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A B S T R A C T This paper provides an account of the performance of a multimodel ensemble for real time forecasts of Atlantic tropical cyclones during 2004, 2005 and 2006. The Florida State University (FSU) superensemble is based on a suite of model forecasts and the interpolated official forecast that were received in real time at the National Hurricane Center. The FSU superensemble is a multimodel ensemble that utilizes forecasts from the member models by removing their individual biases based on a recent past history of their performances. This superensemble carries separate statistical weights for track and intensity forecasts for every 6 h of the member model forecasts. The real time results from 2004 show an improvement up to 15% for track forecasts and up to 11% for intensity forecasts for the superensemble compared to other models and consensus aids. During 2005, the superensemble intensity performance was best for most lead times. The consistency of the superensemble forecasts of track are also illustrated for several storms of 2004 season. The superensemble methodology produced impressive intensity forecasts for Rita and Wilma during 2005. The study shows the capability of the superensemble in predicting rapidly intensifying storms when most member models failed to capture their strengthening.

A mesoscale mixed‐layer model of the planetary boundary layer is applied to the flow past a mountain island during a cold air outbreak over the Kuroshio Current. Utilizing data taken during AMTEX '75, the governing equations are integrated in time to simulate development of a Karmán vortex street downstream of the island of Cheju‐do. The use of open lateral boundary conditions and an encroachment scheme which allows some mountain grid points to experience occasional encroachment of mixed‐layer fluid as the mixed‐layer deepens (and decroachment as the mixed layer thins) is also discussed. Comparing various non‐dimensional parameters on vortex‐street characteristics, it is shown that the simulated vortex street resembles the observed atmospheric one rather well. Uncertainty in formulating the proper value of the eddy viscosity and the implication this has on Reynolds number comparisons are also discussed.

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