TC 11S(FREDDY) set to turn North-westward and gradually intensify next 36h//SS 16P(KEVIN) still significant//Invest 97P//Invest 98S//0603utc

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 11S(FREDDY). 3HOURLY SATELLITE BULLETINS ARE ISSUED ON SUBTROPICAL STORM 16P(KEVIN).

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TROPICAL CYCLONE 11S (FREDDY) CONTINUES TO STRUGGLE AGAINST MULTIPLE FACTORS INHIBITING DEVELOPMENT INCLUDING MODERATE WESTERLY VERTICAL WIND SHEAR (VWS) AND LOW LEVEL FLOW DISRUPTION DUE TO PROXIMITY TO MADAGASCAR. WHILE CONVECTION HAS FLARED FROM TIME TO TIME, OVERALL IT HAS FAILED TO CONSOLIDATE AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC), AND THUS TC 11S HAS BEEN UNABLE TO INTENSIFY SIGNIFICANTLY. A SERIES OF RECENT HIGH-RESOLUTION MICROWAVE IMAGES INCLUDING A 052249Z AMSR2 AND A PARTIAL 052348Z GMI 36GHZ IMAGE INDICATE THAT THE SYSTEM HAS A WEAK MICROWAVE EYE IN THE LOWER LEVELS BUT THAT THE UPPER-LEVEL ROTATIONAL CENTER IS DISPLACED TO THE SOUTHEAST. ADDITIONALLY, ANALYSIS OF ANIMATED PROXY VISIBLE AND SHORTWAVE INFRARED (SWIR) IMAGERY INDICATES THE LOWER-LEVEL SPIRAL BANDS ARE CLEARLY EVIDENT, OUT IN THE OPEN, ACROSS THE WESTERN HALF OF THE LARGER CIRCULATION. THUS, IT CAN BE SAID WITH HIGH CONFIDENCE THAT AFTER MAKING A HEAD-FAKE TOWARDS TOLIARA, THE SYSTEM HAS TURNED AWAY, BACK TOWARDS THE SOUTHWEST. THE INITIAL INTENSITY REMAINS ASSESSED AT 45 KNOTS, CLOSE TO THE ADT ESTIMATES, WITH MEDIUM CONFIDENCE DUE TO THE LACK OF ANY RECENT WIND MEASUREMENTS AND THE LARGE SPREAD IN THE AGENCY FIXES. THE SYSTEM IS DRIFTING SOUTHWESTWARD BUT IN REALITY, IS QUASI-STATIONARY, AS THE PRIMARY STEERING MECHANISM BEGINS TO SHIFT FROM THE NEAR-EQUATORIAL RIDGE (NER) TO THE NORTH TO THE SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE SOUTH AND SOUTHWEST. ENVIRONMENTAL ANALYSIS REVEALS WARM SSTS AND STRONG POLEWARD AND EASTWARD OUTFLOW, WHICH IS BEING OFFSET BY MODERATE TO HIGH WESTERLY VWS. PROXIMITY TO LAND AND A DEEP LAYER OF VERY DRY AIR TO THE WEST ARE ADDING TO THE CHALLENGES FACING TC 11S.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: RECENT MICROWAVE IMAGERY PROVIDES HIGH CONFIDENCE TO THE FACT THAT THE PRIMARY STEERING MECHANISM IS CURRENTLY IN THE PROCESS OF SHIFTING FROM THE NER, WHICH HAS DRIVEN THE SYSTEM EAST-SOUTHEASTWARD OVER THE PAST 24 HOURS, TO THE STR TO THE SOUTH. ALL GLOBAL AND MOST MESOSCALE DEEP-LAYER MEAN MODEL FIELDS INDICATE THE STEERING GRADIENT WILL COMPLETELY SHIFT FROM THE NORTH SIDE OF THE SYSTEM TO THE SOUTH WITHIN THE NEXT 12 HOURS. AT THIS POINT, TC 11S WILL END UP ON A NORTHWESTWARD HEADING, AS THE STR BUILDS OVER ZAIRE AND EXTENDS FAR TO THE SOUTHEAST OF MADAGASCAR, PROVIDING A NICE GRADIENT FOR TC 11S TO SLIDE UP THROUGH THE REMAINDER OF THE FORECAST. THE NER DOES NOT DISAPPEAR HOWEVER, AND IN FACT BEGINS TO BUILD ONCE MORE AFTER TAU 72, AND TAU 96 THE NER AND STR WILL BE ROUGHLY EQUAL IN STRENGTH, LEADING TO ANOTHER ROUND OF COMPETITION OVER WHICH WILL DOMINATE THE STEERING FLOW. IN RESPONSE, TC 11S BEGINS TO SLOW TO BARE STEERAGEWAY BY THE END OF THE FORECAST. LITTLE IN THE WAY OF INTENSIFICATION IS EXPECTED THROUGH THE FIRST 12 HOURS OR SO OF THE FORECAST, AS THE SYSTEM REMAINS RELATIVELY CLOSE TO LAND, FACES MODERATE TO HIGH SHEAR AND MODERATE AMOUNTS OF UPWELLING, AND HAVING PARKED OVER THE SAME GENERAL AREA FOR 24 HOURS. AS THE SYSTEM STARTS MOVING NORTHWESTWARD AND AWAY FROM LAND, CONDITIONS ARE EXPECTED TO IMPROVE, ALLOWING THE SYSTEM TO JUMP UP IN INTENSITY BY TAU 36. HOW STRONG THE SYSTEM CAN GET IN THE FIRST 36 HOURS WILL HAVE A MAJOR IMPACT ON SUBSEQUENT INTENSIFICATION, AS CONVERGENT SOUTHERLY FLOW WILL MOVE IN BY TAU 48 AND IF THE SYSTEM CANNOT ESTABLISH A STRONG CORE OF CONVECTION AND AN ANTICYCLONE ALOFT, THEN IT WILL NOT BE ABLE TO INTENSIFY MUCH. THE JTWC FORECAST ASSUMES THE ESTABLISHMENT OF THE ABOVE FACTORS, AND THUS CALLS FOR STEADY INTENSIFICATION THROUGH TAU 96. AROUND THIS TIME THE SYSTEM WILL MOVE OVER A POOL OF HIGH OHC WATERS, WHILE SIMULTANEOUSLY SLOWING, WHICH SHOULD ALLOW FOR A BURST OF INTENSIFICATION THROUGH THE END OF THE FORECAST PERIOD.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE, WITH THE EXCEPTION OF HWRF, GALWEM AND NAVGEM, IS IN FAIRLY GOOD AGREEMENT. THE BULK OF THE CONSENSUS MEMBERS LIE WITHIN A VERY TIGHT ENVELOPE THAT TRACKS OFF TO THE NORTHWEST AND SUPPORTS THE JTWC FORECAST. THE HWRF MEANWHILE TRACKS THE SYSTEM TOWARDS BEIRA, MOZAMBIQUE, SIGNIFICANTLY FURTHER SOUTHWEST THAN ALL THE OTHER MODELS, WHILE THE NAVGEM AND GALWEM TURN THE SYSTEM BACK TOWARDS MADAGASCAR AFTER TAU 72. FOR THE PURPOSES OF THIS FORECAST, THESE MODELS ARE DISCARDED AS UNREALISTIC OUTLIERS. THE GFS AND GEFS ENSEMBLE, WHILE CONTAINED WITHIN THE NARROW TRACK ENVELOPE, SIGNIFICANTLY OUTPACE ALL THE OTHER GUIDANCE, TRACKING THE SYSTEM INLAND OVER MOZAMBIQUE JUST AFTER TAU 96. THE JTWC FORECAST LIES CLOSE TO ECMWF DETERMINISTIC AND ECMWF ENSEMBLE MEAN TRACKERS WITH MEDIUM CONFIDENCE DUE TO THE SIGNIFICANT ALONG-TRACK SPREAD. INTENSITY GUIDANCE IS IN GENERAL AGREEMENT, WITH ALL MEMBERS INDICATING SLOW AND STEADY INTENSIFICATION. HWRF DIVERGES FROM THE PACK AFTER TAU 48, REACHING A PEAK NEAR 90 KNOTS, WHILE THE COAMPS-TC MODELS SUPPORT FASTER INTENSIFICATION AFTER TAU 96. ADDITIONALLY, THE 1800Z COAMPS-TC (GFS) ENSEMBLE NOW SHOWS 25 PERCENT PROBABILITIES OF RAPID INTENSIFICATION AFTER TAU 72. THE JTWC FORECAST TRACKS THE CONSENSUS PACK TO TAU 96 THEN MOVES UP TO MEET THE HWRF AND COAMPS-TC WITH MEDIUM CONFIDENCE.

