Fujita vs Enhanced Fujita
The original Fujita Scale used tornado wind estimates that turned out to be too high. Here is what changed in 2007 — and what did not.
The original Fujita Scale (1971-2006)
Ted Fujita — Japanese meteorologist at University of Chicago — created the F-scale in 1971 as a way to categorize tornado damage.
F0 was the mildest, F5 the strongest. Each level had an associated wind speed range based on Fujita's estimates of what winds would cause each damage category.
- F0: 40-72 mph
- F1: 73-112 mph
- F2: 113-157 mph
- F3: 158-206 mph
- F4: 207-260 mph
- F5: 261-318 mph
The problem
By the 1990s, engineers had studied actual wind loading on structures. Fujita's wind estimates were too high — by 40+ mph for the higher categories. A house didn't need 261 mph winds to be swept clean; 200 mph would do it.
This meant F5 ratings were often assigned to tornadoes that actually had lower peak winds. It also meant damage that should have been F4 or F5 was sometimes rated lower because the damage indicators didn't match Fujita's original mental picture.
The Enhanced Fujita Scale (2007-present)
The EF-scale was developed by a team led by Texas Tech's Wind Science and Engineering Research Center.
It kept the 0-5 category structure but rewrote everything else.
- EF0: 65-85 mph
- EF1: 86-110 mph
- EF2: 111-135 mph
- EF3: 136-165 mph
- EF4: 166-200 mph
- EF5: over 200 mph
Winds are 3-second gust estimates at ground level.
The Damage Indicators (DIs)
The heart of the EF-scale is 28 Damage Indicators — specific building types and structures, each with 8-10 damage description levels called Degrees of Damage (DoD).
Instead of guessing wind speed from damage, engineers look up the DoD in a table.
- Small barn or shed — 6 DoDs.
- One- or two-family residence — 10 DoDs.
- Manufactured home (mobile home) — 9 DoDs.
- Motel — 10 DoDs.
- Motel — masonry apartment — 9 DoDs.
- Small retail building — 8 DoDs.
- Small warehouse — 9 DoDs.
- Strip mall — 8 DoDs.
- Institutional building (school) — 10 DoDs.
- Church — 10 DoDs.
- Large steel-frame building — 9 DoDs.
- Metal warehouse or hangar — 8 DoDs.
- Bridge or overpass — 8 DoDs.
- Vehicle transportation — 6 DoDs.
- Free-standing tower or pole — 8 DoDs.
- Trees — 6 DoDs. Softwood vs hardwood.
What changed with historical ratings
When the EF-scale was adopted in 2007, the NWS declared: historical tornado ratings stay as they are. There would be no reassessment of past events.
This means a 1974 F5 and a 2013 EF5 are different in absolute terms — the F5 was rated in Fujita's original framework, the EF5 in the enhanced one.
Some engineers have retroactively assessed historical damage using EF standards. Most F5 tornadoes would still be EF5 today, but many F4s might drop to EF3.
The direct-measurement problem
Neither scale is based on measured winds. Almost no tornadoes have direct wind measurements — instruments are usually destroyed or miss the peak.
The two famous exceptions:
- 1999 Bridge Creek-Moore F5: mobile Doppler measured 301 mph. That single measurement helped calibrate the EF scale.
- 2013 El Reno EF3: mobile Doppler measured 296 mph. But the ground-level damage rating was only EF3 because the widest winds didn't hit strong structures.
This mismatch drove the debate that led to the proposed EF-Scale Update (2027 target).
The 2027 EF-Scale Update (proposed)
- Adds new DIs for solar farms, wind turbines, and modern light-frame construction.
- Recalibrates DoDs based on updated engineering data.
- May allow direct-wind measurement to be considered.
- Under active review by NWS and academic partners.