science

International Fujita scale

International Fujita scale is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand International Fujita scale rather than just read about it. In short: The International Fujita scale (abbreviated as IF-Scale) is a scale that rates the intensity of tornadoes and other wind events based on the severity of the damage they cause. It is used by the European Severe Storms Laboratory (ESSL) and various other organizations including Deutscher Wetterdienst (DWD) and State Meteorological Agency (AEMET).

Key takeaways

International Fujita scale belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect International Fujita scale to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of International Fujita scale from memory before moving on to harder problems.

Reference excerpt

The International Fujita scale (abbreviated as IF-Scale) is a scale that rates the intensity of tornadoes and other wind events based on the severity of the damage they cause. It is used by the European Severe Storms Laboratory (ESSL) and various other organizations including Deutscher Wetterdienst (DWD) and State Meteorological Agency (AEMET). The scale is intended to be analogous to the Fujita and Enhanced Fujita scales, while being more applicable internationally by accounting for factors such as differences in building codes. In 2018, the first draft version of the IF-scale, version 0.10 was published. This version was based on a 12-step rating scale. Over the next few years, dozens of tornadoes would be rated on this version of the scale. Most notably, the 2021 South Moravia tornado received a rating (IF4) and full damage survey on the IF-scale conducted by ESSL, the Czech Hydrometeorological Institute and four other organizations. On May 6, 2023, version 0.99.9d was published, which changed it to a 9-step rating scale. In late July 2023, the first official version of the IF scale was published.

2018 version

Parameters The 12 categories for the International Fujita scale are listed below, in order of increasing intensity. Although the wind speeds and photographic damage examples are updated, which are more or less still accurate. However, for the actual IF-scale in practice, damage indicators (the type of structure which has been damaged) are predominantly used in determining the tornado intensity. The IF-scale steps are defined by a central value and an error. The errors have been estimated to be 30% of the central value, resulting in overlapping speed ranges. The distances between the central values of the steps have been so chosen that the upper bound exceeds the central value of the next step, ensuring a balance between the resolution of the scale and the expected errors. Since ESSL required that the steps be consistent with the original Fujita scale, they introduced steps with − and + suffixes indicating steps one third higher or lower than the central value of the original scale, e.g. IF2− equals "IF2 − 1⁄3IF2" and IF2+ equals "IF2 + 1⁄3IF2". Above F2, such a subdivision was not introduced and only full steps are used.

2023 version On May 6, 2023, version 0.99.9d was published, which changed it to a 9-step rating scale. In this version, the wind speed damage indicator was introduced, which made it the first tornado intensity and damage scale to use measured wind speeds and Doppler weather radar measured wind speeds. When the first official publication of the IF scale, the 9-step rating scale was kept. It was noted that each scale's wind speed is to be taken with a 20% error margin on each side of the central value. This was done to ensure the lower or upper bound of the overlapping rating came close to the central value of the other rating.

Damage indicators, subclasses, and degrees of damage The IF scale currently has 23 damage indicators (DI), each with a varying number of subclasses and degrees of damage (DoD).

DI: Wind Speed Measurement A unique feature of the International Fujita scale compared to the Fujita or Enhanced Fujita scale is a new damage indicator based on measured wind speeds. For the IF scale, only wind speeds measured at or below 10 metres (11 yd) can be used to determine a rating. Doppler weather radar measurements are also able to be used to determine a rating if they are measured within damaging distance. For radar measurements, any readings below 60 metres (66 yd) can be used to determine a rating.

Three second measurement For three-second wind speed measurements, it is assumed to be an average of 88.8% of the three-second measurement.

Two second measurement For two-second wind speed measurements, it is assumed to be an average of 90.9% of the two-second measurement.

One second measurement For one-second wind speed measurements, it is assumed to be an average of 92.5% of the one-second measurement.

Zero second measurement For zero-second wind speed measurements, it is assumed to be an instantaneous wind speed measurement. This can only be used if it was 10Hz or higher sample rate.

Worked examples

Example 1 — a first encounter with International Fujita scale

Start with the simplest possible case. Write down what International Fujita scale claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to International Fujita scale before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about International Fujita scale ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of International Fujita scale

In research: International Fujita scale appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses International Fujita scale in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: International Fujita scale is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hazard scales, Scales in meteorology, Tornado, so understanding it makes those chapters shorter.
In everyday life: Look for International Fujita scale outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study International Fujita scale in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what International Fujita scale means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain International Fujita scale out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is International Fujita scale in simple terms?

Why does International Fujita scale matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study International Fujita scale?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on International Fujita scale.