TC 08S set to intensify gradually over 72hours while approaching the Mascarenes area, 27/03utc

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY. FORECAST DISCUSSION: TC 08S HAS CONSOLIDATED WITHIN THE FAR EASTERN END OF THE MONSOON TROUGH, AND HAS SEPARATED ITSELF INTO A DISTINCT ENTITY OVER THE PAST 24 HOURS. OVER THE PAST 12 HOURS, IT HAS BECOME INCREASINGLY ORGANIZED AND WELL DEFINED AS A TROPICAL CYCLONE. THE SYSTEM IS FORECAST TO TRACK WEST-SOUTHWESTWARD THROUGH 48 HOURS ALONG THE NORTH-NORTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) TO THE SOUTH. WHILE THE SCATTEROMETER AND MODEL FIELDS SUGGEST THE PRESENCE OF A CIRCULATION TO THE NORTH WITHIN THE MONSOON TROUGH, WHICH IS FAIRLY CLOSE TO TC 08S, AT THIS TIME IT IS NOT EXPECTED TO SIGNIFICANTLY IMPACT THE TRACK OF TC 08S. BY 48H, THE RIDGE TO THE SOUTH WILL WEAKEN DUE TO PASSAGE OF A MID-LATITUDE TROUGH, THOUGH THE IMPACT ON TC 08S IS EXPECTED TO BE MINIMAL, WITH ONLY A SLOWDOWN IN TRACK SPEED EXPECTED. BY 72H, A BUILDING RIDGE TO THE SOUTHWEST WILL TAKE OVER STEERING, PUSHING TC 08S ONTO A MORE WESTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST. ENVIRONMENTAL CONDITIONS ARE COMPLEX, WITH MULTIPLE COMPETING FACTORS INFLUENCING THE FORECAST. IN THE NEAR-TERM, THE LACK OF A STRONG OUTFLOW MECHANISM WILL OFFSET THE LOW VWS AND WARM SSTS, LEADING TO SLOW BURSTS OF INTENSIFICATION FOLLOWED BY PERIODS OF STEADY INTENSITY. AFTER 48H, THE SYSTEM WILL BRIEFLY ESTABLISH A POLEWARD OUTFLOW CHANNEL, ALLOWING FOR A SHORT BURST OF INTENSIFICATION TO A PEAK OF 55 KNOTS AT 72H. AFTER THIS POINT, INCREASING DRY AIR INTRUSION, NORTHEASTERLY SHEAR AND CONVERGENT FLOW ALOFT WILL CONSPIRE TO WEAKEN THE SYSTEM THROUGH THE END OF THE FORECAST PERIOD.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES THAT TC 08S HAS STEADILY CONSOLIDATED AND DEVELOPED AN IMPROVED CONVECTIVE STRUCTURE OVER THE PAST SIX HOURS. AT THE 270000Z HOUR, A SMALL BURST OF CONVECTION WAS SEEN TO BE DEVELOPING NEAR THE ASSESSED CENTER AND OBSCURING THE LOW LEVEL CIRCULATION CENTER (LLCC). A 262229Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTED WELL DEFINED CONVECTIVE BANDS TO THE NORTH AND SOUTH, WRAPPING INTO A THE OBSCURED LLCC. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED MICROWAVE IMAGERY. THE INITIAL INTENSITY OF 35 KNOTS IS ASSESSED WITH MEDIUM CONFIDENCE, ON THE HIGHER END OF AGENCY DVORAK CURRENT INTENSITY ESTIMATES RANGING BETWEEN T2.0 (PGTW) TO T2.5 (FMEE) AND THE OVERALL IMPROVED CONVECTIVE AND MICROWAVE STRUCTURE. THE SYSTEM LIES IN AN OVERALL MARGINALLY FAVORABLE ENVIRONMENT, WITH THE VERY WARM (28-29C) SSTS AND RELATIVELY LOW VWS BEING OFFSET SOMEWHAT BY FAIR OUTFLOW ALOFT, SOME MID-LEVEL DRY AIR INTRUSION AND THE SMALL SIZE OF THE SYSTEM.

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH 72H, THEN DEPICTS SIGNIFICANT DIVERGENCE, WITH THE UKMET ENSEMBLE, GALWEM AND ECMWF ENSEMBLE PEELING OFF TO THE SOUTH, WHILE THE GFS ENSEMBLE AND ECMWF DETERMINISTIC DRIFT OFF TO THE NORTH OF THE TIGHTEST GROUPING OF GUIDANCE MEMBERS. SPREAD IS ONLY 130KM AT 72H, BUT INCREASES TO 295KM AT 120H. THE JTWC FORECAST TRACK LIES ON THE NORTHERN SIDE OF THE GUIDANCE ENVELOPE THROUGH THE FORECAST PERIOD WITH MEDIUM TRENDING TO LOW. INTENSITY GUIDANCE IS MIXED, WITH THE DECAY SHIPS-GFS INDICATING STEADY INTENSIFICATION TO A PEAK OF 95 KNOTS BY THE END OF THE FORECAST PERIOD, WHILE THE COAMPS-TC DEPICTS BASICALLY STEADY INTENSITY THROUGH THE PERIOD, AND THE BULK OF THE REMAINDER OF THE GUIDANCE MEMBERS BETWEEN 55 AND 70 KNOTS. THE JTWC FORECAST TRACKS SLIGHTLY BELOW THE CONSENSUS THROUGH 72H, THEN WELL BELOW THE MEAN THROUGH THE END OF THE FORECAST PERIOD. CONFIDENCE IS LOW WITH THE OVERALL INTENSITY FORECAST DUE TO THE VERY LARGE SPREAD IN THE GUIDANCE.