WDPN31 PGTW 100300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 05W WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 05W (DIANMU), LOCATED APPROXIMATELY 
390 NM SOUTH-SOUTHWEST OF SEOUL, SOUTH KOREA, HAS TRACKED NORTHWARD 
AT 13 KNOTS OVER THE PAST SIX HOURS. THE TS HAS INTENSIFIED A MODEST 
05 KNOTS OVER THE PAST 12 HOURS. DEEP CONVECTION HAS BEEN SEVERELY 
LIMITIED WITHIN THE WESTERN SEMICIRCLE DUE TO AN UPPER LEVEL TROUGH 
LOCATED NEAR SHANGHAI, CHINA. THIS LACK OF CONVECTION HAS KEPT 
DVORAK ESTIMATES LOW DESPITE A STRONG AND WELL-DEFINED LOW LEVEL 
CIRCULATION CENTER (LLCC) EVIDENT IN A 092243Z AMSUB MICROWAVE 
IMAGE. IN FACT, THERE IS SO LITTLE CONVECTION WITHIN THE WESTERN 
SEMICIRCLE THAT THE LLCC HAS BECOME PARTLY EXPOSED. THE OUTER RAIN 
BANDS ARE NOW BEGINNING TO AFFECT CHEJU AND SOUTHERN JAPAN. MORE 
RECENTLY DVORAK INTENSITY ESTIMATES FROM PGTW HAVE RISEN FROM A 3.0 
TO A 3.5 OVER THE PAST 12 HOURS, AND RJTD HAS INCREASED FROM 2.5 TO 
A 3.0 AS WELL. THIS INCREASE IS LIKELY IN RESPONSE TO SLIGHTLY 
IMPROVED POLEWARD OUTFLOW AHEAD OF A MID-LATITUDE TROUGH AND A 
SUBTLE WEAKENING OF THE TROUGH TO THE WEST.
3. FORECAST REASONING.
   A. THE FORECAST TRACK PHILOSOPHY HAS NOT CHANGED. 
   B. TS 05W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF A 
MID TO UPPER LEVEL STEERING RIDGE TO THE EAST. IT IS FORECAST TO
CREST THE RIDGE WITHIN 24 HOURS AND MAKE LANDFALL OVER SOUTH KOREA
AT 55 KNOTS. IT IS POSSIBLE THAT IT COULD MAKE LANDFALL STRONGER
THAN 55 KNOTS IF CONVECTION BEGINS TO BUILD WITHIN THE WESTERN SEMI-
CIRCLE AND/OR POLEWARD OUTFLOW IMPROVES AHEAD OF A FINGER OF THE
SUBTROPICAL JET. AFTER MAKING LANDFALL THE CYCLONE WILL WEAKEN AND 
BEGIN EXTRATROPICAL TRANSITION UNDER THE INFLUENCE OF STRONG UPPER 
LEVEL WESTERLIES AND A STATIONARY BAROCLINIC BOUNDARY. THE
CYCLONE WILL ACCELERATE THROUGH THE SEA OF JAPAN AND WILL BECOME
FULLY EXTRATROPICAL AFTER 12/0000Z. THE REMNANT EXTRATROPICAL LOW
WILL PASS SOUTH OF MISAWA AROUND TAU 72. MODEL GUIDANCE IS IN
EXCEPTIONAL AGREEMENT WITH THIS TRACK SCENARIO.//
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