ABIO10 PGTW 071800 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE INDIAN /OCEAN/071800Z-081800ZAPR2021// REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/071352ZAPR2021// REF/B/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/071351ZAPR2021// NARR/REFS A AND B ARE TROPICAL CYCLONE WARNINGS.// 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 07APR21 1200Z, TROPICAL CYCLONE 27S (TWENTYSEVEN) WAS LOCATED NEAR 16.4S 105.9E, APPROXIMATELY 578 NM NORTHWEST OF LEARMONTH, AUSTRALIA, AND HAD TRACKED EASTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. MAXIMUM SUSTAINED SURFACE WINDS WERE ESTIMATED AT 40 KNOTS GUSTING TO 50 KNOTS. SEE REF A (WTXS32 PGTW 071500) FOR FURTHER DETAILS. (2) AT 07APR21 1200Z, TROPICAL CYCLONE 26S (SEROJA) WAS LOCATED NEAR 14.9S 115.9E, APPROXIMATELY 456 NM NORTH-NORTHEAST OF LEARMONTH, AUSTRALIA, AND HAD TRACKED SOUTHWESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. MAXIMUM SUSTAINED SURFACE WINDS WERE ESTIMATED AT 45 KNOTS GUSTING TO 55 KNOTS. SEE REF B (WTXS31 PGTW 071500) FOR FURTHER DETAILS. (3) NO OTHER TROPICAL CYCLONES. B. TROPICAL DISTURBANCE SUMMARY: (1) THE AREA OF CONVECTION (INVEST 91S) PREVIOUSLY LOCATED NEAR 9.7S 91.4E IS NOW LOCATED NEAR 9.8S 91.9E, APPROXIMATELY 326 NM NORTH-NORTHWEST OF COCOS ISLANDS, AUSTRALIA. ANIMATED ENHANCED INFRARED IMAGERY AND A PARTIAL 071501Z AMSU-B 89 GHZ MICROWAVE PASS REVEAL DISORGANIZED BANDING WITH CYCLING CONVECTION TO THE SOUTH-SOUTHWEST OF A BROAD LOW LEVEL CIRCULATION (LLC). INVEST 91S IS IN A MARGINAL ENVIRONMENT FOR TROPICAL DEVELOPMENT WITH GOOD POLEWARD OUTFLOW ALOFT AND WARM (29-30C) SEA SURFACE TEMPERATURES OFFSET BY STRONG (25-30KTS) VERTICAL WIND SHEAR (VWS). GLOBAL MODELS ARE IN GOOD AGREEMENT THAT INVEST 91S WILL CONSOLIDATE AND INTENSIFY OVER THE NEXT 24-48 HOURS AS IT TRACKS TO THE SOUTHEAST UNDER AN AREA OF WEAK (10-20KTS) VWS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS REMAINS LOW. (2) NO OTHER SUSPECT AREAS. C. SUBTROPICAL SYSTEM SUMMARY: NONE.// NNNN