Welcome to the NOAA Atlas 15 Informational Page

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News: The NOAA Atlas 15 Pilot over Montana is now available for early feedback, HERE. Click to explore the pilot data and how the NOAA Atlas 15 framework differs from NOAA Atlas 14. Feedback can be submitted through this survey. A Quick Start Video is available. See the NOAA Atlas 15 Pilot Technical Report for more information.
  • What is NOAA Atlas 15?

    NOAA Atlas 15 is the new authoritative, spatially continuous and climate-informed National Precipitation Frequency Atlas of the United States, currently under development by the NOAA National Weather Service (NWS) Office of Water Prediction (OWP). As with previous Precipitation Frequency Atlases, NOAA Atlas 15 will provide spatially independent estimates of expected precipitation depth (or intensity) for a specified storm duration (e.g., 6 hours), at a particular location of interest (e.g., Tulsa, Oklahoma). The statistically expected precipitation estimates will be presented as exceedance probabilities ranging from 50% average annual exceedance to 0.1%, and will cover storm durations ranging from 5 minutes to 60 days. As an example, a NOAA Atlas 15 precipitation estimate with a 20% average annual exceedance probability has a 20% chance of being exceeded in the year of interest (see table below for a range of examples).

    Atlas 15 table

    In contrast to NOAA Atlas 14, NOAA Atlas 15 will provide spatially continuous coverage over the entire United States and, for the first time, will also account for future climate variability (through the year 2100). When published, NOAA Atlas 15 will be the authoritative source for precipitation frequency information across the United States. The current standard, NOAA Atlas 14, is referenced in many engineering design standards and floodplain regulations, published by entities outside of NOAA, and engineers and other practitioners use those standards and regulations to make local decisions (designs for drainage infrastructure, city and regional planning, etc.) Among the civil engineering community, precipitation frequency estimates for various durations are often referred to as Depth-Duration-Frequency (DDF) or Intensity-Duration-Frequency (IDF) curves.

  • Why is NOAA Atlas 15 important?

    NOAA Atlas 15 can help communities nationwide become more climate-resilient when planning for and designing new infrastructure. This objective will be supported by (1) the delivery of spatially continuous precipitation frequency estimates that cover the entire United States and (2) the incorporation of nonstationary statistical methods and information from climate models to account for future climate variability.

    Although precipitation frequency estimates have existed for many decades (since the late 1930s) and have incrementally improved with advancements in data, science and technology, NOAA Atlas 15 represents a shift from a stationary (i.e., extreme precipitation events do not change significantly over time) to nonstationary assumption (i.e., extreme precipitation events change over time), a key modification that may impact the manner in which precipitation frequency information is applied. NOAA recognizes that projecting precipitation frequency information into the future introduces additional uncertainties, such as the degree to which global temperatures are increasing and climate model physics, and parameter configurations thus impacting stakeholders who use this information to assess risk across a range of applications, including the planning, management, and design of engineering infrastructure.

    As a provider of high quality scientific data, NOAA’s objective is to update national precipitation frequency estimates to include climate information, based on the best available and actionable science at the time of development. NOAA is committed to clearly describing the data that are generated, communicating how they were developed and providing service delivery to ensure equitable access to the information. As this dataset is used for a wide-range of applications, it will be up to users, organizations and government agencies to identify the appropriate bounds for the application of these estimates in the areas in which they have missions and expertise. To help with the transition from the current national standard, NOAA Atlas 14, to NOAA Atlas 15, NOAA plans to partner with several entities and to engage a wide range of stakeholders.

  • Who funded NOAA Atlas 15?

    The United States Congress, through the Bipartisan Infrastructure Law (BIL), provided NOAA with funding to revise and update the current precipitation frequency standard, known as NOAA Atlas 14, and develop NOAA Atlas 15.

    “...To support the design, development, and operation of our nation’s built infrastructure, from new power plants to transportation systems, NOAA will update and revise precipitation frequency atlases for the United States that account for climate change…”
  • Who is developing NOAA Atlas 15?

    NOAA's Office of Water Prediction, which is part of NOAA's National Weather Service, is developing NOAA Atlas 15.

