It’s been over 11 years since an EF5 tornado tore across the United States—a historically rare gap for the country known for hosting Earth’s most violent twisters.
But according to groundbreaking research published in the Bulletin of the American Meteorological Society, this “drought” of EF5 tornadoes may not reflect calmer skies—it may come down to how we assess tornado damage.
The EF5 Drought: A Statistical Oddity
As of early 2025, the U.S. has not recorded an EF5 tornado since the Moore, Oklahoma event on May 20, 2013. That’s the longest period without an EF5 since modern records began in 1950.
To put this in perspective:
- From 1880 to 2013, the odds of an EF5 occurring in any given year were 44%.
- Including the dry stretch from 2014–2023, that probability dips slightly to 41%.
- The odds of 10 straight years passing without an EF5? Just 0.3%—highly improbable.
So if violent tornadoes haven’t disappeared, what has?
How Damage Ratings Changed Everything
The EF5 rating, the most severe on the Enhanced Fujita Scale, is assigned not by wind measurement but by damage indicators (DIs)—a standardized list of structural and object-based clues surveyed after a tornado.
The original Fujita Scale, used from 1971 to 2007, allowed more subjectivity and often rated “well-built homes swept from foundations” as F5. But under the EF scale, introduced in 2007, those same homes typically rate only as EF4, unless they were built above code and anchored to a degree rarely found in the field.
The result?
- Fewer homes qualify as EF5 damage, even if the actual winds might have reached EF5 intensity.
- The threshold for EF5 begins at 201 mph (324 km/h), but only 4 of 28 official damage indicators can realistically qualify.
EF5-Candidate Tornadoes: Overlooked Giants?
The study identifies 16 tornadoes since 2011 that were officially rated EF4 but could likely qualify as EF5 if the older Fujita standards—or a less conservative interpretation of the EF scale—were applied.
Examples include:
- Tuscaloosa, AL (2011) – 190 mph estimated winds
- Shawnee, OK (2013) – 190 mph
- Mayfield, KY (2021) – 190 mph
- Rolling Fork, MS (2023) – 195 mph
Most of these cases involved well-built homes swept cleanly off foundations—classic F5 indicators before 2007.
If these EF5 candidates were reclassified, the annual EF5 occurrence probability would rise to 55.6%, nearly restoring the historical baseline of 56% seen before the current drought.
Should the EF5 Threshold Be Lowered?
The researchers argue that simply lowering the EF5 wind speed threshold from 201 mph to 190 mph (306 km/h) could:
- Restore rating continuity across decades
- Improve consistency with actual structural damage observations
- Better reflect tornado climatology from 1880 onward
They also ask whether tornado ratings should rely solely on wind estimates—or be more impact-based, factoring in the total devastation, context, or radar-confirmed velocities.
Tornado Ratings: Science or Symbol?
At the heart of the debate is this key question: What should an EF5 rating represent?
Should it be:
- A narrowly-defined engineering standard requiring nearly perfect home construction?
- Or a symbolic recognition of a storm’s rare intensity and societal impact?
The answer may reshape how we understand tornado risk, preparedness, and forecasting in an era of increasing extreme weather. We would love to hear what you think in the comments!
