International Fujita scale
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).
Source: Wikipedia — International Fujita scale (CC BY-SA 4.0)