WTPN21 PGTW 170800
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91P)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 13.7S 171.8E TO 15.4S 170.0E
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 25 TO 30 KNOTS. METSAT
IMAGERY AT 170600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 13.8S 171.9E. THE SYSTEM IS MOVING SOUTHEASTWARD AT 04
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91W) PREVIOUSLY LOCATED 
NEAR 13.7S 171.E IS NOW LOCATED NEAR 13.8S 171.9E, APPROXIMATELY 313 
NM NORTHEAST OF PORT VILA VANUATU. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY DEPICTS A CONSOLIDATING SYSTEM WITH FORMATIVE BANDING 
FEEDING IN FROM THE NORTHEAST. A 170703Z SSMIS MICROWAVE IMAGE SHOWS 
DEEP CONVECTION OVER THE LOW LEVEL CIRCULATION (LLC) AND CURVED, 
CONVECTIVE BANDING TO THE SOUTHEAST WRAPPING INTO THE EASTERN 
QUADRANT OF THE LLC. A 170714Z ASCAT (METOP-C) IMAGERY REVEALS 20-24 
KNOT WINDS TO THE SOUTH-SOUTHEAST OF THE LLC. UPPER-LEVEL ANALYSIS 
REVEALS A FAVORABLE ENVIRONMENT WITH LIGHT TO MODERATE (10-15 KNOTS) 
VERTICAL WIND SHEAR AND ROBUST RADIAL OUTFLOW. DYNAMIC MODELS 
INDICATE GRADUAL INTENSIFICATION OVER THE NEXT 24-36HRS AS THE 
SYSTEM TRACKS TO THE SOUTHWEST. MAXIMUM SUSTAINED SURFACE WINDS ARE 
ESTIMATED AT 25 TO 30 KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED 
TO BE NEAR 1006 MB WITH WARM (29-30 C) SEA SURFACE TEMPERATURES. 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
180800Z.//
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