WDPN31 PGTW 291500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W WARNING NR 17//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. ANIMATED SATELLITE AND RADAR IMAGERY INDICATE THAT TROPICAL 
STORM 09W HAD TEMPORARILY DECOUPLED FROM THE UPPER LEVEL STORM 
STRUCTURE AS IT HAD TRACKED GENERALLY NORTHWESTWARD ACROSS CENTRAL 
TAIWAN. AS EXPECTED, THE TRANSIT HAD CONSIDERABLY WEAKENED THE 
SYSTEM WITH THE EYE FEATURE RADILY DISSOLVING INTO TIGHTLY CURVED 
BANDING AND AN ASSOCIATED LOSS OF DEEP CONVECTION. ANIMATED RADAR 
AND MULTISPECTRAL IMAGERY ALSO INDICATE THE LOW LEVEL CIRCULATION 
CENTER (LLCC) BRIEFLY PARALLELING THE NORTH-SOUTH RIDGELINE, TO THE 
EAST, BEFORE EMERGING TO THE WEST OF THE MOUNTAIN RANGE AS AN EVEN
WEAKER SYSTEM. THE UPPER LEVEL CIRCULATION, ON THE OTHER HAND, HAD 
CONTINUED TO TRACK GENERALLY WESTWARD WITH LITTLE FRICTIONAL EFFECT
FROM THE HIGH TERRAIN. THE DISSOLUTION OF THE EYE AND OVERALL DEEP 
CONVECTION, COMBINED WITH OROGRAPHICALLY INDUCED CLOUD COVER THAT 
HAD OBSURED THE LLCC, HAD MADE POSITIONING OVER LAND DIFFICULT.  
   B. MORE RECENTLY THE LOW LEVEL STRUCTURE HAS BECOME VERTICALLY
ALIGNED WITH THE UPPER LEVEL CIRCULATION, BUT WITH SIGNIFICANTLY 
WEAKENED CONVECTIVE BANDING, ESPECIALLY WITHIN THE WESTERN SEMICIRCLE.
CONTINUED EQUATORWARD DIFFLUENCE HAS MITIGATED AN EVEN WEAKER SYSTEM. 
THE LLCC HAS BECOME INCREASINGLY IDENTIFIABLE IN INFRARED SATELLITE 
IMAGERY AS WELL, IMPROVING FIX CONFIDENCE WHEN COMPARED TO RADAR 
FIXES FROM TAIWAN. THE INTENSITY ESTIMATE IS BASED ON DVORAK 
SATELLITE INTENSITY FIXES FROM PGTW, KNES AND RJTD RANGING FROM 
55 TO 65 KNOTS AND HAS SINCE BEEN DOWNGRADED TO A TROPICAL STORM.
TS 09W CONTINUES TO MOVE GENERALLY NORTHWESTWARD ALONG THE SOUTHERN 
PERIPHERY OF A SUBTROPICAL STEERING RIDGE EXTENSION TO THE NORTH, AND
IS PERCHED JUST OFFSHORE OF MAINLAND CHINA.
3. FORECAST REASONING
   A. THERE HAVE BEEN NO SIGNIFICANT CHANGES IN THE FORECAST
PHILOSOPHY OVER THE PREVIOUS TWELVE HOURS.
   B. THE SYSTEM WILL MOVE ASHORE MAINLAND CHINA AS A STRONG TROPICAL
STORM SLIGHTLY AFTER TAU 0. AFTER WHICH A CONTINUED NORTHWESTWARD 
TRACK WILL INDUCE A CONTINUED WEAKENING TREND OVER LAND WITH 
DISSIPATION BELOW 25 KNOTS OCCURING SLIGHTLY AFTER TAU 36. THIS 
FORECAST IS BASED ON THE CONSENSUS OF THE AVAILABLE OBJECTIVE AIDS
WITH SEVERAL OF THE MEMBERS INDICATING CONSIDERABLE WEAKENING AFTER 
TAU 12, AS INDICATED BY MORE ERRATIC PATHS AND INCONSISTENT SPEEDS.
CONSEQUENTLY, DISSIPATION OVER LAND COULD OCCUR EARLIER THAN 
PROJECTED. 
FORECAST TEAM: BRAVO//
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