WDPN31 PGTW 180300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W
/WARNING NR 17//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 180000Z9 TO 210000Z3 AUG 2004.
    A. TYPHOON (TY) 18W (MEGI), LOCATED APPROXIMATELY 185
NM NORTHWEST OF OKINAWA, JAPAN, HAS TRACKED NORTH-NORTH-
WESTWARD AT 09 KNOTS OVER THE PAST 06 HOURS. THE WARNING
POSITION IS BASED ON 172330Z6 MULTISPECTRAL SATELLITE 
IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT 
INTENSITY ESTIMATES OF 65 KNOTS. ANIMATED WATER VAPOR
IMAGERY DEPICTS THE CONVECTION BEGINNING TO ELONGATE AS TY
18W INTERACTS WITH AN APPROACHING TROUGH FROM THE NORTHWEST.
    B. TY 18W IS TRACKING ALONG THE WESTERN PERIPHERY OF THE
MID-LEVEL STEERING RIDGE. TY 18W IS BEGINNING TO INTERACT WITH
THE APPROACHING UPPER LEVEL TROUGH NEAR THE YELLOW SEA. TY 18W
IS EXPECTED TO ACCELERATE TO THE NORTHEAST AFTER 12 HOURS AS
IT INTERACTS WITH THE MID-LATITUDE WESTERLIES. THE AVAILABLE
DYNAMIC AIDS, CONSISTING OF NOGAPS, COAMPS, JTYM, JGSM, UKMET
EGRR, NCEP GFS AND WBAR ARE IN EXCELLENT AGREEMENT WITH THIS
SCENARIO. THIS FORECAST IS BASED ON A CONSENSUS OF ALL
AVAILABLE DYNAMIC AIDS.   
   C. TY 18W IS FORECAST TO MAINTAIN INTENSITY OVER THE NEXT 12
HOURS AND THEN WEAKEN RAPIDLY AS IT INTERACTS WITH THE WESTERLIES
AND TRANSITION INTO AN EXTRATROPICAL CYCLONE.
   D. CURRENT AND FORECAST WIND RADII ARE BASED ON CLIMATOLOGY 
FOR AN AVERAGE SIZED SYSTEM. 
3. FORECAST TEAM: WINGEART/JACOBS/LEWIN//