Tornadoes are violently rotating columns of air, extending from a thunderstorm, which are in contact with the ground. Tornadoes develop when wind variations with height support rotation in the updraft. As seen below, 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. However, in the southeast, and especially Georgia, tornadoes are often hidden in large swaths of rain and hail, making them very difficult to see and even more dangerous. Visibility is often affected by terrain constraints in Georgia as well.

As stated before, tornadoes come in different shapes and sizes. The majority of tornadoes which occur are classified as a weak tornado. Usually a weak tornado will last for just a few minutes and have wind speeds of 100 mph or less. Some tornadoes intensify further and become strong or violent. Strong tornadoes last for twenty minutes or more and may have winds of up to 200 mph, while violent tornadoes can last for more than an hour with winds between 200 and 300 mph!! These violent tornadoes are rare in occurrence.

The key atmospheric ingredients that lead to tornado potential are instability - warm moist air near the ground, with cooler dry air aloft and wind shear - a change in wind speed and/or direction with height. An unstable airmass promotes the development of strong updrafts, while wind shear will further increase the strength of the updraft, and promotes the rotation from which tornadoes are produced.

All thunderstorms have the potential to produce tornadoes, but the type of storm that is most commonly tornadic is the supercell. This very severe, long-lived thunderstorm contains circulation aloft (mesocyclone) that grows upward through the storm and downward toward the ground. When conditions are favorable, tornadoes will be produced. Supercells may produce strong, violent tornadoes, or several tornadoes over a period of several hours. The last major supercell outbreak in North or Central Georgia was during the Palm Sunday Tornadoes of March 27,1994.

Our WSR-88D Doppler radar can detect the circulation associated with a tornado producing thunderstorm. Once the circulation is identified, a warning is issued. However, Doppler radar is not perfect, because it can only indicate rotation aloft, and does not indicate what may be happening on the ground. This is where our storm spotters come in. Only feedback from someone in the area can confirm whether the radar signature is associated with a tornado.