Several factors combine to complicate warm-season numerical model rainfall forecasts.
Much warm season rainfall is convective in nature, and therefore too small to be resolved well by even the higher-resolution operational models used today. Convective parameterizations must be used, and it appears that no one scheme works best in all situations. In this study, we use a 10 km version of the Eta model to examine the impact on QPF of better initialization of mesoscale boundaries that play an important role in precipitation events in the Midwest. In general, subsequent convection in these events resulted in a maximum of at least 50 mm of rainfall within a 24 hour period, and several of the events were associated with over 150 mm and severe flooding. Eta simulations have been performed for these cases, using 10 km horizontal resolution, over limited domains of roughly 1000 X 1000 km.