Dennis Mersereau | @wxdam
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EF-Scale | Why are EF-5s so rare? | Damage Indicators | All F5/EF-5 Tornadoes


How tornadoes are rated...
The Enhanced Fujita Scale

Meteorologists use damage to estimate the maximum winds of a tornado at any given point. Engineers and meteorologists worked together to figure out how strong winds have to be to cause certain levels of damage.

Dr. Theodore Fujita pioneered the study of tornado damage in the mid-20th century. He developed the Fujita (F) Scale to rate damage to buildings, vehicles, and vegetation on a scale ranging from F0 (weak) to F5 (extreme).

Scientists began using a revamped version of the scale in 2007. This Enhanced Fujita (EF) Scale reflects the fact that objects like homes and trees require much lower wind speeds to incur damage.

The Fujita/Enhanced Fujita scales are damage rating scales. Some ratings are controversial as a result. There are several cases where meteorologists have gotten accurate measurements of a tornado's winds, but couldn't find damage to warrant a higher F/EF-Scale rating.


Why are F5/EF-5 tornadoes so rare?
EF-4 damage to a home in Rolling Fork, Mississippi, on March 24, 2023. Estimated winds were 170 mph.
EF-4 damage to a home in Rolling Fork, Mississippi, on March 24, 2023.
Estimated winds were 170 mph. (PHOTO: NWS Jackson)

Scale-topping EF-5 tornadoes probably aren't as rare as they seem. These high-end tornadoes produce maximum winds stronger than 200 mph.

Since the EF-Scale is based on damage, meteorologists have to look for certain levels of destruction amid the rubble in order to assign a tornado its ultimate rating. Very few structures can withstand the 201+ mph winds needed to achieve EF-5 level damage.

Homes are usually uninhabitable and need extensive repairs after an EF-2 tornado. Many homes that suffer EF-3 damage are total losses, and EF-4 damage often causes complete failure of the structure with only the occasional interior room left standing.

An EF-5 tornado scrubs a home clean off its foundation, leaving behind a bare slab in its wake. Given this extreme level of destruction, surveyors have to look for context clues to find EF-5 level damage. This includes things like catastrophic damage to reinforced school buildings and less conventional damage like exceptionally heavy objects lifted and tossed a long distance.

I wrote more about this topic for The Weather Network in April 2024.


 
DI No. Damage Indicator (DI) DI No. Damage Indicator (DI)
1 Small Barns or Farm Outbuildings (SBO) 15 Elementary School [Single Story; Interior or Exterior Hallways] (ES)
2 One- or Two-Family Residences (FR12) 16 Junior or Senior High School (JHSH)
3 Manufactured Home – Single Wide (MHSW) 17 Low-Rise Building [1-4 Stories] (LRB)
4 Manufactured Home – Double Wide (MHDW) 18 Mid-Rise Building [5-20 Stories] (MRB)
5 Apartments, Condos, Townhouses [3 stories or less] (ACT) 19 High-Rise Building [More than 20 Stories] (HRB)
6 Motel (M) 20 Institutional Building [Hospital, Government or University Building] (IB)
7 Masonry Apartment or Motel Building (MAM) 21 Metal Building System (MBS)
8 Small Retail Building [Fast Food Restaurants] (SRB) 22 Service Station Canopy (SSC)
9 Small Professional Building [Doctor's Office, Branch Banks] (SPB) 23 Warehouse Building [Tilt-up Walls or Heavy-Timber Construction](WHB)
10 Strip Mall (SM) 24 Electrical Transmission Lines (ETL)
11 Large Shopping Mall (LSM) 25 Free-Standing Towers (FST)
12 Large, Isolated Retail Building [K-Mart, Wal-Mart] (LIRB) 26 Free-Standing Light Poles, Luminary Poles, Flag Poles (FSP)
13 Automobile Showroom (ASR) 27 Trees: Hardwood (TH)
14 Automobile Service Building (ASB) 28 Trees: Softwood (TS)

Links to more information on each damage indicator open in a separate tab to the Storm Prediction Center's website.


A map of all 60 F5/EF-5 tornadoes in the U.S. and Canada since 1950.

Numbers in the table below correspond to the numbers on the map above. This table lists the state/province in which the tornado touched down.

