WDPN32 PGTW 200300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 05W (FIVE) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 15.0N 129.7E INITIAL INTENSITY: 30 KTS GEOGRAPHIC REFERENCE: 698 NM SOUTH OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 13 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL DEPRESSION (TD) 05W (FIVE) CONTINUES TO SLOWLY CONSOLIDATE EAST OF THE PHILIPPINES. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THAT THE LOW LEVEL CIRCULATION CENTER (LLCC) REMAINS PARTIALLY EXPOSED TO THE EAST OF AN AREA OF DEEP CONVECTION WHICH IS ROTATING IN THE MID-LEVELS. THE LATEST GFS AND ECMWF MODEL SOUNDINGS AS WELL AS THE CIMSS OBJECTIVE SHEAR ESTIMATES POINT TO AN EASTERLY SHEAR VECTOR OF ABOUT 15 KNOTS, WHICH SUPPORTS THE PRESENTATION IN THE ANIMATED MSI. BOTTOM LINE, THE VORTEX REMAINS HIGHLY TILTED AND MISALIGNED AND IS THUS NOT INTENSIFYING AT A RAPID CLIP FOR THE MOMENT. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC IN THE ANIMATED MSI. THE INITIAL INTENSITY OF 30 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE, IN LINE WITH THE MAJORITY OF THE OBJECTIVE ESTIMATES (ADT IS 29 KNOTS, AIDT IS 30 KNOTS) AND ON THE HIGHER END OF THE SUBJECTIVE AGENCY DVORAK FIXES. AN EARLIER SCATTEROMETER PASS FROM 2230Z SHOWS NON-FLAGGED WINDS OF 30 KNOTS ACROSS THE NORTHERN PORTION OF THE CIRCULATION. THE ENVIRONMENT IS GENERALLY FAVORABLE, WITH LOW TO MODERATE (10-15 KTS) EASTERLY SHEAR, OFFSET SOMEWHAT BY THE ROBUST POLEWARD OUTFLOW WHICH TURNS EASTWARD AND FLOWS INTO A STRONG TUTT- CELL TO THE SOUTHEAST OF IWO TO. SSTS ARE QUITE WARM, NEAR 31C, AND OHC IS HIGH. THE SYSTEM IS CURRENTLY HINDERED BY THE LACK OF A WELL- ORGANIZED AND VERTICALLY ALIGNED VORTEX. INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND RADII). CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF HONSHU. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T1.5 - 25 KTS RJTD: T1.5 - 25 KTS KNES: T2.0 - 30 KTS CIMSS ADT: 29 KTS AT 200000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE VWS: 10-15 KTS SST: 30-31 CELSIUS OUTFLOW: STRONG POLEWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: NOT APPLICABLE 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 05W (FIVE) IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN SIDE OF THE STRONG STR CENTERED SOUTH OF HONSHU FOR THE NEXT 36-48 HOURS. TRACK SPEED IS EXPECTED TO SLOW DRAMATICALLY OVER THE NEXT 48 HOURS AS THE SYSTEM GRADUALLY BECOMES SURROUNDED BY RIDGING, BOTH NORTH AND SOUTH AND THE STEERING GRADIENTS LOOSEN. AROUND TAU 72, TWO FACTORS WILL DRIVE A CHANGE IN THE TRACK MOTION. FIRST, THE RIDGING TO THE NORTH IS ERODED FROM WEST TO EAST AND BUILDS SOUTHWARD, REORIENTING TO A NORTH-SOUTH AXIS. THIS SHIFT IN THE RIDGE PATTERN IS PARTICULARLY PRONOUNCED IN THE ECMWF MODEL WHILE IN THE GFS IT IS MORE SUBTLE. SECOND, A MID-LATITUDE TROUGH PASSES OVER THE KOREAN PENINSULA, OPENING UP A GAP IN THE STR TO THE NORTH. THE COMBINED EFFECTS OF THESE SHIFTS IN THE UPPER-LEVEL