TC 21S(CHARLOTTE): CAT 1 US and weakening// Invest 94S: likely marked intensification next 72hours//Invest 91B: off the map,23/06utc

JTWC IS ISSUING 6HOURLY WARNINGS ON TC 21S(CHARLOTTE). 3HOURLY SATELLITE BULLETINS ARE ISSUED ON TC 21S, INVEST 94S AND INVEST 91B.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC CHARLOTTE REMAINS UNDER THE INFLUENCE OF THE STR TO THE SOUTHEAST AS IT CONTINUES TO ROUND THE SUBTROPICAL RIDGE (STR) AXIS. TC 21S WILL STAY ON A SOUTHWEST TRACK THROUGH 36H, THEN ROUND THE STR AXIS AND TRACK SOUTHERLY UNTIL 60H, WHEN IT BEGINS TO ENCROACH UPON COOLER WATERS AND ENHANCED VWS FROM AN UPPER-LEVEL TROUGH. THE APPROACHING TROUGH WILL BEGIN TO INFLUENCE THE OVERALL TRACK MOTION TOWARDS THE AUSTRALIAN COAST NEAR PERTH THROUGH THE REMAINDER OF THE FORECAST. NEARING 60H AND BEFORE 72H, TC 21S WILL BEGIN TRANSITIONING INTO A SUBTROPICAL SYSTEM. AT 96H, TC CHARLOTTE WILL COMPLETE TRANSFORMATION INTO A GALE FORCED SUBTROPICAL SYSTEM WITH AN EXPANDING WIND FIELD BEFORE IT NEARS THE AUSTRALIAN COAST.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A MEDIUM-SIZED SYSTEM WITH DEEP CENTRAL CONVECTION REMAINING ON THE SOUTH SIDE OF THE THE LOW-LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MSI LOOP AND EXTRAPOLATION FROM A 230115Z GMI 37GHZ IMAGE. THE INITIAL INTENSITY OF 75KTS/CAT 1 US IS ASSESSED WITH HIGH CONFIDENCE BASED ON MULTIPLE AGENCY DVORAK FIXES, EACH SHOWING A DECREASING TREND ALONG WITH THE ADVANCED DVORAK TECHNIQUE (ADT). ANALYSIS INDICATES A MARGINALLY UNFAVORABLE ENVIRONMENT WITH STRONG POLEWARD OUTFLOW AND WARM SST OFFSET BY MODERATE TO STRONG VERTICAL WIND SHEAR. THE CYCLONE IS TRACKING ALONG THE NORTHWEST PERIPHERY OF THE STR TO THE SOUTHEAST.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN FAIR AGREEMENT OVERALL UNTIL 48H. THE TRACK GUIDANCE BEGINS TO DIVERGE SIGNIFICANTLY ONCE TC 21S BEGINS THE SUBTROPICAL TRANSITION. NEAR 60H, THE MODELING GUIDANCE DEPICTS ERRATIC MOTION WITH THE STORMS ALONG-TRACK AND CROSS-TRACK SPREAD. DUE TO THIS UNCERTAINTY, THE OVERALL JTWC TRACK AND INTENSITY GUIDANCE IS MEDIUM UP TO 48H AND LOW THEREAFTER.

FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 120 NM EITHER SIDE OF A LINE FROM 12.8S 77.7E TO 14.1S 74.7E WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 28 TO 33 KNOTS. METSAT IMAGERY AT 230000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 12.8S 77.2E. THE SYSTEM IS MOVING WESTWARD AT 20 KM/H. 2. REMARKS: THE AREA OF CONVECTION (INVEST 94S) PREVIOUSLY LOCATED NEAR 12.7S 79.3E IS NOW LOCATED NEAR 12.8S 77.2E, APPROXIMATELY 810 KM SOUTHEAST OF DIEGO GARCIA. ENHANCED ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 222233Z SSMIS 91GHZ IMAGE DEPICTS ACCELERATED INTENSIFICATION AND STRUCTURE WITH CONSOLIDATING DEEP CONVECTION NEAR THE LOW-LEVEL CIRCULATION (LLC). ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT DEFINED BY STRONG POLEWARD AND WESTWARD OUTFLOW ALOFT, LOW (10-15KTS) VERTICAL WIND SHEAR, AND WARM (29-30C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 94S WILL CONTINUE TO CONSOLIDATE AND DEVELOP WITH POTENTIAL FOR RAPID INTENSIFICATION OVER THE NEXT 72 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1003 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.

THE AREA OF CONVECTION (INVEST 91B) PREVIOUSLY LOCATED NEAR 17.1N 94.1E HAS DISSIPATED AND IS NO LONGER SUSPECT FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE IN THE NEXT 24 HOURS.