    The NOAA Atlas 15 Pilot dataset would not have been possible without the support and contributions of grantees, contractors, and individuals from government, private industry, and academia. For more information on the development of the NOAA Atlas 15 Pilot data, please refer to the NOAA Atlas 15 Pilot Technical Report.

  • How is NOAA Atlas 15 being developed and presented?

    NOAA Atlas 15 will consist of two volumes. NOAA Atlas 15 Volume 1 will provide a snapshot of current estimates that account for temporal changes in historical observations. When published, NOAA Atlas 15 Volume 1 will supersede the current NOAA Atlas 14 precipitation frequency estimates.

    NOAA Atlas 15 Volume 2 will provide model-based precipitation frequency estimates projected into the future, utilizing climate model information. Volume 2 estimates will be developed by applying adjustment factors to Volume 1 estimates (i.e. future relative changes obtained from downscaled climate model data).

  • What is the NOAA Atlas 15 timeline and when will it be released?

    All NOAA precipitation frequency standards will go through the public peer review process following the timeline presented below. Datasets will be released to the public at different points to ensure NOAA can collect feedback on NOAA Atlas 15, using NOAA’s service delivery model, as guidance.

    Montana
    • 2024 - Pilot project available for early feedback
    Contiguous United States (CONUS)
    The lower 48 states
    • 2025 - Preliminary estimates available for peer review and feedback
    • 2026 - Published estimates available for use and application
    Outside the Contiguous United States (oCONUS)
    Alaska, Hawaii, Puerto Rico and the U.S. Virgin Islands, Pacific Islands and Guam
    • 2026 - Preliminary estimates available for peer review and feedback
    • 2027 - Published estimates available for use and application
    Atlas 15 Timeline
  • What is the NOAA Atlas 15 Pilot?

    The NOAA Atlas 15 Pilot is a first look at the structure of the NOAA Atlas 15 dataset over the state of Montana to collect early feedback on development frameworks and Web dissemination strategies. With this early release, collaborative NOAA teams, including the National Centers for Environmental Information (NCEI), seek to engage with a large number of stakeholders who will use this dataset. The intent of the Pilot release is to demonstrate the nature of the data and help ensure practitioners have the precipitation information they need, upon final publication.

    The NOAA Atlas 15 Pilot covers a subset of storm durations (1 hour to 10 days) and average annual exceedance probabilities (50% to 1%), and is presented as two volumes. The NOAA Atlas 15 Pilot Volume 1 estimates are based on historical observations and provide estimates for the year of 2023. The NOAA Atlas 15 Pilot Volume 2 estimates are developed by applying adjustment factors to the 2023 Volume 1 estimates (i.e. future relative changes obtained from downscaled climate model data). Moreover, the NOAA Atlas 15 Pilot Volume 2 data are presented for future time periods as part of two distinct frameworks: global warming level (GWL) and emission scenario.

    The GWL framework provides estimates at specified levels of model-average global temperature anomalies. These estimates are derived from the points in time at which models have warmed to each specified benchmark (1.5 – 5°C) relative to preindustrial values. In contrast to the GWL framework, the emission scenario framework provides estimates at specified points in time, at the resolution of decades (2030 – 2100), under two different shared socioeconomic pathways (SSP2-4.5 and SSP5-8.5).

    Atlas 15 scenario graph

    Availability of NOAA Atlas 15 Pilot estimates over Montana. Volume 1 estimates are informed by historical observation data and provide current estimates (as of 2023). Volume 2 estimates are informed by climate model output data and estimate future conditions for specific global temperature anomalies according to the Global Warming Level framework (top) and for future decades according to the climate scenario framework (bottom).

    A full report describing the methods used to generate the NOAA Atlas 15 Pilot data is available for review.

    The release of NOAA Atlas 15 pilot data is intended for comparison and feedback purposes as it has not completed the peer review process. Both the data and web dissemination strategies are subject to change as a result of public feedback received and planned enhancements, as part of the full NOAA Atlas 15 release in 2026 and 2027.

    The NWS Public Notification Statement announcing the NOAA Atlas 15 Pilot can be found here.

