC MODEL GUIDANCE LEADS TO OVERALL LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK. THE JTWC FORECAST TRACK REMAINS HEDGED TO THE WEST OF THE MULTI-MODEL CONSENSUS, FAVORING THE ECMWF SOLUTION. C. BEYOND TAU 72, TD 12 WILL CONTINUE TO TRACK NORTHWESTWARD UNDER THE INFLUENCE OF THE STR. FAVORABLE ENVIRONMENTAL CONDITIONS WILL LEAD TO AN INTENSITY OF 60 KNOTS BY TAU 96. TD 12W WILL MAKE LANDFALL SOUTH OF SHANGHAI, CHINA SHORTLY AFTER TAU 96 WITH AN INTENSITY OF 55 KNOTS. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT, THEREFORE THERE IS LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN