WTPN21 PGTW 040630
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE FORMATION ALERT (INVEST 97W)//
RMKS/
1. FORMATION OF A SIGNIFICANT TROPICAL CYCLONE IS POSSIBLE WITHIN
120 NM EITHER SIDE OF A LINE FROM 19.3N 138.0E TO 26.7N 135.2E
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 040000Z INDICATES THAT A CIRCULATION CENTER IS LOCATED
NEAR 19.2N 138.3E. THE SYSTEM IS MOVING NORTH-NORTHWESTWARD AT 09
KNOTS.
2. REMARKS: THE AREA OF CONVECTION (INVEST 97W) PREVIOUSLY LOCATED NEAR 
17.6N 138.9E IS NOW LOCATED NEAR 19.2N 138.3E, APPROXIMATELY 370 NM 
SOUTH-SOUTHWEST OF IWO TO, JAPAN. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY (MSI) DEPICTS A DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) 
PARTIALLY OBSCURED BY MID- AND HIGH-LEVEL CLOUDS. DEEP CONVECTION HAS 
PERSISTED IN THE NORTHERN AND SOUTH-SOUTHWESTERN PERIPHERIES, WITH 
WEAKER BURSTS NEAR THE CENTER, REFLECTING AN IMPROVED CONVECTIVE 
SIGNATURE OVER THE PAST 12 HOURS. DRIER AIR IS WEDGED ALONG THE 
NORTHWESTERN PERIPHERY, LIMITING CONVECTION IN THAT AREA. A 040007Z 
METOP-C ASCAT PASS REVEALED A COMPACT CIRCULATION WITH ELEVATED WINDS 
NEAR THE CORE, INDICATING THAT THE SYSTEM IS ON THE VERGE OF BECOMING 
A TROPICAL DEPRESSION. OVERALL ENVIRONMENTAL CONDITIONS ARE ASSESSED 
AS MARGINALLY FAVORABLE WITH LOW TO MODERATE (15-20 KTS) VERTICAL WIND 
SHEAR, WARM (28-29 C) SEA SURFACE TEMPERATURES, GOOD EQUATORWARD 
UPPER-LEVEL OUTFLOW, AND A ROBUST AMOUNT OF MOISTURE IN THE AREA. 
GLOBAL MODELS ARE RELATIVELY CONSERVATIVE WITH DEVELOPMENT ON 97W, 
WITH THE GFS AND ECMWF DETERMINISTIC MODELS DEPICTING LIMITED 
ADDITIONAL DEVELOPMENT DURING THE NEXT 12 HOURS, BEFORE BROADENING OUT 
THE LLCC THEREAFTER. MULTIPLE ENSEMBLE SYSTEMS AND THESE DYNAMICAL 
MODELS AGREE ON 97W LARGELY HAVING A BROAD WIND FIELD WHILE 
ACCELERATING NORTHWESTWARD. MAXIMUM SUSTAINED SURFACE WINDS ARE ESTIMATED 
AT 18 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 
050630Z.//
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