TC 08S(BATSIRAI): microwave and Cimss analysis suggest intensification possible next 24h// TC 09P up-date, 01/03utc

JTWC IS ISSUING 12HOURLY WARNINGS ON TC 08S(BATSIRAI) AND 6HOURLY WARNINGS ON TC 09P. 3HOURLY SATELLITE BULLETINS ARE ISSUED FOR BOTH SYSTEMS.

01/0145UTC.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: OVER THE PAST TWELVE HOURS, TC 08S HAS SLOWED, REACHED A MAXIMUM EQUATORWARD POINT, AND THEN TURNED SOUTHWESTWARD, AS THE STEERING MECHANISM HAS SWITCHED FROM A WEAK STEERING PATTERN DOMINATED BY THE NEAR-EQUATORIAL RIDGE (NER) TO THE NORTH, TO ONE DOMINATED BY THE STR TO THE SOUTHWEST. THROUGH THE FORECAST PERIOD, THE STR IS EXPECTED TO SLOWLY DRIFT EASTWARD TO A POSITION DUE SOUTH OF TC 08S BY 72H. AS THE RIDGE PASSES BY TO THE SOUTH, TC 08S WILL FIRST TRACK SOUTHWESTWARD TRACK THROUGH 72H, THEN TURN TO A MORE WESTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST PERIOD. LANDFALL ALONG THE CENTRAL COAST OF MADAGASCAR IS EXPECTED PRIOR TO 120H. IN THE NEAR-TERM, PERSISTENT MODERATE TO STRONG EASTERLY SHEAR WILL LEAD TO A STEADY INTENSITY, OR SLIGHT WEAKENING THROUGH 24H. AFTER 36H, THE SHEAR IS FORECAST TO BEGIN TO SLACKEN, ALLOWING TC 08S TO REESTABLISH THE CONVECTIVE CORE, AND EMBARK UPON A PERIOD OF STEADY INTENSIFICATION. AND MESOSCALE UPPER-LEVEL ANTICYCLONE OR POINT SOURCE IS FORECAST TO DEVELOP OVER TOP OF THE SYSTEM AROUND 48H, WHICH SHOULD ALLOW FOR A FASTER RATE OF INTENSIFICATION TO PEAK OF 110 KNOTS/CAT 3 US BY 96H. IT IS POSSIBLE THAT A SLIGHTLY HIGHER PEAK COULD BE REACHED BETWEEN 96H AND LANDFALL, BUT SSTS ARE SLIGHTLY LOWER (27C) NEAR THE COAST, WHICH COULD LIMIT THE PEAK INTENSITY POTENTIAL. ONCE THE SYSTEM MAKES LANDFALL, IT WILL WEAK RAPIDLY AS IT INTERACTS WITH THE ROUGH TERRAIN OF CENTRAL MADAGASCAR.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THAT TC 08S CONTINUES TO STRUGGLE AGAINST PERSISTENT EASTERLY VERTICAL WIND SHEAR (VWS). THE CONVECTION ASSOCIATED WITH TC 08S HAS STEADILY WARMED OVER THE PAST TWELVE HOURS, BECOME INCREASINGLY DISORGANIZED AND EXHIBITS A SHARP UPSHEAR EDGE, INDICATIVE OF THE PERSISTENT SHEAR VECTOR. A 312052Z AMSR2 37GHZ MICROWAVE PASS SHOWED WELL DEFINED BANDING FEATURES AND A WEAK MICROWAVE EYE WITH A WEAK OR OPEN EYEWALL ON THE SOUTHERN SIDE. WHILE THE LOWER FREQUENCY DEPICTED A WELL DEFINED EYE FEATURE, THE SAME CANNOT BE SAID FOR THE UPPER 91GHZ FREQUENCY, WHICH SHOWED A COMPLETE LACK OF A EYEWALL STRUCTURE ACROSS THE ENTIRE SOUTHERN HEMISPHERE OF THE CIRCULATION. THE INITIAL POSITION IS ASSESSED WITH MEDIUM CONFIDENCE, RELIANT PRIMARILY UPON EXTRAPOLATION OF THE MICROWAVE EYE IN THE AMSR2 PASS. THE INITIAL INTENSITY REMAINS ASSESSED AT 75 KNOTS, BELOW THE PGTW T5.0 FIX INTENSITY, AND MORE IN LINE WITH THE FMEE T4.5 ESTIMATE, BUT WELL ABOVE THE ADT ESTIMATE OF T3.6. CONFIDENCE IS INCREASED IN LIGHT OF AN AMSR2 PASSIVE MICROWAVE WINDSPEED ESTIMATE OF 70-77 KNOTS, WITH THE HIGHEST WINDS PRESENT IN THE NORTHWESTERN QUADRANT. ANALYSIS REVEALS A MARGINALLY FAVORABLE ENVIRONMENT, WITH MODERATE (20-25 KNOTS) EASTERLY SHEAR BEING OFFSET BY MODERATE TO STRONG WEST AND POLEWARD OUTFLOW AND WARM SSTS.

