 Often referred to as nature's most violent storms, tornadoes come in many sizes and shapes. Some are very strong and make the headlines, but many are not. In fact, recent studies have found that many tornadoes are never recorded because very few people see them or are able to identify them. Very weak tornadoes are often discovered because they hit mobile home communities. The important thing to remember is that the size of a tornado is not necessarily an indication of its intensity. Large tornadoes can be weak, and small tornadoes can be violent. A "small" tornado may have been larger, and is at the "shrinking" stage of its life cycle. Why does it really matter? The appropriate thing to do is be in your safe place and not out trying to get video or some kind of estimate of how severe the storm is.
Fujita Scale
Before 1971, there was no way for scientists to rank tornadoes by their strength. The visual size really had no bearing on how strong it was. Due to tornadoes intensity, wind speed or presence they are not able to be measured like a hurricane. T. Theodore Fujita, a professor at the University of Chicago, and Dr. Allen Pearson developed a system to rank tornadoes according to amount of damage they cause. This scale measures damage after the storm not wind speed during the storm like the Saffir-Simpson Scale used with hurricanes. The Fujita scale also measures the path width and the path length of a tornado.
Scale |
Severity |
Wind Speed |
Potential Damages caused by the tornado. |
F0 |
Gale tornado |
40-72 mph |
Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards |
F1 |
Moderate tornado |
73-112 mph |
The lower limit is the beginning of hurricane wind speed; peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos pushed off the roads; attached garages may be destroyed. |
F2 |
Significant tornado |
113-157 mph |
Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars pushed over; large trees snapped or uprooted; light object missiles generated. |
F3 |
Severe tornado |
158-206 mph |
Roof and some walls torn off well constructed houses; trains overturned; most trees in forested areas uprooted. |
F4 |
Devastating tornado |
207-260 mph |
Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated. |
F5 |
Incredible tornado |
261-318 mph |
Strong frame houses lifted off foundations and carried considerable distances to disintegrate; automobile sized missiles fly through the air in excess of 100 meters; trees debarked; steel re-inforced concrete structures badly damaged. |
F6 |
Inconceivable tornado |
319-379 mph |
These winds are very unlikely. The small area of damage they might produce would probably not be recognizable along with the mess produced by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and refrigerators would do serious secondary damage that could not be directly identified as F6 damage. If this level is ever achieved, evidence for it might only be found in some manner of ground swirl pattern, for it may never be identifiable through engineering studies |
Interesting Tornado Facts
- On February 19, 1884 the largest tornado outbreak on record occurred. At least 60 tornadoes were recorded. The death toll was at least 800 and another 2,500 people were listed as injured. 10,000 buildings were destroyed.
- On March 13, 1917, the longest distance that a tornado stayed on the ground was recorded. The twister was on the ground for 7 hours and 20 minutes. In that time it covered 293 miles in Missouri, Illinois and Indiana.
- The shortest tornado path ever recorded was seven feet. Most tornadoes are on the ground less than 5 miles with an average width of 150 yards. Some tornadoes are recorded as almost a mile wide.
- The winds in the 1999 Oklahoma City tornadoes were as high as 315 miles per hour.
- The single deadliest tornado on record occurred on March 18, 1925. The twister killed 695 persons as it crossed Missouri, Illinois, and Indiana.
Appropriate Response Actions for Tornadoes
- Never waste time opening windows for pressure equalization. The tornado is much bigger than your home and the debris in the tornado will probably open windows for you anyway.
- Never try to outrun a tornado, especially in a highly populated area where traffic might keep you in harms way. A tornado can blow a car off a road, pick a car up and hurl it, or tumble a car over and over.
- Take cover in a strong, interior, windowless room and have a blanket or pillow to help shield you from flying debris.
- If in a car, take shelter as low as possible, but be wary of rainfall and the potential of flash flood conditions
- Never try to hide under an overpass. A memorable news video has some individuals believing that overpasses are good shelter locations. The tornado the news team captured was actually a fairly weak tornado. A stronger tornado might have blown them right out from their shelter location, injuring or killing them.
- Follow the suggestions listed at the sheltering page for more information.
Photos are courtesy of the National Weather Service and Josh Gilpatrick |
