WDPN31 PGTW 011500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W (AERE) WARNING NR 005// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 22.2N 131.2E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 318 NM SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWARD AT 12 KTS SIGNIFICANT WAVE HEIGHT: 16 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY OVER THE PAST SIX HOURS DEPICTS A MASS OF FLARING CONVECTION DEVELOPED JUST EAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC) BUT NEVER CONSOLIDATED OVER THE LLCC DUE TO THE PERSISTENT STRONG WESTERLY WINDS ALOFT. THE CONVECTIVE CLOUD TOPS HAVE STARTED TO WARM AND THE OVERALL STRUCTURE OF THE MASS HAS DEGRADED SIGNIFICANTLY BY THE 1200Z HOUR, WITH THE LLCC ONCE AGAIN BECOMING EXPOSED. UPPER AIR SOUNDINGS FROM ISHIGAKI JIMA CONTINUE TO INDICATE STRONG (50-60 KNOTS) OF NORTHWESTERLY FLOW, PUSHING STRAIGHT INTO THE HEART OF TS 05W. HOWEVER, THE ORIENTATION OF THE TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL TO THE NORTHWEST OF THE LLCC, HAS CHANGED SLIGHTLY, BECOMING MORE ELONGATED EAST-WEST, HAS LED TO THE DEVELOPMENT OF A STRONGLY DIVERGENT AREA DIRECTLY UPSTREAM FROM TS 05W. THIS AREA HAS ALLOWED A REDUCTION IN RELATIVE SHEAR AND THE RECENT CONVECTIVE FLARE UP, SHORT-LIVED THOUGH IT WAS. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON SPIRAL BAND ANALYSIS OF THE VISIBLE LOW LEVEL BANDING FEATURES. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, SLIGHTLY HIGHER THAN THE AGENCY FIXES, BASED ON THE CIMSS SATCON AND A 010923Z SCATTEROMETER PASS WHICH CONTINUED TO SHOW A BAND OF 40 KNOT WINDS IN THE EASTERN HEMISPHERE OF THE CIRCULATION. THE SYSTEM CONTINUES TRACKING NORTHWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR). THE ENVIRONMENT IS MARGINALLY FAVORABLE WITH DIVERGENT OUTFLOW OFFSETTING HIGH VWS. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST. AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS KNES: T2.0 - 30 KTS CIMSS SATCON: 40 KTS AT 011044Z CIMSS ADT: 37 KTS AT 011140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 20-25 KTS SST: 28-29 CELSIUS OUTFLOW: MODERATE POLEWARD AND EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: MEDIUM INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: LOW 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. HOWEVER THE FORECAST TRACK HAS SHIFTED FURTHER SOUTHWARD AFTER TAU 72. FORECAST DISCUSSION: TS 05W HAS PICKED A HEAD OF STEAM OVER THE PAST SIX HOURS, WITH FORWARD MOTION NOW UP TO 12 KNOTS, AS THE STEERING RIDGE TO THE EAST STRENGTHENING AND MOVING EAST, INCREASING THE STEERING GRADIENT. OVER THE NEXT 12 HOURS, THE SYSTEM IS EXPECTED TO TAKE ON A MORE NORTHWESTWARD TRACK WHILE MAINTAINING AN 10-12 KNOT SPEED OF ADVANCE, MOVING THROUGH THE RYUKU CHAIN BETWEEN