. "4 Communicating Forecast Uncertainty." Completing the Forecast: Characterizing and Communicating Uncertainty for Better Decisions Using Weather and Climate Forecasts. Washington, DC: The National Academies Press, 2006.
and weaknesses, and each may best communicate a different type of uncertainty to a different user group. Products can be tailored to specific user needs, but when communicating with a diverse audience such as the public, one product is unlikely to meet all users’ needs or to be readily understandable to all subgroups (Chapter 2). When such a broad audience is anticipated, a mix of products will likely be most useful (Chapter 2). In addition, an NWS National Digital Guidance Database (recommendation 3.6) would help support this mix of products by providing users and intermediaries with data and tools for customizing communication of uncertainty information.
NWS and other members of the Enterprise generate a variety of textual, verbal, and visual products that communicate uncertainty (Annex 4). However, most weather forecasts specifically generated for the public contain little or no useful uncertainty information; they are simplified and deterministic. Members of the public have been conditioned to these deterministic forecasts and have been given little objective information on the inherent errors in these simplified predictions. Instead, users in the public have developed their own informal methods of estimating the uncertainty. This highlights the need for user education as the Enterprise transitions to probabilistic forecasting.
One major example of a predominantly deterministic product is the NWS public weather forecasts produced by the Interactive Forecast Preparation System (IFPS) and distributed as the National Digital Forecast Database (NDFD). IFPS/NDFD’s strength is that it allows forecasters to generate, present, and communicate forecasts of multiple weather elements as a digital database, both for the local area and as a nationally unified grid. Its main weakness is that the forecasts contain limited information about uncertainty. Most variables are estimated and presented as “point forecasts”
Suggestions for Improving Communication ofUncertainty Information
The following practical suggestions were made during an NRC workshop to improve information delivery (NRC, 2003b):
View communicating uncertainty to all information users as a key part of the decision-making process.
Communicate why information is uncertain, not just the fact that it is uncertain.
Communicate why information about uncertainty is important.
Use multiple measures of uncertainty and ways of communicating uncertainty to reach diverse audiences.
Use both qualitative and quantitative forms to communicate uncertainty.
Effectively communicating uncertainty and its context shifts the burden and responsibility of decision making to the information user. The following suggestions from the NRC workshop could improve communications to decision makers:
The careful and strategic use of context (a tie to a past experience) in the face of complexity and uncertainty frequently makes the meaning of the uncertainty tangible.
Comprehensively communicate what is known rather than only what it is thought the decision maker needs to know.
Perceived success or failure of forecasts and the portrayal of forecasts by the media and decision makers guide opinions and help determine the credibility of future forecasts. The following actions were suggested:
Expect misinterpretation. Make an effort to correct problems as soon as possible. Feedback from users is critical.
Provide a “measuring stick” to decision makers to guide their evaluation of forecasts and forecast uncertainty.
Avoid overselling or overinterpreting the science.
Provide follow-on information about forecast quality to help ensure the credibility of future communications. This information is particularly important following the forecast of significant events (e.g., when a forecast was successful despite a large uncertainty or when a forecast was highly credible and failure resulted).