WDPN32 PGTW 050300 
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC// 
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (RAMMASUN) WARNING 
NR 28// 
RMKS/ 
1. FOR METEOROLOGISTS. 
2. PROGNOSTIC REASONING FOR 050000Z5 TO 080000Z8 JUL 02. 
   A. TYPHOON (TY) 09W (RAMMASUN), LOCATED APPROXIMATELY 70 
NM EAST-NORTHEAST OF SHANGHAI, HAS TRACKED NORTHWARD AT 14 KNOTS 
OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 042330Z2 
MULTISPECTRAL SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON 
SATELLITE CURRENT INTENSITY ESTIMATES OF 65 KNOTS. ANIMATED VISIBLE 
SATELLITE IMAGERY DEPICTS A RAPIDLY WEAKENING SYSTEM AS IT INTERACTS 
WITH THE LONG WAVE TROUGH SITUATED OVER THE CHINA COAST AND 
CONTINUES TO TRACK OVER INCREASINGLY COOLER WATERS.
   B. A MID-LEVEL HIGH HEIGHT CENTERED JUST OFF OF THE COAST OF 
JAPAN IS FORECAST TO REMAIN QUASI-STATIONARY THROUGH THE PERIOD. 
THEREFORE, TY 09W SHOULD TRACK GENERALLY NORTHWARD TO NORTHEASTWARD 
FOR THE NEXT 48 HOURS. AVAILABLE DYNAMIC AIDS INCLUDING NCEP AVN
(AVIATION), NOGAPS (NGPS), UK-MET GLOBAL (EGRR), JAPAN GLOBAL (JGSM) 
AND TYPHOON (JTYM) MODELS AND GFDN ALL AGREE ON A NORTHEAST 
DIRECTION OF TRACK FOR THE FIRST 48 HOURS, BUT DIFFER GREATLY ON THE 
SPEED AT WHICH THE SYSTEM WILL TRACK WITH JGSM BEING THE FASTEST AND 
EGRR THE SLOWEST. THE PRIMARY DIFFERENCE IN THE MODEL FIELDS APPEARS 
TO BE THE DEPTH OF THE SYSTEM WITH TIME. WITH THE EXCEPTION OF JTYM 
(WHICH HAS NO FIELDS TO EXAMINE) THE MODELS ARE KEEPING THE SYSTEM 
DEEPER THAN PREVIOUS RUNS THOUGH SATELLITE IMAGERY AND SYNOPTIC 
REPORT CLEARLY INDICATES A RAPID WEAKENING TREND. THEREFORE, OUR 
FORECAST IS BASED ON PERSISTENCE AND A BLEND OF ALL DYNAMIC AIDS, 
THOUGH SIGNIFICANTLY SLOWED THROUGHOUT THE PERIOD.
   C. A Q/S LONG WAVE TROUGH SITUATED OVER THE CHINA COAST CONTINUES 
TO ERODE THE WESTERN SEMI-CIRCLE OF THE SYSTEM. UPPER SOUTHERLIES 
ASSOCIATED WITH THE TROUGH AND COOLER SSTS SHOULD CONTINUE TO 
RAPIDLY WEAKEN THE SYSTEM OVER THE FORECAST PERIOD.   
   D. WIND RADII ANALYSIS BASED ON MICROWAVE IMAGERY, SYNOPTIC DATA 
AND SCATTEROMETER DATA. FORECAST WIND RADII BASED ON CLIMATOLOGY FOR 
A LARGE SYSTEM. 
FORECAST TEAM: BRYANT/RONSSE/NUTONGLA//



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