International Fujita scale

Tornado rating system

"IF2-" redirects here; not to be confused with IF2.

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.^[1] 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.^[2] On May 6, 2023, version 0.99.9d was published, which changed it to a 9-step rating scale.^[3] In late July 2023, the first official version of the IF scale was published.^[4]

2018 version

[edit ]

Tornado rating classifications^[5]
IF0−	IF2−	IF3	IF4
Weak	Strong		Violent
	Significant
		Intense

Parameters

[edit ]

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.

Scale Wind speed
(Estimated)

mph km/h m/s

58EBF8"}]]}'>IF0− 45 ± 14 72 ± 22 20 ± 6

4DFFFF"}]]}'>IF0 56 ± 17 90 ± 27 25 ± 7

89FFF3"}]]}'>IF0+ 67 ± 20 108 ± 32 30 ± 9

C4FFE6"}]]}'>IF1− 70 ± 24 128 ± 38 36 ± 11

FFFFD9"}]]}'>IF1 92 ± 28 149 ± 45 41 ± 12

FFF2BF"}]]}'>IF1+ 106 ± 32 170 ± 51 47 ± 14

FFE5A5"}]]}'>IF2− 120 ± 36 193 ± 58 54 ± 16

FFD98C"}]]}'>IF2 135 ± 40 217 ± 65 60 ± 18

FFC57B"}]]}'>IF2+ 150 ± 45 241 ± 72 67 ± 20

FF9E59"}]]}'>IF3 182 ± 55 293 ± 88 81 ± 24

FF738A"}]]}'>IF4 234 ± 70 376 ± 113 105 ± 31

A188FC"}]]}'>IF5 290 ± 87 466 ± 140 130 ± 39

2023 version

[edit ]

On May 6, 2023, version 0.99.9d was published, which changed it to a 9-step rating scale.^[3] 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.^[3] 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.^[4] This was done to ensure the lower or upper bound of the overlapping rating came close to the central value of the other rating.^[4]

Tornado rating classifications^[5]
IF0	IF2	IF3	IF4
Weak	Strong		Violent
	Significant
		Intense

Scale Wind speed
(Estimated)
(Central value; Full range of the 20% error margin)

mph km/h m/s

4DFFFF"}]]}'>IF0 55; 44–66 90; 72–108 25; 20–30

89FFF3"}]]}'>IF0.5 75; 60–90 120; 96–144 33; 27–40

FFFFD9"}]]}'>IF1 90; 72–108 150; 120–180 40; 32–48

FFF2BF"}]]}'>IF1.5 110; 88–132 180; 144–216 50; 40–60

FFD98C"}]]}'>IF2 135; 108–162 220; 176–264 60; 48–72

FFC57B"}]]}'>IF2.5 160; 128–192 250; 200–300 70; 56–84

FF9E59"}]]}'>IF3 180; 144–216 290; 232–348 80; 64–96

FF738A"}]]}'>IF4 230; 184–276 380; 304–456 105; 84–126

A188FC"}]]}'>IF5 290; 232–348 470; 376–564 130; 104–156

Damage indicators, subclasses, and degrees of damage

[edit ]

The IF scale currently has 23 damage indicators (DI), each with a varying number of subclasses and degrees of damage (DoD).^[4]^[3]

