WTPN21 PGTW 030930
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 96W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 21.0N 117.8E TO 24.1N 115.0E
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 17 TO 23 KNOTS. METSAT
IMAGERY AT 030600Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 21.2N 117.3E. THE SYSTEM IS MOVING NORTH-NORTHWESTWARD AT 06
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 96W) PREVIOUSLY LOCATED NEAR 
20.8N 117.3E IS NOW LOCATED NEAR 20.2N 117.3E, APPROXIMATELY 186 NM EAST-
SOUTHEAST OF HONG KONG. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) 
AND A RECENT MICROWAVE PASS DEPICT A RAPIDLY CONSOLIDATING LOW-LEVEL 
CIRCULATION (LLC) BURIED BENEATH DEEP CONVECTIVE BANDING AND CIRRUS BLOW 
OFF OVER THE SOUTH AND EAST QUADRANTS OF INVEST 96W. A 030806Z SSMIS 
91GHZ MICROWAVE SHOWS THE WESTERN AND SOUTHERN DEEP CONVECTIVE BANDS 
WRAPPING TOWARDS AN IMPROVING, IF SOMEWHAT STILL ILL DEFINED LLCC. 
ENVIRONMENTAL ANALYSIS IS FAVORABLE FOR DEVELOPMENT OF 96W WITH MODERATE 
EQUATORWARD OUTFLOW, LOW (5-10 KNOT) VERTICAL WIND SHEAR, AND 30-31C SEA 
SURFACE TEMPERATURES.  FUNNELING OF THE NORTHERLY WINDS DOWN THE TAIWAN 
STRAIT IS ALSO IMPARTING SOME INCREASED CYCLONIC VORTICITY, HELPING THE 
LLCC TO CONSOLIDATE AND DECREASING THE TIMELINE OF DEVELOPMENT. LAND 
PROXIMITY HAS NOT BEEN MUCH OF A FACTOR IN SLOWING DOWN THE SPEED OF 
INTENSIFICATION BUT WILL PROVE A HINDRANCE TO DEVELOPMENT BEYOND TROPICAL 
DEPRESSION STRENGTH WITHIN ITS LIMITED TIME REMAINING OVER WATER.  
DETERMINISTIC AND ENSEMBLE GUIDANCE SUPPORTS AN IMMINENT TURN TO THE 
NORTHWEST, WITH THE SYSTEM EXPECTED TO MAKE LANDFALL EAST OF HONG KONG IN 
THE NEXT 18-24 HOURS. INTENSITY GUIDANCE SHOWS A SHORT PERIOD OF 
INTENSIFICATION PRIOR TO MAKING LANDFALL, FOLLOWED BY RAPID DISSIPATION 
ONCE ASHORE. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED AT 17 TO 23 
KNOTS. MINIMUM SEA LEVEL PRESSURE IS ESTIMATED TO BE NEAR 1005 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 
040930Z.
//
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