WDPN31 PGTW 030300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 26.1N 130.2E INITIAL INTENSITY: 40 KTS GEOGRAPHIC REFERENCE: 131 NM EAST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 14 KTS SIGNIFICANT WAVE HEIGHT: 21 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED AND WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) TRACKING NORTHWESTWARD, WITH DEEP CONVECTION DISPLACED TO ITS SOUTH BY MODERATE 15-20 KT NORTHERLY VERTICAL SHEAR. THE CONVECTION IS WEAKER AND DISPLACED FARTHER FROM THE CENTER THAN SIX HOURS AGO. UPPER-LEVEL OUTFLOW REMAINS WEAK EQUATORWARD AS THE STORM WRESTLES WITH A WEAK UPPER-LEVEL TROUGH OVERHEAD. DEEP-LAYER DRY AIR IS OBSERVED IN WATER VAPOR IMAGERY THROUGHOUT THE NORTHERN SEMICIRCLE. A 020003Z ASCAT PASS REVEALED THE STRONGEST WINDS IN THE SOUTHEAST AND NORTHEAST QUADRANTS, WITH THE LLCC SLIGHTLY ELONGATED TOWARDS THE WEST, RESULTING IN SOME SHORT-TERM WOBBLES IN THE TRACK MOTION. THE INITIAL INTENSITY IS SET AT 40 KT BASED ON THE ASCAT DATA AND SURFACE OBSERVATIONS FROM KITA-DAITO, WHICH HAVE RANGED FROM 40 TO 45 KT AT AN ANEMOMETER HEIGHT OF 32 METERS ABOVE SEA LEVEL DURING THE PAST SEVERAL HOURS. INITIAL WIND RADII BASIS: SCATTEROMETER DATA CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE SOUTHEAST OF JAPAN AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.5 - 35 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 41 KTS AT 022150Z CIMSS ADT: 35 KTS AT 022340Z CIMSS AIDT: 38 KTS AT 022340Z CIMSS D-MINT: 34 KTS AT 022150Z CIMSS D-PRINT: 36 KTS AT 022340Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 10-15 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK EQUATORWARD ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH 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: TROPICAL STORM 22W (KROVANH) CONTINUES TO TRACK NORTHWESTWARD TOWARD THE RYUKYU ISLANDS AND APPEARS TO HAVE HELD A STEADY INTENSITY OVER THE PAST SIX HOURS. THE STORM HAS BEEN WRESTLING WITH A WEAK UPPER-LEVEL TROUGH FOR SOME TIME, RESULTING IN WEAK UPPER-LEVEL OUTFLOW AND INTRUSIONS OF DRY AIR THAT HAVE THUS FAR LIMITED INTENSIFICATION. THE STORM'S CORE WIND FIELD HAS BECOME BETTER DEFINED, AND ANY FURTHER BURSTS OF DEEP CONVECTION NEAR THE LLCC COULD CAUSE SHORT-TERM FLUCTUATIONS IN INTENSITY PRIOR TO 22W PASSING OVER THE RYUKYU ISLAND CHAIN. THE JTWC FORECAST PROJECTS A NET-STEADY INTENSITY NEAR 40 KT THROUGH TAU 24. THE STORM'S SHORT-TERM MOTION IS BEING GOVERNED BY A SUBTROPICAL RIDGE SOUTHEAST OF JAPAN, WHICH WILL DRIVE KROVANH NORTHWESTWARD FOR APPROXIMATELY THE NEXT 24 HOURS, PASSING BETWEEN OKINAWA AND AMAMI OSHIMA DURING WITHIN THE NEXT 12 HOURS. THEREAFTER, STEERING CURRENTS WILL BECOME WEAK AND COMPLEX AS AN UPPER-LEVEL TROUGH QUICKLY SCOOTS EASTWARD OVER THE KOREAN PENINSULA AND SEA OF JAPAN, USHERING IN A LOW- TO MID-LEVEL RIDGE IN ITS WAKE. THE RESULTING LOW-LEVEL NORTHEASTERLY COOL AND DRY FLOW IS EXPECTED TO HALT 22W'S NORTHWARD PROGRESS IN AROUND 24-36 HOURS, FORCING A STALL AND EVENTUALLY A NEAR-REVERSAL OF THE STORM'S MOTION IN A SOUTHWARD OR SOUTHEASTWARD DIRECTION, BACK INTO THE VICINITY OF OKINAWA IN AROUND 60 TO 72 HOURS. DURING THE STALL, THE JUXTAPOSITION OF UPPER-LEVEL WESTERLIES ASSOCIATED WITH THE STJ OVERLAPPING THE SURFACE NORTHEASTERLIES WILL SUBSTANTIALLY INCREASE VERTICAL SHEAR AND DRY AIR ENTRAINMENT, LIKELY WEAKENING 22W SOMEWHAT, THOUGH SOME MODELS RETAIN GALES DURING THIS TIME, GRADUALLY EXPANDING FROM THE NORTHERN SEMICIRCLE INTO THE WESTERN SEMICIRCLE AS THE TRACK TURNS SOUTHWARD. AFTER 72 HOURS, THERE IS LESS CONFIDENCE IN THE TRACK FORECAST, AS THE STORM WILL BE MAROONED IN WEAK STEERING CURRENTS BETWEEN A RIDGE OVER CHINA, A RIDGE EAST OF JAPAN, AND POTENTIALLY A NEW AREA OF LOW PRESSURE DEVELOPING WITHIN THE MONSOON TROUGH TO ITS SOUTHEAST. BOTH PHYSICS- BASED AND AI-BASED MODELS GENERALLY AGREE ON KROVANH BEING POSITIONED SOUTHEAST OF THE RYUKYU ISLANDS DURING THE 96 TO 120 HOUR PERIOD, BUT MODEL SPREAD REMAINS RATHER LARGE. THE INTENSITY FORECAST DURING THIS LONG-RANGE PERIOD IS ALSO LOWER CONFIDENCE, AS IT IS SENSITIVE TO THE DEGREE TO WHICH THE STORM INGESTS MID-LATITUDE AIR DURING ITS BRIEF VISIT TO THE EAST CHINA SEA. DYNAMICAL GLOBAL MODELS FAVOR A BROADENING, HOLLOWED-OUT CIRCULATION THAT WEAKENS THROUGH THE END OF THE FORECAST PERIOD, WHILE AI-BASED MODELS SHOW THE POTENTIAL FOR REINTENSIFICATION AFTER THE STORM RETURNS EAST OF THE RYUKYU ISLANDS. THE JTWC FORECAST IS A COMPROMISE OF THESE TWO OUTCOMES, SHOWING A STEADY INTENSITY OF 35 KT NEAR THE END OF THE FORECAST PERIOD. MODEL DISCUSSION: THE JTWC TRACK FORECAST CLOSELY FOLLOWS A BLEND OF THE PREVIOUS FORECAST AND THE MEAN OF THE PHYSICS-BASED MULTI-MODEL CONSENSUS AND THE AI-BASED MULTI-MODEL CONSENSUS. THE JTWC INTENSITY FORECAST IS SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS THROUGH TAU 24 DUE TO SHORT-TERM TRENDS IN STORM STRUCTURE, THEN NEAR THE CONSENSUS THEREAFTER. THE TRACK AND INTENSITY FORECASTS HAVE MEDIUM (NEAR AVERAGE) CONFIDENCE THROUGH 72 HOURS, THEN LOWER THAN AVERAGE CONFIDENCE THEREAFTER. FORECAST CONFIDENCE: TRACK 00-72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 00-72 HR: MEDIUM INTENSITY 72-120 HR: LOW// NNNN