The Probability of an EF-5 Tornado Being an EF-5 Torando: A Quantified Comparison of Damage Indicator Availability

The National Weather Service assigns official EF-scale ratings to tornadoes based on damage, which can cause a strong bias in tornado rating by the availability of targets. The Moore, Oklahoma, tornado on 20 May 2013 moved through a suburban area with a very high density of damage indicators (DI). Ground and aerial surveys documented 4,222 damage indicators of various intensities along the tornado path. The high number of DIs combined with housing unit density from the U.S. Census Bureau provides a unique opportunity to investigate the potential bias of under-estimating violent tornado intensity in more rural areas. Using these data sets, this study calculates the probability that the 2013 Moore tornado would have been rated EF-5 had it occurred at other locations within the United States. Additionally, a comparison is made of DI density associated with both the 2013 Moore tornado (228 DIs per square km) and the 2013 El Reno tornado (5.3 DIs per square km) that occurred in a less populated area 11 days later and the resultant effect on tornado ratings.