Coastal Services Center

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Precipitation Atlas

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Precipitation Atlas

As part of the Coastal Storms Program, the National Oceanic and Atmospheric Administration (NOAA) will update precipitation frequency estimates for the state of California to be included in NOAA Atlas 14. The updates will be published as subsequent Volumes of NOAA Atlas 14 “Precipitation-Frequency Atlas of the United States ” on the Web at www.nws.noaa.gov/ohd/hdsc.

The new NOAA Atlas 14 estimates represent vastly improved data in terms of both period of record and station density, state of the art statistical techniques, and a new approach that accounts for variation in terrain. The precipitation frequency atlas’ are used for a multitude of planning and design purposes—from developing flood plain maps, determining flood insurance rates, and designing storm drainage systems, flood control structures, roads and bridges. The provided information allows civil engineers and public officials to account for different levels of rainfall in their designs and plans and make more informed decisions.

How the Project Will Work

Combining the resources of the Army Corps of Engineers, the California Department of Transportation, and NOAA’s Coastal Storms Program, NOAA will update the NOAA Atlas 14 for the state of California . The study will determine the annual exceedance probabilities (AEP) and average recurrence intervals (ARI) for durations ranging from 5 minutes to 60 days and for ARIs from 1 to 1,000 years. The point estimates will be spatially interpolated to a resolution of approximately 4km x 4km.

The publication of the study results will include access through the Precipitation Frequency Data Server, base grids in standard formats, electronic copies of maps, results from trend analyses, charts of seasonal distributions and probabilistic temporal distributions, and detailed documentation. The project will review and process all reasonably available rainfall data necessary to the regional update.

For Additional Information

Christopher McAloon
NOAA National Weather Service
Office of Science and Technology
Telephone: (301) 713-3557, ext. 158
E-mail: Christopher.Mcaloon@noaa.gov