Numerical Simulations and Analysis of Typhoon Morakot (2009) Using the Navy's Mesoscale Prediction Model

Typhoon Morakot (2009) was the deadliest typhoon ever to strike Taiwan. Its slow movement combined with its interaction with the southwest monsoon produced tremendous amounts of rainfall in the southern central mountain range of Taiwan. Numerical simulations of Typhoon Morakot (2009) are performed using the Naval Research Laboratory's Coupled Ocean/Atmosphere Mesoscale Prediction System for Tropical Cyclones (COAMPS®-TC) in order to understand the multi-scale dynamic and physical processes that caused the tremendous rainfall associated with this landfalling typhoon. In a previous paper, the control simulation of Morakot was analyzed with regard to its ability to predict the track, intensity, structure and precipitation of Morakot. While the control simulation produced reasonably accurate track and intensity forecasts over the life cycle of Morakot, there existed a significant quantitative precipitation forecast (QPF) error in the southern central mountain range of Taiwan. In the present work, sensitivity tests are performed with respect to the model physics, initialization, horizontal resolution, domain size, and large-scale environment in order to understand the factors causing the QPF error in the southern central mountain range of Taiwan. This work lends insight into what aspects of mesoscale models can be improved for more accurate deterministic precipitation forecasts for landfalling tropical cyclones. COAMPS® is a registered trademarks of the Naval Research Laboratory.