WTPN21 PGTW 220330
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
160 NM EITHER SIDE OF A LINE FROM 9.5N 115.3E TO 12.0N 110.7E
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 220330Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 9.8N 114.8E. THE SYSTEM IS MOVING WESTWARD AT 05 KNOTS.

2. REMARKS: THE AREA OF CONVECTION (INVEST 99W) PREVIOUSLY LOCATED AT 
9.9N 115.3E IS NOW LOCATED NEAR 9.8N 114.8E, APPROXIMATELY 464 NM SW OF 
MANILA. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A PERSISTENT 
PLUME OF DEEP CONVECTION FLARING ON THE WEST SIDE OF AN AREA OF LOW LEVEL 
CONVERGENCE. A 21/2250Z SSMI/S 37 GHZ IMAGE DEPICTS FORMATIVE BANDING 
CURVED AROUND THE WESTERN EDGE. VIGOROUS NORTHERLY LOW LEVEL FLOW 
THROUGHOUT THE WESTERN SOUTH CHINA SEA IS EXPECTED TO BEGIN WRAPPING 
AROUND THE AREA OF LOW PRESSURE ASSOCIATED WITH 99W, ESTABLISHING A LOW 
LEVEL CIRCULATION. ANALYSIS REVEALS A FAVORABLE ENVIRONMENT FOR 
DEVELOPMENT WITH DIFFLUENCE ALOFT, MODERATE POLEWARD OUTFLOW, LOW TO 
MODERATE VERTICAL WIND SHEAR (15-20 KTS), AND WARM SEA SURFACE 
TEMPERATURES (28-29C). GLOBAL MODELS ARE COMING INTO GOOD AGREEMENT THAT 
99W WILL BECOME THE DOMINANT CENTER OF WHAT HAS BEEN A BROAD AREA OF LOW 
PRESSURE THROUGHOUT THE EASTERN SOUTH CHINA SEA, FOREGOING THE 
DEVELOPMENT OF THE PREVIOUSLY IDENTIFIED CENTER ASSOCIATED WITH 98W. THE 
ENSEMBLES SHOW A GENERALLY SLOW, NORTHWESTWARD MOTION IN THE NEXT 12-36 
HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 18 TO 23 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 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 
230330Z.//
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