WDPN31 PGTW 031500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (CHATAAN) WARNING 
NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 030000Z3 TO 060000Z6 JUL 02.
   A. TROPICAL STORM (TS) 08W (CHATAAN), LOCATED APPROXIMATELY 170 
NM NORTHWEST OF CHUUK, HAS TRACKED WESTWARD AT 10 KNOTS OVER THE 
PAST 6 HOURS. THE WARNING POSITION IS BASED ON 031130Z8 INFRARED 
SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE 
CURRENT INTENSITY ESTIMATES OF 55 KNOTS. ANIMATED SATELLITE IMAGERY 
DEPICTS IMPROVED ORGANIZATION OVER THE PAST 6 HOURS.
   B. TS 08W IS FORECAST TO TRACK NORTHWESTWARD UNDER THE STEERING 
INFLUENCE OF A RIDGE NORTH OF THE SYSTEM. THIS RIDGE IS FORECAST TO 
RE-ORIENTATE INTO A NORTHWEST-SOUTHEAST DIRECTION WITHIN 12 HOURS, 
FURTHER AIDING THE SYSTEM TO CONTINUE TRACKING NORTHWESTWARD. THE 
AVAILABLE DYNAMIC AIDS CONSIST OF THE NCEP AVIATION (AVN), NOGAPS, 
COAMPS, GFDN, AFWA MM5, UKMET GLOBAL (EGRR), AND JAPANESE GLOBAL 
(JGSM) MODELS. ALL AIDS AGREE IN DIRECTION BUT DIFFER IN SPEED. 
AVN AND JGSM ARE THE OUTLINERS, TRACKING TS 08W NORTHWESTWARD FAR 
MORE RAPIDLY THAN THE OTHER AIDS. THESE SOLUTIONS APPEAR UNLIKELY  
BASED THE STRENGTH OF THE PERIPHERAL RIDGE THAT THESE MODELS 
INDICATE. OUR FORECAST IS BASED ON A BLEND OF PERSISTENCE AND ALL 
AVAILABLE MODELS, WITH A MINOR SLOWER SPEED BIAS.
   C. THE UPPER LEVEL LOW NORTH OF GUAM HAS PROPAGATED WESTWARD AND 
HAS ENHANCED THE POLEWARD OUTFLOW. FURTHER INTENSIFICATION WILL BE 
AT A CLIMATOLOGICAL RATE UNTIL THE UPPER LEVEL LOW FILLS IN 12 HOURS 
AND THE OUTFLOW DIMINISHES. 
   D. CURRENT WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE 
SIZE SYSTEM.
FORECAST TEAM: LEEJOICE/AYALA/HARRISON/BOSTIC//

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