WDPN31 PGTW 021500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (KROVANH) WARNING NR 006// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 23.9N 131.7E INITIAL INTENSITY: 35 KTS GEOGRAPHIC REFERENCE: 263 NM SOUTHEAST OF KADENA AB MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL STORM 22W (KROVANH) WITH A PARTIALLY EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH CONVECTIVE BANDING WRAPPING AROUND THE WESTERN AND SOUTHERN PERIPHERIES. A 021137Z METOP-B ASCAT PASS REVEALED THAT THE CORE OF THE CIRCULATION REMAINS SLIGHTLY STRETCHED IN THE EAST-WEST DIRECTION. THE ASCAT PASS MISSED MOST OF THE EASTERN SEMICIRCLE, BUT SHOWED WINDS WITHIN THE WESTERN SEMICIRCLE ARE AROUND 25-30 KTS. HOWEVER, AN EARLIER 020922Z RCM-3 SAR PASS CAUGHT THE NORTHEASTERN QUADRANT AND SHOWED A SWATH OF 35 KNOT WINDS WITH A VMAX RIGHT AROUND 38 KTS. AS A RESULT, THE INITIAL 34 KNOT WIND RADII ARE NOW ONLY CONFINED TO THE NORTHEASTERN QUADRANT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ASCAT PASS. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SAR DATA WHICH IS SUPPORTED BY THE AGENCY DVORAK AND CIMSS INTENSITY ESTIMATES LISTED BELOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 22W IS IN A MARGINALLY FAVORABLE ENVIRONMENT CHARACTERIZED BY WEAK EQUATORWARD OUTFLOW ALOFT, LOW (5-10 KTS) VERTICAL WIND SHEAR, DRY AIR, AND WARM (28-29 C) SEA SURFACE TEMPERATURES. INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SAR DATA CURRENT STEERING MECHANISM: THE SOUTHWESTERN FLANK OF A SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T2.5 - 35 KTS RJTD: T2.0 - 30 KTS RCTP: T2.5 - 35 KTS KNES: T2.5 - 35 KTS CIMSS SATCON: 38 KTS AT 021140Z CIMSS ADT: 33 KTS AT 021140Z CIMSS AIDT: 36 KTS AT 021140Z CIMSS D-MINT: 32 KTS AT 020920Z CIMSS D-PRINT: 34 KTS AT 021140Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VWS: 5-10 KTS SST: 28-29 CELSIUS OUTFLOW: WEAK EQUATORWARD OTHER FACTORS: DRY AIR ENTRAINMENT ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: HIGH INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE 34 KNOT WIND RADII HAVE BEEN SIGNIFICANTLY ALTERED COMPARED TO THE PREVIOUS FORECAST TO MORE ACCURATELY MATCH THE STORM MOTION FORECAST DISCUSSION: TS 22W IS FORECAST TO CONTINUE TRACKING NORTHWESTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH TAU 36. NEAR TAU 36, AN UPPER-LEVEL TROUGH IS EXPECTED TO DIG IN FROM THE NORTH AND BREAK DOWN THE STEERING RIDGE. THIS WILL CAUSE 22W TO BE PLACED WITHIN A WEAK STEERING ENVIRONMENT WITH RIDGING OVER EASTERN CHINA, RIDGING TO THE EAST, AND A NEAR EQUATORIAL RIDGE TO THE SOUTH. ONCE THE SYSTEM ENTERS THIS WEAK STEERING ENVIRONMENT, THE TRACK IS LIKELY TO BE ERRATIC. MODELS SHOW THE VORTEX TAKING A VARIETY OF TRAJECTORIES FROM TAU 36 TO TAU 60. SOME KEEP THE SYSTEM QUASISTATIONARY, SOME TAKE AN EASTWARD TURN, AND OTHERS TAKE A WESTWARD TURN. HOWEVER, THERE HAS BECOME A BIT MORE AGREEMENT ON A SOUTHWARD TRACK FROM TAU 60 TO 96. THERE IS NOW A CLEAR LACK OF MODELS SHOWING A RECURVE SCENARIO. AS IT STANDS, THE JTWC TRACK FORECAST CALLS FOR A SLOW SOUTHWARD TURN FROM TAU 36 TO TAU 96 FOLLOWED BY AN EASTWARD TURN THROUGH TAU120. ACCOMPANYING THE UNCERTAINTY IN THE TRACK IS AN EXTREME UNCERTAINTY IN THE 34-KNOT WIND RADII, WHERE MODELS VARY SIGNIFICANTLY ON THE SYMMETRY AND EXTENT OF GALE-FORCE WINDS. THIS FORECAST NOW HAS THE 34-KNOT WIND RADII SHIFTING TO THE WESTERN SIDE OF THE CIRCULATION AFTER IT MAKES THE SOUTHWARD TURN, WHICH APPEARS MORE REALISTIC WHEN ACCOUNTING FOR THE STORM MOTION. IN TERMS OF INTENSITY, 22W IS FORECAST TO GRADUALLY INTENSIFY THROUGH TAU 48 TO A PEAK OF AROUND 45 KTS AS THE WIND FIELD CONTINUES TO CONSOLIDATE AND SHEAR REMAINS LOW. THE SYSTEM MAY ALSO BE ABLE TO TAP INTO A POLEWARD OUTFLOW CHANNEL ONCE THE UPPER-LEVEL TROUGH OVER JAPAN SETS UP AROUND TAU 36. AFTER TAU 48, THE SYSTEM WILL BE VERY SLOW MOVING, SO THE UPWELLING OF COOLER WATERS COULD BECOME A FACTOR. ADDITIONALLY, SHEAR AND DRY AIR ARE EXPECTED TO INCREASE, CAUSING 22W TO WEAKEN THROUGH TAU 120. MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN MODERATE AGREEMENT ONLY THROUGH TAU 36 WITH MODELS AGREEING ON A NORTHWESTWARD TRACK. THE CROSS-TRACK SPREAD AT TAU 36 IS MEASURED TO BE ABOUT 130 NM WITH THE ECMWF NOW BEING THE WESTERNMOST MODEL AND THE JGSM REMAINING THE EASTERNMOST MODEL. AFTER TAU 36, MODELS BEGIN TO DIVERGE IN NEARLY EVERY DIRECTION. THE ECMWF AND EC-AIFS TAKE THE WIDEST TURN OUT TO THE WEST BEFORE MAKING THE COUNTERCLOCKWISE LOOP. THE GFS AND GEFS HAVE STARTED TO BECOME IN BETTER AGREEMENT, SHOWING A SHARP SOUTHWARD TURN SIMILAR TO THE EXPERIMENTAL GOOGLE DEEPMIND ENSEMBLE MEAN. THE JTWC TRACK FORECAST IS PLACED NEAR THE CONSENSUS THROUGH TAU 36 AND THEN CLOSER TO THE GOOGLE DEEPMIND THROUGH TAU 120 WITH LOW CONFIDENCE. INTENSITY GUIDANCE GENERALLY AGREES ON A GRADUAL INCREASE TO A PEAK AT TAU 48 FOLLOWED BY WEAKENING. PEAK INTENSITIES RANGE FROM 40 TO 55 KTS WITH THE HAFS-A BEING THE MOST AGGRESSIVE MODEL. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE CONSENSUS THROUGHOUT THE FORECAST PERIOD WITH LOW CONFIDENCE DUE TO THE HIGH UNCERTAINTY IN THE TRACK. FORECAST CONFIDENCE: TRACK 00-72 HR: LOW TRACK 72-120 HR: LOW INTENSITY 00-72 HR: LOW INTENSITY 72-120 HR: LOW// NNNN