Since the late 18th century, meteorologists and engineers have worked to assess the intensity of tornadoes, typically through the work of a tornado damage survey or a scientific case study. This work has led to the creation of the Fujita scale (F-scale) in 1971 and the TORRO scale in 1975. However, the original Fujita scale lacked the incorporation of diverse empirical damage to estimate wind speeds, such as construction quality; to address this, the Enhanced Fujita scale (EF-scale) was created in 2007, followed by the International Fujita scale (IF-scale) in 2023. Despite these efforts to help assess the strength of tornadoes, engineers, scientists and academics have disagreed with each other on how strong various tornadoes were. This is a list of notable disagreements on the intensity of a particular tornado.
Background
The Fujita scale was the first method to systematically rate tornadoes based on damage assessment. It linked damage descriptions—like debarked trees or destroyed houses—to a bracket of wind speeds that would have been necessary to cause the damage, assigning each a rating from F0 to F5. This approach to rating tornadoes and concluding their probable wind speeds was revolutionary and was replicated and adapted into the various scales used today.
It is often difficult to distinguish tornadoes in the upper echelons of the Fujita scale as minute details must be analyzed in order to provide an accurate rating. Conversely, tornadoes which leave behind little to no damage can not be accurately represented using damage assessment methods. Tornadoes that happened farther in the past or in regions outside of more tornado-prepared areas will have similar difficulty in receiving an accurate rating due to a dearth of information. The situation is further muddled by the fact that these scales incorporate different types of data, leading to differing ratings based on which scale is used. For example, the International Fujita scale uniquely uses measured wind speeds via Doppler weather radar alongside damage assessment techniques.
Pre-1950s 1931 Lublin tornado
On July 20, 1931, a violent tornado struck the city of Lublin in Poland. The damage from the tornado was rated F4 on the Fujita scale by the European Severe Storms Laboratory. The Polish Weather Service estimated that the tornado had winds between . The lower rating is a result of comparing the damage with modern scales. The older, higher rating was the result of calculating the wind pressure needed to cause the specified damage. This means it was potentially at F5 intensity, as F5 tornadoes begin with winds at . But in publication by members of staff of the University of Warsaw and Adam Mickiewicz University in Poland as well as the National Oceanic and Atmospheric Administration in the United States doubts were expressed about this assessment: " ...this estimate is highly uncertain since no typical F5 damage was reported. Instead, F4 damage was plausible".
1970s
Super Outbreak (1974)
On April 3, 1974, one of the most destructive tornado outbreaks on record would affect much of the United States. This included a violent tornado struck the towns of Xenia and Wilberforce in Ohio. Immediately following the tornado, Dr. Ted Fujita and a team of colleagues from the University of Chicago, University of Oklahoma, and National Severe Storms Laboratory, undertook a 10-month study of the 1974 Super Outbreak. Along with discovering new knowledge about tornadoes, such as downbursts and microbursts, and assessing damage to surrounding structures, the Xenia tornado was determined to be the worst out of 148 storms. Fujita initially assigned a preliminary rating of F6 intensity ± 1 scale. This rating was later officially downgraded by the National Weather Service office in Cincinnati, Ohio (now located in Wilmington, Ohio), which rated the worst of the damage in Xenia F5.
Another violent tornado struck several towns in Lincoln County, Franklin County, and Coffee County in Tennessee. The worst of the damage in Franklin County was rated F5 by the National Weather Service, however, in March 2012, the National Weather Service stated they could not confirm if the United States Weather Bureau ever conducted a damage survey after the tornado. Professor Ted Fujita and several of his graduate students did conduct a damage survey, where they "were unable to locate the reference to 'incredible damage' that results from an F5" rating. After their survey and analysis, Fujita and his students sent a letter to the Storm Prediction Center, recommending the tornado be downgraded to an F4 rating. Following this letter, the National Weather Service downgraded the tornado to an F4 rating.
1980s
Speer–Messer–Golden–Broken Bow, Oklahoma (1982)
On April 2, 1982, a large, violent, and at times multiple-vortex tornado traveled from south of Speer, Oklahoma and across the southern tip of Broken Bow before dissipating southeast of Eagletown. At one point it was wide. It destroyed 30-40 homes, 30-40 large barns as well as other farm buildings, trailer homes, a church, and a motel. A sign from the motel was carried and a wooden board was driven into a tree. Twenty-nine people were injured. The NWS officially rated the tornado F5 based on the destruction of a small, newly constructed home near Messer. It was completely swept away with only carpet tack strips left on the foundation. In 1993, Grazulis rated the tornado F4, stating that the home near Messer was poorly anchored, and its destruction may not even indicate F4 intensity. Several ranch homes were leveled, garnering the F4 rating. In his 2023 book, Grazulis listed this tornado as F5, stating that Fujita agreed to an F5 rating "in order to avoid confusion."
