The question of the “strongest” tornado ever recorded does not have a simple answer based on a single wind speed measurement. Tornado strength is primarily determined by the destruction left behind, which is then correlated with estimated wind speeds. This measurement method is necessary because these powerful, short-lived events rarely strike weather instruments capable of recording their top wind speeds. Therefore, the strongest tornado is defined by the maximum classification on the standardized severity scale used by meteorologists and engineers.
Defining Tornado Strength Through Rating Scales
The formal method for classifying tornado strength in the United States began with the Fujita Scale (F-Scale), introduced by Dr. T. Theodore Fujita in 1971. This scale assigned a rating from F0 to F5 based on the severity of the damage observed after a storm had passed. The F-Scale relied on estimated wind speeds, but these estimates were later found to be significantly higher than the winds actually required to cause that level of destruction.
The need for a more accurate and standardized tool led to the development of the Enhanced Fujita Scale (EF-Scale), which the National Weather Service fully implemented in February 2007. The EF-Scale retained the six-category structure (EF0 to EF5) but incorporated 28 different damage indicators, such as building type and construction quality, to standardize the assessment process. This refinement provides a better correlation between the damage observed and a more realistic estimate of the three-second wind gusts. The scale remains an estimate based on damage, not a direct measurement of the wind at the surface.
The Maximum Rating: EF5 and F5
The maximum classification for a tornado on both the historical F-Scale and the modern EF-Scale is 5, representing the highest possible level of damage. An EF5 tornado is estimated to have three-second wind gusts exceeding 200 miles per hour (322 kilometers per hour). This intensity is applied when the damage survey confirms a complete and catastrophic level of destruction.
The damage required for an EF5 rating is highly specific and extreme, going beyond the mere leveling of a structure. Well-built frame homes are often swept clean off their foundations, leaving only the bare concrete slab behind. Steel-reinforced concrete structures may be severely damaged, and automobile-sized debris can be thrown considerable distances. The winds are also capable of stripping bark completely from trees and causing significant ground scouring.
Notable Historical Examples of Maximum Strength
The strongest tornadoes are defined by specific events that attained the F5 or EF5 rating. The 1925 Tri-State Tornado is widely recognized as one of the most destructive in United States history, traveling 219 miles across Missouri, Illinois, and Indiana. Although it occurred before the F-Scale was devised, experts retroactively agree the damage was consistent with an F5 rating, making it the deadliest single tornado on record. The storm’s average forward speed was 62 miles per hour, and it was responsible for 695 fatalities.
A modern example of a maximum-strength event is the 2011 Joplin, Missouri tornado, which was rated EF5, resulting in massive damage across the city. This storm was one of the deadliest tornadoes in recent decades. Another notable event is the 2013 Moore, Oklahoma tornado, which also achieved an EF5 rating.
The 1999 Bridge Creek-Moore tornado, an F5 event that struck Oklahoma, holds the record for the highest wind speed ever measured inside a tornado. A mobile Doppler-on-Wheels (DOW) radar recorded a wind speed of 321 miles per hour (517 kilometers per hour) within the funnel cloud. This measured speed is often cited as the strongest wind speed associated with any tornado, even though the official rating is based on the damage inflicted on the ground.
Scientific Challenges in Absolute Wind Speed Measurement
Directly measuring the absolute wind speed near the ground within a tornado remains a significant challenge for meteorologists. The extreme intensity and short duration of violent tornadoes make it nearly impossible to place instruments directly in their path to survive. Instruments that do exist, like the mobile Doppler radar used in the 1999 event, are rare and only capture a snapshot of the wind field at a specific moment and altitude.
Because of these observational limitations, the official classification system must rely on post-storm damage surveys as a proxy for wind speed. The EF-Scale is a damage scale, not a direct wind speed measurement scale. Therefore, a single “strongest” tornado cannot be definitively named based on pure speed. The rating is determined by the maximum damage found, which is a practical necessity given the unpredictable nature of these powerful atmospheric events.