Development of a tropical storm surge prediction system for Australia

The Australian tropical storm surge forecasting system is described, including the development of a tropical cyclone atmospheric forcing model and the configuration of the ocean hydrodynamic model. The atmospheric model is developed as an asymmetric modified Rankine vortex and the resulting time dependent stress and pressure fields are applied to a shallow water hydrodynamic model. The system was benchmarked against seven contemporary tropical cyclones occurring within the northern Australian region between 2011and 2017. The model storm surge response to the synthetic forcing was compared against tide gauge observations. For the seven test cases, the root mean square error for maximum sea level was 0.30 m, the mean absolute error was 0.21 m and the mean bias error was 0.11 m. For peak timings, the root mean square error of the model was 62 min, the mean absolute error was 48 min and the mean bias error was 8 min. Surface forcing fields were compared against observations for TC Yasi and found to be in general agreement.