WTPN21 PGTW 162230 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 160 NM EITHER SIDE OF A LINE FROM 11.1N 112.8E TO 10.2N 106.0E 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 161800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 10.8N 112.3E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 05 KNOTS. 2. REMARKS: THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED NEAR 9.5N 113.9E, IS NOW LOCATED NEAR 10.8N 112.3E, APPROXIMATELY 330 NM EAST OF HO CHI MINH CITY. ANIMATED ENHANCED INFRARED IMAGERY SHOWS PERSISTENT DEEP CONVECTION OVER THE LOW LEVEL CIRCULATION CENTER WITH FORMATIVE BANDING FEATURES. A 161938Z SSMI 85GHZ IMAGE ALSO SHOWS DEEP CONVECTION OVER THE LLCC ALONG WITH LOWER LEVEL BANDING BEGINNING TO FORM. 91W IS IN A MODERATELY FAVORABLE ENVIRONMENT WITH STRONG POLEWARD OUTFLOW, VERTICAL WIND SHEAR (VWS) OF 15 TO 20 KNOTS, AND SEA SURFACE TEMPERATURES (SST) OF 26 TO 28 DEGREES CELSIUS. GLOBAL MODELS ARE IN VERY GOOD AGREEMENT THAT 91W WILL TRACK WEST TOWARDS VIETNAM AND QUICKLY INTENSIFY. 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 172230Z. // NNNN