TAU 24 AND TAU 36. AFTER CROSSING INTO THE EAST CHINA SEA, THE SYSTEM IS EXPECTED TO SLOW DOWN AS THE STEERING PATTERN BEGINS TO SHIFT, WITH AN EXTENSION OF THE STR BUILDING IN ACROSS THE NORTH OF THE SYSTEM, ACROSS THE KOREAN PENINSULA. THE RIDGE EXTENSION PINCHES OFF AS A SEPARATE AREA OF HIGH HEIGHTS BY TAU 60 WITH AN INDUCED TROUGH BETWEEN THIS NEW STR CENTER OVER NORTH KOREA AND THE STR SOUTHEAST OF TOKYO, ENTICING TS 05W TO TURN INTO THE WEAKNESS IN THE RIDGE BY TAU 72. THE SYSTEM WILL THEN BEGIN TO PICK UP SPEED ONCE MORE AS IT MOVES EASTWARD ALONG THE NORTHWEST PERIPHERY OF THE STR SOUTHEAST OF JAPAN. THE SYSTEM IS EXPECTED TO SKIRT THE NORTHWEST COAST OF KYUSHU THEN TRACK ALONG THE NORTHWESTERN COAST OF HONSHU THROUGH THE END OF THE FORECAST PERIOD. WHILE UPPER-LEVEL WINDS REMAIN STRONG TO THE WEST-SOUTHWEST OF THE SYSTEM, THE FORECAST FIELDS CALL FOR A RELAXATION OF THE VWS GRADIENT IN VICINITY OF TS 05W, WHICH SHOULD ALLOW FOR SOME INTENSIFICATION OVER THE NEXT 24 HOURS BEFORE PASSING THE RYUKUS, THOUGH THIS WILL DEPEND IN LARGE PART ON THE ABILITY OF THE VORTEX TO CONSOLIDATE. ONCE IN THE ECS, DECREASED SHEAR AND INCREASED POLEWARD OUTFLOW INTO THE BASE OF AN UPPER-LEVEL TROUGH WILL ALLOW FOR A SHORT BURST OF ADDITIONAL INTENSIFICATION TO A PEAK OF 55 KNOTS BEFORE INCREASED SHEAR, DRY AIR ENTRAINMENT AND COOLER SSTS CONSPIRE TO WEAKEN THE SYSTEM. BY TAU 96 THE SYSTEM WILL BEGIN TO WEAKEN MORE RAPIDLY AS THE TERRAIN OF HONSHU DISRUPTS THE LOW LEVEL INFLOW AND SHEAR CONTINUES TO INCREASE. MODEL DISCUSSION: TRACK GUIDANCE S IN GOOD AGREEMENT THROUGH TAU 72, WITH THE EXCEPTION OF NAVGEM WHICH CONTINUES TO TRACK THE SYSTEM INTO THE LOW LEVEL RIDGE FROM THE INITIAL POSITION. THE REMAINDER OF THE GUIDANCE SHOWS A 120NM SPREAD AT TAU 48 INCREASING TO 150NM AT TAU 72. THEREAFTER THE MODELS SHOW A SIGNIFICANT UNCERTAINTY WITH A LARGE CROSS AND ALONG-TRACK SPREAD AFTER TAU 96. THE GALWEM, GFS, JGSM AND ECMWF ALL NOW SHOW A TRACK CLOSE TO THE NORTHWEST TIP OF KYUSHU AT TAU 96 BUT THEN TAKE THE VORTEX TO A POINT NEAR KYOTO BY TAU 120, WHILE THE UKMET, ECMWF AND GFS ENSEMBLE MEANS KEEP THE VORTEX IN THE SEA OF JAPAN. THE JTWC FORECAST TRACK LIES ON THE EASTERN EDGE OF THE ENVELOPE THROUGH TAU 48 BUT THEN CROSSES OVER TO THE NORTHERN EDGE OF THE ENVELOPE, AND NORTH OF THE CONSENSUS MEAN, THROUGH TAU 120. CONFIDENCE IS HIGH THROUGH TAU 72 BUT LOW THEREAFTER. INTENSITY GUIDANCE IS MIXED, WITH THE SHIPS-GFS SUGGESTING NO ADDITIONAL INTENSIFICATION, WHILE THE COAMPS-TC IS BULLISH, PEAKING AT 70 KNOTS BY TAU 48. THE JTWC FORECAST LIES CLOSE TO, BUT JUST ABOVE, THE CONSENSUS MEAN THROUGH THE FORECAST PERIOD WITH MEDIUM TO LOW CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: HIGH TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN