WTPN21 PHNC 261700 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91E)// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 150 NM EITHER SIDE OF A LINE FROM 12.5N 94.4W TO 13.5N 99.0W 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 20 TO 25 KNOTS. METSAT IMAGERY AT 221630Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 12.7N 94.5W. THE SYSTEM IS MOVING NORTHWESTWARD AT 05 KNOTS. 2. REMARKS: AN AREA OF CONVECTION (INVEST 91E) HAS PERSISTED NEAR 12.7N 94.5W, APPROXIMATELY 1720NM SOUTHEAST OF SAN DIEGO, CA. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A CONSOLIDATING LOW LEVEL CIRCULATION WITH IMPROVED CONVECTIVE BANDING WRAPPING INTO THE CENTER. A 261240Z SSMIS 91GHZ MICROWAVE IMAGE DEPICTS MULTIPLE FRAGMENTED CONVECTIVE BANDS OVER THE SOUTHEAST QUADRANT WRAPPING INTO THE NORTHWEST QUADRANT. A 261130Z SCATTEROMETER IMAGE DEPICTS A DEFINED, ELONGATED CIRCULATION WITH 15-20 KNOT WINDS AND POSSIBLY HIGHER WINDS IN THE NORTHERN QUADRANT. ENVIRONMENTAL ANALYSIS INDICATES ROBUST POLEWARD OUTFLOW ENHANCED BY A SUBTROPICAL JET TO THE NORTH WITH IMPROVED EQUATORWARD OUTFLOW, LOW VERTICAL WIND SHEAR (5-10 KNOTS) AND WARM SEA SURFACE TEMPERATURES (29-30C). GLOBAL MODELS INDICATE A WESTWARD TO NORTHWESTWARD TRACK OVER THE NEXT TWO DAYS WITH STEADY INTENSIFICATION. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 20 TO 25 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 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 271700Z.// NNNN