MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (BAILU) WARNING NR 07// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 12W (BAILU), LOCATED APPROXIMATELY 579 NM SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY SHOWS A LOW LEVEL CIRCULATION CENTER (LLCC) TO THE NORTHEAST OF THE CENTRAL DENSE OVERCAST, OBSCURED BY AN ISOLATED FLARE OF CONVECTION. THE INITIAL POSITION IS PLACED WITH FAIR CONFIDENCE ON LOW LEVEL INFLOW INTO THE LLCC AND SUPPORTED BY A 1720 ATMS 88.2GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY OF 50 KNOTS IS BASED ON A 221200Z SMOS PASS THAT SHOWED 50 KT WINDS IN THE SOUTHEAST QUADRANT OF THE SYSTEM. THE INTENSITY ESTIMATE IS ABOVE ALL AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T3.0 (45 KTS) AND A 221628Z SATCON ESTIMATE OF 46 KTS. ENVIRONMENTAL ANALYSIS SHOWS THAT TS 12W IS EXPERIENCING FAVORABLE (10 TO 15 KNOT) VERTICAL WIND SHEAR, ALTHOUGH THE LOCATION OF A POINT SOURCE JUST TO THE NORTH OF THE SYSTEM IS PUSHING THE BULK OF THE DEEP CONVECTION TO THE SOUTHWEST OF THE LLCC. THE EQUATORWARD OUTFLOW CHANNEL REMAINS EXCELLENT, WHILE POLEWARD OUTFLOW IS DISORGANIZED. SEA SURFACE TEMPERATURES REMAIN FAVORABLE FOR ADDITIONAL DEVELOPMENT, BETWEEN 29 AND 30 DEGREES CELSIUS. TS 12W IS TRACKING NORTHWARD WHILE UNDER THE INFLUENCE OF A SUBTROPICAL RIDGE (STR) LOCATED TO THE NORTHEAST. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. IN THE SHORT TERM, TS 12W WILL TRACK NORTHWESTWARD AS THE AFOREMENTIONED STR SHIFTS SLIGHTLY EASTWARD, RESPONDING TO A MIDLATITUDE TROUGH PASSING BY TO THE NORTH. FAVORABLE SEA SURFACE TEMPERATURES AND LOW VERTICAL WIND SHEAR WILL ALLOW TS 12W TO REACH 65 KNOTS BY TAU 24. THE JTWC PEAK INTENSITY IS HIGHER THAN THE MULTI- MODEL INTENSITY CONSENSUS INDICATES, BUT UNDER THE HWRF PREDICTION. SHORTLY AFTER TAU 36, TS 12W WILL MAKE LANDFALL IN SOUTHERN TAIWAN AND VEER MORE WEST-NORTHWESTWARD AS THE STR BUILDS BACK INTO THE AREA. TS 12W WILL THEN MAKE LANDFALL IN CHINA AFTER TAU 48. TS 12W WILL BEGIN TO WEAKEN AS IT CROSSES THE MOUNTAINOUS TERRAIN OF TAIWAN, THEN WEAKEN MORE RAPIDLY WHEN IT MAKES LANDFALL IN CHINA. DYNAMIC MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH ALL MEMBERS INDICATING A NORTHWESTWARD TRACK. HOWEVER, THE JTWC FORECAST TRACK IS PLACED SLOWER THAN THE MULTI-MODEL CONSENSUS IN THE NEAR TERM DUE TO SLOW PREVIOUS TRACK MOTION AND THE TEMPORARY WEAKENING OF THE STEERING FLOW AS THE STR SHIFTS TO THE EAST. DUE TO THE FASTER THAN EXPECTED MODEL TRACK SPEED AND FAIR CERTAINTY IN THE INITIAL POSITION, THERE IS FAIR CONFIDENCE IN THIS PORTION OF THE FORECAST TRACK. C. AFTER TAU 72, TS 12W WILL CONTINUE TO TRACK NORTHWESTWARD ALONG THE SOUTHERN BOUNDARY OF ANOTHER STR TO THE NORTH. LAND INTERACTION WITH CHINA WILL CAUSE TS 12W TO WEAKEN TO 20 KNOTS BY TAU 96. DYNAMIC MODEL GUIDANCE HAS A SPREAD OF 525 NM BY TAU 96, WITH GFS AND NAVGEM BEING THE SOUTHERN OUTLIERS, AND ECMWF THE EASTERN OUTLIER. THE JTWC TRACK IS HEDGED EAST OF THE MULTI-MODEL CONSENSUS BASED ON THE ECMWF SOLUTION. DUE TO THE TIGHT GROUPING OF MODEL TRACKS, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.// NNNN NNNN