Prediction of a flash flood in complex terrain. Part II: A comparison of flood discharge simulations using rainfall input from radar, a dynamic model, and an automated algorithmic system

Three techniques were employed for the estimation and prediction of precipi tation from a thunderstorm that produced a flash flood in the Buffalo Creek watershed located in the mountainous Front Range near Denver, Colorado, on 12 July 1996. The techniques included 1) quantitative precipitation estima tion using the National Weather Service's Weather Surveillance Radar-1988 D oppler and the National Center for Atmospheric Research's S-band, dual-pola rization radars, 2) quantitative precipitation forecasting utilizing a dyna mic model, and 3) quantitative precipitation forecasting using an automated algorithmic system for tracking thunderstorms. Rainfall data provided by t hese various techniques at short timescales (6 min) and at fine spatial res olutions (150 m to 2 km) served as input to a distributed-parameter hydrolo gic model for analysis of the flash hood. The quantitative precipitation es timates from the weather radar demonstrated their ability to aid in simulat ing a watershed's response to precipitation forcing from small-scale, conve ctive weather in complex terrain. That is, with the radar-based quantitativ e precipitation estimates employed as input, the simulated peak discharge w as similar to that estimated. The dynamic model showed the most promise in providing a significant forecast lead time for this flash-flood event. The algorithmic system did not show as much skill in comparison with the dynami c model in providing precipitation forcing to the hydrologic model. The dis charge forecasts based on the dynamic-model and algorithmic-system inputs p oint to the need to improve the ability to forecast convective storms, espe cially if models such as these eventually are to be used in operational hoo d forecasting.