JTWC IS ISSUING 12HOURLY WARNINGS ON TC 13S(EMNATI) AND 3HOURLY SATELLITE BULLETINS ON TC 13S AND INVEST 97S.
SOUTHERN HEMISPHERE/SOUTH INDIAN OCEAN: TC 13S(EMNATI). WARNING 4 ISSUED AT 18/03UTC. CLICK ON THE IMAGERY BELOW TO ENLARGE IT.
FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 13S WILL BEGIN TURNING WEST-SOUTHWESTWARD WITHIN THE NEXT 12 HOURS AS IT TRACKS TOWARD A BREAK IN THE SUBTROPICAL RIDGE DUE TO AN APPROACHING MID-LATITUDE TROUGH FROM THE SOUTHWEST. THE SYSTEM WILL CONTINUE THIS GENERAL DIRECTION AND REACH A PEAK INTENSITY OF 95 KTS/CAT 2 US AROUND 72H. AFTERWARDS, LOW OCEAN HEAT CONTENT NEAR MADAGASCAR CAUSED BY UPWELLING DUE TO THE PASSAGE OF ANOTHER TROPICAL CYCLONE A FEW DAYS EARLIER, WILL LEAD TO A DECREASE IN INTENSITY, REACHING 80 KTS/CAT 1 US BY TAU 96H. BY 120H, THE CENTER OF THE SYSTEM WILL BE OVER CENTRAL MADAGASCAR, FURTHER DECREASING THE SYSTEM TO 65 KTS/CAT 1 US.
1322021700 141S 674E 45
1322021706 140S 658E 45
1322021712 139S 645E 55
1322021718 137S 637E 50
1322021800 134S 630E 55
1322021706 140S 658E 45
1322021712 139S 645E 55
1322021718 137S 637E 50
1322021800 134S 630E 55
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CIMSS ANALYSIS: FAVOURABLE OVER 24HOURS. CLICK ON THE IMAGERY BELOW TO ENLARGE IT.
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SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A CONSOLIDATING SYSTEM ATTEMPTING TO FORM AN SUSTAINED EYE WITHIN CENTRAL, FLARING CONVECTION. A 1747Z ASCAT-B IMAGE DEPICTS A WELL-DEFINED CIRCULATION 45-50 KT WINDS AT THE CENTER OF THE WIND FIELD. A 172137Z AMSR2 37GHZ IMAGE DEPICTS A MICROWAVE EYE FROM WHICH THE INITIAL POSITION IS EXTRAPOLATED AND LENDS SUPPORT TO THE PGTW FIX POSITION. THE INITIAL INTENSITY IS BASED ON AN AVERAGE OF THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES AND ADT.
MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT WITH ONLY A 185KM CROSS-TRACK SPREAD AT 96H EXCLUDING NVGM AS AN OUTLIER TO THE SOUTH. TC 13S WAS EXPECTED TO HAVE ALREADY TURNED SOUTH-SOUTHWEST, SO THE JTWC FORECAST TRACK IS PLACED JUST SLIGHTLY NORTH OF CONSENSUS TO OFFSET THIS. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT WITH HWRF AND GFS BOTH PEAKING INTENSITY AT 95 KTS AT 72H.
HWRF AT 17/18UTC: 98KNOTS AT +66H.
ECMWF ENSEMBLE AT 17/18UTC.
THE AREA OF CONVECTION (INVEST 97S) PREVIOUSLY LOCATED NEAR 20.7S 88.5E IS NOW LOCATED NEAR 24.6S 87.4E, APPROXIMATELY 1700KM SOUTHWEST OF THE COCOS ISLANDS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 180047Z SSMIS 91GHZ PARTIAL MICROWAVE IMAGE DEPICT LARGE FRONTAL BANDING ON THE EASTERN PORTION OF A BROAD, POORLY-DEFINED LOW LEVEL CIRCULATION (LLC). ENVIRONMENTAL ANALYSIS INDICATES MARGINAL DEVELOPMENT WITH ROBUST POLEWARD OUTFLOW AND WARM (27-28C) SEA SURFACE TEMPERATURES (SSTS) OFFSET BY MODERATE VERTICAL WIND SHEAR (15-20 KTS). ADDITIONALLY, THE SYSTEM WILL SOON BE ENTERING SSTS LESS THAN 26C. GLOBAL MODELS TO INCLUDE GFS, ECMWF, AND NAVGEM ARE IN AGREEMENT TRACKING THE SYSTEM SOUTHWARD OVER THE NEXT 24 TO 48 HOURS AND BEGINNING SUBTROPICAL TRANSITION AS IT ENTERS THE MID- LATITUDES. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 997 MB. IN VIEW OF THE UNFAVORABLE FORECAST FOR THIS SYSTEM, THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS DOWNGRADED TO MEDIUM.
GLOBAL MODELS TO INCLUDE GFS, ECMWF, AND NAVGEM ARE IN AGREEMENT TRACKING THE SYSTEM SOUTHWARD OVER THE NEXT 24 TO 48 HOURS AND BEGINNING SUBTROPICAL TRANSITION AS IT ENTERS THE MID- LATITUDES.
ECMWF ENSEMBLE AT 17/18UTC.
