TC 22S(HALIMA): Rapid Intensification likely next 48h up to CAT 3 US// TC 21S(CHARLOTTE): Final Warning, 24/03utc

JTWC IS ISSUING 12HOURLY WARNINGS ON TC 22S(HALIMA).WARNING 15/FINAL WAS ISSUED ON TC 21S(CHARLOTTE) AT 22/03UTC. 3HOURLY SATELLITE BULLETINS ARE ISSUED FOR BOTH SYSTEMS.

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 SUBTROPICAL RIDGE (STR) CENTERED ALONG THE 85E LONGITUDE LINE. THIS GENERAL MOTION IS FORECAST TO CONTINUE TO 72H, BUT THE TRACK WILL TURN EASTWARD BY 120H 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/CAT 3 US BY 48H. 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.

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 IMAGE 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.

MODEL DISCUSSION: TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT WITH A SPREAD OF 340KM SPREAD AT 72H. THE MODELS DIVERGE SIGNIFICANTLY THEREAFTER, WITH THE GFS AND GFS ENSEMBLE, ALONG WITH HWRF TO A LESSER DEGREE, SHOWING A SHARP TURN NORTHWARD AFTER 72H, AND TURNING THE SYSTEM NORTH OF 20S BY 120H. 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 490KM ENVELOP AT 120H. 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 72H, THUS LENDING MEDIUM CONFIDENCE THROUGH 72H AND LOW CONFIDENCE IN THE EXTENDED FORECAST. 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 72H, WITH MEDIUM CONFIDENCE.

240300Z POSITION NEAR 20.3S 107.1E. 24MAR22. TROPICAL CYCLONE 21S (CHARLOTTE), LOCATED APPROXIMATELY 412 NM WEST-NORTHWEST OF LEARMONTH, AUSTRALIA, HAS TRACKED SOUTH- SOUTHWESTWARD AT 11 KM/H OVER THE PAST SIX HOURS. TC 21S HAS RAPIDLY WEAKENED OVER THE PAST SIX HOURS UNDER STRONG AND PERSISTENT NORTHWESTERLY VERTICAL WIND SHEAR (VWS). THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS BECOME FULLY EXPOSED IN ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND THERE WAS HIGH CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY HAS BEEN LOWERED TO A GENEROUS 35 KNOTS, WITH THE PGTW CURRENT INTENSITY ESTIMATED AT 2.5 (35 KNOTS) WITH A FINAL-T OF T2.0. ADT WAS AT 2.7 BUT THE RAW ADT WAS DOWN TO T1.5. ADDITIONALLY A 232305Z SMOS PASS SHOWED WINDS PREDOIMINANTLY OF 30 KNOTS OR LESS AROUND THE SYSTEM. THE SYSTEM HAS TURNED SOUTHWARD ALONG THE WESTERN PERIPHERY OF A LOW TO MID-LEVEL SUBTROPICAL RIDGE (STR) AND IS EXPECTED TO ACCELERATE ALONG THE TIGHTENING GRADIENT BETWEEN THE SUBTROPICAL RIDGE (STR) AND AN APPROACHING SUBTROPICAL LOW. THE SYSTEM IS FORECAST TO CONTINUE TO WEAKEN, TO BELOW WARNING THRESHOLD WITHIN THE NEXT 12 HOURS. HOWEVER, THE REMNANT CIRCULATION IS EXPECTED TO CONTINUE TRACKING SOUTHWARD OVER THE NEXT 36 HOURS BEFORE TURNING EAST TOWARDS THE COAST OF AUSTRALIA BY 48H. THE ASSOCIATED WIND FIELD IS EXPECTED TO EXPAND AS THE SYSTEM BECOMES SUBTROPICAL IN NATURE BY 36H. IT IS POSSIBLE THAT THE SYSTEM COULD REINTENSIFY AS A SUBTROPICAL LOW AFTER 36H WITH WINDS UP TO GALE-FORCE AT TIMES THROUGH THE NEXT FEW DAYS. THIS IS THE FINAL WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI. THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF REGENERATION. MAXIMUM SIGNIFICANT WAVE HEIGHT AT 240000Z IS 16 FEET.