CR 24:103-117 (2003)  -  doi:10.3354/cr024103

ABSTRACT: Losses from all natural hazards have increased steadily over the past 3 decades and a continuous cycle of Presidential disaster declarations was generated as communities rebuilt and recovered from these often devastating events. Using a 50 yr record, this paper examines the temporal variability and spatial distribution of tornado hazards in the United States. Tornado hazards are defined very specifically as any reported tornado that resulted in human injury, human fatality, or some amount of economic loss. The results suggest that, while the actual number of tornadoes (tornado segments) doubled over the entire time period, there was a smaller overall increase in the number of tornado hazards from 1950 to 2000. The ratio of tornado hazards to all tornadoes has remained relatively constant since the 1960s. There has been a steady decline in fatalities and reductions in injuries caused by tornado hazards. Losses are more variable over the past 50 yr, but the 1990s showed near record lows, in terms of both total dollar losses and mean losses per tornado hazard event. The statistical center of tornado hazard activity is in south-central Missouri, southeast of the statistical center of tornadoes identified by previous research. The density of tornado hazards has expanded outward from the historic ŒTornado Alley¹ region. The distribution of other high-density regions suggests additional tornado hazard regions in Florida, the lower Mississippi Valley, the Gulf Coast, and in the Carolinas.

KEY WORDS: Tornado hazards · GIS · Spatial variation · Temporal trends