ABPW10 PGTW 012030 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/SIGNIFICANT TROPICAL WEATHER ADVISORY FOR THE WESTERN AND /SOUTH PACIFIC OCEANS REISSUED/012030Z-020600ZSEP2021// REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI 011951ZSEP2021// AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT.// RMKS/ 1. WESTERN NORTH PACIFIC AREA (180 TO MALAY PENINSULA): A. TROPICAL CYCLONE SUMMARY: NONE. B. TROPICAL DISTURBANCE SUMMARY: NONE. C. SUBTROPICAL SYSTEM SUMMARY: (1) THE AREA OF CONVECTION (INVEST 93W) PREVIOUSLY LOCATED NEAR 24.9N 163.3E IS NOW LOCATED NEAR 26.1N 160.3E, APPROXIMATELY 538 NM NORTHWEST OF WAKE ISLAND. THE SYSTEM IS CURRENTLY CLASSIFIED AS A SUBTROPICAL DEPRESSION, GENERALLY CHARACTERIZED AS HAVING BOTH TROPICAL AND MID-LATITUDE CYCLONE FEATURES. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) AND A 011808Z SSMIS 91GHZ MICROWAVE IMAGE DEPICT FLARING CONVECTION WRAPPING INTO A CONSOLIDATING LOW LEVEL CIRCULATION (LLC). UPPER LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH GOOD POLEWARD OUTFLOW DUE TO ITS PROXIMITY TO AN UPPER LEVEL LOW, LOW TO MODERATE VWS (10-20 KTS) AND WARM SSTS (28-29C). AMSU THERMAL CROSS-SECTIONS, THE HIGHLY ASYMMETRIC WIND FIELD AND A RADIUS OF MAXIMUM WINDS GREATER THAN 100 NM ALL LEND SUPPORT TO THE CURRENT ASSESSMENT THAT INVEST 93W IS A SUBTROPICAL LOW. HOWEVER, THE SYSTEM IS EXHIBITING SIGNS OF TRANSITIONING TO A TROPICAL SYSTEM, WITH THE WIND FIELD BECOMING MORE SYMMETRIC AND THE RMW DECREASING. FULL TRANSITION TO A TROPICAL LOW IS POSSIBLE WITHIN THE NEXT 12 TO 24 HOURS. GLOBAL MODELS DO NOT DEPICT INTENSIFICATION BEYOND 24 HOURS. HOWEVER, THE ENVIRONMENT AND CURRENT CONDITIONS STILL ALLOW FOR THE POSSIBILITY OF DEVELOPMENT. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 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 IS UPGRADED TO HIGH. SEE REF A (WTPN21 PGTW 012000) FOR FURTHER DETAILS. (2) NO OTHER SUBTROPICAL SYSTEMS. 2. SOUTH PACIFIC AREA (WEST COAST OF SOUTH AMERICA TO 135 EAST): A. TROPICAL CYCLONE SUMMARY: NONE. B. TROPICAL DISTURBANCE SUMMARY: NONE. C. SUBTROPICAL SYSTEM SUMMARY: NONE. 3. JUSTIFICATION FOR REISSUE: UPGRADED AREA IN PARA. 1.C.(1) TO HIGH.// NNNN