TC 21S(CHARLOTTE): peaking as a CAT 2 US Northwest of Australia//Invest 91B :Medium//Invest 94S: development next several days,22/06utc

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

22/05UTC.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 21S WILL CONTINUE TRACKING TOWARD THE SOUTHWEST UNDER THE STEERING INFLUENCE OF THE STR TO THE SOUTHEAST. VERTICAL WIND SHEAR IS GRADUALLY INCREASING, WITH RESTRICTED EQUATORWARD OUTFLOW. OVER THE LAST 6 HOURS, TC 21S APPEARS TO HAVE REACHED ITS PEAK INTENSITY, AND THE RAGGED EYE IS BEGINNING TO FILL WITH CONVECTIVE CLOUD TOPS WARMING. GRADUAL WEAKENING IS OCCURING AND SHOULD BECOME MORE RAPID WITH TIME AS THE ENVIRONMENT BECOMES MORE HOSTILE. BY TAU 48, TC 21S IS FORECAST TO MAKE A TURN TOWARD THE SOUTH AND SOUTHEAST WITH AN INCREASE IN SPEED AS THE STR TO THE EAST WEAKENS AND THE SYSTEM INTERACTS WITH AN APPROACHING MID-LATITUDE TROUGH FROM THE WEST. INCREASING VERTICAL WIND SHEAR, DRY AIR ENTRAINMENT, AND INTERACTION WITH THE BAROCLINIC ZONE WILL INDUCE SUBTROPICAL TRANSITION AROUND TAU 72. TC 21S IS FORECAST TO COMPLETE SUBTROPICAL TRANSITION BY TAU 96.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS DEEP CONVECTION IN A GRADUALLY WARMING CENTRAL DENSE OVERCAST WRAPPING AROUND A RAGGED EYE THAT IS CURRENTLY IN THE PROCESS OF FILLING. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE GIVEN THE SMALL EYE EVIDENT IN THE 212237Z SSMIS 91GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS SET AT 90 KNOTS WITH MEDIUM CONFIDENCE USING A BLEND OF AGENCY DVORAK ESTIMATES AND A 211821Z AMSR2 PASS INDICATING WINDS JUST ABOVE 80 KNOTS. BASED ON THE BRIEF CLEARING OF THE EYE IN ANIMATED EIR, FOLLOWED BY SUBSEQUENT FILLING AND THE WARMING OF CLOUD TOPS, THE PEAK INTENSITY OF TC 21S WAS LIKELY REACHED IN THE HOURS BETWEEN THAT AMSR2 PASS AND THE CURRENT WARNING. THE UPPER-LEVEL OUTFLOW IS BEGINNING TO BE CONSTRICTED IN THE NORTHERN SEMICIRCLE, BUT POLEWARD OUTFLOW REMAINS EXCELLENT.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH CONTINUES TO BE THE WESTERN OUTLIER, NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH A 165NM SPREAD AT TAU 72, SUPPORTING THE JTWC FORECAST TRACK WITH MEDIUM CONFIDENCE. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE MULTI-MODEL CONSENSUS (CONW), BUT ACCOUNTING FOR THE NAVGEM OUTLIER. THE JTWC INTENSITY FORECAST FOLLOWS THE WEAKENING TREND OF THE INTENSITY GUIDANCE BUT MORE GRADUALLY, GIVEN THE INTENSIFICATION PERIOD THAT OCCURRED TODAY. ONCE THE RAGGED EYE COLLAPSES AND DRY AIR ENTRAINS INTO THE SYSTEM, MORE RAPID WEAKENING SHOULD COMMENCE. DSHA AND DSHN REMAINS WELL ABOVE THE REST OF THE INTENSITY GUIDANCE, BUT THOSE STATISTICAL-DYNAMICAL SOLUTIONS ARE BEING FORCED BY THE RAPID INTENSIFICATION OF THE LAST 12 HOURS, SO THOSE SOLUTIONS ARE DISREGARDED FOR THIS WARNING CYCLE.

THE AREA OF CONVECTION (INVEST 91B) PREVIOUSLY LOCATED NEAR 13.5N 94.3E IS NOW LOCATED NEAR 15.1N 94.7E, APPROXIMATELY 235 KM SOUTHWEST OF YANGON, MYANMAR. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS CONVECTION BEGINNING TO CONSOLIDATE OVER THE LOW LEVEL CIRCULATION CENTER (LLCC). HOWEVER, LANDFALL IN MYANMAR IS IMMINENT, SO THE WINDOW OF OPPORTUNITY FOR DEVELOPMENT IS CLOSING. ANALYSES INDICATE A MARGINAL ENVIRONMENT FOR DEVELOPMENT CHARACTERIZED BY WARM (29-30C) SEA SURFACE TEMPERATURES (SST), AND POLEWARD OUTFLOW OFFSET BY LOW TO MODERATE (10-20KT) VERTICAL WIND SHEAR (VWS). GLOBAL MODELS GENERALLY AGREE THAT INVEST 91B WILL CONTINUE TO TRACK NORTHWARD OVER MYANMAR AND DISSIPATE. OF NOTE, ECMWF SUGGEST THAT 91B MAY BRIEFLY CROSS BACK OVER THE BAY OF BENGAL AND UNDERGOING MINOR REORGANIZATION BEFORE MOVING BACK OVER LAND. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS DOWNGRADED TO MEDIUM.

GLOBAL MODELS GENERALLY AGREE THAT INVEST 91B WILL CONTINUE TO TRACK NORTHWARD OVER MYANMAR AND DISSIPATE. OF NOTE, ECMWF SUGGEST THAT 91B MAY BRIEFLY CROSS BACK OVER THE BAY OF BENGAL AND UNDERGOING MINOR REORGANIZATION BEFORE MOVING BACK OVER LAND.

THE AREA OF CONVECTION (INVEST 94S) PREVIOUSLY LOCATED NEAR 10.4S 84.6E IS NOW LOCATED NEAR 11.2S 81.7E, APPROXIMATELY 1100 KM SOUTHEAST OF DIEGO GARCIA. ANIMATED EIR AND A 212245Z SSMIS 91GHZ SATELLITE IMAGE DEPICT MARGINALLY IMPROVED LOW LEVEL STRUCTURE AND FLARING CONVECTION. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT WITH LOW TO MODERATE (10-20KTS) VWS, POLEWARD AND WESTWARD OUTFLOW, AND WARM (28-29C) SSTS. GLOBAL MODELS AGREE THAT INVEST 94S WILL CONTINUE TO CONSOLIDATE AND DEVELOP AS THE SYSTEM SLOWLY DRIFTS WESTWARD OVER THE NEXT 24-48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1007 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS MEDIUM.

GLOBAL MODELS AGREE THAT INVEST 94S WILL CONTINUE TO CONSOLIDATE AND DEVELOP AS THE SYSTEM SLOWLY DRIFTS WESTWARD OVER THE NEXT 24-48 HOURS.