Tornadoes are defined as violently rotating columns of air in contact with the ground. When they are not in contact with the ground, they are called funnel clouds. Tornadoes come in different sizes, many as narrow rope-like swirls, others as wide funnels. Across the Plains, tornadoes can be seen from miles away. Across the eastern United States and the Deep South, tornadoes are often hidden in large swaths of rain and hail, making them very difficult to see, and thus even more dangerous.

A majority of tornadoes are labeled weak, with wind speeds of 100 mph or less, and are usually on the ground for a few minutes. Even weak tornadoes can produce substantial damage. Some tornadoes intensify further and become strong or violent. Strong tornadoes produce winds up to around 200 mph. Most of the Mississippi tornadoes that produce major damage are labeled strong. Only a few tornadoes across the country each year are labelled violent, with winds of 200 to 300 mph. These tornadoes produce catastrophic damage, and can be on the ground for half an hour or longer.

In 2005, Mississippi had record number of tornadoes with a total of 99. Of those 99 tornadoes, 14 were rated as strong. There was one fatality, and there were 22 injuries as direct result of these tornadoes.

The key atmospheric ingredients that lead to tornado potential are instability (warm moist air near the ground, cool dry air aloft) and wind shear (change in wind speed and direction with height). An unstable airmass promotes the development of strong updrafts. Wind shear not

All thunderstorms have the potential to produce tornadoes, but the type of storm that is most commonly tornadic is the supercell. This very severe and long-lived thunderstorm contain a circulation aloft (mesocyclone) that grows upward through the storm and downward toward the ground. When conditions are just right, tornadoes rapidly spin up from mesocyclones.

Supercells produce the strong and violent tornadoes, and are capable of producing a series of tornadoes over a period of several hours. A large percentage of tornado-related deaths in Mississippi, and across the country, are associated with this type of thunderstorm.

Doppler radar can detect the circulation associated with a tornado-producing storm. Once the circulation is identified, a warning is issued. Doppler radar is not perfect though. In fact, the radar only indicates rotation aloft, and does not indicate what may be occurring at ground level.

This makes the work of storm spotters very important. Only feedback from spotters can confirm whether the radar signature is associated with a tornado. The National Weather Service relies heavily on the help of trained spotters.

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