This bears on building codes and as well as on a community's ability to bounce back after a tornado. The NIST study of the Joplin disaster noted that Joplin and its environs were no stranger to tornadoes. Since 1950, 182 tornadoes had touched down within 80 miles of the city. Yet the tornado hazard assessment for the area seriously underestimated the damage that would occur from a tornado of the intensity and duration that struck the city in 2011.
The assessment focused on the likelihood of a tornado striking an individual point, and it didn't take into account damage inflicted by debris a twister would generate, damaging structures far beyond the immediate track beneath the funnel. NIST researchers recommended that tornado risks be determined on the likelihood of a tornado striking the area to account for damage that can extend beyond a twister's path.
"If we're looking at community resiliency, and the effect on the economic viability of communities, we need to consider not just the probability of a tornado hitting an individual structure, a house, or a school, we need to consider the effect on the community as a whole," says Eric Letvin, NIST's project manager for the study.