subj/prognostic reasoning for typhoon 18w warning nr 15//
rmks/
1. For meteorologists.
2. Prognostic reasoning for 290000z Sep to 020000z Oct 2006.
   A. Typhoon (TY) 18w (xangsane), located approximately 540 nm east
of hue, Vietnam, has tracked westward at 12 knots over the past six
hours.
   B. TY 18w is tracking westward along the southern periphery of 
the subtropical ridge (str) located over southeastern China.
Throughout tau 72, TY 18w will continue to be steered westward by
the str. The available dynamic aids are in good agreement with this
forecast scenario. This forecast is based on a blend of persistence
and the consensus of the available dynamic aids.
   C. TY 18w will intensify slightly in an environment of light
vertical wind shear with good divergence aloft as it moves out over
the open warm waters of the South China Sea. Interaction with the
landmasses of hainan and Vietnam will begin to weaken the system
as it makes landfall near tau 48.
   D. Current wind radii are based on a 281830z AMSU pass. Forecast
wind radii are based on climatology for an average-sized system.
Forecast team: Alpha//
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