WTPN21 PGTW 260500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99W) REISSUED//
REF/A/JOINT TYPHOON WRNCEN PEARL HARBOR HI/250521Z OCT 21//
AMPN/REF IS TROPICAL CYCLONE FORMATION ALERT (WTPN21 PGTW 250530)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 11.2N 113.8E TO 12.7N 110.6E
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 18 TO 23 KNOTS. METSAT
IMAGERY AT 260000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 11.3N 111.7E. THE SYSTEM IS MOVING NORTHWESTWARD AT 04
KNOTS.
2. REMARKS: AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED 
NEAR 11.2N 113.7E IS NOW LOCATED NEAR 11.3N 111.7E, APPROXIMATELY 
295NM EAST HO CHI MINH, VIETNAM. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY (MSI) DEPICTS CURVED DEEP CONVECTIVE BANDING WRAPPING INTO A 
PARTIALLY-EXPOSED LLC SUPPORTED BY A 252321Z 91GHZ SSMIS IMAGE, AND 
A 2500157Z ASCAT PASS REVEALING A TIGHT SYMMETRICAL WIND FIELD WITH 
15-20 KNOTS ON THE EASTERN PERIPHERY, UNASSOCIATED WITH THE 25-30 
KNOT NORTHERLY SURGE TO THE WEST. ENVIRONMENTAL ANALYSIS INDICATES 
FAVORABLE CONDITIONS FOR DEVELOPMENT, WITH EQUATORWARD OUTFLOW, LOW 
(10-15 KTS) VERTICAL WIND SHEAR (VWS) AND WARM (29-30 C) SEA SURFACE 
TEMPERATURES (SST). ANTICIPATE A FIRST WARNING ON THIS SYSTEM. 
GLOBAL NUMERICAL MODELS ARE IN GOOD AGREEMENT THAT INVEST 99W WILL 
MAKE LANDFALL OVER VIETNAM WITHIN THE NEXT 36 HOURS.  MAXIMUM 
SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS. MINIMUM SEA 
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1006 MB. THE POTENTIAL FOR 
THE DEVELOPMENT OF A SIGNIFICANT TROPICAL CYCLONE WITHIN THE NEXT 24 
HOURS IS HIGH. THIS SUPERSEDES REF A. 
3. THIS ALERT WILL BE REISSUED, UPGRADED TO WARNING OR CANCELLED BY 
270500Z.
//
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