Tornado's are natures most violent storms on earth with estimated wind speeds in excess of 300 miles per hour. A Tornado is a rotating column of air that connects all the way to the ground from the base of a thunderstorm. The rotating motion of a thunderstorm is mostly counterclockwise (cyclonic rotation).

Thunderstorms develop when warm moist air and cool and dry air mix. (warm, moist, cool and dry are relative terms in weather. This means when a warm or cold front is moving in, it can only be a few degrees warmer or colder, the larger the difference is, the better chance of severe weather).

The figure below is the Fujita scale, it measures the intensity of tornados by the amount of damage it causes (not by how large it is).


Wind Speed



40-72 mph

Light damage: Some damage to chimneys; branches break from trees; shallow rooted trees pushed over; sign boards damaged


73-112 mph

Moderate damage: Roof surfaces peeled off; mobile homes pushed from foundations or overturned; cars pushed off roads


113-157 mph

Considerable damage: Roofs torn off frame houses; mobile homes demolished; large trees snapped or uprooted


158-206 mph

Severe damage: Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted


207-260 mph

Devastating damage: Well-constructed houses leveled; structures with weak foundations blown off some distance


261-318 mph

Incredible damage: Strong frame houses lifted off foundations and carried considerable distance to disintegrate

  • F0 and Fl tornadoes comprise 70% of all tornadoes that occur in the U.S. They usually touch down briefly and cause minor damage. However, forecasting these tornadoes is less reliable than for stronger tornadoes, so less than 50% occur during tornado watches.
  • F2 and F3 tornadoes comprise about 28% of the tornadoes in the U.S. They can cause significant damage, injuries, and deaths.
  • F4 and F5 tornadoes comprise about 2 percent of the tornadoes in the U.S. and cause 70% of the death and destruction. Fortunately, the NWS has identified precursor conditions for the more damaging tornadoes. Over 95% of these tornadoes, therefore, occur during tornado watches.


Data from the National Weather Service



There four types of thunderstorms

1. Single-cell thunderstorm

2. Multi-cell Thunderstorm

3. Squall Line

4. Super Cell thunderstorm