WDPN31 PGTW 111500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 29W (PAKHAR) WARNING NR 004// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 18.2N 127.0E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 407 NM EAST-NORTHEAST OF MANILA, PHILIPPINES MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 11 KTS SIGNIFICANT WAVE HEIGHT: 15 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: NOW DESIGNATED TROPICAL STORM PAKHAR, 29W HAS QUICKLY CONSOLIDATED AND IS SHOWING SIGNS OF VERTICAL ALIGNMENT AND IS SLOWLY BUT STEADILY INTENSIFYING. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A NASCENT CENTRAL DENSE OVERCAST (CDO) FEATURE, WITH CLOUD TOP TEMPERATURES NEAR -70C WITH SOME OVERSHOOTING TOPS APPROACHING -83C. AS IS COMMON WITH SYSTEMS WITH A CDO, LOCATING THE LOW LEVEL CIRCULATION CENTER (LLCC) IS CHALLENGING, ESPECIALLY IN CASES SUCH AS THIS, WITHOUT ANY RECENT MICROWAVE IMAGERY TO ASSIST. THE MOST RECENT MICROWAVE PASS WAS A 110924Z SSMIS, PRIOR TO THE DEVELOPMENT OF THE CDO, WHICH DEPICTED THE LLCC ON THE EASTERN SIDE OF AN AREA OF ELONGATED CONVECTION ON THE WESTERN SIDE OF THE CIRCULATION. THE INITIAL POSITION IS THUS PLACED WITH LOW CONFIDENCE, ON THE EASTERN SIDE OF THE CDO, NEAR THE PGTW AND KNES FIX POSITIONS. THE INITIAL INTENSITY IS ASSESSED WITH GREATER CONFIDENCE, HEDGED A BIT HIGHER THAN THE AGENCY FIXES IN LIGHT OF BOTH THE ADT AND AIDT AS WELL AS A 110920Z SMAP PASS SHOWING A LARGE AREA OF 35-43 KNOT WINDS PRIMARILY IN THE WESTERN AND SOUTHERN QUADRANTS. VERTICAL WIND SHEAR (VWS) HAS STARTED TO PICK UP A BIT BUT REMAINS IN THE LOW (5-10 KNOTS) RANGE, AND THE UPPER-LEVEL ANTICYCLONE REMAINS IN PLACE, PROVIDING GOOD RADIAL OUTFLOW. TS 29W HAS PICKED UP SOME SPEED AS IT MOVES QUICKLY ALONG THE NORTHWEST PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE EAST AND PARALLEL TO A SURFACE FRONT WHICH LIES ALONG ROUGHLY 21N AND EXTENDS FAR TO THE NORTHEAST. INITIAL WIND RADII BASIS: SMAP DATA CURRENT STEERING MECHANISM: NORTHWEST PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.0 - 30 KTS RJTD: T2.0 - 30 KTS KNES: T2.5 - 35 KTS CIMSS ADT: 41 KTS AT 111140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE RADIAL ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: HIGH INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: NO MAJOR CHANGES TO THE FORECAST TRACK ARE EXPECTED, AS THE SYSTEM WILL TRACK NORTHEAST FOR THE FIRST 24 HOURS ALONG THE NORTHWEST SIDE OF THE STRONG STR TO THE EAST, AND ROUGHLY PARALLEL TO THE STATIONARY FRONT THAT LIES ABOUT THREE DEGREES OR SO TO THE NORTH. AS DISCUSSED IN THE ANALYSIS SECTION ABOVE, TS PAKHAR IS EXHIBITING SIGNS OF BECOMING MORE VERTICALLY ALIGNED, AND IS NOW DEVELOPING A CDO AND BEGINNING TO INTENSIFY. RAW ADT NUMBERS ARE APPROACHING T3.5 BY THE 1400Z HOURS, POTENTIALLY HINTING AT A FASTER RATE OF INTENSIFICATION THAN ANTICIPATED. THE FORECAST CALLS FOR THE SYSTEM TO REACH 50 KNOTS BY TAU 12 AND THEN HOLD STEADY THROUGH TAU 24. IT IS VERY LIKELY HOWEVER THAT TS 29W WILL ACTUALLY REACH A SLIGHTLY HIGHER PEAK INTENSITY (AROUND 55 KNOTS) BY TAU 18. BY TAU 24 THE SYSTEM WILL REACH A VERY SHARP SHEAR BOUNDARY AND BECOME DECOUPLED OR DECAPITATED SHORTLY THEREAFTER. COMBINED WITH AN INFLUX OF LOW AND MID-LEVEL DRY AIR WHICH WILL ENGULF THE SYSTEM AFTER TAU 36, TS 29W WILL RAPIDLY WEAKENING SHORTLY AFTER THE 24-HOUR POINT IN THE FORECAST. AS IT WEAKENS, IT WILL COME UNDER THE STEERING INFLUENCE OF PROGRESSIVELY LOW LAYERS OF THE ATMOSPHERE. AS THE LOWER-LEVEL FLOW WILL BE COMING OUT OF THE NORTH-NORTHEAST AT THIS POINT, THE SYSTEM WILL TURN SHARPLY SOUTHWARD AFTER TAU 36, ULTIMATELY CURVING BACK TO THE SOUTHWEST AS IT DISSIPATES NO LATER THAN TAU 72. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE HAS COME INTO BETTER AGREEMENT ON THE OVERALL SCENARIO WITH THIS RUN, WITH ALL BUT THE NAVGEM AND CTCX TRACKER SHOWING THE SHARP TURN TO THE SOUTH AFTER TAU 24. THERE REMAIN SOME DIFFERENCES IN THE EXACT TIMING AND SHARPNESS OF THE TURN WITH THE UKMET ENSEMBLE MARKING THE LATEST AND FURTHEST EAST TURN AND THE GFS THE EARLIEST AND MOST WEST TURN. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND LIES JUST INSIDE THE CONSENSUS TRACK WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS MIXED WITH THIS RUN, WITH THE COAMPS-TC ENSEMBLE RAPID INTENSIFICATION AID (CHR4) INDICATING A PEAK NEAR 70 KNOTS BY TAU 24 WHILE THE REMAINDER OF THE GUIDANCE PACKAGE PEAKS AT OUR BELOW 45 KNOTS. BASED ON THE RECENT TRENDS, THE JTWC FORECAST LIES ABOVE THE BULK OF THE GUIDANCE, BUT WELL BELOW THE CHR4 WHICH IS CONSIDERED UNREALISTIC AT THIS POINT. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: MEDIUM// NNNN