TC 16P(KEVIN) subtropical transition//TC 11S(FREDDY) intensifying beyond 24h//SS 15P(JUDY)//Invest 97P// 0503utc

JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 16P(KEVIN). 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ARE ISSUED ON TC 11S(FREDDY). 3HOURLY SATELLITE BULLETINS ARE ISSUED ON SUBTROPICAL STORM 15P(JUDY).

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TC 16P (KEVIN) CONTINUES TO RAPIDLY WEAKEN AND HAS BEGUN SUBTROPICAL TRANSITION (STT). ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AS WELL AS ENHANCED INFRARED (EIR) IMAGERY SHOWS THE SYSTEM IS BEGINNING TO DECOUPLE, WITH THE LOW LEVEL CIRCULATION CENTER (LLCC) STARTING TO LAG BEHIND THE MID AND UPPER-LEVEL ROTATION, WHICH IS RACING TO THE SOUTHEAST. THE OUTER BANDS OF THE LLCC ARE STARTING TO PEAK OUT FROM UNDER THE CONVECTIVE CANOPY AND PROVIDED GOOD SUPPORT FOR PLACEMENT OF THE INITIAL POSITION A BIT BEHIND THE PGTW FIX POSITION. A 042105Z AMSU-B 89GHZ MICROWAVE IMAGE REVEALED WELL-ORGANIZED LOW-LEVEL BANDS WRAPPING INTO THE CENTER FROM THE NORTH, WITH MORE VIGOROUS CONVECTIVE BANDING FEATURES DRAPED ACROSS THE SOUTHERN PERIPHERY. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE AT 90 KNOTS, WHICH IS RIGHT IN THE MIDDLE BETWEEN THE AGENCY DVORAK FINAL-T (FT) AND CURRENT INTENSITY (CI) ESTIMATES (T4.5 AND T5.5 RESPECTIVELY) AND CLOSE THE AIDT ESTIMATE OF 88 KNOTS. THE ENVIRONMENT IS DETERIORATING FAST, CHARACTERIZED BY HIGH VWS, AND MODEST SSTS OFFSET BY VERY STRONG POLEWARD OUTFLOW.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: THE FORECAST HAS BEEN TRUNCATED TO 24 HOURS, DURING WHICH TIME TC 16P IS EXPECTED TO TRANSITION TO A STORM-FORCE SUBTROPICAL LOW. THE SYSTEM WILL RAPIDLY TRACK SOUTHEASTWARD ALONG THE SOUTHWEST SIDE OF THE STRONG STR CENTERED FAR TO THE NORTH, THROUGH THE SHORT FORECAST PERIOD. STT HAS ALREADY BEGUN AS THE SYSTEM HAS BEGUN TO BE DECAPITATED BY STEADILY INCREASING WESTERLY SHEAR. VERY DRY AIR TO THE WEST IS ALSO BEGINNING TO MOVE EVER CLOSER TO THE CENTER AND WILL SOON ENGULF TC 16P, EFFECTIVELY PUTTING AN END TO THE SYSTEM AS A TROPICAL CYCLONE. BY TAU 24, ALL THAT WILL REMAIN OF TC 16P WILL BE A LOW-LEVEL NAKED VORTEX, WHICH WILL RETAIN SIGNIFICANT INERTIA WHICH WILL TAKE TIME TO SPIN DOWN AND IN THE FUTURE THE SYSTEM WILL LIKELY LINGER AS A GALE-FORCE SUBTROPICAL LOW THAT EVENTUALLY TRANSITIONS TO AN EXTRATROPICAL LOW.

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THOUGH THE SHORT DURATION OF THE FORECAST, WITH VERY LITTLE IN THE WAY OF EITHER CROSS OR ALONG-TRACK SPREAD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. ALL MEMBERS OF THE INTENSITY CONSENSUS CONCUR ON SHARP WEAKENING THROUGH THE FORECAST PERIOD AND THE JTWC FORECAST LIES ON THE HIGHER END OF THE ENVELOPE WITH HIGH CONFIDENCE.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: TC 11S (FREDDY) HAS ONCE MORE ROARED BACK TO LIFE IN THE MOZAMBIQUE CHANNEL, CONSOLIDATING AND INTENSIFYING TO TROPICAL STORM STRENGTH OVER THE PREVIOUS 24 HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY INDICATES THE SYSTEM HAS BEEN SLOW TO INTENSIFY HOWEVER, WITH CONVECTION CAPPED AND STILL SOMEWHAT DISORGANIZED AROUND THE DEVELOPING CENTER. RECENT MICROWAVE PASSES INCLUDING A 042205Z AMSR2 AND A 040042Z GMI PASS, SHOWED THAT THE VORTEX CONTINUES TO ALIGN VERTICALLY BUT REMAINS DEVOID OF SIGNIFICANT CONVECTION, PARTICULARLY ON THE EAST SIDE. HOWEVER, THE MICROWAVE IMAGERY REVEALS WELL-FORMED LOW-LEVEL SPIRAL BANDS WRAPPING INTO THE MORE DEFINED LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE GMI 36GHZ MICROWAVE IMAGE. THE INITIAL INTENSITY IS ALSO SET WITH HIGH CONFIDENCE, IN AGREEMENT WITH THE BULK OF THE AGENCY CURRENT INTENSITY ESTIMATES AND THE ADT. WHILE DEEP-LAYER AVERAGED SHEAR IS RELATIVELY LOW, MID-LEVEL SHEAR IS A BIT HIGHER, APPROACHING 20 KNOTS FROM THE SOUTHWEST. ADDITIONALLY, MODEL FIELDS AND THE CIRA ADVECTED LAYER PRECIPITABLE WATER PRODUCT INDICATE A SOLID CAP OF DRY AIR POSITIONED OVER THE SYSTEM AT THE 500-300MB LEVEL, EFFECTIVELY CAPPING CONVECTIVE ACTIVITY AND PROHIBITING CONVECTIVE CONSOLIDATION. ROBUST OUTFLOW, INITIALLY POLEWARD BUT TURNING EAST AND THEN EQUATORWARD, IS PROVIDING AMPLE VENTING ALOFT. THE SYSTEM IS MOVING GENERALLY SOUTHEASTWARD ALONG THE SOUTHERN SIDE OF A NEAR EQUATORIAL RIDGE (NER) CENTERED TO THE NORTH.

