Typhoon Morakot (2009) was the deadiest 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 (COAMPSŪ-TC) in order to understand the multi-scale dynamic and physical processes that caused the tremendous rainfall associated with this landfalling typhoon, and to understand aspects of its predictability. 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 and vertical resolution, domain size, and large-scale environment. The sensitivity tests provide insight into factors that contributed to the QPF error in the southern central mountain range of Taiwan, as well as aspects of mesoscale models that could be improved to more accurately forecast impacts for landfalling typhoons such as Morakot.