National Weather Service Vision for Communicating Information
The NWS vision of communicating information to users is to
SOURCE: NWS, http://www.nws.noaa.gov/om/disemsys.shtml.
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 of Uncertainty Information
The following practical suggestions were made during an NRC workshop to improve information delivery (NRC, 2003b):
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:
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:
SOURCE: NRC, 2003b.