WTPS21 PGTW 251400
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/TROPICAL CYCLONE FORMATION ALERT//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
180 NM EITHER SIDE OF A LINE FROM 15.8S 163.8W TO 19.6S 166.4W
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 25 TO 30 KNOTS. METSAT
IMAGERY AT 251330Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 16.2S 164.6W. THE SYSTEM IS MOVING WEST-SOUTHWESTWARD AT 06
KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 15.9S
164.1W, IS NOW LOCATED NEAR 16.2S 164.6W, APPROXIMATELY 370 NM EAST-
SOUTHEAST OF PAGO PAGO, AMERICAN SAMOA. ANIMATED INFRARED IMAGERY
AND A 250540Z AMSU IMAGE DEPICT IMPROVING ORGANIZATION OVER THE PAST
12 HOURS WITH DEEP CONVECTION INCREASING IN AREAL EXTENT AND CURVED
CONVECTIVE BANDING OVER THE EASTERN SEMI-CIRCLE. A 250845Z PARTIAL
ASCAT IMAGE INDICATES 25-30 KNOT WINDS ASSOCIATED WITH THE IMPROVED
BANDING. UPPER-LEVEL ANALYSIS INDICATES AN IMPROVING ENVIRONMENT
WITH A DEVELOPING ANTICYCLONE OVER THE SYSTEM AND WEAK (DECREASING
TREND) VERTICAL WIND SHEAR. ANIMATED WATER VAPOR IMAGERY SHOWS A
WEAKENING UPPER-LEVEL TROUGH WEST OF THE SYSTEM WITH EXPANDING
OUTFLOW WEST OF THE CENTER WITH CONTINUED GOOD POLEWARD OUTFLOW
ENHANCED BY STRONG WESTERLIES SOUTH OF THE SYSTEM. MAXIMUM SUSTAINED
SURFACE WINDS ARE ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL
PRESSURE IS ESTIMATED TO BE NEAR 1001 MB. BASED ON THE IMPROVING
ENVIRONMENT AND CURVED CONVECTIVE BANDING, THE POTENTIAL FOR THE
DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24
HOURS IS GOOD.
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED
BY 261400Z.//
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