WTPN21 PGTW 221400
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 90W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 18.1N 151.6E TO 17.4N 149.1E
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 17 TO 23 KNOTS. METSAT
IMAGERY AT 221200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 18.0N 151.5E. THE SYSTEM IS MOVING SOUTHWESTWARD AT 12
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 90W) PREVIOUSLY LOCATED NEAR 
19.4N 153.1E IS NOW LOCATED NEAR 18.0N 151.5E, APPROXIMATELY 482 NM 
NORTHEAST OF GUAM. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY AND A 
220730Z SSMIS 91GHZ MICROWAVE IMAGE DEPICT A FULLY EXPOSED, TIGHTLY 
WRAPPED LOW LEVEL CIRCULATION (LLC) WITH FLARING CONVECTION OFFSET TO THE 
SOUTH AND EAST THAT IS SLOWLY CREEPING INTO THE CENTER. SCATTEROMETER 
DATA FROM A 220830Z PASS SHOWS A SWATH OF 20 KNOTS OVER THE CIRCULATION. 
ANALYSIS SHOWS THAT INVEST 90W IS IN A FAVORABLE ENVIRONMENT FOR 
DEVELOPMENT DEFINED BY ROBUST POLEWARD OUTFLOW, WARM (30C) SEA SURFACE 
TEMPERATURES AND LOW VERTICAL WIND SHEAR (5-10KTS). GLOBAL MODELS AGREE 
THAT 90W WILL DRIFT WESTWARD TO WEST-SOUTHWESTWARD OVER THE NEXT 24 HOURS 
WITH GRADUAL DEVELOPMENT THEN TURN MORE NORTHERLY AFTER TAU 36. MAXIMUM 
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 17 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.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 
231400Z.
//
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