The Development of New Dis for the EF-Scale

In 2006, Texas Tech University (TTU) published the Enhanced Fujita (EF) Scale to rate tornado intensity (WSEC 2006). It was developed by a team of atmospheric scientists and wind engineers to address certain limitations and inconsistencies with the Fujita (F) Scale developed in the 1970s. In 2007, the EF-Scale was adopted by the National Weather Service (NWS). It kept the same 0 to 5 damage ratings but changed the range of failure wind speeds for specific degrees of damage (DoD) for certain damage indicators (DIs), based on how well a building or object was constructed. While the EF-Scale was a great improvement over the F-Scale, there were still shortcomings identified (Edwards et al., 2013). One such shortcoming was the lack of DIs in rural areas to assist in determining tornado intensity and associated wind speeds. The lack of DIs, or lack of DIs that are relatively undamaged at all but the highest wind speeds, can lead to an underestimation of the wind speeds associated with a tornado.

In 2014, the American Society of Civil Engineers (ASCE)/Structural Engineering Institute (SEI) and the American Meteorological Society (AMS) undertook an effort to develop a consensus standard for tornado wind speed estimation. The forthcoming ASCE/SEI/AMS standard, Wind Speed Estimation in Tornadoes, will officially standardize the EF-Scale. This paper describes the development of new DIs that have been proposed and are in various states in the ASCE standards development process. These new DIs will supplement the existing DIs from the 2006 EF-Scale, and will introduce structure types that may be more common in rural areas to aid in wind speed estimation of tornadoes. These new DIs include passenger vehicles, farm silos and grain bins, religious buildings and classic architecture religious buildings, center pivot irrigation systems, wind turbines, and rooftop units.