WTPN21 PGTW 192030
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W) REISSUED//
REF/A/MSG/JOINT TYPHOON WRNCEN PEARL HARBOR HI/182021ZDEC20//
AMPN/REF A IS A TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
140 NM EITHER SIDE OF A LINE FROM 10.1N 117.1E TO 9.6N 111.2E
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 191800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 10.0N 116.9E. THE SYSTEM IS MOVING WESTWARD AT 14 KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 8.7N 
123.2E IS NOW LOCATED NEAR 10.0N 116.9E, APPROXIMATELY 111 NM WEST 
OF PUERTO PRINCESA. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND 
A 191345Z GMI 89GHZ PARTIAL SATELLITE IMAGE DEPICT A CONSOLIDATING 
LOW LEVEL CIRCULATION CENTER WITH FLARING CONVECTION IN THE 
NORTHWEST QUADRANT. ENVIRONMENTAL ANALYSIS REVEALS INVEST 99W IS IN 
A MODESTLY FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH WARM (29-30C) 
SEA SURFACE TEMPERATURES AND STRONG OUTFLOW ALOFT, BUT MODERATE TO 
HIGH (20-25KTS) VERTICAL WIND SHEAR. GLOBAL MODELS ARE IN GOOD 
AGREEMENT THAT INVEST 99W WILL CONTINUE TO CONSOLIDATE AS IT TRACKS 
WESTWARD AND INTERACTS WITH THE NORTHEAST SURGE EVENT IN THE SOUTH 
CHINA SEA. 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 REMAINS HIGH. THIS SUPERSEDES REF A. 
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 
202030Z.//
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