WDPN31 PGTW 190300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W
/WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 190000Z0 TO 210000Z3 AUG 2004.
    A. TROPICAL STORM (TS) 18W (MEGI), LOCATED APPROXIMATELY 620
NM WEST-SOUTHWEST OF MISAWA, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD
AT 29 KNOTS OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED
ON 182330Z7 MULTI-SPECTRAL SATELLITE IMAGERY. THE WARNING INTENSITY
IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 55 AND 65 KNOTS.
    B. TS 18W IS FORECAST TO CONTINUE TRACKING POLEWARD ALONG THE
NORTHWESTERN PERIPHERY OF THE STEERING RIDGE SOUTHEAST OF THE SYSTEM.
BY THE 12 TO 24 HR TAU, TS 18W WILL BEGIN TO MERGE WITH THE MID-
LATITUDE WESTERLIES AND ACCELERATE NORTHEASTWARDS. TS 18W WILL BECOME
COMPLETELY EMBEDDED IN THE BAROCLINIC ZONE BY TAU 24 AND WILL COMPLETE
TRANSITION TO AN EXTRATROPICAL LOW. THE AVAILABLE DYNAMIC AIDS
CONSISTING OF NOGAPS, UKMET EGRR, NCEP GFS, GFDN, AFWA MM5, WBAR,
JGSM, JTYM AND COAMPS ARE IN GOOD AGREEMENT WITH THIS SCENARIO. THIS
FORECAST IS BASED ON A CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS. 
   C. TS 18W WILL CONTINUE TO STEADILY DROP IN INTENSITY AS IT
TRANSITIONS TO AN EXTRATROPICAL LOW AND BECOMES EMBEDDED IN THE
BAROCLINIC ZONE.  
   D. CURRENT AND FORECAST WIND RADII ARE BASED ON CLIMATOLOGY 
FOR AN AVERAGE SIZED SYSTEM. 
3. FORECAST TEAM: ARENDS/PITTS/FJELD/VOHS//