WTPN21 PGTW 170330MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W)//RMKS/1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN140 NM EITHER SIDE OF A LINE FROM 19.0N 122.1E TO 20.8N 116.1EWITHIN THE NEXT 12 TO 24 HOURS. AVAILABLE DATA DOES NOT JUSTIFYISSUANCE OF NUMBERED TROPICAL CYCLONE WARNINGS AT THIS TIME.WINDS IN THE AREA ARE ESTIMATED TO BE 15 TO 20 KNOTS. METSATIMAGERY AT 170000Z INDICATES THAT A CIRCULATION CENTER IS LOCATEDNEAR 19.2N 121.8E. THE SYSTEM IS MOVING NORTHWESTWARD AT 14KNOTS.2. REMARKS: THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED 18.4N 123.0E IS NOW LOCATED NEAR 19.2N 121.8E, APPROXIMATELY 215 NM NORTH OF APARRI, PHILIPPINES. ANIMATED MULTISPECTRAL SATELLITE IMAGERY AND A 162240Z SSMIS 91GHZ MICROWAVE IMAGE DEPICT A CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING CONVECTION ON THE EASTERN PERIPHERY OF THE DISTURBANCE. A 170101Z METOP-B ASCAT PASS SHOWS 20KT WINDS EMBEDDED TO THE NORTH OF THE LLCC. UPPER LEVEL ANALYSIS INDICATES A GOOD ENVIRONMENT FOR DEVELOPMENT AS 99W IS EXPERIENCING FAIR EQUATORWARD OUTFLOW, LOW VWS (< 15KTS), AND WARM SEA SURFACE TEMPERATURES (30-31C). MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 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 180330Z.//NNNN