WDPN31 PGTW 080300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (HAGUPIT) WARNING NR 010// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 8.4N 139.9E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 125 NM EAST-SOUTHEAST OF YAP MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL STORM (TS) 05W (HAGUPIT) REMAINS RELATIVELY DISORGANIZED IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI), PULSATING DEEP CONVECTION MASKING AN ILL-DEFINED LOW LEVEL CIRCULATION CENTER (LLCC). MORE INTENSE AND PERSISTENT CONVECTIVE ACTIVITY IS PRESENT IN THE EASTERN PERIPHERY OF THE CIRCULATION, WHERE A MESOSCALE UPPER- LEVEL POINT SOURCE IS LOCATED, SUPPORTING LOCALIZED ENHANCED UPPER- LEVEL EXHAUST. A 072029Z RCM-2 SAR PASS REVEALED A HIGHLY ASYMMETRIC WIND FIELD, WITH AN ARC OF GALE-FORCE WINDS PRESENT ALONG THE NORTHERN SEMICIRCLE, WHILE LIGHT WINDS OF LESS THAN 20 KNOTS PERSIST ACROSS THE SOUTHERN SEMICIRCLE. UPPER-AIR SOUNDINGS FROM YAP INDICATE DEEP EASTERLY FLOW UP TO APPROXIMATELY 500MB, AND LIGHT SOUTHEASTERLIES ABOVE THAT, GENERATING ENHANCED SHEAR IN THE MID- LEVELS. ADDITIONALLY, THE SOUNDING SHOWS AN EXTENSIVE LAYER OF EXTREMELY DRY AIR BETWEEN ROUGHLY 500-250MB, CONSISTENT WITH THE CIRA ADVECTED LAYER PRECIPITABLE WATER (ALPW) PRODUCT SHOWING AND EXTENSIVE REGION OF VERY DRY, SUBSIDENT AIR EXTENDING FROM PALAU NORTHWARD PAST IWO TO. THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE BASED ON AN EXTRAPOLATION OF THE WEAK AND ILL-DEFINED LLCC EVIDENT IN THE SAR NRCS DATA. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE USING A BLEND OF THE AVAILABLE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES OUTLINED BELOW, SUPPORTED BY THE SAR DATA. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE, WITH GOOD UPPER-LEVEL OUTFLOW, LOW DEEP-LAYER SHEAR AND CONDUCIVE SSTS OFFSET BY DRY AIR INTRUSION AND MODERATE MID-LEVEL SHEAR. INITIAL WIND RADII BASIS: SAR DATA CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) POSITIONED FAR TO THE NORTHEAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS RJTD: T2.5 - 35 KTS RCTP: T3.0 - 45 KTS KNES: T3.0 - 45 KTS CIMSS ADT: 45 KTS AT 080000Z CIMSS AIDT: 37 KTS AT 080000Z CIMSS D-PRINT: 38 KTS AT 080000Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: MODERATE RADIAL OTHER FACTORS: PRONOUNCED DRY MID-LEVEL AIR ALONG THE WESTERN FLANK; MODERATE MID-LEVEL SOUTHWESTERLY SHEAR. ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: HIGH 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TS 05W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWESTWARD, ALONG THE SOUTHERN FLANK OF THE DEEP-LAYER STR FOR THE NEXT 48 HOURS. BEGINNING AS EARLY AS TAU 36, THE SYSTEM IS ANTICIPATED TO DECELERATE IN RESPONSE TO A GENERAL WEAKENING OF THE STEERING PATTERN AS THE WESTERN EXTENT OF THE STR RECEDES EASTWARD. AS THE RIDGE RECEDES, A SECONDARY AREA OF RIDGING IS EXPECTED TO BUILD SOUTHWESTWARD FROM THE MARIANAS, EXTENDING TO THE EQUATOR AND UNDERCUTTING TS 05W, RESEMBLING A REVERSE-ORIENTED MONSOON TROUGH (ROMT) PATTERN. AS THIS RIDGE EXTENDS EQUATORWARD TO THE