NWS asked the committee to (1) provide guidance on how to identify and characterize needs for uncertainty information among various users of forecasts; (2) identify limitations in current methods for estimating and validating forecast uncertainty, relating these limitations to users’ needs, and recommending improvements or new methods and approaches; and (3) identify sources of misunderstanding and recommend improvements in the methods used to communicate forecast uncertainty.

Recognizing the breadth and depth of this task, NWS advised the committee at its opening meeting to “teach us how to fish as opposed to giving us a fish.” The committee approached the task accordingly. Relative to the first component of the task, the report reviews how decision makers interpret and use uncertainty information with the aim of helping NWS and others in the Enterprise understand key relevant concepts in decision making under uncertainty. Building from these concepts, the committee recommends a process by which NWS can develop an effective system of user–provider interactions that will lead to more effective products. Relative to the second component of the task, the committee takes the view that generating comprehensive uncertainty information to support all forecasts is central to the mission of NWS and will benefit all users. Such information must be made easily accessible and include all raw and post-processed products as well as verification and measurement information.6 The committee addresses the third component of the task by exploring the roles of graphics and language, dissemination technologies, and the media in communication of uncertainty information. In addition, the committee proposes refinements to NWS’s product development processes and highlights the need for education and research to support Enterprise-wide progress on communication of uncertainty information.

NWS asked the committee to recognize the diverse roles of participants in the Enterprise and the varied needs of forecast users. In addition, NWS requested that the committee’s recommendations focus primarily on the NWS mission, but may also address other components of NOAA or seek to guide other relevant government agencies and nongovernmental entities. In cases where a recommendation states that “NWS should …” it is the committee’s intention that the recommendation also applies to any relevant group or activity within NOAA, such as the Office of Oceanic and Atmospheric Research (OAR). The committee met five times between April 2005 and February 2006. One of its meetings was held in parallel with the annual American Meteorological Society Numerical Weather Forecasting and Broadcast Meteorology Conference, and another was held at the National Center for Atmospheric Research. NWS provided significant informational input to the process, both at meetings and in responses to questions posed by the committee.


Moving toward effective estimation and communication of uncertainty information has broad and deep implications for the Enterprise and the community it serves. Because of the immense breadth and depth of this challenge, detailed solutions are beyond the reach of a single committee. Consequently, this report provides general ideas for consideration by NWS and the entire Enterprise.

The committee presents nine overarching recommendations all with equal priority. In addition, detailed recommendations appear in Chapters 2, 3, and 4 that add further specificity and breadth. All recommendations should be considered in the context of NOAA’s Policy on Partnerships in the Provision of Environmental Information.7

Enterprise-wide Involvement

Finding 1:8 Hydrometeorological services in the United States are an Enterprise effort. Therefore, effective incorporation of uncertainty information will require a fundamental and coordinated shift by all sectors of the Enterprise. Furthermore, it will take time and perseverance to successfully make this shift. As the nation’s public weather service, NWS has the responsibility to take a leading role in the transition to widespread, effective incorporation of uncertainty information into hydrometeorological prediction.

Recommendation 1: The entire Enterprise should take responsibility for providing products that effectively communicate forecast uncertainty information. NWS should take a leadership role in this effort.

Product Development Incorporating Broad Expertise and Knowledge from the Outset

Finding 2:9 Understanding user needs and effectively communicating the value of uncertainty information for addressing those needs are perhaps the largest and most important tasks for the Enterprise. Yet, forecast information is often provided without full understanding of user needs or how to develop products that best support user decisions. Parts of the Enterprise (e.g., within the private sector and academia) have developed a sophisticated understanding of user needs. In addition, there is a wealth of relevant knowledge in the social and behavioral sciences that could be more effectively incorporated into product research and development. Currently, this variety of resources is not being fully tapped by


Forecast verification is the means by which the quality of forecasts is assessed. Forecast post-processing converts model output into human-comprehensible information and corrects for model biases.


 See http://www.nws.noaa.gov/partnershippolicy/ and also Box 1.2.


 See Section 1.5 for further discussion on this topic.


 See Sections 2.4, 4.2.6, and 4.2.7.

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