WTPS21 PGTW 031830
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 99P)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 15.1S 163.9E TO 20.3S 164.1E
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 23 TO 32 KNOTS. METSAT
IMAGERY AT 031800Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 15.7S 164.0E. THE SYSTEM IS MOVING EAST-NORTHEASTWARD AT 04
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 99P) PREVIOUSLY LOCATED 
NEAR 17.1S 164.6E IS NOW LOCATED NEAR 15.7S 164.0E, APPROXIMATELY 
276 NM WEST-NORTHWEST OF PORT VILA, VANUATU. ANIMATED MULTISPECTRAL 
SATELLITE IMAGERY DEPICTS AN OBSCURED LOW-LEVEL CIRCULATION CENTER 
(LLCC) WITH DEEP CONVECTION FLARING TO THE NORTHWEST AND SOUTHEAST 
OF THE ASSESSED LLCC. A 031433Z AMSR2 89GHZ MICROWAVE IMAGE SHOWS 
FRAGMENTED, FORMATIVE BANDING  OVER THE NORTHWESTERN PORTIONS OF 99P 
WITH WEAKER CONVECTIVE BANDING BEGINNING TO DEVELOP ON THE 
SOUTHEASTERN SIDE. A 031123Z PARTIAL ASCAT-C IMAGE SHOWS HALF OF A 
CIRCULATION WITH BROAD WIND FIELDS OF 15-20 KNOTS AND EMBEDDED AREAS 
OF 20-25 KNOTS OVER THE SOUTHWEST AND NORTHERN PORTIONS WRAPPING 
TOWARDS THE LLCC. UPPER-LEVEL ANALYSIS REVEALS EXTENSIVE POLEWARD 
AND EQUATORWARD OUTFLOW, LOW TO MODERATE (10-20 KNOT) VERTICAL WIND 
SHEAR, AND A ZESTY 29-30C SEA SURFACE TEMPERATURE, PAINT THE PICTURE 
OF A VERY CONDUCIVE ENVIRONMENT FOR TROPICAL DEVELOPMENT. 
DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE SHOWS THAT 99P WILL LIKELY 
DRIFT IN A QUASISTATIONARY FASHION OVER THE NEXT FEW HOURS BUT 
ULTIMATELY TURN SOUTHWESTWARD WITHIN THE NEXT DAY AS THE STEERING 
RIDGE SHIFTS TO THE EAST. INTENSITY GUIDANCE IS IN AGREEANCE ON A 
STEADY RISE IN INTENSITY, WITH 99P REACHING TROPICAL STORM STATUS 
WITHIN 12 TO 24 HOURS WITH ADDITIONAL RAPID INTENSIFICATION 
THEREAFTER AS IT MAKES ITS SOUTHERLY TURN. MAXIMUM SUSTAINED SURFACE 
WINDS ARE ESTIMATED AT 23 TO 32 KNOTS. MINIMUM SEA 
LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1004 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 
041830Z.
//
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