[14] Outside the United States and Canada, seven tornadoes have been officially rated F5/EF5/IF5: two each in France and Germany, and one each in Italy, Argentina and Australia.
[15] Additionally, because tornado ratings are damage-based, many tornadoes capable of causing F5/EF5/T10+ damage, such as those that move through rural areas, may receive lower ratings because their strongest winds do not strike any suitable damage indicators.
[17] In March 2024, Anthony W. Lyza, Matthew D. Flournoy, and A. Addison Alford, researchers with the National Severe Storms Laboratory, Storm Prediction Center, CIWRO, and the University of Oklahoma's School of Meteorology, published a paper stating, ">20% of supercell tornadoes may be capable of producing EF4–EF5 damage".
At the end of the analysis, the researchers stated, "the lofting wind speeds given by this model are much higher than the rating based on the ground survey EF-scale assessment.
This may be due to the current tendency to bias strong EF5 tornadoes lower than reality, or limitations in conventional EF-scale assessments".
[21] From 1950 to 1970, tornadoes were assessed retrospectively, primarily using information recorded in government databases, as well as newspaper photographs and eyewitness accounts.
[23] As of February 1, 2007, tornadoes in the United States are rated using the Enhanced Fujita scale, which replaced the Fujita scale in order to more accurately correlate tornadic intensity with damage indicators and to augment and refine damage descriptors.
Worldwide, a total of 67 tornadoes have been officially rated F5/EF5/IF5: 59 in the United States, two each in France and Germany, and one each in Argentina, Australia, Canada, and Italy.
These indications can come from the United States government, Doppler on Wheels, tornado experts (i.e. Thomas P. Grazulis, Ted Fujita), or meteorological research institutions (i.e. European Severe Storms Laboratory).
Many other tornadoes have never been formally rated by an official government source but have nonetheless been described as F5/EF5/T10+ or equivalent, often by independent studies.