MODEL FIELDS AND THE CIRA ADVECTED LAYER PRECIPITABLE WATER PRODUCT INDICATE A SOLID CAP OF DRY AIR POSITIONED OVER THE SYSTEM AT THE 500-300MB LEVEL, EFFECTIVELY CAPPING CONVECTIVE ACTIVITY AND PROHIBITING CONVECTIVE CONSOLIDATION.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: OVER THE NEXT 12 TO 24 HOURS, TC 11S WILL CONTINUE TRACKING SLOWLY TOWARDS THE SOUTHEAST UNDER THE STEERING INFLUENCE OF THE STRONG NER CENTERED JUST NORTH OF MADAGASCAR. BY TAU 24 HOWEVER, THE NER BEGINS TO WEAKEN WHILE THE WEAK SUBTROPICAL RIDGE (STR) CURRENTLY SOUTH OF 30S BEGINS TO BUILD AND EXTEND NORTHWESTWARD. THE COMPETING STEERING INFLUENCES WILL RESULT IN A WEAK STEERING ENVIRONMENT IN WHICH TC 11S WILL REMAIN QUASI-STATIONARY, PARKED JUST OFF THE SOUTHWEST COAST OF MADAGASCAR. BY TAU 48 THE STR TO THE SOUTH WILL HAVE STRENGTHENED AND EXTENDED TO THE NORTHWEST TO ANOTHER STR CENTERED OVER ZAIRE, ESTABLISHING A SOLID RIDGE ACROSS THE SOUTHWEST SIDE OF THE SYSTEM. THIS WILL OVERCOME THE STEERING INFLUENCE OF THE WEAKENING NER AND PUSH TC 11S OUT OF ITS PARKING SPOT AND ONTO A NORTHWESTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST PERIOD. DUE TO THE CONTINUED PRESENCE OF THE DRY CAPPING LAYER OVER THE SYSTEM, LITTLE TO NO INTENSIFICATION IS EXPECTED IN THE NEXT 12 HOURS. THE ATMOSPHERE MOISTENS UP AFTER TAU 24, ALLOWING FOR MORE ROBUST CONVECTIVE ACTIVITY, AS THE SYSTEM SIMULTANEOUSLY MOVES INTO AN AREA OF VERY WARM (30-31C) WATERS WITH MODERATELY HIGH OHC OFF THE WEST COAST OF MADAGASCAR. THIS WILL KICK OFF A ROUND OF MORE RAPID INTENSIFICATION THROUGH TAU 48. AFTER THE SYSTEM DEPARTS THE WARM POOL AND BEGINS MOVING NORTHEAST, IT WILL FACE A MODEST INCREASE IN SOUTHERLY SHEAR AND AS THE OUTFLOW AND SHEAR COMPETE FOR DOMINANCE, THIS PROCESS WILL KEEP A LID ON INTENSIFICATION THROUGH THE REMAINDER OF THE FORECAST.

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS HIGHLY UNCERTAIN, WITH LARGE DISAGREEMENTS IN BOTH TRACK DIRECTION AND SPEED ACROSS THE CONSENSUS MEMBERS. ALL THE MEMBERS AGREE ON THE SOUTHEAST TRACK AND QUASI-STATIONARY PERIOD THROUGH TAU 48. BUT THATS WHERE THE AGREEMENT ENDS. THE US MODELS THEN CURVE THE SYSTEM TO THE SOUTHWEST AND THEN ONTO A NORTHWESTWARD TRACK CLOSE TO EUROPA ISLAND, WITH THE GFS AND GEFS ENSEMBLE SHOWING LANDFALL ON THE MOZAMBIQUE COAST BY TAU 120. MEANWHILE THE EUROPEAN MODELS TURN THE SYSTEM TO THE EAST, THEN NORTHWESTWARD ON THE OTHER SIDE OF THE CONSENSUS MEAN, AT A MUCH SLOWER PACE, KEEPING THE SYSTEM OVER WATER THROUGH THE FIVE-DAY FORECAST PERIOD. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST PHILOSOPHY AND HEDGES TOWARDS THE US MODELS, BUT CONFIDENCE IS LOW DUE TO THE LARGE SPREAD IN BOTH THE ENSEMBLE MEMBERS AND DETERMINISTIC TRACKERS. INTENSITY GUIDANCE IS MORE WELL-BEHAVED, WITH ALL BUT THE HWRF INDICATING RELATIVELY SLOW AND GRADUAL INTENSIFICATION THROUGH THE FORECAST PERIOD. THE HWRF HOWEVER SHOOTS UP DRAMATICALLY AFTER TAU 48, TO A PEAK OF 110 KNOTS AT TAU 96. WHILE POSSIBLE, THIS SOLUTION IS CURRENTLY ASSESSED AS LOW PROBABILITY DUE TO THE FACT THAT THE HWRF IS UNCOUPLED IN THIS REGION AND THUS DOES NOT TAKE INTO ACCOUNT OCEANIC UPWELLING AND OTHER FACTORS THAT THE COUPLED COAMPS-TC MODEL IS TAKING INTO ACCOUNT.