WDXS32 PGTW 240300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HALIMA) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. SUMMARY: INITIAL POSITION: 12.8S 75.6E INITIAL INTENSITY: 60 KTS GEOGRAPHIC REFERENCE: 388 NM SOUTH-SOUTHEAST OF DIEGO GARCIA MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 03 KTS SIGNIFICANT WAVE HEIGHT: 18 FEET SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A STEADILY IMPROVING CONVECTIVE SIGNATURE WITH A STRONG BAND OF CONVECTION ON THE WEST SIDE WRAPPING INTO A SYMMETRICAL MASS OF CONVECTION WITH A WARM SPOT OR NASCENT EYE FEATURE. A 232330Z SSMIS 37GHZ MICROWAVE PASS SHOWED THAT AT LEAST IN THE LOW LEVELS, THE EYE IS BEGINNING TO TAKE FORM, WITH A CYAN RING EVIDENT IN THE COLORIZED 37GHZ ENHANCEMENT, INDICATIVE OF POTENTIAL RAPID INTENSIFICATION (RI). THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED MICROWAVE IAMGE AND THE NASCENT EYE IN THE GOES-IO BD-ENHANCED INFRARED IMAGERY. THE INITIAL INTENSITY IS SET AT 60 KNOTS WITH MEDIUM CONFIDENCE, HEDGED SLIGHTLY HIGHER THAN THE AGENCY CURRENT INTENSITY ESTIMATES OF T3.5 (55 KNOTS) IN LIGHT OF THE CIMSS ESTIMATE OF 60 KNOTS AND THE OVERALL IMPROVING STRUCTURE. THE SYSTEM IS MOVING SLOWLY WEST-SOUTHWEST IN A WEAK STEERING PATTERN AT PRESENT. ANALYSIS REVEALS AN ENVIRONMENT VERY CONDUCIVE TO RAPID INTENSIFICATION, WITH WARM SSTS, LOW VWS AND STRONG RADIAL OUTFLOW AND A TAP INTO A DEVELOPING POLEWARD OUTFLOW CHANNEL. INITIAL WIND RADII BASIS: PERSISTENCE CURRENT STEERING MECHANISM: WEAK STEERING PATTERN AGENCY DVORAK AND AUTOMATED FIXES: PGTW: T3.5 - 55 KTS FMEE: T3.5 - 55 KTS CIMSS SATCON: 60 KTS AT 232000Z CIMSS ADT: 53 KTS AT 232115Z FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE VWS: 0-5 KTS SST: 29-30 CELSIUS OUTFLOW: STRONG RADIAL OTHER FACTORS: DEVELOPING POLEWARD OUTFLOW CHANNEL. ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM INITIAL WIND RADII: MEDIUM 3. FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THE OVERALL FORECAST PHILOSOPHY HAS NOT CHANGED IN TERMS OF TRACK, BUT THE PEAK INTENSITY HAS BEEN INCREASED BY 25 KNOTS TO REFLECT UPDATED RAPID INTENSITY GUIDANCE. FORECAST DISCUSSION: TC 22S HAS BEEN DRIFTING SLOWLY WESTWARD OVER THE PREVIOUS 12 HOURS, AS THE STEERING RIDGE TO THE SOUTH HAS WEAKENED AND ERODED AS AN UPPER-LEVEL TROUGH MOVES IN FROM THE SOUTHWEST. OVER THE PAST SIX HOURS THE TRACK HAS STARTED TO BEND OVER MORE TOWARDS THE SOUTHWEST, BUT STILL RELATIVELY SLOWLY, INTO A DEVELOPING WEAKNESS IN THE RIDGE. THIS WEAKNESS IS EXPECTED TO BECOME MORE PRONOUNCED IN THE NEXT 12 HOURS, AND THE SYSTEM WILL IN TURN ACCELERATE SOUTHWARD INTO THE WEAKNESS AND ALONG THE