Tornado Data Characterization and Windspeed Risk

Tornado data records are analyzed for potential classification error, F-scale windspeed correlation, and tornado intensity variation. This assessment provides quantification of the uncertainties inherent in tornado wind loading specification and risk analysis as a result of the indirect measuring techniques utilized in the current national tornado classification methodology. A data base of over 4,500 tornadoes is analyzed according to three broad geographic regions to demonstrate the methodology and to provide input for tornado loading risk analyses. The results indicate that the potential classification error is significant for the intense tornadoes and tends to underestimate the likelihood of the rare events by several hundred percent. A set of updated windspeed transformations are presented which suggest that the original windspeed ranges are 10% to 20% too high. The maximum tornado windspeeds are suggested as 300 mph, 225 mph, and 200 mph for three identified tornado regions in the United States.