WTPN21 PGTW 182030
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
200 NM EITHER SIDE OF A LINE FROM 8.5N 123.7E TO 10.4N 116.0E
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 182000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 8.7N 123.2E. THE SYSTEM IS MOVING WEST-NORTHWESTWARD AT 12
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED 
NEAR 6.8N 126.3E IS NOW LOCATED NEAR 8.7N 123.2E, APPROXIMATELY 
311NM EAST-SOUTHEAST OF PUERTO PRINCESA, PHILIPPINES. ANIMATED 
ENHANCED INFRARED SATELLITE IMAGERY AND AN 181736Z AMSR2 GW1 89GHZ 
MICROWAVE IMAGE DEPICT A SLOWLY CONSOLIDATING LOW LEVEL CIRCULATION 
(LLC) WITH FLARING CONVECTION SHEARED TO THE NORTHWEST QUADRANT. 
UPPER LEVEL ANALYSIS REVEALS THAT 99W IS IN A MARGINALLY FAVORABLE 
ENVIRONMENT FOR DEVELOPMENT WITH WARM SST (28-29C), MODERATE 
VERTICAL WIND SHEAR (15-20 KNOTS), AND STRONG POLEWARD OUTFLOW. 
GLOBAL MODELS INDICATE THE SYSTEM WILL INTENSIFY AS IT BEGINS TO TAP 
INTO A NORTHEAST SURGE EVENT AS THE SYSTEM CONTINUES TO TRACK WEST-
NORTHWESTWARD. 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 
192030Z.//
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