At F5 Shelters, we use the internationally recognized Fujita scale to rate the structures that we construct. The Fujita scale is used as a way to measure the intensity of tornadoes. The intensity of a tornado is determined by the examination of damage done to man made structures and local vegetation. Meteorologists and engineers determine the grade to assign to each tornado, based not only on destruction, but ground swirl patterns left in the wake of the tornado, tracking technology, and eyewitness accounts. Motion videos are a great help to advancing current warning systems and determining what kind of force and speed the tornado was moving with. Bystanders can be a huge help in the advancement of tornado technology.
The Fujita scale was initially created to go to F13, that way it could coordinate with the Mach number scale. After there was more understanding of wind speeds and it was realized that to achieve a mach 1 category, and an F12 rating, wind speed would have to be moving at 738 mph, that not being a possibility the only ratings intended for use became F0 thru F5. F6 was left as an option, but was referred to as an “inconceivable tornado”. F5 was already the rating for incredible destruction, which meant that everything was destroyed, so there was little possibility that there would ever be a use for F6. Even F5 shelters would theoretically be destroyed by F6 tornadoes, but since F6 tornadoes themselves are theoretical, and have never occurred, we have nothing to worry about. In 2007 the United switched to using the Enhanced Fujita scale which is essentially the same except the wind speed was modified.
Lower Enhanced Fujita Ratings
The working numbers of the Fujita scale are 0 thru 6. The least damaging one of course is F0. F0 tornadoes have wind speed of 65 to 85 mph and cause very light damage, and have a path of generally between 10 and 50 meters wide. Things like broken branches and light roof damage are common with F0 tornadoes. Tornadoes that carry a wind speed that is between 86 and 110 mph are classified as F1s. F1s have a much wider destructive of 30 to 150 meters. They are classified as causing moderate damage and known for doing things like blowing off shingle roofs, pushing around cars, and moving mobile homes. 73 mph is also coincidentally the beginning of what would be considered hurricane speed. F2 tornadoes create a significant amount of damage. Large trees can be broken in half, mobile homes can get demolished, and complete roofs can be torn off of homes. Wind speeds climb to 135 mph at the high end of F2 tornadoes and they can leave a path that is up to 250 meters wide. F5 Shelters will protect you from all of these threats easily.
F3 tornadoes are where you really start to see the type of devastation that wind can cause. Wind can get up to 165 mph with a damage path that ranges from 200 to 500 meters wide. Houses can be torn apart, large building twisted, and even heavy cars become projectiles. With wind speeds of 166 to 200 mph and a path of devastation that can be 900 meters wide, there is very little in the path of an F4 that survives in one piece. F5 tornadoes are the big boys, leaving complete and utter annihilation of everything in their 1110 meter paths. The tornadoes that hit Oklahoma were F5 and had a path of over 1 mile wide. Wind speeds are over 200 mph, 318 is where the scale stops, and nothing stands after and F5 comes through, nothing but F5 Shelters that is.