WTPS21 PGTW 092330 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99P)// RMKS/ 1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 200 NM EITHER SIDE OF A LINE FROM 19.0S 168.2W TO 23.0S 159.3W 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 27 TO 32 KNOTS. METSAT IMAGERY AT 091800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 19.2S 167.7W. THE SYSTEM IS MOVING EAST-SOUTHEASTWARD AT 09 KNOTS. 2. REMARKS: THE AREA OF CONVECTION (INVEST 99P) PREVIOUSLY LOCATED NEAR 19.2S 168.8E IS NOW LOCATED NEAR 19.2S 167.7E, APPROXIMATELY 126 NM EAST OF NIUE ISLAND. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 091725Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS A VERY COMPACT SYSTEM, WITH A CONSOLIDATING LOW LEVEL CIRCULATION (LLC) WITH DEEP CONVECTION COVERING THE POSSIBLE LOW LEVEL CIRCULATION CENTER (LLCC) AS WELL AS FORMATIVE BANDING ON THE NORTHERN AND SOUTHERN PERIPHERIES WRAPPING TOWARDS THE LLCC. A 092103Z ASCAT METOP-B SCATTEROMETRY PARTIAL PASS REVEALED A LARGE SWATH OF 15-20 KNOT WIND FIELDS ALONG THE WESTERN EDGES AND SMALLER FIELDS OF 25-30 KNOTS NEAR THE POSSIBLE LLCC. 99P CONTINUES TO BE DEEPLY EMBEDDED WITHIN THE SPCZ, AND ENVIRONMENTAL CONDITIONS ARE FAVORABLE WITH WARM (27-28C) SEA SURFACE TEMPERATURES, EXCELLENT UPPER LEVEL OUTFLOW (AIDED BY AN UPPER LEVEL ANTICYCLONE OVER THE SYSTEM AND THE TAIL END OF THE STJ TO THE SOUTHEAST), AND LOW TO MODERATE (10-15KT) VWS. DUE TO THE RAPID DEVELOPMENT OF THIS SYSTEM, MODEL GUIDANCE IS CURRENTLY LIMITED TO GLOBAL DETERMINISTIC MODELS, WHICH GENERALLY INDICATE AN EAST- SOUTHEASTWARD TRACK ALONG OR WITHIN A SURFACE TROF, WITH THE GFS AND NAVGEM BEING THE FRONTRUNNERS. NO MESOSCALE INTENSITY GUIDANCE IS AVAILABLE, BUT THE GLOBAL GFS AND NAVGEM CONCUR ON STEADY DEVELOPMENT OF THE SYSTEM INTO A TROPICAL CYCLONE OVER THE NEXT 24 TO 36 HOURS. HOWEVER, DUE TO THE EXTREMELY SMALL NATURE OF THE SYSTEM, THE GLOBAL FIELDS ARE LIKELY UNDERESTIMATING THE POTENTIAL OF THE SYSTEM TO DEVELOP AND WARNING CRITERIA COULD BE REACHED SOONER THAN ANTICIPATED. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 27 TO 32 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 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 102330Z.// NNNN