WTPN21 PGTW 271100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
130 NM EITHER SIDE OF A LINE FROM 15.7N 141.7E TO 16.1N 137.8E
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 15 TO 20 KNOTS. METSAT
IMAGERY AT 270600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 15.8N 141.4E. THE SYSTEM IS MOVING NORTHWESTWARD AT 06
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED 
NEAR 15.4N 141.8E IS NOW LOCATED NEAR 15.8N 141.4E, APPROXIMATELY 
234 NM NORTHWEST OF GUAM. ANIMATED ENHANCED INFRARED IMAGERY (EIR) 
DEPICTS PERSISTENT CONVECTION CONSOLIDATING AND TURNING AROUND AN 
OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC). A 270656Z SSMIS 91GHZ 
SATELLITE IMAGE DEPICTS LOWER LEVEL BANDING WITH DEEP CONVECTION TO 
THE EASTERN PERIPHERY. INVEST 99W IS TRACKING NORTHWESTWARD AT 09 
KNOTS AND CURRENTLY IN A FAVORABLE ENVIRONMENT WITH MARGINAL UPPER 
LEVEL OUTFLOW, WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES AND LOW 
(10-15KT)VERTICAL WIND SHEAR. GLOBAL MODELS ARE IN GOOD AGREEMENT 
THAT 99W WILL GRADUALLY TRACK WESTWARD UNDER THE SUBTROPICAL RIDGE 
TO THE NORTH, STRENGTHEN AND CONSOLIDATE. MAXIMUM SUSTAINED SURFACE 
WINDS ARE ESTIMATED AT 15 TO 20 KNOTS. MINIMUM SEA LEVEL PRESSURE IS 
ESTIMATED TO BE NEAR 1007 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 
281100Z.//
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