  • What are the differences between the NOAA Atlas 15 Pilot and the full release?

    NOAA is sharing the Pilot data with the public to facilitate understanding of the new framework, development process and methods as well as to provide early insights into the Web dissemination strategy. The Pilot data shared are not final, and may significantly differ from the data shared upon publication and full release. Some major differences are highlighted in the table below.

    Pilot Full Release
    Spatial Coverage Montana United States and Territories
    Storm Durations 1-hour to 10-days 5-minutes to 60-days
    Exceedance Probabilities 50% to 1% 63% to 0.1%
    Methods Preliminary Fully Developed
  • How can I access the NOAA Atlas 15 Pilot data?

    The NOAA Atlas 15 Pilot data are available for early review HERE, as part of the NOAA National Weather Service’s National Water Prediction Service (NWPS) Web platform.

    NOAA invites you to review the website for the NOAA Atlas 15 Pilot that includes both Volume 1 and Volume 2 precipitation frequency estimates over Montana for a subset of storm durations (1-hour to 10-days) and average annual exceedance probabilities (AEPs) (50% to 1%).

    The NOAA Atlas 15 Pilot data and website are being shared to facilitate understanding and provide early insight into the development of NOAA Atlas 15, and to help ensure that practitioners have the precipitation frequency information they need, upon final publication. The NOAA Atlas 15 methods, data, and website will be refined through 2026 and 2027, when NOAA Atlas 15 is fully published.

    NOAA invites stakeholders to review the NOAA Atlas 15 Pilot website and share feedback. A Quick Start Video for the NOAA Atlas 15 Pilot website is available HERE.

  • How can I provide feedback?

    NOAA is seeking public feedback through survey questions available HERE. Full documentation describing the technical approach used to generate the NOAA Atlas 15 Pilot data is available in the NOAA Atlas 15 Pilot Technical Report. Feedback will be accepted through December 31, 2024.

  • How does the NOAA Atlas 15 Pilot differ from the recently released NOAA Atlas 14 Volume 12 study?

    The NOAA Atlas 15 Pilot study only covers the state of Montana, whereas the NOAA Atlas 14, Volume 12 study spans the states of Montana, Idaho, and Wyoming. Moreover, the NOAA Atlas 15 Pilot implements nonstationary statistical methods and uses climate model information to project precipitation frequency estimates into the future. In contrast, the NOAA Atlas 14, Volume 12 study assumes a stationary climate when deriving precipitation frequency estimates. Though NOAA is working to implement NOAA Atlas 15, the NOAA Atlas 14 studies (Volumes 1 - 12) are the existing national standard and authoritative source for precipitation frequency information today. NOAA Atlas 14, Volume 12 data can be found on the NOAA National Weather Service Precipitation Frequency Data Server (PFDS).

  • What happens after the NOAA Atlas 15 Pilot?

    NOAA will collect and review feedback on the NOAA Atlas 15 Pilot and consider refining its technical approach based on the feedback received. In 2025, NOAA plans to release preliminary NOAA Atlas 15 data for peer review for an area that covers the contiguous United States (i.e., the lower 48 states). The preliminary data and dissemination strategy for this dataset may reflect some of the feedback received during the NOAA Atlas 15 Pilot. See above for the full NOAA Atlas 15 timeline.

  • What happens after NOAA Atlas 15 is published and fully released?

    The Bipartisan Infrastructure Law provided NOAA with one-time federal funding to update precipitation frequency estimates nationwide while accounting for a changing climate (i.e., NOAA Atlas 15). After completing peer review and upon publication in 2026 (contiguous United States) and 2027 (outside the contiguous United States), NOAA Atlas 15 will supersede NOAA Atlas 14 as the national standard and will become the authoritative source for precipitation frequency information across the United States.

  • How do I access the current precipitation frequency standard, NOAA Atlas 14?

    NOAA Atlas 14 data can be accessed on the NOAA Precipitation Frequency Data Server (PFDS). Supporting documentation for NOAA Atlas 14 can be found HERE.

  • How do I receive updates on NOAA Atlas 15?

    Please visit this page to subscribe to updates and new information regarding NOAA Atlas 15.