WDPN31 PGTW 251500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 03W (SONCA)
/WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 251200Z0 TO 270000Z9 APR 2005.
   A. TYPHOON (TY) 03W (SONCA), LOCATED APPROXIMATELY 660 NM
SOUTHWEST OF IWO JIMA, HAS TRACKED NORTHEASTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. OUTFLOW OF CIRRUS CLOUDS
TO THE NORTHEAST AND A 251135Z7 SSMI IMAGE INDICATES
TY 03W IS UNDERGOING EARLY EXTRATROPICAL TRANSITION.
   B. TY 03W HAS CRESTED THE AXIS OF THE SUBTROPICAL RIDGE
AND IS NOW INCREASING SPEED NORTHEASTWARD ALONG THE
NORTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE ANCHORED
TO THE EAST-SOUTHEAST. TY 03W IS FORECAST TO CONTINUE TO
ACCELERATE NORTHEASTWARD AND BECOME EMBEDDED INTO THE
MID-LATITUDE FLOW. AVAILABLE DYNAMIC AIDS CONSISTING OF
NOGAPS, GFDN, COAMPS, NCEP GFS, JGSM, TCLAPS, UKMET EGRR,
AND WBAR ARE IN GOOD AGREEMENT WITH THIS SCENARIO. THIS
FORECAST IS BASED ON A CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS.
   C. TY 03W IS FORECAST TO WEAKEN AS THE SYSTEM ENCOUNTERS
DRIER AIR AND INCREASED VERTICAL WIND SHEAR ASSOCIATED WITH
THE MID-LATITUDE WESTERLIES. TY 03W HAS BEGUN TRANSITION TO
AN EXTRATROPICAL CYCLONE, AND IS FORECAST TO COMPLETE THIS
TRANSITION BY TAU 36.
   D. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR AN
AVERAGE SIZED SYSTEM UNDERGOING EXTRATROPICAL TRANSITION.
3. FORECAST TEAM: ALPHA//
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