Fujita Scale

Tuesday, December 18th 2007, 6:58 pm
By: News 9

Fujita Scale, or F-Scale, levels are based on the damage caused by tornado wind speed. Dr. T. Theodore Fujita developed the scale in the early 1970s. Experts caution that the F-Scale is not a completely reliable measure, due to difficulties in precisely judging wind speeds.

Engineers and meteorologists have recently come up with a more accurate way to assess tornado damage called the Enhanced F-Scale. The new scale was put into effect February 7, 2007. In the Enhanced F-scale, there are customized standards for the different types of structures damaged in the tornado's path. As with the original F-scale, the enhanced version will rate the tornado as a whole based on most intense damage within the path. When determining the EF-rating, the EF-scale begins with the 28 Damage Indicators. Each of these indicators has a brief description of the typical structure for that category. They decided when assessing damage that it was important to continue to support and maintain the original F-scale, but that surveys should include additional data not used before, such as:

  • Mean and maximum damage path width
  • Basis for damage assignment
  • Latitude/longitude of where the path began and ended
  • Number of hours spent on the damage survey
  • Names of survey team member(s)

Enhanced F Scale Wind Speeds

Old IndicatorNew Indicator
F NumberWind Speed (mph)EF NumberWind Speed (mph)
0 45 - 78 0 65 - 85
1 79 - 117 1 86 - 110
2 118 - 161 2 111 - 135
3 162 - 209 3 136 - 165
4 210 - 261 4 166 - 200
5 262 - 317 5 Over 200

 Enhanced F Scale Damage Indicators

NumberDamage IndicatorAbbreviation
1 Small barns, farm outbuildings SBO
2 One- or two-family residences FR12
3 Single-wide mobile home (MHSW) MHSW
4 Double-wide mobile home MHDW
5 Apt, condo, townhouse (three stories or less) ACT
6 Motel M
7 Masonry apt. or motel MAM
8 Small retail building (fast food) SRB
9 Small professional (doctor office, branch bank) SPB
10 Strip mall SM
11 Large shopping mall LSM
12 Large, isolated ("big box") retail bldg. LIRB
13 Automobile showroom ASR
14 Automotive service building ASB
15 School - one-story elementary (interior or exterior halls) ES
16 School - junior or senior high school JHSH
17 Low-rise (1-4 story) building LRB
18 Mid-rise (5-20 story) building MRB
19 High-rise (over 20 stories) HRB
20 Institutional building (hospital, govt. or university) IB
21 Metal building system MBS
22 Service station canopy SSC
23 Warehouse (tilt-up walls or heavy timber) WHB
24 Transmission line tower TLT
25 Free-standing tower FST
26 Free standing pole (light, flag, luminary) FSP
27 Tree - hardwood TH
28 Tree - softwood TS

See also: the Saffir-Simpson scale