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH 72H, WITH INCREASED UNCERTAINTY THEREAFTER. SPREAD BETWEEN OUTLIERS IS APPROXIMATELY 185KM AT 72H, AND 555KM AT 120H, WITH NAVGEM MARKING THE POLEWARD SIDE AND THE GFS ENSEMBLE MEAN THE EQUATORWARD MARGIN OF THE GUIDANCE ENVELOPE. THE ALONG-TRACK SPREAD IS MINIMAL THROUGH THE DURATION OF THE FORECAST. ENSEMBLE GUIDANCE SHOWS A GOOD DEAL OF SPREAD, PARTICULARLY AFTER 72H, WITH MEMBERS STRETCHING ACROSS EIGHT DEGREES OF LATITUDE ALONG THE COAST OF MADAGASCAR. WHILE THE ENSEMBLE MEANS FOR BOTH ECMWF AND GFS ARE IN CLOSE ALIGNMENT, THE LARGE SPREAD IN BOTH THE DETERMINISTIC AND ENSEMBLE MEMBERS LENDS LOW CONFIDENCE TO THE JTWC TRACK AFTER 72H. INTENSITY GUIDANCE IS MIXED, WITH THE COAMPS-TC REACHING A PEAK OF 125 KNOTS/CAT 4 US AT 96H, WHILE THE DECAY SHIPS SUGGESTS A PEAK AS LOW AS 80 KNOTS/CAT 1 US AND THE HWRF PEAKING AT 90 KNOTS/CAT 2 US CLOSER TO 72H. THE JTWC FORECAST TRACKS THE HWRF THROUGH 36H, THEN IS ABOVE ALL BUT THE COAMPS-TC GUIDANCE THEREAFTER. CONFIDENCE IS LOW THROUGH THE ENTIRE FORECAST.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 09P HAS CONTINUED TO STRUGGLE TO CONSOLIDATE A WELL DEFINED LOW LEVEL CORE. DRY AIR ENTRAINMENT IN THE MID-LEVELS COMBINED WITH PERSISTENT, THOUGH DECREASING, SOUTHEASTERLY SHEAR BEING THE PRIMARY LIMITED FACTORS TO CONSOLIDATION AND DEVELOPMENT. TC 09P IS FORECAST TO CONTINUE TO TRACK GENERALLY EASTWARD FOR THE NEXT 12 TO 24 HOURS ALONG THE SOUTHWEST PERIPHERY OF THE NER CENTERED TO THE NORTHEAST. THE SYSTEM WILL GRADUALLY TURN ONTO A MORE SOUTHEASTWARD TRACK AFTER 24H AS THE SYSTEM TRACKS ALONG THE GRADIENT BETWEEN THE NER AND A DEVELOPING DEEP CUTOFF LOW WHICH IS EXPECTED TO DEVELOP JUST SOUTH OF NEW CALEDONIA BY 48H. IN THE NEAR-TERM TC 09P IS NOT EXPECTED TO INTENSIFY, MAINTAINING CURRENT INTENSITY AS IT STRUGGLES AGAINST THE MID-LEVEL DRY AIR AND PERSISTENT SHEAR. AFTER 36H THE SYSTEM WILL MOVE INTO A MORE FAVORABLE OUTFLOW ENVIRONMENT, TAPPING INTO STRONGER DIVERGENT POLEWARD OUTFLOW AND DECREASED SHEAR, WHILE THE ATMOSPHERE MOISTENS SIMULTANEOUSLY, ALLOWING FOR STEADY INTENSIFICATION TO A PEAK OF 55 KNOTS BY 96H.

