Where Have All The EF5 Tornadoes Gone? The Surprising Reason Behind The 11-Year Drought

New Study Reveals The Lack Of EF5 Tornadoes

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It may be hard to believe that with an average of 1,200 tornadoes each year in the United States, we haven’t seen an EF5-rated twister in more than 11 years.

But that doesn’t mean the number of tornadoes is decreasing. In fact, it’s quite the opposite. In 2024, the U.S. had more than 1,800 confirmed tornadoes – the second-most on record.

And although the U.S. has not experienced an officially classified EF5 tornado in over a decade, this does not necessarily mean extreme tornadoes are becoming less frequent, either. The reality is that our standards for measuring them have simply changed.

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Here's What’s Causing The Sharp Decline In EF5 Tornadoes

A new study published in the Bulletin of the American Meteorological Society suggests that the decline in Earth’s most violent twisters isn’t because tornadoes are becoming weaker; rather, it's due to a change in how they're classified.

Tornado classifications have evolved since the original Fujita (F scale) was developed in 1971. Under the original F scale, an F5 rating was given as follows:

“Whole frame houses tossed off foundations; steel-reinforced concrete structures badly damaged; automobile-sized missiles generated; incredible phenomena can occur.”

However, scientists believed there were two major problems with the original F-scale:

• Wind speeds: Wind speeds were estimated at 261-318 mph for an F5 tornado. However, several engineering studies indicated that no evidence existed of tornado wind speeds above 250 mph.
• Structural Integrity: There were concerns about the lack of consideration for the integrity of structures with the original F-scale. Fujita even agreed that structural integrity should be taken into account when assigning an F-scale rating.

So the Enhanced Fujita (EF) scale was established in 2006 and remains the standard for tornado classification today. This new scale lowers the maximum wind speeds to "over 200 mph."

But the biggest difference, and what’s believed to be the reason behind the decline in EF5 numbers, is that the EF scale accounts for structural engineering principles, incorporating different degrees of damage (DODs) for various types of buildings and structures.

As a result, tornadoes that might have been classified as F5 under the old system could now be assigned an EF4 rating under the EF scale due to stricter criteria.

The EF Scale's Impact On EF5 Classification

A key distinction between the F and EF scales is how they evaluate damage to single-family homes. Under the F-scale, a well-constructed home being swept away was automatically considered F5 damage.

However, under the EF scale, the same level of destruction is typically classified as EF4 unless the home is explicitly proven to be built beyond standard construction codes. The study points out that building codes are ever-evolving, so even under these parameters, it will be difficult to maintain consistency with tornado classification in future years.

This change in methodology significantly reduced the number of EF5 ratings. The study’s authors argue that adjusting the EF5 wind speed threshold downward just 11 mph from 201 mph to 190 mph, or upgrading tornadoes with 190-200 mph estimated winds to EF5, would create a more consistent classification system that aligns with historical records dating back to 1880.

This would reclassify 15 tornadoes over the last 14 years from EF4 to EF5, most recently the Rolling Fork, Mississippi, from March 2023.

(​MORE: America's F/EF5 Tornadoes Since 1950)

The last official EF5 tornado to hit the U.S. was the infamous 2013 Moore, Oklahoma, tornado. This violent tornado was on the ground for more than 40 minutes, carving a path of devastation more than a mile wide at times. It was responsible for two dozen deaths, more than 200 injuries and upward of $2 billion in damage.

To the untrained eye, most would immediately assume that it was an EF5 tornado. However, the EF scale is much more specific than what our mind can determine while emotionally invested in such a natural disaster.

At the conclusion of the Moore tornado survey, it was determined that nine homes sustained EF5 damage. Not only were homes evaluated that were swept off their foundations, but field surveyors took into account "the foundation anchoring and estimation of how much force was applied to the foundation anchors before the house completely failed (i.e., how long did the walls remain attached prior to failure and removal from the foundation, as indicated by the degree of anchor bolt bending, bolt spacing, presence of proper washers and nuts on anchor bolts, and fraction of sill plates remaining)."

In other words, this was a much more specific and detailed survey than one using the original F scale, which didn’t take structural integrity into account at all.

Could Tornado Classification Change Once Again?

While there is no word on whether tornado ratings will be adjusted again, this shift in classification does raise important questions for meteorologists, engineers and policymakers on how top-tier tornado intensities are defined. These considerations could have profound implications for emergency preparedness, building codes and insurance assessments.

J​ennifer Gray is a weather and climate writer for weather.com. She has been covering some of the world's biggest weather and climate stories for the last two decades.