WTPN21 PGTW 232130 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 98W)// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 190 NM EITHER SIDE OF A LINE FROM 10.2N 141.4E TO 18.0N 139.8E 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 18 TO 23 KNOTS. METSAT IMAGERY AT 232100Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 11.4N 140.1E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 07 KNOTS. 2. REMARKS: THE AREA OF CONVECTION (INVEST 98W) PREVIOUSLY LOCATED NEAR 11.2N 142.4E IS NOW LOCATED NEAR 11.4N 140.1E, APPROXIMATELY 298 NM WEST-SOUTHWEST OF GUAM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 231857Z SSMIS 91 GHZ MICROWAVE IMAGE DEPICT DEEP CONVECTION WRAPPING INTO A LOW LEVEL CIRCULATION CENTER (LLCC). ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS FOR DEVELOPMENT, WITH RADIAL OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), AND WARM (30-31 C) SEA SURFACE TEMPERATURES (SST). NUMERICAL MODELS AGREE THAT 98W WILL TRACK NORTHWARD AS IT INTENSIFIES OVER THE NEXT 24-36 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1007 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 242130Z. // NNNN