WTPS21 PGTW 150600
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
A 130 NM RADIUS OF 18.1S 171.0W 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 29 TO 34 KNOTS. METSAT IMAGERY AT 150000Z INDICATES THAT A
CIRCULATION CENTER IS LOCATED NEAR 18.1S 171.0W. THE SYSTEM IS
MOVING NORTH-NORTHEASTWARD AT 04 KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 91P) PREVIOUSLY LOCATED NEAR 
18.9S 170.7W IS NOW LOCATED NEAR 18.1S 171.0W, APPROXIMATELY 85 NM 
NORTHWEST OF NIUE ISLAND. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) 
AND A 150058Z AMSR2 89GHZ MICROWAVE IMAGE DEPICT A RAPIDLY ORGANIZING LOW 
LEVEL CIRCULATION CENTER (LLCC) AND A BURST OF INTENSE CONVECTION WITH 
VERY COLD OVERSHOOTING TOPS, DIRECTLY OVER OR VERY NEAR THE ASSESSED LLCC 
POSITION. THE 37GHZ IMAGERY ALSO SHOWS WHAT SEEMS TO BE A MICROWAVE EYE 
PEAKING OUT FROM THE CONVECTION. THE SYSTEM IS CURRENTLY IN A MARGINALLY 
FAVORABLE ENVIRONMENT WITH AN UPPER LEVEL ANTICYCLONE TRYING TO FORM OVER 
THE SYSTEM TO AID IN THE LACK LUSTER OUTFLOW, LOW (5-10KT) VWS, AND WARM 
(28-29C) SST. THE SYSTEM IS EXPECTED TO CONTINUE ON A GENERALLY EASTWARD 
TRACK AND POSSIBLY DEVELOP IN THE UPCOMING DAY OR SO. THE DETERMINISTIC 
AND ENSEMBLE GUIDANCE ARE VERY NOT EXCITED ABOUT 91P AND SHOW LITTLE IN 
THE WAY OF DEVELOPMENT AND HAVE HEAVILY BACKED OFF ON THE INTENSIFICATION 
TREND. HOWEVER, DUE TO THE VERY COMPACT NATURE OF THE SYSTEM, LARGE AND 
RAPID CHANGES IN INTENSITY CAN BE EXPECTED AND IT REMAINS POSSIBLE THE 
SYSTEM MAY IN FACT REACH WARNING CRITERIA IN SHORT ORDER.  
MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 29 TO 34 KNOTS.
MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1002 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 
160600Z.//
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