Extended Abstract (292K)P1.11
Mesoscale model predictions of typhoon structure and motion in the western Pacific during October 2004
Ramesh Vellore, DRI, Reno, NV; and D. R. Koracin and J. Lewis
In this study, two successive typhoons in the western Pacific Ocean that made the landfall in Japan during October 2004, that moved under different synoptic environments are investigated. The first typhoon, Ma-on (26W), one of the most powerful typhoons to strike eastern Japan over the last ten years, lasted for a period of 4-9 October 2004; the second typhoon Tokage (27W) occurred during 12-20 October 2004.
Supertyphoon Ma-on (26W) originated as a weak low level circulation center (LLCC) 130 km north-northwest of Guam on 29 September 2004. After days of sputtering as a weak LLCC across the western Pacific, Ma-on intensified to a tropical storm on 5 October. It reached category 1 [category 1 typhoon: maximum sustained winds (MSW) of 33-43 m s-1, described as a minimal typhoon] on the 6th at 1200 UTC, and its center was located 760 km southeast of Okinawa, Japan. It rapidly intensified to a category 5 [category 5: MSW 70-87 m s-1, described as a devastating typhoon] moving northeastward in a span of 24 hours. Ma-on made landfall on the Izu Peninsula, Honshu, Japan, on the 9th at 0700 UTC with MSW of 50 m s-1. The storm system had completed its transformation at 1800 UTC to an extratropical system and further moved east-northeastward. The second typhoon Tokage (27W) originated from an area of convection 770 km east-southeast of Guam on Oct 12th, reached typhoon intensity (40 m s-1) at 1560 km southeast of Okinawa, Japan on the 14th persisted in its northwest direction of motion and recurved towards Japan at its weakened stage.
Numerical weather forecasting models such as the Mesoscale Model 5 (MM5) and the Weather Research and Forecasting Model (WRF) are used to evaluate the typhoon motion of these two typhoon cases. An axially symmetric vortex centered at the best track positions issued by the Joint Typhoon Warning Center (JTWC) is bogussed into the National Center for Environmental Prediction (NCEP) 1° x 1° global reanalysis fields for initializing the models. Nearly identical choices of model setup and physics will be considered in both of the models. A preliminary MM5 investigation showed that NCEP-reanalyzed large scale flow crucially impacts the typhoon motion and the initial axi-symmetric bogus vortices that use exponential relation in the wind profile is able to reproduce the vortex structure and intensity at a later time better than the linear relations used in the bogus vortices in the default MM5 preprocessing. The structural evolution, impact of typhoon motion under the reanalyzed synoptic environment, and sensitivity of the vortex parameters in the bogussing will be investigated in detail. Furthermore, an ensemble of nine predictions of the described typhoons will be combined to investigate the 24-36h predictability and the random error in the typhoon motion using a lagged-average forecasting method.
Poster Session P1, 7Coastal Posters
Monday, 10 September 2007, 6:00 PM-8:00 PM, Macaw/Cockatoo
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