Updating U.S. Precipitation Frequency Estimates for the Midwestern Region

The National Weather Service (NWS) rainfall maps have not been updated for approximately 50 years. This means that the design of storm sewers, culverts, dams, detention basins, etc. has been performed by the engineering community using outdated data. The NWS proposes updating precipitation frequency estimates (TP-40) for the Midwest States (MN, SD, ND, MO, IA, NE, and KS) by including the last 50 years of rainfall data. This project is part of a national effort to update the rainfall/frequency relationships for the entire United States. The Southwest (NV, UT, AZ, and NM) and Mid Atlantic (IL, IN, OH, PA, NJ, DE, MD, WV, VA, KY, TN, NC, and SC) States have completed the research. The new estimates will represent vastly improved data in terms of both period of record and station density. The purpose of the study is to determine annual exceedance probabilities and average recurrence intervals for rainfall durations ranging from 5 minutes to 60 days and frequencies from 1 - 500 years. The study results will be a web based publication available at www.nws.noaa.gov/ohd/hdsc. The project will review and process all reasonably available rainfall data. It is recognized that the rainfall data archived by NOAA's National Climatic Data Center (NCDC) may not be sufficient to accomplish the objectives of the project. Therefore, other data available from sources such as State Climatologists and other Federal, State and local agencies will be examined and included if appropriate. The state of the art techniques and processes developed and applied for NOAA Atlas 14 will be applied. The proposed research tasks are as follows: Task 1 - Data Collection and Quality Control Task 2 - Regionalization Task 3 - Frequency Distribution Selection and Fitting Studies Task 4 - Frequency Calculations Task 5 - Short Duration Estimates Task 6 - Internal Consistency at Observing Locations Task 7 - Spatial Interpolation and Consistency Task 8 - Mapping and other Spatial Artifacts Task 9 - Temporal Distributions Task 10 - Peer Reviews Task 11 - Documentation Task 12 - Final Deliverables Task 13 - Status Reporting A web based Precipitation Frequency Data Server will be developed for accessing Precipitation frequency estimates for rainfall durations of 5, 15, 30, and 60 minutes, 2, 3, 6 12 24 and 48 hours, 4, 7, 10, 20, 30, 45, and 60 days with frequencies of 1, 2, 5, 10, 25, 50, 100, 200, and 500 years. Contour maps and high resolution grids will be available for each combination of rainfall frequency and duration. Charts of the seasonal distribution of annual rainfall will be developed and the results will be documented.


    • English


    • Status: Completed
    • Contract Numbers:


    • Sponsor Organizations:

      Iowa Department of Transportation

      800 Lincoln Way
      Ames, IA  United States  50010
    • Project Managers:

      Dunn, Mark

    • Performing Organizations:

      National Weather Service

      1325 East-West Highway
      Silver Spring, MD  United States  20910-
    • Start Date: 20080401
    • Expected Completion Date: 20110331
    • Actual Completion Date: 0
    • Source Data: RiP Project 17008

    Subject/Index Terms

    Filing Info

    • Accession Number: 01460001
    • Record Type: Research project
    • Source Agency: Iowa Department of Transportation
    • Contract Numbers: TR-589
    • Files: RIP, STATEDOT
    • Created Date: Jan 3 2013 1:16PM