PATTERN WILL RESULT IN A SHARP TURN POLEWARD AND INCREASE IN TRACK SPEED OF TD 05W AFTER TAU 72. IN THE EXTENDED FORECAST BEYOND TAU 72, RIDGING IS EXPECTED TO BUILD IN AFTER PASSAGE OF THE TROUGH, WHICH WILL PUSH TD 05W ONTO A MORE NORTHWESTWARD TRACK BEGINNING AT THE END OF THE CURRENT FORECAST PERIOD. IN TERMS OF INTENSITY, THE SYSTEM IS STILL STRUGGLING TO ORGANIZE A DISCRETE AND VERTICALLY ALIGNED VORTEX, AND THUS IS ONLY SLOWLY INTENSIFYING EVEN IN LIGHT OF THE OTHERWISE FAVORABLE CONDITIONS. HIGH-RESOLUTION MODELS SUGGEST A BURST OF MODERATE SHEAR WILL IMPACT THE SYSTEM BETWEEN TAUS 36 AND 72, KEEPING A LID ON THE AXISYMMETRIZATION PROCESS AND THUS INTENSIFICATION. THE SYSTEM WILL STILL INTENSIFY, ALBEIT SLOWLY THROUGH TAU 72, WHILE TRACKING INTO A MORE FAVORABLE ENVIRONMENT. BY TAU 72, THE SHEAR IS EXPECTED TO BACK OFF, THE SYSTEM WILL SYMMETRIZE, AND MOVE OVER A POOL OF HIGH OHC WATERS, TRIGGERING A PERIOD OF RAPID INTENSIFICATION AFTER TAU 72. THE ACTUAL PEAK MAY OCCUR BETWEEN THE TAU 96 AND TAU 120 FORECAST POINTS AS THE SYSTEM CROSSES THE RYUKYU CHAIN. AFTER MOVING INTO THE EAST CHINA SEA, COOLER SSTS AND INCREASING SHEAR WILL START TO WEAKEN THE SYSTEM BY THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE REMAINS CONSISTENT WITH THE OVERALL SCENARIO, WITH SPREAD HAVING DECREASED SLIGHTLY SINCE THE PREVIOUS FORECAST. THE WESTERN-SOUTHERN OUTLIER REMAINS THE UKMET ENSEMBLE MEAN, WHICH STILL TAKES THE SYSTEM OVER TAIWAN THOUGH IT HAS MOVED FURTHER NORTH TOWARDS THE OTHER TRACKERS. THE GFS REMAINS THE EASTERN OUTLIER THROUGH TAU 72, THEN TURNS SHARPLY WESTWARD THEREAFTER SUCH THAT IT IS NEAR THE CONSENSUS MEAN AT TAU 120, A SIGNIFICANT SHIFT IN JUST ONE RUN. OVERALL SPREAD IN THE CONSENSUS MEMBERS IS 240NM AT TAU 72, INCREASING SLIGHTLY TO 310NM AT TAU 120, WITH THE BULK OF THE MEMBERS CONFINED TO A MUCH TIGHTER ENVELOPE CENTERED ON THE JTWC TRACK FORECAST. THE BULK OF THE MULTI-MODEL ENSEMBLE MEMBERS CONTINUE TO TRACK ROUGHLY BETWEEN TAIWAN AND OKINAWA, WITH THE ENSEMBLE MEANS TIGHTLY PACKED, PASSING JUST EAST OF ISHIGAKIJIMA. THE JTWC FORECAST TRACK IS PLACED EAST OF THE CONSENSUS MEAN TO OFFSET THE UKMET ENSEMBLE MEAN WHICH IS PULLING THE MEAN TOO FAR WEST, WITH HIGH CONFIDENCE. INTENSITY GUIDANCE HAS COME INTO BETTER AGREEMENT SINCE THE LAST RUN, WITH ALL MEMBERS NOW GENERALLY CONSISTENT WITH THE JTWC FORECAST, WHICH LIES ABOUT 5 KNOTS BELOW THE CONSENSUS MEAN TO TAU 72, THEN SHIFTS TO SLIGHTLY HIGHER THAN THE MEAN AT THE PEAK. NOTABLY, THE HAFS-A AND HWRF GUIDANCE BOTH SHOW A SHARP PEAK NEAR 115 KNOTS AT TAU 120 FOLLOWED BY SLOW WEAKENING, WHILE COAMPS-TC CONTINUES TO INTENSIFY THE SYSTEM THROUGH TAU 120. THE COAMPS-TC IS UNREALISTIC DUE TO SST VALUES IN THE ECS, THOUGH A HIGH PEAK CLOSER TO 115 KTS IS CERTAINLY REASONABLE, AS THE SYSTEM APPROACHES THE RYUKYU CHAIN BETWEEN TAU 96 AND 120. THE JTWC INTENSITY FORECAST SET WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: HIGH INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN