ABIO10 PGTW 271800 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE INDIAN /OCEAN 271800Z-281800ZDEC2020// REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/270751ZDEC2020// AMPN/REF A IS A TROPICAL CYCLONE WARNING.// 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 27DEC20 0600Z, TROPICAL CYCLONE 07S (CHALANE) WAS LOCATED NEAR 18.1S 47.6E, APPROXIMATELY 48 NM NORTH OF ANTANANARIVO, MADAGASCAR, AND HAD TRACKED WESTWARD AT 11 KNOTS OVER THE PAST SIX HOURS. MAXIMUM SUSTAINED SURFACE WINDS WERE ESTIMATED AT 25 KNOTS GUSTING TO 35 KNOTS. SEE REF A (WTXS31 PGTW 270900) FOR FURTHER DETAILS. (2) NO OTHER TROPICAL CYCLONES. B. TROPICAL DISTURBANCE SUMMARY: (1) THE AREA OF CONVECTION (INVEST 93S) PREVIOUSLY LOCATED NEAR 10.9S 92.4E, IS NOW LOCATED NEAR 10.7S 91.8E, APPROXIMATELY 306 NM WEST-NORTHWEST OF THE COCOS ISLANDS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 271221Z 91GHZ SSMIS IMAGE DEPICT A BROAD LOW LEVEL CIRCULATION WITH SHEARED CONVECTION TO THE SOUTHWEST. A 271547Z ASCAT-C IMAGE SHOWS A DEFINED CIRCULATION WITH 20 KNOT WINDS WRAPPING IN FROM THE NORTH. INVEST 93S IS CURRENTLY IN A MARGINALLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH WARM (29-30C) SEA SURFACE TEMPERATURES, GOOD POLEWARD OUTFLOW ALOFT, AND MODERATE TO STRONG (15-25 KNOTS) VERTICAL WIND SHEAR. GLOBAL MODELS ARE IN GENERAL AGREEMENT THAT INVEST 93S WILL TRACK GENERALLY WESTWARD WITH LITTLE TO NO INTENSIFICATION OVER THE NEXT 24 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 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 REMAINS LOW. (2) NO OTHER SUSPECT AREAS. C. SUBTROPICAL SYSTEM SUMMARY: NONE. NNNN