Understanding the Implications of Categorical vs. Continuous Graphical Depictions of Risk: Different Colors, Risk Conditions, and Risk Boundaries.

Severe weather poses a serious safety hazard to the general public making advanced guidance critical for effective planning and decision-making. Currently, the Storm Prediction Center (SPC) produces the Day 1 Convective Outlook, which uses categorical risk boundaries to indicate the likelihood of severe weather. However, these categorical risk boundaries can be overly simplistic, as they do not capture the nuanced progression of risk across an area. Continuous risk displays, on the other hand, may offer a more detailed depiction by showing incremental changes in risk levels. This study explores how risk perception, uncertainty, and behavioral intentions are affected by different types of weather risk graphics--categorical vs. continuous-- when risk categories and colors are changed. A survey on severe weather graphics and messaging was deployed to a representative sample of the U.S. public (n=696), employing an experimental design that manipulated graphical type (continuous vs. categorical), risk gap (-1, 0, +1), and color (SPC color scheme, light color scheme, and Weather Channel color scheme). This design allows for analysis of differences between categorical and continuous formats as well as measuring its implications on message consistency. Our findings revealed statistically significant differences in the perceptual variables when changing the risk gap (-1, control, +1) for both categorical and continuous graphics. However, the results were mixed regarding the impact of different color schemes (lighter color, SPC color, Weather Channel color) between the two graphic types. These findings may have implications on both severe weather risk communication and message consistency, providing preliminary research-guided recommendations on the most effective ways to visually convey severe weather risk information.