WDPN31 PGTW 141500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (KAI-TAK) WARNING NR 09// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 14W (KAI-TAK), LOCATED APPROXIMATELY 220 NM NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED SOUTHWESTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) SHOWS THE CENTRAL DENSE OVERCAST CONVECTION APPEARS TO BE BUILDING NORTHWARD OVER THE LOW LEVEL CIRCULATION CENTER (LLCC) WITHIN THE PAST SIX HOURS. ADDITIONALLY, IN OLDER MULTISPECTRAL IMAGERY, THE LLCC HAD BEGUN TO TURN SOUTHWESTWARD AND APPEARS TO PERSIST IN THE EIR AS WELL. THIS APPEARS TO BE IN PART DUE TO A CONSOLIDATION OF THE LOW LEVEL TO A MORE SYMMETRICALLY ORGANIZED LLCC. THE CURRENT POSITION IS BASED ON A CONSOLIDATION OF POSITION FIXES FROM PGTW AND RJTD AND IS SUPPORTED BY A RECENT 141129Z SSMIS 91 GHZ IMAGE. UPPER LEVEL ANALYSIS INDICATES A POINT SOURCE ANTICYCLONE LOCATED TO THE NORTHEAST OF TS 14W PERSISTS IN CREATING 15 TO 20 KNOTS OF VERTICAL WIND SHEAR (VWS) OVER THE LLCC. THE VWS IS PROVIDING AN AMPLE EQUATORWARD OUTFLOW CHANNEL. THE CURRENT INTENSITY HAS BEEN INCREASED TO 50 KNOTS BASED ON THE IMPROVING DVORAK ESTIMATES FROM PGTW AND IS SUPPORTED BY THE INCREASING CENTRAL CONVECTION AND COOLING CLOUD TOPS OBSERVED IN EIR. TS 14W IS BEING STEERED IN A GENERAL WEST-NORTHWESTWARD DIRECTION UNDER THE INFLUENCE OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE NORTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 14W IS FORECASTED TO TRACK WEST-NORTHWESTWARD UNDER THE INFLUENCE OF THE STR THROUGHOUT THE FORECAST PERIOD. DUE TO THE RECENT SOUTHWESTWARD TRACK OF THE LLCC, THIS FORECAST BRINGS THE OVERALL TRACK SOUTHWARD SLIGHTLY. THE FORECAST IS SLIGHTLY SOUTH OF CONSENSUS, AS THE RECENT DIP WAS NOT PREVIOUSLY INDICATED WITHIN MODEL GUIDANCE, THROUGH TAU 48. A SERIES OF WEAK MID-LATITUDE TROUGHS ARE EXPECTED TO SLIGHTLY WEAKEN THE STR OVER THE NEXT 36 HOURS, BUT WILL NOT CREATE A FULL BREAK WITHIN THE STR. THIS WEAKENING EXPLAINS THE MODEL GUIDANCE SHOWING THE SHIFT IN THE TRACK TO THE WEST-NORTHWESTWARD. BEYOND TAU 36, THE TROUGHS WILL TRACK RAPIDLY EASTWARD ALLOWING THE STR TO BUILD BACK IN OVER EASTERN CHINA. GRADUAL INTENSIFICATION AFTER TAU 12 IS EXPECTED AS THE SYSTEM TRACKS OVER LUZON INTO THE SOUTH CHINA SEA. DUE TO THE COMPETING INFLUENCES OF VERY WARM ALONG TRACK SEA SURFACE TEMPERATURES (SST) (28-30 DEGREES CELSIUS) AND MODERATE VWS, ONCE TS 14W MOVES BACK OVER WATER, THE EXPECTED INTENSIFICATION RATE WILL REMAIN SLOW. THE FORECASTED MAXIMUM INTENSITY OF 65 KNOTS AT TAU 48 DOES NOT REFLECT THE EXPECTED MAXIMUM INTENSITY OF ABOUT 70 TO 75 KNOTS AROUND TAU 60 SLIGHTLY BEFORE MAKING LANDFALL TO THE EAST OF HONG KONG. A VERY WARM POOL OF SST’S ALONG THE COASTAL REGION ARE EXPECTED TO FURTHER INTENSITY THE SYSTEM BETWEEN TAU 48 AND 60. THE TIMING OF LANDFALL REMAINS BETWEEN TAU 48 AND 72 WITH FRICTIONAL LAND INFLUENCES QUICKLY WEAKENING THE LLCC UPON LANDFALL. C. AFTER TAU 72 TS 14W WILL CONTINUE TO WEAKEN UNDER THE INFLUENCE OF FRICTIONAL DRAG AND THE LOSS OF THE OCEAN HEATING LINK. NUMERICAL MODEL GUIDANCE REMAINS IN FAIR AGREEMENT THROUGH TAU 48, WITH NGPS AND WBAR BEING THE NORTHERN OUTLIERS. ECMWF, GFS, AND GFDN ARE THE SOUTHERN OUTLIERS, AND ARE IN BETTER AGREEMENT WITH THE OFFICIAL FORECAST. ALTHOUGH THERE IS LOW CONFIDENCE IN THE CURRENT POSITION, THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK BASED ON ANALYSIS OF THE SYNOPTIC ENVIRONMENT AND NUMERICAL MODELS SHOWING A SIMILAR PICTURE WITH ONLY SLIGHT VARIATIONS IN THE AMOUNT OF WEAKENING DEPICTED FOR THE STR.// NNNN