CS19C - Concurrent Session 19C: NOAA Atlas 15 - Climate-Informed Precipitation Frequency Estimates for the U.S.

Abstract Description: The Office of Water Prediction (OWP) of the National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service (NWS) is developing a new authoritative precipitation frequency (PF) standard which are used in dam safety applications (e.g., spillway design and hydrologic risk assessment). When complete in 2027, NOAA Atlas 15 will provide seamless estimates across the contiguous United States (CONUS), as well as estimates for domains outside the contiguous United States (oCONUS), including Alaska, Hawaii, and select U.S. territories. NOAA Atlas 15 will consist of two volumes: Volume 1 will provide a snapshot of PF estimates for present day accounting for nonstationarity captured by historical gauge observations, and Volume 2 will provide future estimates corresponding to potential changes in global temperature based on model projections.
Preliminary PF estimates across CONUS were released in early 2026 for review by federal partners, stakeholders, and the public. Atlas 15 will be provided for durations 5-minutes through 60-days and annual exceedance probabilities through 0.1% (or 1 in 1,000) on a high-resolution grid, displayed as interactive graphics on a new web interface. This presentation describes ongoing efforts to develop a quality controlled extreme precipitation time series database, the evolution of a framework used to generate present-day preliminary estimates, and the development and application of adjustment factors used to provide future estimates.