Number Date Time State/Prov. Fatalities Injuries Path Length Path Width Number Date Time State/Prov. Fatalities Injuries Path Length Path Width
1 5/11/1953 16:10:00 Texas 114 597 20.9 mi. 583 yds. 31 4/3/1974 17:15:00 Alabama 28 267 52 mi. 500 yds.
2 5/29/1953 17:00:00 North Dakota 2 20 14.8 mi. 600 yds. 32 4/3/1974 18:35:00 Alabama 16 190 83.3 mi. 500 yds.
3 6/8/1953 19:30:00 Michigan 116 844 18.9 mi. 833 yds. 33 4/3/1974 19:50:00 Alabama 28 272 79.5 mi. 500 yds.
4 6/27/1953 15:45:00 Iowa 1 2 0.1 mi. 100 yds. 34 3/26/1976 15:28:00 Oklahoma 2 64 11.9 mi. 440 yds.
5 12/5/1953 17:45:00 Mississippi 38 270 9 mi. 500 yds. 35 4/19/1976 17:30:00 Texas 0 11 10.5 mi. 440 yds.
6 5/25/1955 21:26:00 Oklahoma 20 280 28.4 mi. 500 yds. 36 6/13/1976 14:10:00 Iowa 0 9 21.3 mi. 880 yds.
7 5/25/1955 22:00:00 Oklahoma 80 273 56.4 mi. 1320 yds. 37 4/4/1977 15:00:00 Alabama 22 130 14.7 mi. 550 yds.
8 4/3/1956 16:40:00 Michigan 17 292 58.8 mi. 400 yds. 38 4/2/1982 15:50:00 Oklahoma 0 29 53 mi. 500 yds.
9 12/18/1957 16:35:00 Illinois 1 6 5.4 mi. 200 yds. 39 6/7/1984 23:41:00 Wisconsin 9 200 36 mi. 450 yds.
10 5/20/1957 18:15:00 Kansas 44 207 69.4 mi. 440 yds. 40 5/31/1985 16:30:00 Ohio 18 310 47 mi. 450 yds.
11 6/20/1957 18:40:00 North Dakota 10 103 52.4 mi. 500 yds. 41 3/13/1990 16:34:00 Kansas 1 60 48 mi. 1320 yds.
12 6/4/1958 17:30:00 Wisconsin 21 74 33.7 mi. 880 yds. 42 3/13/1990 17:30:00 Kansas 1 0 22 mi. 1320 yds.
13 5/5/1960 17:00:00 Oklahoma 5 81 71.8 mi. 800 yds. 43 8/28/1990 14:30:00 Illinois 29 350 16.4 mi. 600 yds.
14 4/3/1964 14:35:00 Texas 7 111 4.7 mi. 500 yds. 44 4/26/1991 16:57:00 Kansas 17 225 46 mi. 440 yds.
15 5/5/1964 18:30:00 Nebraska 4 50 79.7 mi. 880 yds. 45 6/16/1992 16:00:00 Minnesota 1 35 16 mi. 280 yds.
16 5/8/1965 17:15:00 South Dakota 0 1 30.1 mi. 1760 yds. 46 7/18/1996 18:05:00 Wisconsin 0 12 13.3 mi. 400 yds.
17 10/14/1966 13:55:00 Iowa 6 172 9.7 mi. 1000 yds. 47 5/27/1997 14:40:00 Texas 27 12 5.1 mi. 650 yds.
18 3/3/1966 18:30:00 Mississippi 58 518 202.5 mi. 900 yds. 48 4/16/1998 15:50:00 Tennessee 3 36 69.4 mi. 1760 yds.
19 6/8/1966 19:00:00 Kansas 16 450 21.1 mi. 880 yds. 49 4/8/1998 18:42:00 Alabama 32 259 30.3 mi. 1320 yds.
20 4/23/1968 15:05:00 Ohio 7 93 34 mi. 400 yds. 50 5/3/1999 17:26:00 Oklahoma 36 583 37 mi. 1430 yds.
21 5/15/1968 15:10:00 Iowa 13 462 62.1 mi. 600 yds. 51 5/4/2007 20:00:00 Kansas 11 63 28.81 mi. 3000 yds.
22 5/15/1968 15:57:00 Iowa 5 156 13.1 mi. 500 yds. 52 6/22/2007 18:35:00 Manitoba 0 0 2.69 mi. 325 yds.
23 6/13/1968 17:50:00 Minnesota 9 150 9.1 mi. 150 yds. 53 5/25/2008 15:48:00 Iowa 9 70 40.97 mi. 2100 yds.
24 5/11/1970 20:35:00 Texas 26 500 8.4 mi. 1333 yds. 54 4/27/2011 13:30:00 Mississippi 3 6 28.28 mi. 900 yds.
25 2/21/1971 14:50:00 Louisiana 47 510 109.2 mi. 500 yds. 55 4/27/2011 14:05:00 Alabama 72 145 132 mi. 2200 yds.
26 5/6/1973 19:25:00 Texas 0 0 10.6 mi. 100 yds. 56 4/27/2011 14:42:00 Mississippi 23 137 37.1 mi. 1320 yds.
27 4/3/1974 13:20:00 Indiana 6 86 68 mi. 10 yds. 57 4/27/2011 17:19:00 Alabama 25 0 36.63 mi. 1320 yds.
28 4/3/1974 13:30:00 Ohio 36 1150 31.3 mi. 533 yds. 58 5/22/2011 16:34:00 Missouri 158 1150 21.62 mi. 1600 yds.
29 4/3/1974 14:20:00 Kentucky 31 270 32 mi. 440 yds. 59 5/24/2011 14:50:00 Oklahoma 9 181 63.1 mi. 1760 yds.
30 4/3/1974 15:20:00 Indiana 3 210 20.8 mi. 533 yds. 60 5/20/2013 13:56:00 Oklahoma 24 212 13.85 mi. 1900 yds.
#31-#60 continue top-right →

SOURCES: NOAA/SPC | NTP




I didn't stick to the weather.