WTPN21 PGTW 162030
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN 125 NM 
EITHER SIDE OF A LINE FROM 15.1N 111.0E TO 18.0N 108.3E 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 161800Z INDICATES THAT A 
CIRCULATION CENTER IS LOCATED NEAR 15.3N 110.9E. THE SYSTEM IS MOVING 
NORTH-NORTHWESTWARD AT 03 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED NEAR 
14.6N 110.9E IS NOW LOCATED NEAR 15.3N 110.9E, APPROXIMATELY 161 NM 
EAST-SOUTHEAST OF DANANG, VIETNAM. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY AND A 161746Z ATMS 88.2 GHZ MICROWAVE IMAGE DEPICT A PARTIALLY 
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH FLARING DEEP CONVECTION 
IN THE WESTERN PERIPHERY AND WEAK FORMATIVE BANDING WRAPPING INTO THE 
LLCC FROM THE NORTH. ENVIRONMENTAL ANALYSIS INDICATES THAT 99W IS IN A 
FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH ROBUST POLEWARD OUTFLOW 
ALOFT, LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR, AND WARM (28-29 
C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN GOOD AGREEMENT THAT 
99W WILL TRACK NORTH-NORTHWESTWARD AND CONTINUE TO DEVELOP OVER THE NEXT 
24-48 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 15 TO 20 
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 
172030Z.//
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