A Systematic Approach to Improve Tornado Warnings (69)

Kevin Laws, National Weather Service, Birmingham, AL




Discussion of the National Weather Service's storm-based warnings has been ongoing since being introduced in 2007. As originally conceived, polygon warnings were intended to spatially enclose severe weather hazards without regard to county or other geopolitical boundaries. In fact, statistics and visual evidence confirm that many storm-based warnings are issued from this perspective. However, NOAA Weather Radio All Hazards and most other warning dissemination systems remain county-based, and the polygons are often unnecessarily large dimensions in either space or time, which can lead to the reality or perception of over-warning. Recent social science research indicates that the public's perception of false alarms is much greater than the actual number of warnings issued, regardless of event verification. Adding improved polygonology and properly analyzed environmental data to the warning decision process allows forecasters to reduce the false alarm ratio, without reducing the more important probability of detection and lead time. The strategies and best practices that will be presented are intended to reduce the public's perception, either real or perceived, of false alarms, thereby increasing the overall confidence in the warning decisions.