Wdpn31 Pgtw 211500 

msgid/genadmin/navpacmetoccen Pearl Harbor hi/jtwc// 

subj/prognostic reasoning for typhoon 02w warning nr 21//
rmks/
1. For meteorologists.
2. Prognostic reasoning for 211200z may to 221200z may 2007.
   A. Typhoon (TY) 02w (Yutu), located approximately 55 nm
southwest of Iwo Jima, has tracked northeastward at 18 knots
over the past six hours. Recent Dvorak satellite intensity
estimates and subjective analysis of storm core convective
signature core suggest that the system has begun to weaken
significantly under the influence of increasing southwesterly
wind shear.
   B. TY 02w continues to accelerate northeastward on the
northwestern periphery of a subtropical steering ridge
anchored northeast of the Mariana islands. Strengthening
southwesterly flow ahead of an appraoching mid-latitude
trough to the west of the system will augment forward
track speed through the forecast period and allow TY 02w
to continue tracking northeastward.
   C. Steadily increasing vertical wind shear and decreasing
sea surface temperatures will continue to weaken the storm
and induce a rather rapid extratropical transition. The
system is expected to begin this transition by tau 12 and
become fully embedded in the mid-latitude flow as a strong
extratropical low by tau 24.
    D. Current wind radii are based on estimates derived from
microwave satellite imagery, convective signature and recent
synoptic observations from the island of Iwo Jima. Forecast
wind radii are based on climatology for an average-sized
system and analysis of wind field distortions typically
associated with extratropical transition.
Forecast team: Alpha//
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