Localized heavy rainfall associated with a backdoor cold front and sub tropical moisture produced extreme rainfall over localized regions in the upper Catawba River Basin. SPAS analysis and model gridded quantitative precipitation forecasts were utilized as input to hydrologic modeling to understand the timing of the flood compared to operational decisions and outcomes. AWA’s information proved to be key in the settlement as it demonstrated in detail when and where the rainfall accumulated compared to the model forecasted precipitation. AWA’s SPAS rainfall was provided detailed, gridded rainfall accumulation data at 5-moute time steps and the annual exceedance probability of those accumulations over various times scales on the same grid locations. AWA provided the gridded model forecast precipitation over the same domain to allow for hydrologic evaluations of the predicted rain-runoff. This information was provided to support the legal defense and arguments.