WESTERN PERIPHERY OF A MERIDIONAL ORIENTED STR CENTERED ALONG THE 85E LONGITUDE LINE. THIS GENERAL MOTION IS FORECAST TO CONTINUE TO TAU 72, BUT THE TRACK WILL TURN EASTWARD BY TAU 120 AS EXTENSION OF A SUBTROPICAL RIDGE WILL BUILD IN TO THE SOUTH OF THE SYSTEM. TC 22S IS IN A HIGHLY FAVORABLE ENVIRONMENT, WITH ALL THE INGREDIENTS IN PLACE TO SUPPORT RI. THE ONLY HINDRANCE AT THE MOMENT IS THE FACT THAT THE POINT SOURCE ALOFT IS NOT QUITE DIRECTLY OVER TOP OF THE SYSTEM RESULTING IN SOME EASTERLY SHEAR, LEADING TO SOME SLIGHT EAST TO WEST VORTEX TILT WITH HEIGHT. MESOSCALE AND STORM-SCALE MODELS SUGGEST THE VORTEX WILL ALIGN WITHIN THE NEXT FEW HOURS, WHICH SHOULD ALLOW FOR ONSET OF RI. PEAK INTENSITY IS CURRENTLY ANTICIPATED TO BE 110 KNOTS BY TAU 48. THE SYSTEM BEGINS TO WEAKEN FAIRLY QUICKLY THEREAFTER AS SHEAR INCREASES AHEAD OF A SHARP TROUGH IN THE MID-LEVELS, AND MID-LEVEL DRY AIR BEGINS TO ENTRAIN INTO THE CORE. BY THE END OF THE FORECAST PERIOD, THE SYSTEM WILL BEGIN TO LOSE SOME OF ITS TROPICAL CHARACTERISTICS AND BEGIN SUBTROPICAL TRANSITION, THOUGH WINDS ARE EXPECTED TO BE ABOVE STORM-FORCE DURING THIS EARLY PHASE OF THE TRANSITION. MODEL DISCUSSION: TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT WITH A SPREAD OF 185NM SPREAD AT TAU 72. THE MODELS DIVERGE SIGNIFICANTLY THEREAFTER, WITH THE GFS AND GFS ENSEMBLE, ALONG WITH HWRF TO A LESSER DEGREE, SHOWING A SHARP TURN NORTHWARD AFTER TAU 72, AND TURNING THE SYSTEM NORTH OF 20S BY TAU 120. THE GFS AND ENSEMBLE MEAN ARE ASSESSED AS BEING UNREALISTIC AT THIS TIME, AND DISCOUNTING THESE MODELS, THE REMAINDER OF THE GUIDANCE LIES WITHIN A 265NM ENVELOP AT TAU 120. THE JTWC FORECAST LIES ALONG THE WESTERN SIDE OF THE DETERMINISTIC GUIDANCE ENVELOPE, FAVORING THE ECMWF TRACKING. ENSEMBLE GUIDANCE INCLUDING GEFS AND ECENS SHOW A HIGH DEGREE OF UNCERTAINTY IN THE TRACK AFTER TAU 72, THUS LENDING MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW CONFIDENCE IN THE LATER TAUS. INTENSITY GUIDANCE, WITH THE EXCEPTION OF THE NAVGEM DRIVEN COAMPS-TC, ALL INDICATE VERY QUICK TO RAPID INTENSIFICATION. ADDITIONALLY, ALL AVAILABLE RI GUIDANCE IS CURRENTLY TRIPPED, AND THE COAMPS-TC ENSEMBLE INTENSITY GUIDANCE SUGGESTS A 70-80 PERCENT PROBABILITY OF RI WITHIN THE NEXT 24-48 HOURS. THUS THE JTWC FORECAST FORECASTS RI OF 30 KNOTS IN 24 HOURS AND 50 KNOTS IN 48 HOURS WITH HIGH CONFIDENCE. THE LONGER-TERM FORECAST INTENSITY FORECAST IS MORE UNCERTAIN BUT THE FORECAST TRACKS THE CONSENSUS MEAN AFTER TAU 72, WITH MEDIUM CONFIDENCE. FORECAST CONFIDENCE: TRACK 0 - 72 HR: MEDIUM TRACK 72-120 HR: LOW INTENSITY 0 - 72 HR: HIGH INTENSITY 72-120 HR: MEDIUM// NNNN