New NOAA Precipitation Frequency Estimates for Colorado Now Available

New precipitation frequency estimates across Colorado are available in NOAA Atlas 14 Volume 8 which was published by the NWS Hydrometeorological Design Studies Center and supported by the Colorado Water Conservation Board. Estimates are available on the Precipitation Frequency Data Server (PFDS) in a variety of formats with supplementary information and documentation. This includes precipitation frequency estimates and 90 percent confidence intervals for a selected location, ASCII grids of precipitation frequency estimates, cartographic maps, etc. The PFDS is located at Here is an example of a 100-year/60-minute cartographic map zoomed in to north central and northeast Colorado


Precipitation frequency estimates are estimates of climate variability. They are used as design standards for civil infrastructure built to cope with rainfall and runoff such as storm water drainage systems, roads, bridges, culverts, small dams, roofs, airport runways, in-stream ecosystems including fish habitat, stream erosion control, pollution control systems, flood insurance rate maps, soil conservation, etc. These new estimates directly contribute to the preparation of more cost effective designs, plans, maps, etc.; protecting lives and property and preventing pollution.

The last time that these estimates were updated was back in 1973 (NOAA Atlas 2). The new estimates in NOAA Atlas 14 are based on improvements in three primary areas: denser data networks with a greater period of record, the application of regional frequency analysis using L-moments for selecting and parameterizing probability distributions, and new techniques for spatial interpolation and mapping.

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