The Enhanced Fujita Scale: For Use Beyond Tornadoes?

Abstract

The Enhanced Fujita (EF) Scale was developed specifically for the estimation of wind speeds based on damage caused by tornado winds. Recently, the question has arisen as to whether or not the EF Scale can be reliably used in reverse to predict the amount of wind damage based on measured or estimated hurricane wind speeds, particularly when wind action is co-mingled with severe storm-surge action and evidence of the exact level of wind damage is obliterated. In considering such use of the EF Scale, we examine separately its two major components: (1) Degrees of Damage and (2) ranges of tornado wind speeds associated with these damage levels. Our experience suggests that, in general, the EF Scale properly describes the overall progression of damage with increasing wind speeds in both tornadoes and hurricanes; however, the wind speeds associated with various degrees of damage are generally expected to be different for structures exposed to hurricanes and tornadoes. Use of the EF Scale to predict hurricane damage based on peak wind speeds is therefore discouraged. DEVELOPMENT AND USE OF THE EF SCALE The original Fujita Scale (Fujita, 1971) was designed as a wind speed scale to provide relative ratings of tornado intensity (McDonald et al., 2009). The scale divided intensity into multiple wind speed ranges and attempted to describe the type of damage one might expect for each wind speed range. This original Fujita Scale did not account for differences in the resistance of various structures. Prior to the 1970s, there was little understanding of the true magnitudes of maximum wind speeds in tornadoes due to a scarcity of tornado wind speed measurements. Engineeringoriented investigations of tornado damage subsequently highlighted the importance of