The Urban Drainage and Flood Control District (UDFCD) maintains an ALERT gauging network, for real-time monitoring of rainfall, and operates a Flash Flood Prediction (FFP) Program, to forecast rainfall events up to 24 hours in advance, within the Denver metropolitan area. The Program Meteorologists communicate directly with area emergency management and public works agencies to prepare for and assess flash flood events. Spatially comprehensive rainfall estimates that are both timely and accurate are critical in this mission, to determine the level of threat in real-time.

Weather Decision Technologies (WDT) Inc. provides UDFCD rainfall estimates that are automatically derived from NEXRAD Level II mosaicked radar data and adjusted using the ALERT rain gauge data. These data are provided in Geographic Information System (GIS) format in real-time on a high-resolution 1 km grid. Traditionally Meteorologists have used NWS single site radar data in conjunction with point ALERT data to estimate basin rainfall and communicate the potential flash flood threat with local agencies. During the 2007 Program, WDT integrated the ALERT rain gauge data into their high resolution gridded radar rainfall mosaics, updated every 15 minutes. Both the radar-only Quantitative Precipitation Estimates (QPE) using multiple radars and the gauge-adjusted QPE products were provided at l km resolution. Observations of 24-hour rainfall from the Community Collaborative Rain Hail and Snow (CoCoRaHS) database provided a dense network of independent data to perform statistical assessment of gauge adjusted QPE products on a daily basis.

The purpose of this presentation will be to discuss the gauge-adjusted radar QPE techniques, the integration of QPE products in local flash flood prediction and verification of the rainfall estimates for a few cases from the 2007 season.