Prediction of waves generated by tropical cyclones with a quadtree-adaptive model

In this paper, we describe the application of a quadtree-adaptive model to hindcast the wave spectrum during Hurricanes Katrina and Rita. In the simulation, the quadtree grid system can be adapted to the vicinity of the hurricanes and/or some prescribed regions of interest, which require higher resolutions. In other words, the quadtree grid system can move with the hurricanes. Furthermore, all the details of prescribed simulations can be plugged into a global simulation with input wind fields at different resolutions. In addition, the prescribed model is implemented in a unified framework of code and performed in one thread or multiple parallel threads. The proposed adaptive model can significantly reduce the time required for a specific simulation and is very convenient for large-scale operational forecasting when multiple resolutions are required. For Hurricane Katrina, only 3 h of computing time is required to simulate the entire ten days of the hurricane event with a resolution of 0.25 h and 1/8 degree for the region of interest near Mexico bay. The difference between the predicted significant wave heights and the buoy measurements is less than 0.5 m. In addition, the codes of the models are freely available and thus can be easily extended to an operational forecast system of tropical cyclones.