The Science Behind the Desctruction
A tornado is a violently rotating column of air descending from a thunderstorm while in contact with the ground. Although tornadoes are usually brief, lasting only a few minutes, they can sometimes last several hours and cause extreme damage or even worse, death. Tornadoes are the #3 most hazardous aspect of thunderstorms (#2 is lightning) while flash flooding is #1.
 |
| Large tornado that occurred in Chicot County in 2008 |
Most tornadoes are spawned from supercellular thunderstorms. Supercell thunderstorms are characterized by a persistent rotating updraft and form in environments of strong vertical wind shear. Wind shear is the change in wind speed or direction with height. Directional wind shear is the change in wind direction with height.
As the elevation increases the direction veers, becoming south, then southwest, and finally, west. Speed shear is the change in wind speed with height. In the illustration below, the wind is increasing with height. Strong vertical shear is the combination of a veering directional shear and strong speed shear and is the condition that is most supportive of supercells involving tornadoes.
The funnel cloud of a tornado consists of moist air. As the funnel descends to the ground the water vapor within it condenses into small liquid droplets. The liquid droplets are identical to cloud droplets, yet they are not considered part of the cloud since they form within the funnel itself. The descending funnel is made visible because of the water droplets. The funnel takes on the color of the cloud droplets, which is white. Due to the air movement, dust and debris on the ground will begin rotating, often becoming several feet high and hundreds of yards wide.
After the funnel touches the ground and becomes a tornado, the color of the funnel will change. The color of the tornado often depends on the terrain, or debris it collects while on the ground. Tornadoes can last from several seconds to more than an hour but most last only minutes.
Tornado Ratings
 |
| Tornado ratings on the enhanced Fujita Scale |
When a possible tornado passes through your community, your National Weather Service coverage office will be there to inspect the damage. You can often see them out and about, observing property damage, looking for possible tracks, and doing their own research. This is crucial for us to learn more of tornadoes, and severe weather in general.
Tornadoes are rated by damage rather than size, or how scary they might look. In fact, there could be a large tornado that is rated lower than a tornado that may appear smaller in stature. The key to rating a tornado involves the damage it causes. Tornadoes are ranked on the enhanced Fujita Scale from the lowest tier (EF-0) to the most powerful and deadly (EF-5). Arkansas has only experienced one tornado that reached the rating of an EF-5. This was the "Sneed" tornado, which occurred in 1929 in northeastern Arkansas.
Below are several photos of tornadoes that have occurred in Arkansas:
 |
| Tornado that occurred in Hampton (Calhoun County) |
 |
| EF-3 tornado that occurred in north central Arkansas during the super-Tuesday outbreak of February 5th, 2008. |
 |
| Rope tornado that occurred near Grady (Lincoln County) Photo credit: Stas Speransky |
 |
| Large tornado during the Super Tuesday Outbreak Photo credit: Ty Graham |
 |
| Large tornado from Wynne (Cross County) |
