Evaluation of the high-resolution model forecasts over the Taiwan area during GIMEX

During the 2001 Green Island Mesoscale Experiment (GIMEX), the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) was run at a horizontal resolution of 5 km twice a day and forced by initial and boundary conditions from the operational models of the Central Weather Bureau of Taiwan. The purpose of the paper is to evaluate the performance of the surface forecasts of the high-resolution numerical model and to verify quantitative precipitation forecasts (QPFs) over Taiwan Island within the 2-month period. The major errors in the forecasts are surface warm and dry biases. The model also tends to predict a stronger surface wind speed and an inland wind component, which suggest that the model overpredicted the sea breeze, a result that is consistent with the surface warm bias. The underprediction of the precipitation and poor skill scores are possibly due to the inadequate description of the humidity in the initial condition, and a spinup problem due to the steep Central Mountain Range.