TC 24S(IALY) intensifying a bit//INVEST 93W//INVEST 93S// ECMWF 10 Day Storm Tracks//1706utc

JTWC IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON TC 24S(IALY)

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) THAT IS TUCKED UNDER THE NORTHEASTERN CORNER OF THE PRIMARY CONVECTIVE CELL. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 162208Z AMSR2 89GHZ MICROWAVE IMAGE WHICH SHOWED A MOMENTARILY FULLY EXPOSED LLCC WITH TIGHTLY WRAPPING LOW LEVEL CLOUD LINES IN ALL FOUR QUADRANTS. THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A RECENT 161755Z PARTIAL ASCAT-C SCATTEROMETERY PASS WHICH SHOWED A MODERATE FIELD OF 35KT WINDS TO THE WEST-SOUTHWEST OF THE LLCC AND 15-20KT WINDS TO THE NORTHWEST. FURTHERMORE, ADT, AIDT, D-PRINT AND ALL AGENCY DVORAK INTENSITY ESTIMATES ALSO SUPPORT 35-40KTS.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 24S (IALY), IS FORECAST TO CONTINUE MEANDERING GENERALLY WESTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE SOUTH. AS THE SYSTEM PROPAGATES WESTWARD, MODERATE VERTICAL WIND SHEAR (VWS) AND MID-LEVEL DRY AIR ENTRAINMENT WILL GENERALLY NEGATE WARM SSTS AND FAVORABLE UPPER-LEVEL OUTFLOW, RESULTING IN STAGNATING INTENSITIES THROUGH TAU 24. AS THE STR TO THE SOUTH REORIENTS AND BREAKS DOWN, STEERING INFLUENCE SHIFTS TO A BUILDING NEAR-EQUATORIAL RIDGE (NER) TO THE WEST. AS THIS SHIFTS TAKES PLACE AND THE SYSTEM IS DEFLECTED EQUATORWARD, MOMENTARILY LOWER VWS VALUES AND INCREASED UPPER-LEVEL OUTFLOW WILL RESULT IN LIMITED INTENSIFICATION TO AROUND 45KTS AND POSSIBLY 50KTS BY TAU 48. BY TAU 72, THE PARTY IS OVER, AS VWS, DRY AIR ENTRAINMENT AND HEAVILY REDUCED OUTFLOW RESULTS IN STEADY WEAKENING THROUGH DISSIPATION NEAR TAU 120 AS THE SYSTEM ACCELERATES EQUATORWARD.

MODEL DISCUSSION: WITH THE EXCEPTION OF NVGM AND COAMPS-TC (NVGM VERSION), THE BULK OF THE MODEL GUIDANCE IS IN SOLID AGREEMENT THROUGH TAU 36 WITH A 80NM SPREAD IN MEMBER GUIDANCE. AFTER TAU 36, NOT ONLY DOES NVGM SAUNTER OFF MORE WESTWARD THAN THE BULK OF THE MODELS BUT ALONG TRACK SPREADING ALSO SLIGHTLY INCREASES. ECMWF AND ITS ENSEMBLE INDICATE A SLOWER EQUATORWARD TRACK SPEED THAN THE REMAINING MEMBERS THROUGH TAU 120. FOR THESE REASONS THE JTWC TRACK FORECAST IS PLACED INITIALLY WITH HIGH CONFIDENCE AND WITH MEDIUM CONFIDENCE THEREAFTER. RELIABLE MODEL INTENSITY GUIDANCE IS IN OVERALL MODERATE AGREEMENT WITH DECAY-SHIPS INCREASING THE SYSTEM TO 55KTS WHILE GFS, HAFS AND COAMPS-TC WEAKEN THE SYSTEM SLOWLY AFTER TAU 36. FOR THESE REASONS THE JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE CONSENSUS WITH MEDIUM CONFIDENCE.