WTPN21 PGTW 200600
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 180 NM 
EITHER SIDE OF A LINE FROM 21.2N 127.6E TO 26.0N 123.0E 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 200530Z INDICATES THAT A 
CIRCULATION CENTER IS LOCATED NEAR 21.7N 127.1E. THE SYSTEM IS MOVING 
NORTHWESTWARD AT 07 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 90W) PREVIOUSLY LOCATED NEAR 
21.2N 127.6E IS NOW LOCATED NEAR 21.7N 127.1E, APPROXIMATELY 368 NM 
EAST-SOUTHEAST OF TAIPEI, TAIWAN. ANIMATED VISIBLE SATELLITE IMAGERY 
DEPICTS EXPOSED LOW LEVEL CLOUD LINES WRAPPING INTO A DEFINED 
CIRCULATION CENTER. CONVECTION IS FLARING IN THE SOUTHERN QUADRANT WITH 
ANVILS SHEARED TO THE SOUTH. A PARTIAL SCATTEROMETRY PASS SHOWS THE 
SYSTEM IS FORMING ADJACENT TO AN EXTENSIVE BELT OF 20-30 KNOT 
SOUTHEASTERLY WINDS TO THE EAST OF THE CIRCULATION. DETERMINISTIC AND 
PROBABILISTIC MODELS DEPICT A DEEPENING SYSTEM FORMING BESIDE THE WIDE 
SWATH OF VIGOROUS LOW-LEVEL FLOW AND HEADING GENERALLY NORTHWESTWARD. 
GLOBAL MODELS INDICATE SLOW DEVELOPMENT; HOWEVER, THEY DO INDICATE A 
POSSIBILITY FOR THE STRONGER WINDS TO THE EAST TO WRAP AROUND THE 
CIRCULATION. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE WITH 
MODERATE EQUATORWARD OUTFLOW ALOFT, MODERATE TO HIGH (20-25 KNOTS) 
VERTICAL WIND SHEAR AND WARM (30-31 C) SEA SURFACE TEMPERATURES CREATING 
A CONDUCIVE AREA FOR FURTHER DEVELOPMENT MOVING FORWARD. 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 
210600Z.//
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