How Tornados Are Made

Basic Ingredients for Formation

Cold air sinks below warm air because it has a greater density. This principal is at the heart of thunderstorm and tornado formation. Ahead of thunderstorms, air movement increases in speed to create an invisible "sideways" tornado. These horizontal areas of rotation do not cause damage, but they can increase in strength when the rotation gets lifted into building thunderstorm clouds.

Warm moist air colliding with colder air causes the warm air to get pushed above the denser cold air. This carries the moisture upward, where it cools and condenses into droplets, which form clouds and sink as they cool. The cooled air around them also sinks, causing downdrafts.

The movement of cold downdrafts and rising warm updrafts in a storm cloud builds the cloud into a super cell, capable of producing hailstones and tornadoes. The rapidly rising warm air of the super cell also grabs onto the horizontally rotating air mass, pulling it into a vertical position.

Inside the Super Cell

The rotating area inside the super cell is known as a mesocyclone. These form in areas of rising warm air in the cloud, and form the cloud roots of the tornado. A tornado builds from the cloud down toward the ground. Until it touches the ground, the rotating cloud mass is known as a funnel cloud, but ground contact changes it into a tornado. Until it picks up dirt and debris, a tornado or funnel cloud remains invisible, but the danger from winds of 100 mph still exists.

Tornado Damage

Tornadoes most often form in the central and southern United States, but they can occur anywhere at any time of the year. The majority (69 percent) of tornadoes have winds below 110 miles per hour and only last for an average of 10 minutes. These account for only 5 percent of tornado deaths but still cause property damage. The most severe tornadoes are also the rarest, making up 2 percent of cases, but their lifespans over one hour and damaging winds of more than 205 mph make them the deadliest, killing 70 percent of people who die in tornadoes annually.

Tornado watches broadcast to the public let people know a storm could develop tornadoes. A tornado warning indicates a tornado has been spotted by a person or radar and everyone in the area needs to immediately find shelter. The safest places include any interior room, without any windows, in a sturdy building. Avoid cars, large open areas and mobile homes.

References

• Tornado Development
• Learn More About Tornadoes
• Tornadoes ... Nature's Most Violent Storms