WTXS21 PGTW 011300 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91S) REISSUED// REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/010251Z APR 20// AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTXS21 PGTW 010300)// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 160 NM EITHER SIDE OF A LINE FROM 11.6S 68.4E TO 14.0S 73.8E 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 25 TO 30 KNOTS. METSAT IMAGERY AT 011200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 11.9S 69.1E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 09 KNOTS. 2. REMARKS: THE AREA OF CONVECTION (INVEST 91S) PREVIOUSLY LOCATED NEAR 13.3S 70.1E IS NOW LOCATED NEAR 11.9S 69.1E, APPROXIMATELY 338 NM SOUTHWEST OF DIEGO GARCIA. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 010125Z MHS NOAA-19 89GHZ MICROWAVE IMAGE DEPICT A BROAD LOW LEVEL CIRCULATION (LLC) WITH FLARING OVERHEAD CONVECTION, SURROUNDED BY FORMATIVE BANDING WRAPPING IN FROM THE NORTH AND WEST. A 010413Z METOP-A PARTIAL ASCAT IMAGE REVEALS AN ELONGATED LLC WITH ELEVATED (20 TO 30 KNOT) WINDS TO THE NORTH AND SOUTH. 91S IS CURRENTLY IN A FAVORABLE ENVIRONMENT WITH MARGINAL (15 TO 25 KNOT) VERTICAL WIND SHEAR BEING OFFSET BY NEAR RADIAL UPPER LEVEL OUTFLOW AND WARM (30 TO 31 CELSIUS) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 91S WILL TRACK SOUTHEASTWARD, BECOMING MORE SYMMETRIC AND INTENSIFYING WITHIN THE NEXT 36 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1000 MB. THE POTENTIAL FOR THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 HOURS IS HIGH. THIS SUPERSEDES REF A. 3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 021300Z.// NNNN