DI Abbr.	Damage indicator (DI)	Subclasses	Degrees of damage
BS	Building - structure	A, AB, B, C, D, E, F	0, 1A, 1B, 2
BR	Building - roof	A, AB, B, C, D, E, F	0, 1, 2
BN	Building - non-structural elements	SW, SS, TW, TS, HW, HS	0, 1, 2, 3
BM	Building - anchoring	SM, SI, DB	1
VH	Road Vehicles	C, E, L, T	0, 1, 2, 3, 4
TR	Trees	W, A, S	0, 1, 2, 3, 4, 5, 6, 7, 8, 9
TS	Tree stands	WA, S	0, 1, 2, 3, 4
WT	Wind turbines	A, S	0, 1, 2, 3
GH	Greenhouses	W, A, S	0, 1, 2, 3
TC	Train cars	S, F	0, 1
MH	Mobile homes / Static caravans	–	0, 1, 2, 3, 4, 5
PT	Poles and towers	W, S, T	0, 1, 2
SP	Solar Panels	–	0, 1
FC	Fences	W, S	0, 1
FW	Free-standing walls	Z, A, AB, B, C, D, E, F	1, 2
SN	Signs and billboards	T, M	0, 1, 2
SW	Connected scaffolding	–	1
CP	Carports / garages	–	1
SS	Service Station Canopies	–	0, 1, 2, 3
SC	Shipping Containers	A, B, C, D, E, F	1, 2, 3
CR	Cranes	G, t	1, 2
OF	Outdoor Furniture	L, H	0, 1, 2
WM	Wind Speed Measurement	See section below	See section below

DI: Wind Speed Measurement

[edit ]

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.^[4]^[3]

Three second measurement

[edit ]

For three-second wind speed measurements, it is assumed to be an average of 88.8% of the three-second measurement.^[4]^[3]

Degree of Damage (DoD) / Measured IF# Speed Three Second Measurement

mph km/h m/s

4DFFFF"}]]}'>DoD 0 / IF0 42.5–56 69–91 19–25

89FFF3"}]]}'>DoD 0.5 / IF0.5 57–74.5 92–120 26–32

FFFFD9"}]]}'>DoD 1 / IF1 73.9–90 119–146 33–40

FFF2BF"}]]}'>DoD 1.5 / IF1.5 91–109 147–176 40–49

FFD98C"}]]}'>DoD 2 / IF2 110–129 177–208 50–57

FFC57B"}]]}'>DoD 2.5 / IF2.5 129–156.5 209–242 58–70

FF9E59"}]]}'>DoD 3 / IF3 151–183.9 243–296 68–82

FF738A"}]]}'>DoD 4 / IF4 184–231 297–373 83–103

A188FC"}]]}'>DoD 5 / IF5 ≥232 ≥374 ≥104

Two second measurement

[edit ]

For two-second wind speed measurements, it is assumed to be an average of 90.9% of the two-second measurement.^[4]^[3]

Degree of Damage (DoD) / Measured IF# Speed Two Second Measurement

mph km/h m/s

4DFFFF"}]]}'>DoD 0 / IF0 43.4–58 70–94 20–26

89FFF3"}]]}'>DoD 0.5 / IF0.5 59–74 95–120 27–33

FFFFD9"}]]}'>DoD 1 / IF1 75–93 121–150 34–40

FFF2BF"}]]}'>DoD 1.5 / IF1.5 93–111.8 150–180 42–50

FFD98C"}]]}'>DoD 2 / IF2 111.8–132 180–213 51–59

FFC57B"}]]}'>DoD 2.5 / IF2.5 133–154 214–248 60–68

FF9E59"}]]}'>DoD 3 / IF3 154–188 249–303 69–84

FF738A"}]]}'>DoD 4 / IF4 188–237 304–382 85–106

A188FC"}]]}'>DoD 5 / IF5 ≥238 ≥383 ≥107

One second measurement

[edit ]

For one-second wind speed measurements, it is assumed to be an average of 92.5% of the one-second measurement.^[4]^[3]

Degree of Damage (DoD) / Measured IF# Speed One Second Measurement

mph km/h m/s

4DFFFF"}]]}'>DoD 0 / IF0 44.1–58 71–95 20–26

89FFF3"}]]}'>DoD 0.5 / IF0.5 59–76 96–123 27–34

FFFFD9"}]]}'>DoD 1 / IF1 77–94 124–152 35–42

FFF2BF"}]]}'>DoD 1.5 / IF1.5 95–113 153–183 43–51

FFD98C"}]]}'>DoD 2 / IF2 114–134 184–220 52–60

FFC57B"}]]}'>DoD 2.5 / IF2.5 135–156 218–252 61–70

FF9E59"}]]}'>DoD 3 / IF3 157–191 253–308 71–85

FF738A"}]]}'>DoD 4 / IF4 192–241 309–388 86–107

A188FC"}]]}'>DoD 5 / IF5 ≥241.5 ≥389 ≥108

Zero second measurement

[edit ]