1990s Texas Panhandle tornado outbreak (1995)
On June 8, 1995, an extremely severe and localized outbreak of tornadoes occurred in the Texas Panhandle. A violent stovepipe tornado struck the city of Pampa, Texas after touching down to its southwest. Its short path length and lack of damage to structures limited its rating. According to Thomas P. Grazulis, the F4 rating it was given was based on the movement of industrial equipment, as the tornado had weakened significantly by the time it entered more populated areas. Grazulis used photogrammetry to conclude that at about 100 feet above ground level, the tornado had wind speeds in the 200–250 miles per hour, not counting a powerful vertical wind component. Grazulis later discussed the Pampa event in F5-F6 Tornadoes and declared "In my opinion, if there ever was an F6 tornado caught on video, it was the Pampa, Texas tornado of 1995". The same supercell responsible for the Pampa tornado cycled and produced another significant tornado near Hoover, Texas, which was officially rated F2. Narrowly missing the Rufe Jordan Unit prison, this tornado displayed significant strength by stripping asphalt from the local highways.
Jarrell, Texas (1997)
On May 27, 1997, a devastating tornado struck the outskirts of Jarrell, Texas, where tens of houses were destroyed and 27 people were killed. A damage survey conducted by the National Weather Service resulted in an official rating of F5 for the tornado. However, a team with the National Institute of Standards and Technology argued that the worst damage could be attributed to F3-strength winds due to issues with the construction quality of the affected homes. Overall, they criticized the lack of consideration for construction quality under the Fujita Scale that they claimed resulted in an overestimation of tornadic wind speeds. In conclusion, this tornado stays classified as F5.
2000s Elie, Manitoba (2007)
On June 22, 2007, a small but powerful tornado struck the southwestern part of Elie, Manitoba. The next day, a preliminary damage assessment by Environment Canada concluded that out of the four houses destroyed by the tornado, the most damaged house received an F4 rating. While they did initially consider rating the tornado as an F5, the lack of any previous F5-rated tornadoes in Canada resulted in the lower rating. Additionally, the investigators were concerned about the scrutiny they would receive from the media and meteorological community if they rated the tornado an F5, and how they could not confirm whether the extreme damage was a result of the tornado's slow motion. In September 2007, Environment Canada officially upgraded the tornado's rating from F4 to F5 based on video evidence and a second damage survey. The videos showed that not only did the tornado remain over each house for no longer than 30 seconds, but also that it showed how exactly the well-built homes were torn their foundations.
In 2008 at the American Meteorological Society's 24th Conference on Severe Local Storms, Patrick J. McCarthy, along with D. Carlsen and J. Slipec, submitted a paper for and hosted a presentation on the Elie tornado. At the conference, it was presented that some of the damage did point to an F5 rating, however, the survey team was concerned the tornado was weaker than F5 strength, and only caused the extreme damage due to moving slowly, where it could have "relentlessly pounded the houses into a higher level of destruction". After further investigation using video evidence captured by people watching the tornado, the surveyors determined that "the structural failures were quick. The structural assessments indicated that the homes were well-built and generally well-secured. In particular, one of the destroyed homes met all of the requirements for the highest damage rating." The team also noted that the damage would have qualified for an EF5 rating on the Enhanced Fujita scale, which was in use in the United States at the time.
2010s Super Outbreak (2011)
On April 27, 2011, the most large-scale tornado outbreak would devastate much of the southern United States, with five tornadoes having a disputed rating.
A large and long-lived tornado struck several towns in rural northern Alabama before tearing through the northern suburbs of Huntsville; in particular the towns of Hackleburg, Phil Campbell, and Tanner in Alabama. The National Weather Service offices in Birmingham and Huntsville, Alabama, rated the worst of the damage caused by the tornado EF5 with winds estimated to be at least . Nearly two-dozen locations along the tornado's track were rated EF5.
In the AMS paper, researchers stated the justification for the EF5 rating was numerous homes that were swept away, however, only a single home was "bolted to its foundation". The researchers also noted that in Hackleburg, the National Weather Service office in Birmingham, Alabama, used "the tossing of vehicles and the wind rowing of debris" as contextual reasons to apply the EF5 rating. The researchers went on to state how "only one home was explicitly noted to have actually been anchored to its foundation", and the only location to warrant an EF5 rating.
Another violent multi-vortex tornado destroyed portions of Tuscaloosa and Birmingham, Alabama, as well as smaller communities and rural areas between the two cities. The National Weather Service office in Birmingham, Alabama rated the worst of the damage caused by the tornado EF4 with winds of at least .