WDXS32 PGTW 042100 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (CLIFF) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 18.6S 83.6E INITIAL INTENSITY: 45 KTS GEOGRAPHIC REFERENCE: 947 NM SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 04 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTION WRAPPING AROUND THE SOUTHERN AND WESTERN SEMICIRCLE WITH TIGHT CURVATURE AROUND THE MID-LEVEL CENTER, THOUGH RAGGED IN APPEARANCE. THE LOW-LEVEL CIRCULATION (LLC) APPEARS TO BE CENTERED NORTH OF THE MID-LEVEL CENTER BENEATH THE EDGE OF THE CONVECTIVE CANOPY, BASED ON A 041627Z ASCAT-C PASS. THE LLC IS ELONGATED NORTH-NORTHEAST TO SOUTH-SOUTHWEST, WITH A BROAD BAND OF 35-45 KT WINDS WRAPPING INTO THE WESTERN SIDE FROM THE SOUTH. THE WIND FIELD STRUCTURE IS CONSISTENT WITH A MODERATELY SHEARED VORTEX, TILTED SOUTHWARD WITH HEIGHT. THIS IS SUPPORTED BY THE PRESENCE OF CIRRUS DEBRIS MOVING QUICKLY INWARD TOWARD THE LLC FROM THE NORTH IN ANIMATED SATELLITE IMAGERY. THE HIMAWARI-8 7.3 MICROMETER BAND REVEALS A DRY AIR MASS ADJACENT TO THE CIRCULATION ON THE WEST SIDE, BEGINNING TO WRAP INTO THE NORTHERN SEMICIRCLE. THE INITIAL INTENSITY IS SET AT 45 KT BASED ON 40-45 KT WINDS IN THE SOUTHWEST QUADRANT IN THE AFOREMENTIONED ASCAT-C PASS, CONSISTENT WITH THE SUBJECTIVE DVORAK ESTIMATE OF T3.0 (45 KT) FROM PGTW. INITIAL WIND RADII BASIS: PARTIAL SCATTEROMETER DATA FOR SOUTHERN SEMICIRCLE CURRENT STEERING MECHANISM: MID-LEVEL RIDGING TO THE EAST AND SOUTH AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.0 - 45 KTS CIMSS ADT: 45 KTS AT 041515Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL VWS: 20-25 KTS SST: 28-28 CELSIUS OUTFLOW: STRONG POLEWARD OTHER FACTORS: DRY AIR MASS TO THE WEST AND NORTH ANALYSIS CONFIDENCE: INITIAL POSITION: LOW INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE SYSTEM IS NOW FORECAST TO DISSIPATE BY TAU 72. FORECAST DISCUSSION: TROPICAL CYCLONE 10S (CLIFF) HAS LIKELY PEAKED IN INTENSITY, OR WILL DO SO WITHIN THE NEXT 12 HOURS. THE MID-LEVEL DRY AIR MASS NOW WRAPPING INTO THE NORTHERN SEMICIRCLE IS LIKELY TO BEGIN DISRUPTING THE INNER CORE AS NORTHERLY SHEAR PUSHES IT INWARD TOWARD THE LOW-LEVEL CENTER (LLC). THE STORM IS ALSO EXPECTED TO TRACK OVER SLIGHTLY COOLER SEA SURFACE TEMPERATURES OF 27 DEGREES CELSIUS (COMPARED TO CURRENT VALUES OF 28), WHICH WILL PROVIDE LESSENING SUPPORT FOR DEEP CONVECTION. NUMERICAL MODELS ARE IN UNANIMOUS AGREEMENT THAT THE LLC WILL BECOME FULLY EMBEDDED WITHIN THE DRY AIR MASS DURING THE 12-24 HOUR PERIOD, RESULTING IN STEADY WEAKENING. ALOFT, AN UPPER-LEVEL TROUGH TO THE SOUTHWEST IS BEGINNING TO SPLIT, A PROCESS WHICH WILL COMPLETE IN AROUND 24 HOURS. IN ITS WAKE, AN UPPER-LEVEL ANTICYCLONE WILL BECOME ESTABLISHED TO THE EAST OF CLIFF, RESULTING IN A CONTINUATION OF NORTHERLY VERTICAL SHEAR. THIS IS EXPECTED TO PREVENT ANY REINTENSIFICATION AS THE SYSTEM REMAINS EMBEDDED IN A DRY AIR MASS FOR THE FORESEEABLE FUTURE. CLIFF'S INTENSITY IS FORECAST TO FALL BELOW WARNING THRESHOLD IN 48 HOURS, AND THE JTWC FORECAST TERMINATES AT 72 HOURS. THE TRACK FORECAST IS STRAIGHT FORWARD, WITH CLIFF BEING STEERED PRIMARILY BY A MID-LEVEL RIDGE TO THE SOUTH DURING THE FORECAST PERIOD, COMBINED WITH INFLUENCE FROM A BROAD MID-LEVEL CYCLONIC CIRCULATION TO THE NORTHWEST. THIS IS EXPECTED TO RESULT IN A GENERALLY WEST-SOUTHWESTWARD MOTION THROUGH 72 HOURS. MODEL DISCUSSION: TRACK GUIDANCE HAS MODERATE SPREAD THROUGH 72 HOURS. THE JTWC FORECAST IS ON THE NORTHERN SIDE OF THE ENVELOPE, STICKING CLOSE TO THE MEAN OF GFS, GEFS ENSEMBLE MEAN, AND ECMWF. THE INTENSITY GUIDANCE IS UNANIMOUS IN SHOWING WEAKENING DURING THE NEXT 72 HOURS, AND THE JTWC FORECAST IS JUST BELOW THE MULTI-MODEL CONSENSUS. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM INTENSITY 0 - 72 HR: HIGH// NNNN