For zero-second wind speed measurements, it is assumed to be an instantaneous wind speed measurement.^[4]^[3] This can only be used if it was 10Hz or higher sample rate.^[4]^[3]^[6]

Degree of Damage (DoD) / Measured IF# Speed Zero Second Measurement

mph km/h m/s

4DFFFF"}]]}'>DoD 0 / IF0 47.8–64 77–103 22–28

89FFF3"}]]}'>DoD 0.5 / IF0.5 64–82 104–132 29–36

FFFFD9"}]]}'>DoD 1 / IF1 82–101.9 133–164 37–45

FFF2BF"}]]}'>DoD 1.5 / IF1.5 102–123 165–198 46–55

FFD98C"}]]}'>DoD 2 / IF2 124–145 199–234 56–65

FFC57B"}]]}'>DoD 2.5 / IF2.5 146–169 235–273 66–75

FF9E59"}]]}'>DoD 3 / IF3 170–207 274–333 76–92

FF738A"}]]}'>DoD 4 / IF4 208–260 334–420 93–116

A188FC"}]]}'>DoD 5 / IF5 ≥261 ≥421 ≥117

References

[edit ]

↑ "The International Fujita (IF) Scale Tornado and Wind Damage Assessment Guide" (PDF). ESSL.org. European Severe Storms Laboratory . Retrieved 26 June 2022.
↑ Tomás Púcik; David Rúva; Miroslav Singer; Miloslav Stanëk; Pieter Groenemeijer (23 June 2022). "Damage Survey of the Violent Tornado in Southeast Czechia on 24 June 2021" (PDF). European Severe Storms Laboratory. pp. 1–31. Retrieved 16 May 2023.
1 2 3 4 5 6 7 8 9 10 "The International Fujita (IF) Scale" (PDF). European Severe Storms Laboratory. Retrieved 8 May 2023.
1 2 3 4 5 6 7 8 9 10 Pieter Groenemeijer (ESSL); Lothar Bock (DWD); Juan de Dios Soriano (AEMet); Maciej Dutkiewicz (Bydgoszcz University of Science and Technology); Delia Gutiérrez-Rubio (AEMet); Alois M. Holzer (ESSL); Martin Hubrig; Rainer Kaltenberger; Thilo Kühne (ESSL); Mortimer Müller (Universität für Bodenkultur); Bas van der Ploeg; Tomáš Púčik (ESSL); Thomas Schreiner (ESSL); Miroslav Šinger (SHMI); Gabriel Strommer (ESSL); Andi Xhelaj (University of Genova) (30 July 2023). "The International Fujita (IF) Scale" (PDF). European Severe Storms Laboratory. Retrieved 30 July 2023.
1 2 "Severe Thunderstorm Climatology". Archived from the original on 2012年10月04日. Retrieved 2022年07月17日.
↑ A. C. M. Beljaars (1 December 1987). "The Influence of Sampling and Filtering on Measured Wind Gusts". Journal of Atmospheric and Oceanic Technology. 4 (4): 613–626. Bibcode:1987JAtOT...4..613B. doi:10.1175/1520-0426(1987)004<0613:TIOSAF>2.0.CO;2 . ISSN 1520-0426.

Retrieved from "https://en.wikipedia.org/w/index.php?title=International_Fujita_scale&oldid=1354507284"

2018 version

Parameters

2023 version

Damage indicators, subclasses, and degrees of damage

DI: Wind Speed Measurement

Three second measurement

Two second measurement

One second measurement

Zero second measurement

See also

References