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS AN ELONGATED SYSTEM WITH ASYMMETRICAL LOW LEVEL BANDS AND A REGION OF DEEP FLARING CONVECTION NEAR THE ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC). A 010020Z GPM 37GHZ MICROWAVE IMAGE DEPICTED THE DISORGANIZED STRUCTURE TO GOOD EFFECT. A FALSE MICROWAVE EYE-LIKE FEATURE IS EVIDENT FAR TO THE NORTHWEST, BURIED UNDER THE FLARING CONVECTIVE ACTIVITY, WHILE A WEAKER LOW EMISSIVITY REGION SURROUNDED BY SHALLOW CURVED BANDING IS PRESENT FURTHER TO THE SOUTHEAST. THIS FEATURE PROVIDED SUPPORT TO PLACEMENT OF THE INITIAL POSITION, HOWEVER IN LIGHT OF THE WEAK NATURE OF THE SIGNATURE AND THE OVERALL ELONGATED CENTER AND THE LARGE SPREAD IN THE AGENCY FIX POSITIONS, THE INITIAL POSITION IS ASSESSED WITH LOW CONFIDENCE. THE INITIAL INTENSITY REMAINS ASSESSED AT 35 KNOTS, WITH MEDIUM CONFIDENCE, ABOVE THE BULK OF THE AGENCY CURRENT INTENSITY ESTIMATES, BUT IN LINE WITH THE OBJECTIVE ADT ESTIMATES OF T2.6. ANALYSIS REVEALS A MARGINAL ENVIRONMENT CHARACTERIZED BY LOW SOUTHEASTERLY VERTICAL WIND SHEAR (VWS) AND WARM SSTS OFFSET BY GENERALLY WEAK POLEWARD OUTFLOW ALOFT AND ENTRAINMENT OF MID-LEVEL DRY AIR FROM THE SOUTH.

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE, WHILE STILL SHOWING A FAIR AMOUNT OF SPREAD, HAS COME INTO BETTER AGREEMENT ON THE OVERALL TRACK, AT LEAST THROUGH 120H. THE MODEL SPREAD DOES INCREASE MODERATELY AFTER 24H, TO 370KM AT 72H AND 880KM AT TAU 120H BETWEEN UKMET ON THE POLEWARD SIDE AND GFS ON THE EQUATORWARD. CONSISTENT WITH THE PREVIOUS RUN, THE REMAINDER OF THE GUIDANCE PACKAGE REMAINS IN A SMALLER ENVELOPE WITH THE CONSENSUS MEAN MARKING THE SOUTHERN EDGE OF THIS SMALLER ENVELOPE. ENSEMBLE GUIDANCE MEANS REMAIN CONSISTENT WITH ONE ANOTHER BUT ALSO SHOW A LARGE AMOUNT OF SPREAD, WITH THE MAJORITY OF THE GFS ENSEMBLE MEMBERS FAVORING A TRACK MORE EQUATORWARD TOWARDS VANUATU. THE JTWC FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST, ON THE NORTHERN EDGE OF THE TIGHTER GROUPING OF MODELS, CLOSEST TO THE ECMWF ENSEMBLE MEAN, WITH LOW CONFIDENCE DUE TO THE UNCERTAINTY IN THE INITIAL POSITION AND LARGE SPREAD IN BOTH THE DETERMINISTIC AND ENSEMBLE GUIDANCE. INTENSITY GUIDANCE REMAINS MIXED, WITH A GUIDANCE SUGGESTING A PEAK BETWEEN 40 AND 75 KNOTS. THE JTWC FORECAST LIES VERY CLOSE TO THE HWRF AND CONSENSUS MEAN SOLUTIONS, WITH LOW CONFIDENCE.