ABIO10 PGTW 152130 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE INDIAN OCEAN /REISSUED/152130Z-161800ZJAN2021// REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/151951ZJAN2021// REF/B/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/152051ZJAN2021// NARR/REF A IS A TROPICAL CYCLONE WARNING. REF B IS A TROPICAL CYCLONE FORMATION ALERT.// RMKS/ 1. NORTH INDIAN OCEAN AREA (MALAY PENINSULA WEST TO COAST OF AFRICA): A. TROPICAL CYCLONE SUMMARY: NONE. B. TROPICAL DISTURBANCE SUMMARY: NONE. C. SUBTROPICAL SYSTEM SUMMARY: NONE. 2. SOUTH INDIAN OCEAN AREA (135E WEST TO COAST OF AFRICA): A. TROPICAL CYCLONE SUMMARY: (1) AT 15JAN21 1800Z, TROPICAL CYCLONE 10S (TEN) WAS LOCATED NEAR 16.4S 94.1E, APPROXIMATELY 1590 NM EAST-SOUTHEAST OF DIEGO GARCIA, AND HAD TRACKED SOUTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. MAXIMUM SUSTAINED SURFACE WINDS WERE ESTIMATED AT 35 KNOTS GUSTING TO 45 KNOTS. SEE REF A (WTXS31 PGTW 152100) FOR FURTHER DETAILS. (2) NO OTHER TROPICAL CYCLONES. B. TROPICAL DISTURBANCE SUMMARY: (1) THE AREA OF CONVECTION (INVEST 99S) PREVIOUSLY LOCATED NEAR 11.9S 68.9E IS NOW LOCATED NEAR 12.3S 67.5E, APPROXIMATELY 407NM SOUTHWEST OF DIEGO GARCIA. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 151152Z SSMIS 91GHZ MICROWAVE IMAGE SHOW A CONSOLIDATING LOW LEVEL CIRCULATION (LLC) OBSCURED BY FLARING CONVECTION SHEARED TO THE WEST WITH CONVECTIVE BANDING WRAPPING INTO THE CIRCULATION FROM THE SOUTH. A 1642Z ASCAT METOP-B IMAGE SHOWS 25- 30 KNOT WINDS WRAPPING INTO THE LLC FROM THE SW QUADRANT. INVEST 99S IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH GOOD OUTFLOW ALOFT, LOW TO MODERATE (15-25KTS) VERTICAL WIND SHEAR, AND WARM (28- 29C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT INVEST 99S WILL CONTINUE TO TRACK WEST-SOUTHWESTWARD AS IT SLOWLY INTENSIFIES. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS UPGRADED TO HIGH. SEE REF B (WTXS21 PGTW 142100) FOR FURTHER DETAILS. (2) THE AREA OF CONVECTION (INVEST 90S) PREVIOUSLY LOCATED NEAR 14.2S 95.7E IS NOW THE SUBJECT OF A TROPICAL CYCLONE WARNING. SEE PARA. 2.A.(1) FOR FURTHER DETAILS. (3) NO OTHER SUSPECT AREAS. C. SUBTROPICAL SYSTEM SUMMARY: NONE. 3. JUSTIFICATION FOR REISSUE: UPGRADED AREA IN PARA. 2.B.(1) TO HIGH AND UPGRADED AREA 2.B.(2) TO WARNING STATUS.// NNNN