EAST OF TS 05W, IT WILL EXERT A WEAK SOUTHERLY STEERING INFLUENCE UPON THE SYSTEM, RESULTING IN A GRADUAL, SLOW RECURVATURE POLEWARD FROM TAU 72 ONWARDS. REGARDING INTENSITY, THE PRIMARY IMPEDIMENTS TO INTENSIFICATION OF THE SYSTEM WILL BE THE DRY AIR ENTRAINMENT FROM THE WEST AND THE PERSISTENT MID-LEVEL SHEAR. WHILE OTHER ENVIRONMENTAL FACTORS, INCLUDING DEEP-LAYER SHEAR AND FAVORABLE SSTS, WILL REMAIN CONDUCIVE, THE COMBINATION OF MODERATE MID-LEVEL SHEAR AND INCREASING DRY AIR WILL INHIBIT POTENTIAL FOR SIGNIFICANT INTENSIFICATION. MODELS SUGGEST A GENERAL WEAKENING OF THE SHEAR OVER THE NEXT 24 HOURS, WHICH SHOULD ALLOW TS 05W TO INTENSIFY SLIGHTLY; HOWEVER, THIS TRANSIENT WINDOW OF FAVORABLE CONDITIONS WILL BE SHORT- LIVED. AFTER TAU 24, THE SYSTEM WILL BEGIN A SLOW WEAKENING TREND AS DRY AIR ENCROACHES AND SHEAR INCREASES. BEYOND TAU 72, THE UPPER- LEVEL FLOW IS FORECAST TO BECOME CONVERGENT, EXACERBATING FURTHER INCREASES IN DRY AIR INTRUSION AND DEEP-LAYER SHEAR, RESULTING IN RAPID WEAKENING AND DISSIPATION BY THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: TRACK GUIDANCE CONTINUES TO BE IN GENERALLY GOOD AGREEMENT IN THE SHORT-TERM, WITH A GRADUALLY INCREASING CROSS-TRACK SPREAD REACHING 220NM BY TAU 72. GFS, NAVGEM AND JGSM COMPRISE A GROUPING ON THE NORTHERN EDGE OF THE ENVELOPE, WHILE THE ECMWF AND ECENS MEAN ARE TIGHTLY CLUSTERED ON THE SOUTHERN SIDE. BY TAU 120, CROSS-TRACK SPREAD INCREASES TO 430NM, BETWEEN THE JGSM ON THE NORTHEAST AND GALWEM ON THE WESTERN EDGES OF THE ENVELOPE. IN GENERAL, ALL MEMBERS OF THE CONSENSUS MODEL PACKAGE INDICATE VARYING DEGREES OF NORTHWARD RECURVATURE AFTER TAU 96, GFS SHOWING THE MOST AGGRESSIVE TRACK AND ECMWF INDICATING THE MINIMAL AMOUNT OF TURNING. ENSEMBLE GUIDANCE HAS TRENDED TOWARDS INCREASED DISPERSION OVER THE LAST 24 HOURS, ESPECIALLY IN THE LATER FORECAST TAUS, DUE TO INCREASING UNCERTAINTY IN THE STEERING PATTERN FORECAST AND THE TIMING OF THE CYCLOLYSIS PHASE OF THE SYSTEM AND THE CORRESPONDING INFLUENCE ON STEERING. INDIVIDUAL ENSEMBLE MEMBERS SHOW A WIDE DISPERSION FROM THE CENTRAL PHILIPPINES TO AS FAR NORTHEAST AS IWO TO, WHILE THE MULTI-MODEL ENSEMBLE MEAN CONTINUES TO TREND TOWARDS A SHARPER POLEWARD ORIENTATION IN THE LONG-RANGE FORECAST TAUS. THE JTWC FORECAST IS POSITIONED NEAR THE MULTI-MODEL CONSENSUS MEAN THROUGH THE FORECAST PERIOD, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS, WITH THE EXCEPTION OF THE DECAY SHIPS (NAVGEM), CONFINED BELOW A 45 KNOT PEAK INTENSITY. OF NOTE, MULTIPLE RAPID INTENSIFICATION (RI) AIDS HAVE TRIGGERED, BUT THESE ARE BASED UPON THE NAVGEM SHIPS GUIDANCE, WHICH IS INCONSISTENT WITH THE CURRENT ENVIRONMENTAL ANALYSIS AND IS THUS UNREPRESENTATIVE IN THE FORECAST DEPICTION. OTHERWISE, THE REMAINDER OF THE PACKAGE INDICATES A RELATIVELY FLAT INTENSITY TREND THROUGH TAU 36, FOLLOWED BY STEADY TO RAPID WEAKENING THROUGH TAU 120. THE JTWC FORECAST IS PLACED NEAR THE HWRF TRACKER WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: MEDIUM INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: MEDIUM// NNNN