WTPN21 PGTW 172300
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 
100 NM EITHER SIDE OF A LINE FROM 19.2N 115.5E TO 21.1N 113.2E 
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 13 TO 18 KNOTS. METSAT IMAGERY AT 
172050Z INDICATES THAT A CIRCULATION CENTER IS LOCATED NEAR 19.4N 
115.4E. THE SYSTEM IS MOVING NORTH-NORTHWESTWARD AT 06 KNOTS.
2. REMARKS: THE AREA OF CONVECTION PREVIOUSLY LOCATED NEAR 18.4N 
115.4E IS NOW LOCATED NEAR 19.4N 115.4E, APPROXIMATELY 188 NM SOUTH-
SOUTHEAST OF HONG KONG. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY 
DEPICTS BANDING WITH FLARING CONVECTION OVERHEAD. A 171805Z AMSR2 
89GHZ MICROWAVE IMAGE REVEALS DEVELOPING LOW LEVEL BANDING WRAPPING 
INTO A LOW LEVEL CIRCULATION CENTER (LLCC) WITH CONVECTION OVER THE 
NORTHEAST QUADRANT. A 171225Z ASCAT-A IMAGE SHOWS A BROAD 
CIRCULATION WITH 15-20 KNOT WINDS IN THE NORTHEAST QUADRANT. 
ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE CONDITIONS FOR 
DEVELOPMENT WITH WESTWARD OUTFLOW ALOFT, LOW (10-15 KTS) VERTICAL 
WIND SHEAR, AND WARM (31-32C) SEA SURFACE TEMPERATURES. NUMERICAL 
MODEL GUIDANCE SHOWS INVEST 99W TRACKING NORTHWESTWARD AS IT 
CONSOLIDATES AND INTENSIFIES OVER THE NEXT 24 HOURS. MAXIMUM 
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 13 TO 18 KNOTS. MINIMUM SEA 
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1009 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 
182300Z.//
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