A design and an application of a regional coupled atmosphere-ocean model for tropical cyclone prediction

The prediction of tropical cyclone (TC) track has improved greatly in recent decades due in part to the implementation and improvement of numerical weather prediction (NWP) models. However, the prediction of TC intensity using NWP models remains difficult. Several hypotheses have been proposed to explain the factors contributing to the TC intensity prediction errors and one of the leading candidates is the implication of an evolving sea-surface temperature (SST) boundary condition beneath the TC. In this study, a regional scale coupled atmosphere-ocean model is developed using the Advanced Research Weather Research and Forecasting (ARW) model and the HYbrid Coordinate Ocean Model (HYCOM). A coupling algorithm and a methodology to define appropriate ocean initial conditions are provided. Experiments are conducted, during the lifecycle of TC Ike (2008), using both the coupled-model and static (e.g., temporally fixed) SST to illustrate the impacts of the coupled-model for the TC track, intensity, and structure, as well as upon the larger (synoptic) scale. The results from this study suggest that the impact of the evolving SST (e.g., from a coupled atmosphere-ocean model) begin to impact the intensity, size, and thermodynamic structure for TC Ike (2008) at forecast lead-times beyond 48-hours. Further, the forecast trajectories (i.e., tracks) do not illustrate large differences between the non-coupled and coupled-models. Finally, the impact of the SST boundary condition upon TC Ike (2008) appears to be a function of the strength of the atmospheric forcing - in particular the size and intensity of the TC wind field.