Communicating forecast uncertainty: Public perception of weather forecast uncertainty

Abstract

The general public understands that there is uncertainty inherent in deterministic forecasts as well as understanding some of the factors that increase uncertainty. This was determined in an online survey of 1340 residents of Washington and Oregon, USA. Understanding was probed using questions that asked participants what they expected to observe when given a deterministic forecast with a specified lead time, for a particular weather parameter, during a particular time of year. It was also probed by asking participants to estimate the number of observations, out of 100, that they expected to fall within specified ranges around the deterministic forecast. Almost all respondents (99.99%) anticipated some uncertainty in the deterministic forecast. Furthermore, their answers suggested that they expected greater uncertainty for longer lead times when the forecasted value deviated from climatic norms. Perhaps most noteworthy was that they expected specific forecast biases (e.g. over-forecasting of extremes), most of which were not borne out by an analysis of local National Weather Service verification data. In summary, users had well-formed uncertainty expectations suggesting that they are prepared to understand explicit uncertainty forecasts for a wide range of parameters. Indeed, explicit uncertainty estimates may be necessary to overcome some of the anticipated forecast biases that may be affecting the usefulness of existing weather forecasts. Despite the fact that these bias expectations are largely unjustified, they could lead to adjustment of forecasts that could in turn have serious negative consequences for users, especially with respect to extreme weather warnings. © 2010 Royal Meteorological Society.