What is already known:
What this study adds:
In this study we looked at several issues regarding the derivation of population exposure and fatality rate estimates during widespread tornado outbreaks. The two events studied were the April 3, 1974 and April 27, 2011 tornado outbreaks in the state of Alabama. We attempted to determine if tornado warnings have become more effective over time at reducing the number of fatalities. We used GIS to perform an analysis on these outbreaks. We found that the effectiveness of tornado warnings did improve between the two outbreaks, and we can have reasonably high confidence in using county level population data to compare recent and historical outbreaks, although the higher resolution of the census track data is preferred for studying a single tornadic event. We also found that the accuracy of fatality rates is directly related to the accuracy of the path data. Finally, GIS can be used to innovatively evaluate tornado warning effectiveness.