Evaluation of numerical weather prediction model rainfall forecasts for streamflow forecasting

This study evaluates rainfall forecasts from the first generation Australian Numerical Weather Prediction (NWP) models over the Ovens catchment in southeast Australia. It also evaluates streamflow forecasts produced using the NWP rainfall forecasts as input to a hydrological model. The rainfall forecasts of four NWP models (ACCESS-G/80 km, ACCESS-R/37.5 km, ACCESS-A/12 km and ACCESS-VT/5 km) are compared to observed rainfall at gauging stations and to derived catchment rainfall for one year period of 2010-2011. The 5 and 12 km resolution NWP models appear to be relatively free from bias (i.e. As an experiment, the raw NWP model rainfall forecasts are used to force a semi-distributed conceptual rainfall runoff model to produce hourly streamflow forecasts. The rainfall forecasts have little influence on streamflow forecasts for lead times shorter than the time of concentration of the forecast point. For longer lead times, however, the rainfall forecasts result in better streamflow forecasts than assuming zero future rain. The streamflow forecasts may be further improved if better rainfall forecasts are obtained through post-processing of the NWP outputs.