TC 06S(ANNGGREK) peaked near CAT 4 US becoming extratropical after 24h// INVEST 93S upgraded// 3003utc

JTWC IS ISSUING IS ISSUING 12HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS TC 06S. 3HOURLY SATELLITE BULLETINS ARE ISSUED ON INVEST 93S.

FORECAST REASONING. SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TC 06S (ANGGREK) IS FORECAST TO CONTINUE TRACKING SOUTHWARD, AND EVENTUALLY SOUTHEASTWARD THROUGH TAU 12 AS THE CYCLONE IS PREDOMINANTLY STEERED BY THE WELL-ESTABLISHED STEERING RIDGE DIRECTLY TO THE EAST AND RECEDES IN RESPONSE TO AN EASTWARD PROGRESSING MID-LATITUDE LONGWAVE TROUGH. THE ENVIRONMENT IS EXPECTED TO BECOME INCREASINGLY UNFAVORABLE AS THE TROPICAL CYCLONE CONTINUES GENERALLY TO THE SOUTHEAST THROUGH TAU 36, AS VERTICAL WIND SHEAR (VWS) ASSOCIATED WITH THE WESTERLIES SIGNIFICANTLY INCREASES TO GREATER THAN 40 KTS BY TAU 12 AND SEA SURFACE TEMPERATURES DECREASE TO BELOW 26C DURING THE SAME FORECAST PERIOD. AT TAU 36 TC 06S IS EXPECTED TO BEGIN THE EXTRA-TROPICAL TRANSITION (ETT) AND CONTINUE EASTWARD ALONG THE WESTERLIES, EVENTUALLY BECOMING COMPLETELY EXTRA- TROPICAL BY TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO REMAIN IN RELATIVELY TIGHT AGREEMENT THROUGH TAU 24, WITH A GRADUAL CROSS-TRACK SPREAD TO 115NM BY TAU 48, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST. INTENSITY GUIDANCE ASSOCIATED WITH TC 06S REMAINS AT A MEDIUM CONFIDENCE AS THE ETT IS EXPECTED TO OCCUR QUICKLY. STATISTICAL-DYNAMICAL GUIDANCE REFLECTS COMPETING AND UNFAVORABLE ENVIRONMENTAL CONDITIONS NEGATIVELY IMPACT ANY CHANCE FOR FURTHER DEVELOPMENT INTO TAU 48, WHILE STRONG VWS, COOLER SST, AND DRY AIR WILL RAPIDLY WEAKEN TC 06S.

THE AREA OF CONVECTION (INVEST 93S) PREVIOUSLY LOCATED NEAR 16.0S 64.3E IS NOW LOCATED NEAR 17.6S 64.4E, APPROXIMATELY 136 NM NORTH-NORTHEAST OF PORT MATHURIN. ENHANCED INFRARED SATELLITE IMAGERY AND A 291216Z SSMIS 91GHZ MICROWAVE SATELLITE IMAGERY DEPICTS AN AREA OF FLARING AND SLOWLY CONSOLIDATING CONVECTION AND SHALLOW BANDING WRAPPING INTO THE LLCC. UPPER LEVEL ANALYSIS DEPICTS A MARGINALLY FAVORABLE ENVIRONMENT WITH MODERATE TO HIGH (20-25 KNOTS) VERTICAL WIND SHEAR, OFFSET BY WARM (29C) SEA SURFACE TEMPERATURES (SST) AND GOOD UPPER LEVEL DIVERGENCE. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 93S WILL GENERALLY TRACK SOUTHEASTWARD AS IT MOVES OVER FAVORABLE CONDITIONS AND INTENSIFIES OVER THE NEXT 24 TO 36 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 23 TO 27 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1006 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO MEDIUM.

GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 93S WILL GENERALLY TRACK SOUTHEASTWARD AS IT MOVES OVER FAVORABLE CONDITIONS AND INTENSIFIES OVER THE NEXT 24 TO 36 HOURS.