WTPN21 PGTW 290730 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 90W)// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 160 NM EITHER SIDE OF A LINE FROM 6.0N 148.7E TO 10.5N 143.8E 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 15 TO 20 KNOTS. METSAT IMAGERY AT 290600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 6.2N 148.4E. THE SYSTEM IS MOVING NORTHWESTWARD AT 04 KNOTS. 2. REMARKS: AN AREA OF CONVECTION (INVEST 90W) HAS PERSISTED NEAR 6.2N 148.4E, APPROXIMATELY 478 NM SOUTH-SOUTHEAST OF GUAM. ANIMATED MULTISPECTRAL SATELLITE IMAGERY, SUPPORTED BY A 290637Z SSMIS F-16 91GHZ MICROWAVE IMAGE, DEPICTS DEEP CONVECTION CONSOLIDATING OVER A RAPIDLY TIGHTENING LOW LEVEL CIRCULATION CENTER (LLCC) WITH FORMATIVE DEEP CONVECTIVE BANDING WRAPPING IN FROM THE EAST AND SOUTH. A 290006Z METOP-C ASCAT PASS REVEALS TIGHT TROUGHING WITH AN EXTENSIVE SWATH OF HIGHER (20 TO 30 KNOTS) WINDS TO THE SOUTH BUT WITH WINDS OF ONLY 5-10 KNOTS ON NORTHERN SIDE OF THE BROAD CIRCULATION. 90W IS CURRENTLY IN A FAVORABLE ENVIRONMENT WITH EXCELLENT EQUATORWARD OUTFLOW AND VERY WARM (30 TO 31 CELSIUS) SEA SURFACE TEMPERATURES BEING SLIGHTLY OFFSET BY MODERATE (15 TO 25 KNOT) VERTICAL WIND SHEAR. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 90W WILL TRACK GENERALLY NORTH-NORTHWESTWARD, QUICKLY INTENSIFYING TO WARNING THRESHOLD OVER THE NEXT 48 HOURS OR LESS. 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 300730Z.// NNNN