THE AREA OF CONVECTION (INVEST 16P) PREVIOUSLY LOCATED NEAR 29.0S 171.3W IS NOW LOCATED NEAR 29.6S 169.9W, APPROXIMATELY 583 NM SOUTH-SOUTHEAST OF TONGA. THE SYSTEM IS CURRENTLY CLASSIFIED AS A SUBTROPICAL CYCLONE, GENERALLY CHARACTERIZED AS HAVING BOTH TROPICAL AND MIDLATITUDE CYCLONE FEATURES. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED LLCC WITH CONVECTION SHEARED TO THE SOUTHEAST. A 060103Z AMSR2 89GHZ IMAGE SHOWS COPIOUS AMOUNTS OF DRY AIR BEING WRAPPED IN THE LLCC FROM THE NORTH-NORTHEAST. ENVIRONMENTAL CONDITIONS ARE HIGHLY UNFAVORABLE FOR TC DEVELOPMENT DUE TO HIGH (40-60KTS) VWS, STRONG EASTWARD OUTFLOW ALOFT AND COOLER (23-24C) SSTS. GLOBAL MODELS AGREE THAT THE REMNANTS OF TC 16P WILL CONTINUE TO TRACK SOUTH-SOUTHEAST AND DECAY AS A SUBTROPICAL SYSTEM. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 57 TO 63 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 978 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS LOW.

GLOBAL MODELS AGREE THAT REMNANTS 16P WILL CONTINUE TO DWINDLE DOWN AS IT GETS PICKED UP WITHIN THE LONG WAVE PATTERN OVER THE COURSE OF THE NEXT FEW DAYS THUS COMPLETELY ENDED ITS REIGN AS A POSSIBLE REGENERATING TC.