WTPN21 PGTW 031900

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//

SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 98W)//

RMKS/

1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN

A 155 NM RADIUS OF 19.4N 119.4E 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 031800Z INDICATES THAT A

CIRCULATION CENTER IS LOCATED NEAR 19.5N 119.5E. THE SYSTEM IS

MOVING SOUTHWESTWARD AT 11 KNOTS.

2. REMARKS: THE AREA OF CONVECTION (INVEST 98W) PREVIOUSLY LOCATED NEAR

17.3N 123.0E IS NOW LOCATED NEAR 19.5N 119.5E, APPROXIMATELY 125 NM

SOUTH-SOUTHEAST OF VIGAN, PHILIPPINES. ENHANCED INFRARED (EIR) SATELLITE

IMAGERY DEPICTS A RAPIDLY ORGANIZING SYSTEM, WITH DEEP CONVECTION

DEVELOPING OVER AND AROUND THE ASSESSED LOW LEVEL CIRCULATION CENTER

(LLCC) WITH FRAGMENTED BANDING DEVELOPING ON THE OUTER PERIMETER OF THE

LLCC. PARTIAL ASCAT PASSES AT 031305Z AND 031356Z OUTLINE THE OUTERMOST

EDGES OF THE CIRCULATION, HOWEVER NOT THE CIRCULATION ITSELF WHICH

WAS IN THE NADIR GAP, AND INDICATED 20-25 KNOT WINDS WRAPPING AROUND

BOTH THE EASTERN AND WESTERN PERIPHERIES. ENVIRONMENTAL ANALYSIS

INDICATE FAVORABLE CONDITIONS FOR DEVELOPMENT WITH LOW (10-15 VWS),

GOOD OUTFLOW ALOFT AND WARM (30-31C) SEA SURFACE TEMPERATURE.

DETERMINISTIC MODELS SUCH AS GFS, ECMWF AND CMC AGREE ON DEVELOPMENT

WITHIN A 24-36 HOUR PERIOD, WHILE TAKING THE SYSTEM GENERALLY

NORTHEASTWARD, ALTHOUGH THE EXACT TRACK REMAINS SOMEWHAT UNCERTAIN.

ENSEMBLES DISAGREE ON TRACK AS WELL, ENCENS MOVES WEST-NORTHWEST AND

GEFS MOVES MORE NORTHEASTWARD, HOWEVER THEY DO AGREE ON DEVELOPMENT

TIMELINE WITHIN 24-36 HOURS.  MAXIMUM SUSTAINED SURFACE WINDS ARE

ESTIMATED AT 18 TO 23 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

041900Z.//

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