The most recent occurrence of a powerful EF5 tornado striking the United States dates back to May 20, 2013, when a devastating twister tore through the Oklahoma City suburbs, leaving a 17-mile path of destruction in its wake. This catastrophic event, described as “40 minutes of terror,” claimed numerous lives and caused injuries to hundreds of individuals. While the past decade has seen the impact of similarly formidable tornadoes, such as the tragic EF4 tornado that ravaged western Kentucky on December 10, 2021, resulting in extensive loss of life and widespread devastation.
A recent study, led by NOAA meteorologist Anthony Lyza, sheds light on the unusual absence of EF5 tornadoes over the past 11 years, marking the longest drought of such severe tornadoes since records began in 1950. Contrary to the assumption of weakening tornadoes, researchers have identified a shift in how tornado intensity is classified, with stricter criteria being applied to categorize large tornadoes.
Lyza emphasizes that although EF5 tornadoes are rare occurrences, the likelihood of an extended period without any such tornadoes is minimal, at 0.3%. In recent years, there have been reports of EF4 tornadoes with wind speeds approaching 200 mph, prompting suggestions that some of these events might warrant an EF5 classification. The study also delves into the Enhanced Fujita scale, which assesses tornado intensity based on wind speeds, observed damage, and post-tornado surveys, offering a comprehensive framework for analyzing tornado impact.
Notably, EF5 tornadoes, characterized by wind speeds exceeding 201 mph, leave a trail of destruction that includes the sweeping away of well-constructed homes, critical damage to concrete structures, and the complete stripping of trees. However, due to their rarity and the structural limitations of most buildings, the occurrence of EF5-rated damage remains infrequent.
The distinction between the former F5 damage rating system and the current EF5 classification lies in the enhanced criteria for assessing tornado impact, emphasizing the severity of damage inflicted on structures and natural elements. Despite the challenges posed by these elusive and destructive tornadoes, ongoing research aims to enhance our understanding of these catastrophic weather events and improve preparedness for future occurrences.
The Enhanced Fujita (EF) scale, in comparison to the original Fujita scale, makes it much more challenging to achieve an EF5 rating. Lyza pointed out that reaching an EF5 rating under the current EF scale is more demanding than attaining an F5 rating under the old Fujita scale. She explained that in their study, every tornado in the EF-scale era with wind speeds at the high end of the EF4 range (190-200 mph) had its rating determined by the destruction of a site-built home being swept off its foundation. It is probable that some of these tornadoes would have been classified as F5 using the older Fujita scale. The absence of EF5-rated tornadoes in the last decade is attributed not to weaker tornadoes but to the stricter criteria of the Enhanced Fujita scale. Lyza mentioned a team of experts from the American Society of Civil Engineers and the American Meteorological Society are collaborating to update the Enhanced Fujita scale. The original source of this information was published on USA TODAY, discussing the perplexity among experts over the fact that the US has not experienced an EF5 tornado in the past 11 years.
