WDPN34 PGTW 270300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NESAT) WARNING NR 05// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM 11W (NESAT), LOCATED APPROXIMATELY 423 NM EAST- NORTHEAST OF MANILA, HAS TRACKED NORTHWARD AT 05 KNOTS OVER THE PAST SIX HOURS. ANIMATED HIGH RESOLUTION VISIBLE SATELLITE IMAGERY INDICATES THAT TS 11W CONTINUES TO CONSOLIDATE AND SLOWLY INTENSIFY, WITH DEEP CORE CONVECTION WITH OVERSHOOTING TOPS HAVING MAINTAINED OVER THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC) FOR THE PAST SIX HOURS. THE INITIAL POSITON IS PLACED WITH MODERATE CONFIDENCE BASED ON SUBJECTIVE SATELLITE FIX POSITIONS AND ANALYSIS OF A 262157Z 89 GHZ SSMIS MICROWAVE IMAGE WHICH SHOWS THE LLCC SLIGHTLY OFF CENTERED TO THE NORTH OF THE DEEPEST CONVECTION. THE SYSTEM HAS SLOWED SLIGHTLY, AND IT IS LIKELY THAT THE CORE CONVECTION HAS FURTHER CONSOLIDATED AROUND THE LLCC, THOUGH WITH NO ADDITIONAL MICROWAVE IMAGERY IT IS DIFFICULT TO ASSESS. THE INITIAL INTENSITY OF 55 KNOTS IS BASED ON SUBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES OF T3.5 FROM ALL AGENCIES. ENVIRONMENTAL ANALYSIS INDICATES THE SYSTEM REMAINS TRACKING IN A HIGHLY FAVORABLE ENVIRONMENT, WITH LOW (10-15 KNOTS) VERTICAL WIND SHEAR (VWS), VERY HIGH SEA SURFACE TEMPERATURES OF 31 TO 32 DEG CELSIUS. UPPER LEVEL ANALYSIS SHOWS THAT A WEAK ANTICYCLONE OR POINT SOURCE HAS DEVELOPED OVER THE SYSTEM, AND IT IS TAPPING INTO A VIGOROUS EQUATORWARD OUTFLOW CHANNEL. A SMALL, WEAK TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL HAS ALSO DEVELOPED NEAR TAIWAN, AND IS PROVIDING A WEAK POLEWARD OUTFLOW CHANNEL, THOUGH THIS LIKELY WON'T REMAIN IN PLACE LONG. TS 11W IS CURRENTLY TRACKING NORTH- NORTHWESTWARD ALONG THE WESTERN EDGE OF AN EXTENSION OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST OF THE SYSTEM. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 11W IS FORECAST TO TRACK NORTH-NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE STEERING RIDGE FOR THE NEXT 12 HOURS, BUT THEN TURN MORE NORTHWESTERLY AS THE STEERING MECHANISM SHIFTS TO A STRONG SUBTROPICAL RIDGE OVER THE EAST CHINA SEA. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN FAVORABLE, WITH LOW VWS, HIGH SSTS AND MODERATELY STRONG OUTFLOW ALLOWING TS NESAT TO STEADILY INTENSIFY, REACHING A PEAK INTENSITY OF 90 KNOTS AT TAU 48. AFTER TAU 48 HOWEVER, INCREASING VWS AND SOME CONVERGENCE ALOFT EMANATING FROM THE STRENGTHENING RIDGE TO THE NORTH WILL COMBINE TO OFFSET THE HIGH SSTS AND SINGLE CHANNEL OUTFLOW, RESULTING IN A WEAKENING TREND PRIOR TO LANDFALL. TS 11W IS FORECAST TO MAKE LANDFALL IN TAIWAN JUST BEFORE TAU 72 AND BEGIN TO RAPIDLY SLOW AND WEAKEN DUE TO TERRAIN INTERACTION. C. IN THE EXTENDED FORECAST PERIOD BEYOND TAU 72, TS 11W IS FORECAST TO CONTINUE ACROSS TAIWAN AFTER MAKING LANDFALL, REEMERGING IN THE TAIWAN STRAIT BY TAU 96 AND MAKING A SECOND LANDFALL OVER MAINLAND CHINA BETWEEN TAUS 96 AND 120. SIMULTANEOUSLY, THE STEERING STR WILL REORIENT TO A SHARP NORTH- SOUTH AXIS, STEERING TS 11W TOWARDS THE NORTH AS IT CROSS INTO CHINA. TS 11W IS FORECAST TO STILL BE A TYPHOON UPON MAKING LANDFALL IN CENTRAL TAIWAN, BUT WILL RAPIDLY WEAKEN DUE TO TERRAIN INTERACTION, REAPPEARING IN THE TAIWAN STRAIT AS A WEAK TROPICAL STORM. DYNAMIC MODEL GUIDANCE IS IN TIGHT AGREEMENT THROUGH TAU 72, WITH JGSM AND ITS ENSEMBLE BEING THE ONLY OUTLIER TO THE NORTH AND ECMWF THE DEFINING THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE. MODELS SHOW INCREASING SPREAD AFTER LANDFALL, BUT ALL INDICATE A NORTHWARD TURN AFTER PASSING TAIWAN. OVERALL THERE IS HIGH CONFIDENCE IN THE FORECAST TRACK.// NNNN