Geographic scale and probabilistic forecasts: a trade-off for protective decisions?

This pilot study aimed to examine the impact of varying geographic scales, probabilities of tornado occurrence, and presentation formats within severe weather forecasts on individuals’ protective decisions. This pilot was unique in its specific examination of the trade-off between highly localized geography and higher valued probabilistic threat information in weather-related decision making. This pilot utilized a 4 (geographic scale) × 12 (probability) × 3 (forecast presentation format) mixed, nested experimental design. Participants were 440 US adults who completed electronic questionnaires containing experimentally manipulated severe weather forecasts. A linear mixed model analysis revealed several findings. First, participants who saw only categorical forecasts made similar preparatory decisions across geographic scales. Additionally, they were more willing to take preparatory action as categorical risk increased. Second, when probabilities were presented, the propensity to take protective action was greater at higher probabilities and at larger geographic scales, affirming the regional geographic reference class selected by the Storm Prediction Center in today’s outlook system. Third, individuals’ propensity for action generally increased as scale and probability increased, but the pattern varied across presentation formats. Lastly, participants reported having a map to look at was moderately important to their decisions and having probabilistic and categorical risk information was highly important to their decisions. Taken together, the findings suggest a complex relationship between geographic scale and probability, which is further complicated by forecast presentation format.