WTXS21 PGTW 152100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99S)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
140 NM EITHER SIDE OF A LINE FROM 12.1S 67.9E TO 13.4S 61.4E
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 28 TO 33 KNOTS. METSAT
IMAGERY AT 151800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 12.3S 67.5E. THE SYSTEM IS MOVING WEST-SOUTHWESTWARD AT 14
KNOTS.
2. REMARKS:
THE AREA OF CONVECTION (INVEST 99S) PREVIOUSLY LOCATED NEAR 11.9S 
68.9E IS NOW LOCATED NEAR 12.3S 67.5E, APPROXIMATELY 407NM  
SOUTHWEST OF DIEGO GARCIA. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY AND A 151152Z SSMIS 91GHZ MICROWAVE IMAGE SHOW A  
CONSOLIDATING LOW LEVEL CIRCULATION (LLC) OBSCURED BY FLARING 
CONVECTION SHEARED TO THE WEST WITH CONVECTIVE BANDING WRAPPING INTO 
THE CIRCULATION FROM THE SOUTH. A 1642Z ASCAT METOP-B IMAGE SHOWS 25-
30 KNOT WINDS WRAPPING INTO THE LLC FROM THE SW QUADRANT.  INVEST 
99S IS IN A FAVORABLE ENVIRONMENT FOR DEVELOPMENT WITH GOOD OUTFLOW 
ALOFT, LOW TO MODERATE (15-25KTS) VERTICAL  WIND SHEAR, AND WARM (28-
29C) SEA SURFACE TEMPERATURES. GLOBAL MODELS ARE IN GOOD AGREEMENT 
THAT INVEST 99S WILL CONTINUE TO TRACK WEST-SOUTHWESTWARD AS IT 
SLOWLY INTENSIFIES.  MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED 
AT 28 TO 33 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 
162100Z.//
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