Damage cost data for tornadoes is avilabale for the years 1996-2013. In this time period, there were about 22,500 tornadoes in the U.S. that caused a total of about $34 billion in damage (adjusted for inflation to 2014 values). This works out to an average damage cost of just over $1.5 million per tornado.
Note, however, that this is higher than the cost of the typical tornado, as the average is skewed upward by rare but extremely costly tornadoes. For example about $10 billion of the total damage from this period was caused by 5 tornadoes. In other words, 0.02% of the tornadoes caused nearly 30% of the damage. If we remove these events from the data set, the average cost per tornado is reduced to between $1.0 million and $1.1 million.
Most damage in a tornado is caused by the extremely fast winds.
The greatest amount of damage in a tornado is caused by extremely strong winds. Additional damage is from flying debris.
Tornado damaged is caused by a tornado's powerful winds and objects carried y those winds.
The largest tornado even recorded caused about $160 million dollars in damage, but keep in mind this wasn't the most damaging tornado or the strongest. The tornado with the strongest recorded winds caused $1 billion in damage (about $1.3 billion in today's dollars). The most damaging tornado recorded caused the equivalent of $1.7 billion in today's dollars.
The Joplin tornado caused about $2.8 billion worth of damage to the city of Joplin.
The size of a tornado, or its width is determined by how wide the area of damage is. The rating of a tornado, which is not dependent on size (though there is some correlation) is based on the severity of the damage caused.
Most of the damage caused by tornadoes is the result of extremely powerful winds.
The average tornado damage path is about 50 yards wide and 5 miles long.
The Fujita and Enhanced Fujita scales assesses damage caused by a tornado to assign a rating.
The tornado that cause the most damage on record touched down on May 22, 2011. It struck Joplin, Missouri causing $2.8 billion in damage.
The May 3, 1999 tornado outbreak caused extensive damage, particularly in Oklahoma, where an F5 tornado resulted in 36 fatalities and over 600 injuries. Thousands of homes were destroyed, and the total damage was estimated to be in the billions of dollars.
The strength of a tornado is determined by the damage it does to man-made structures and vegetation. When a structure takes damage from a tornado, the degree of damage, the type of structure, and its quality of construction are used to estimate the strength of the winds that caused that damage. This is then used to sort the tornado into one of six intensity categories of the Enhanced Fujita Scale, ranging from EF0 at the weakest to EF5 at the strongest.