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 WEAK, FULLY EXPOSED, AND 
RAGGED LOW LEVEL CIRCULATION (LLC) WITH FLARING CONVECTION THAT IS 
OFFSET EASTWARD. FORMATIVE, ALBEIT FRAGMENTED, BANDING IS ALSO FLARING 
TO THE SOUTH. SCATTEROMETER DATA FROM A 220830Z PASS SHOWS 20-KNOT WIND 
BARBS 40-NM TO THE NORTH AND EAST OF THE LLC. ANALYSIS SHOWS THAT INVEST 
90W IS IN A MARGINALLY FAVORABLE ENVIRONMENT WITH STRONG POLEWARD 
OUTFLOW AND WARM (30C) SEA SURFACE TEMPERATURES OFFSET BY MODERATE TO 
STRONG (15-20 KNOT) RELATIVE VERTICAL WIND SHEAR AND SUBSIDENCE ALONG 
THE NORTHERN PERIPHERY CAUSED BY A MID-LATITUDE TROUGH. GLOBAL MODELS 
AGREE THAT 90W WILL DRIFT TO WEST-SOUTHWESTWARD OVER THE NEXT 24 HOURS 
WITH GRADUAL DEVELOPMENT THEN TURN MORE NORTHWARD 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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