WTPN22 PHNC 281200
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 91C)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
140 NM EITHER SIDE OF A LINE FROM 9.5N 142.8W TO 14.2N 142.7W
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 28 TO 33 KNOTS. METSAT
IMAGERY AT 281200Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 12.0N 143.0W. THE SYSTEM IS MOVING WESTWARD AT 09 KNOTS.
2. REMARKS: AN AREA OF CONVECTION (INVEST 91C) HAS PERSISTED NEAR 12.0N 
143.0W, APPROXIMATELY 819 NM EAST-SOUTHEAST OF HILO. ENHANCED 
INFRARED SATELLITE IMAGERY (EIR) DEPICTS BUILDING RADIAL CONVECTION 
OBSCURING A LOW LEVEL CIRCULATION CENTER (LLCC). AN EARLIER 280601Z 
METOP-B ASCAT IMAGE REVEALS ENHANCED WINDS NORTH OF THE LLCC WITH 
RELATIVELY LIGHT WINDS OF 10-15 KNOTS ALONG THE SOUTHERN PERIPHERY. 
ENVIRONMENTAL ANALYSIS INDICATES A MARGINALLY FAVORABLE AREA FOR 
DEVELOPMENT DEFINED BY LOW VERTICAL WIND SHEAR (VWS) OF 10-15 KNOTS, 
MODERATE RADIAL OUTFLOW, AND WARM SEA SURFACE TEMPERATURES OF 27-28 C. 
DETERMINISTIC AND ENSEMBLE MODELS ARE IN AGREEMENT THAT 91C WILL TRACK 
WESTWARD WHILE STEADILY CONSOLIDATING AND INTENSIFYING OVER THE NEXT 24-
36 HOURS. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 28 TO 33 
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1008 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 
291200Z.//
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