WTPN21 PGTW 221130
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W) REISSUED//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/211221Z SEP 21//
AMPN/REF A IS TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
140 NM EITHER SIDE OF A LINE FROM 11.1N 151.6E TO 13.6N 146.6E
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 220600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 10.8N 149.6E. THE SYSTEM IS MOVING WESTWARD AT 07 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED 
NEAR 11.2N 151.5E IS NOW LOCATED NEAR 10.8N 149.6E. APPROXIMATELY 
326 NM EAST-SOUTHEAST OF GUAM. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY AND A 220621Z SSMIS 91GHZ IMAGE DEPICT AN ELONGATED AND 
BROAD LOW LEVEL CIRCULATION (LLC) PARTIALLY OBSCURED BY FLARING 
CONVECTION IN THE NORTH-NORTH WEST QUADRANT. POSITIONING OF THE 
PRECISE CIRCULATION CENTER IS MADE DIFFICULT DUE TO THE PRESENCE OF 
POTENTIALLY MULTIPLE CIRCULATION CENTERS WITHIN THE BROADER 
ROTATION, LENDING LOW CONFIDENCE TO THE INITIAL POSITION. 
ENVIRONMENTAL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT FOR 
DEVELOPMENT WITH A COMBINATION OF STRONG OUTFLOW ALOFT, LOW (10 KT) 
VERTICAL WIND SHEAR (VWS) AND VERY WARM (30-31C) SEA SURFACE 
TEMPERATURES (SST). GLOBAL MODELS ARE GOOD IN AGREEMENT THAT INVEST 
99W WILL CONTINUE TRACKING NORTHWESTWARD OVER THE NEXT 24-48 HOURS 
HOWEVER, THEY ARE SPLIT ON THE DEGREE OF DEVELOPMENT. GFS, ITS 
ENSEMBLE, AND NAVGEM CONTINUE TO BE THE MOST AGGRESSIVE, INDICATING 
RAPID CONSOLIDATION AND INTENSIFICATION, WITH 99W DEVELOPING WITHIN 
THE NEXT 12-24 HOURS. ECMWF AND ITS ENSEMBLE ARE MUCH MORE RESERVED, 
INDICATING LITTLE TO NO DEVELOPMENT UNTIL AFTER TAU 36, WELL TO THE 
WEST OF THE MARIANAS. 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. THIS SUPERSEDES 
REF A. 
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 
231130Z.
//
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