Tornado Rating Scale Comparison

Different countries use different tornado intensity scales. Understanding how they compare helps interpret international tornado data. The US uses the Enhanced Fujita Scale, but Europe uses TORRO, and researchers propose future International Fujita.

The Enhanced Fujita Scale (EF Scale)

Currently used in: US (since 2007), Canada (since 2013), Mexico (adopted for research)

Range: EF0 (65-85 mph) to EF5 (200+ mph)
Method: Damage-based using 28 damage indicators
28 damage indicators covering residential to industrial structures
Derived from Fujita Scale research updated with modern engineering

Full EF Scale explanation →

The Original Fujita Scale (F Scale)

Historical use in: US (1971-2007), most countries using historic classifications

Range: F0 (40-72 mph) to F5 (261-318 mph)
Method: Damage-based using descriptive damage categories
Developed by Ted Fujita in 1971
Wind speed estimates now considered too high by modern research

F5 vs EF5 comparison →

The TORRO Scale

Used in: UK, Ireland, parts of Europe

Range: T0 (17-25 m/s) to T11 (117-135 m/s) - 12 levels
Method: Wind speed direct correspondence
Developed by Tornado and Storm Research Organisation (TORRO) in 1972
More granular than F/EF Scale
T11 hypothetical - no confirmed T11 event ever recorded

TORRO to F/EF Rough Equivalents

TORRO	F/EF	Wind (mph)
T0-T1	EF0	40-84
T2-T3	EF1	85-114
T4	EF2	115-137
T5	EF3	138-165
T6	EF4	166-201
T7+	EF5	202+

The International Fujita Scale (IF Scale)

Proposed replacement for regional scales worldwide:

Range: IF0 to IF5 (matches EF Scale)
Standardized damage indicators across countries
Regional adaptations for local building materials
Not yet officially adopted anywhere
Would harmonize international tornado data

Adoption of the IF Scale would be a major international meteorology achievement. Debate continues about the practicality.

The Japan Meteorological Agency Scale (JMA)

Used in: Japan

Range: F0 to F5 (matches historic Fujita)
Japan uses the original Fujita scale largely
Some Japanese researchers advocate switching to EF Scale

Country-by-Country Overview

United States

EF Scale since Feb 1, 2007. All events rated EF0-EF5.

Canada

EF Scale since April 1, 2013. Environment Canada issues ratings.

UK / Ireland

TORRO Scale primarily. Some events also rated F Scale for historical continuity.

France, Germany, Italy

Original Fujita Scale primarily. Some ratings use TORRO. Standardization ongoing.

Australia

Original Fujita Scale. Bureau of Meteorology (BOM) issues ratings.

Japan

Original Fujita Scale (JMA Scale).

Bangladesh

Fujita Scale. Some tornadoes are undocumented due to record limitations.

Comparing Historical Events Across Scales

To compare historical tornadoes across countries:

Convert TORRO to EF using the rough correspondence above
Convert original F to EF using damage-based (not wind speed) comparison
Recognize that damage indicators differ by region
Use engineering-based analysis for research comparisons

The Modern EF5 Drought Cross-Reference

The US EF5 drought (2013-present) can be examined internationally:

Canada has had no EF5 since scale adoption in 2013
Europe has had rare T5+ (F4+) events but nothing at T6+
Japan has had no F5 since 2007 (or before)
Bangladesh - underreported but likely has had F5-caliber events

The global "violent tornado drought" or lack of it is a subject of ongoing research.

Rating Methodology Challenges

Comparing across scales is complicated by:

Different damage indicators by region
Different building materials and construction quality
Different data collection standards
Historical documentation limitations
Whether rating includes radar-measured winds

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