WDPN32 PGTW 070300 MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (ETAU) WARNING/ NR/17// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 070000Z7 TO 101200Z4 AUG 2003 A. TYPHOON (TY) 11W (ETAU), LOCATED OVER THE ISLAND OF OKINAWA, HAS TRACKED NORTHWARD AT 12 KNOTS OVER THE PAST 06 HOURS. THE WARNING POSITION IS BASED ON 062330Z4 MULTISPECTRAL SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 102 KNOTS. A 062109Z8 QUIKSCAT PASS REVEALED THAT THE 35 AND 50 KNOT WIND RADII WERE APPROXIMATELY TWICE THE SIZE OF THE PREVIOUS WARNING. B. TY 11W IS EXPECTED TO TRACK POLEWARD OVER THE NEXT 12 HOURS UNTIL IT INTERACTS WITH A SHORTWAVE TROUGH PASSING OVER KOREA. AT THAT TIME THE SYSTEM IS EXPECTED TO BEGIN TO WEAKEN SLOWLY WHILE TURNING TOWARDS THE NORTHEAST. TY 11W IS EXPECTED TO TRACK NORTH- EASTWARD THROUGH THE REMAINDER OF THE FORECAST AS IT TRACKS ALONG THE NORTHWESTERN PERIPHERY OF THE LEVEL SUBTROPICAL RIDGE. EXTRA- TROPICAL TRANSITION IS EXPECTED TO BEGIN BY 36 HOURS AND THE SYSTEM IS EXPECTED TO BE COMPLETELY EXTRATROPICAL AT THE END OF THE FORECAST PERIOD AS IT INTERACTS WITH THE BAROCLINIC ZONE. THE AVAILABLE DYNAMIC AIDS CONSISTING OF NOGAPS, NCEP (GFS), GFDN, EGRR, COAMPS, JGSM AND JTYM ARE IN GOOD AGREEMENT WITH THIS SCEN- ARIO. THE MODEL TREND OVER THE LAST 6 HOURS WAS TO TRACK SLIGHTLY WESTWARD OF THE PREVIOUS MODEL RUN. THIS FORECAST REFLECTS THIS CHANGE AND IS BASED ON PERSISTENCE AND A CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS. C. TY 11W HAS INTENSIFIED SLIGHTLY OVER THE PAST 12 HOURS DUE TO OUTFLOW TOWARDS A TROPICAL UPPER TROPOSPHERIC TROUGH TO THE EAST AND CONTINUED ENHANCED EQUATORWARD OUTFLOW. TY 11W IS EXPECTED TO PEAK IN INTENSITY IN THE NEXT 12 HOURS AND THEN BEGIN TO WEAKEN AS THE SYSTEM ENCOUNTERS THE WESTERLIES AND INCREASING VERTICAL SHEAR. THE SYSTEM IS NOT EXPECTED TO WEAKEN SIGNIFICANTLY UNTIL IT INTEARACTS WITH THE JAPANESE COAST. D. CURRENT WIND RADII IS BASED ON A 062109Z8 QUIKSCAT PASS. FORECASTED WIND RADII ARE BASED ON A CLIMATOLOGY FOR A LARGE SIZED SYSTEM. 3. FORECAST TEAM: LEEJOICE/LAM/ANDERSON/ALLEN// NNNN