TC 22S(HALIMA): still cocooned within a small region of relatively moist air//Invest 93W: Tropical Cyclone Formation Alert//Invest 96S, 30/03utc

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 22S(HALIMA).

30/02UTC.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 22S REMAINS ENSCONCED WITHIN A COMPLEX AND COMPETING STEERING ENVIRONMENT, CAUGHT BETWEEN STRONG RIDGES TO THE NORTHWEST AND SOUTHEAST, AND A MID-LATITUDE TROUGH PASSING FAR TO THE SOUTH. WITHOUT A DOMINANT STEERING MECHANISM, THE SYSTEM IS WANDERING GENERALLY NORTHWARD. THIS GENERAL TRACK MOTION, WITH AN EXPECTED GRADUAL TURN TO THE NORTHEAST, OVER THE NEXT 36 HOURS. DURING THIS TIME FRAME, TC 22S IS EXPECTED TO REMAIN COCOONED WITHIN A SMALL REGION OF RELATIVELY MOIST AIR, AND SHOULD BE ABLE TO FIGHT OFF THE RELATIVELY LOW BULK SHEAR, ALLOWING IT TO MAINTAIN INTENSITY FOR ANOTHER TWELVE HOURS, FOLLOWED BY VERY SLOW WEAKENING. BY 48H, STRONG UPPER-LEVEL TROUGH WILL MOVE IN RAPIDLY FROM THE WEST, SHUTTLING IN INCREASING SHEAR AND SIGNIFICANTLY DRIER MID-LEVEL AIR MASS WHICH WILL OVERWHELM THE SYSTEM AND LEAD TO A MORE RAPID WEAKENING. AFTER 48H, A STRONG LOW-LEVEL RIDGE BUILDS IN TO THE SOUTH BEHIND THE AFOREMENTIONED TROUGH, AND AS TC 22S RAPIDLY WEAKENS, THE TRACK WILL SHIFT SHARPLY WESTWARD ALONG THE EQUATORWARD PERIPHERY OF THE RIDGE TO THE SOUTH. TC 22S IS EXPECTED TO DISSIPATE AS A TROPICAL CYCLONE NO LATER THAN 72H, BUT POTENTIALLY AS EARLY AS 60H.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: OVER THE PAST TWELVE HOURS, THE OVERALL STRUCTURE OF TC 22S HAS BEGUN TO DETERIORATE SLIGHTLY, WITH THE DEEP CONVECTION NOW LIMITED TO THE SOUTHERN SEMICIRCLE OF THE CIRCULATION. THE SYSTEM LIES WITHIN AN AREA OF MODERATELY MOIST AIR, BUT IS COCOONED WITHIN A DRY, STABLE AIRMASS. THE CIMSS VERTICAL WIND SHEAR (VWS) PRODUCT AND HWRF SYNTHETIC SOUNDING INDICATE THE BULK SHEAR REMAINS LOW (5-10 KNOTS), THE HWRF SOUNDING SHOWS THE MAXIMUM SHEAR IS CLOSER TO 20-25 KNOTS IN THE MID-LEVELS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE CONVECTIVE DEBRIS IS BEING ELONGATED OFF TO THE SOUTHEAST, INDICATIVE OF A SLIGHTLY INCREASED NORTHWESTERLY SHEAR VECTOR IN THE MID TO UPPER-LEVELS AS INDICATED BY THE HWRF SOUNDING. A 300122Z GMI 37GHZ MICROWAVE IMAGE SHOWS A LARGE REGION OF EXPOSED LOW LEVEL BANDS WRAPPING INTO A SMALL MICROWAVE EYE-LIKE FEATURE. THE INITIAL POSITION WAS PLACED PRIOR TO THE LATE RECEIPT OF THE MICROWAVE IMAGERY, WITH MEDIUM CONFIDENCE, AND WILL BE ADJUSTED SLIGHTLY TO THE SOUTHEAST POST FACTO. THE INITIAL INTENSITY REMAINS AT A SOLID 45 KNOTS, WITH HIGH CONFIDENCE, BASED ON THE HIGHER-END FMEE AND FIMP DVORAK CURRENT INTENSITY ESTIMATES AND CONSISTENT WITH EARLIER SMAP AND SCATTEROMETER DATA.

