WTPN22 PHNC 291330 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 90E)// REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/290821Z JUL 21// AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTPN21 PHNC 290830)// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 120 NM EITHER SIDE OF A LINE FROM 11.7N 104.5W TO 12.3N 109.9W WITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFY ISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME. WINDS IN THE AREA ARE ESTIMATED TO BE 18 TO 23 KNOTS. METSAT IMAGERY AT 291200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 12.0N 106.8W. THE SYSTEM IS MOVING WESTWARD AT 10 KNOTS. 2. REMARKS: AN AREA OF CONVECTION HAS PERSISTED NEAR 12.0N 106.8W, APPROXIMATELY 1368 NM SOUTH-SOUTHEAST OF SAN DIEGO, CALIFORNIA. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) AND A 290838Z AMSR-2 MICROWAVE IMAGE DEPICT WEAK CONVECTIVE BANDING OVER THE NORTHERN SEMI-CIRCLE WRAPPING INTO A CONSLIDATING LOW LEVEL CIRCULATION (LLC). EIR AND MICROWAVE IMAGERY ALSO REVEAL MOST OF THE CONVECTION DISPLACED IN THE SOUTHERN SEMI-CIRCLE. UPPER-LEVEL ANALYSIS INDICTATES A FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR (5-10KT), GOOD EQUATORWARD OUTFLOW, AND WARM SEA SURFACE TEMPERATURES (29-30C). MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 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 HIGH. 3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 301330Z. 4. SEE REF A FOR DETAILS ON A TROPICAL CYCLONE FORMATION ALERT LOCATED NEAR 13.8N 121.5W // NNNN