MODEL DISCUSSION: OVERALL, DETERMINISTIC TRACK GUIDANCE IS IN RELATIVELY GOOD AGREEMENT ON THE SCENARIO BUT DIFFERS ON THE EASTWARD PROGRESSION OF THE TRACK, AND THE TIMING AND EXTENT OF THE TURN TO THE WEST. THE ECMWF AND GALWEM FOR INSTANCE TAKE THE SYSTEM FURTHEST TO THE EAST BY 48H, THEN TURN THE SYSTEM WEST, BUT LAG THE OTHER MODELS DUE TO THE FURTHER EAST TURNING POINT. MEANWHILE THE NAVGEM, AND GFS ENSEMBLE DEPICT A MORE GRADUAL AND SHALLOW TURN TO THE EAST AND A QUICKER TURN WEST, THUS LIE MUCH FURTHER WEST BY 72H. THE JTWC FORECAST CLOSELY FOLLOWS THE GFS SOLUTION, ON THE WESTERN SIDE OF THE ENVELOPE WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE REMAINS MIXED, WITH HWRF STEADILY WEAKENING THE SYSTEM THROUGH 24H FOLLOWED BY INTENSIFICATION THROUGH 120H AND THE DECAY SHIPS INDICATING A PEAK INTENSITY OF 50 KNOTS AT 24H FOLLOWED BY STEADY WEAKENING. THE JTWC FORECAST LIES CLOSE TO THE CONSENSUS MEAN WITH MEDIUM CONFIDENCE.

THE AREA OF CONVECTION (INVEST 93W) PREVIOUSLY LOCATED NEAR 10.8N 114.3E IS NOW LOCATED NEAR 10.8N 113.2E, APPROXIMATELY 750KM SOUTHEAST OF DANANG, VIETNAM. 93W HAS CONSOLIDATED OVER THE LAST 12 HOURS WITH THE STRONG MID-LEVEL TURNING GRADUALLY BURROWING DOWN TO THE SURFACE, THOUGH THE WEAK LOW LEVEL CIRCULATION (LLC) REMAINS OBSCURED BY MID AND UPPER-LEVEL CLOUDS. ENVIRONMENTAL ANALYSIS INDICATES PRIME CONDITIONS FOR DEVELOPMENT WITH NEAR-RADIAL OUTFLOW WITH LOW (05-10KT) VERTICAL WIND SHEAR AND WARM (29-30C) SEA SURFACE TEMPERATURES. THE MAIN HINDRANCES AT THE MOMENT ARE THE RELATIVELY SHORT TIME REMAINING OVER WATER AND THE RELATIVELY SLOW CONSOLIDATION OF THE LLC. GFS REMAINS THE MOST AGGRESSIVE MODEL WITH A TROPICAL DEPRESSION DEVELOPING QUICKLY WITHIN THE NEXT 18-36 HOURS AS THE SYSTEM TRACKS NORTHWESTWARD TOWARD VIETNAM. ECMWF AND NAVGEM SHOW A SIMILAR TRACK BUT WITH SIGNIFICANTLY LESS DEVELOPMENT. THE GFS SOLUTION APPEARS MORE LIKELY CONSIDERING THE FAVORABLE ENVIRONMENTAL CONDITIONS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 12 TO 18 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1006 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO HIGH. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH.

THE AREA OF CONVECTION (INVEST 96S) HAS PERSISTED NEAR 15.6S 109.3E, APPROXIMATELY 950KM NORTHWEST OF LEARMONTH, AUSTRALIA. VERTICAL TILT IS EVIDENT IN ANIMATED MULTISPECTRAL IMAGERY (MSI) WITH LOW LEVEL BANDS WRAPPING INTO A LOW LEVEL CIRCULATION (LLC) OFFSET JUST TO THE NORTHWEST OF THE UPPER-MID LEVEL TURNING. THE TROPICAL ENVIRONMENT IS MARGINAL WITH MODERATE POLEWARD OUTFLOW AND WARM (29-30C) SEA SURFACE TEMPERATURES, OFFSET BY MODERATE (20- 25KTS) VERTICAL WIND SHEAR. GLOBAL MODELS AGREE ON A SIMILAR TRACK WITH 96S MOVING SOUTHEAST OVER THE 48 HOURS, WITH GFS AND ECMWF GLOBAL FIELDS DEPICTING A SMALL FIST OF NEAR-GALE FORCE WINDS ALONG THE EASTERN PERIPHERY AS IT SKIRTS THE COAST NEAR LEARMONTH, AUSTRALIA. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 12 TO 18 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 IS UPGRADED TO LOW.