Tornadoes Reading Comprehension Lesson

How Tornadoes Form

Tornadoes are among the most dangerous storms that nature creates. It is important to take these natural disasters very seriously. Some tornadoes have relatively moderate winds, while others reach devastating speeds. Usually, a tornado starts from a strong thunderstorm. You can recognize a tornado by the rotating, funnel-shaped cloud that drops from a thundercloud toward the ground. Tornadoes can reach a maximum wind speed of about 300 miles per hour, though most are far less powerful than that.

Tornadoes form when warm, moist air near the ground meets cold, dry air higher up. The difference in temperature and humidity causes the air to become unstable, and when wind conditions are right, the rising warm air begins to rotate. This spinning column of air can tighten and speed up — just like a figure skater who pulls in their arms to spin faster. When the rotating column stretches down from the cloud base and touches the ground, it is officially a tornado.

Scientists use the Fujita Scale to measure tornado intensity. The scale runs from F0 to F5. An F0 tornado has winds of 40–72 mph and causes light damage such as broken tree branches. An F2 (113–157 mph) can tear roofs off homes and overturn mobile homes. The most devastating tornadoes are F5, with winds of 261–318 mph that can carry away entire houses and level reinforced concrete structures. Fortunately, F5 tornadoes are extremely rare.

Tornado Alley and Staying Safe

The United States experiences more tornadoes than any other country in the world. A region of the Great Plains known as Tornado Alley sees the highest concentration of tornadoes. States in Tornado Alley include Texas, Oklahoma, Kansas, Nebraska, South Dakota, and Iowa. This region is especially prone to tornadoes because warm, moist air from the Gulf of Mexico frequently collides with cold, dry air from Canada and the Rocky Mountains.

A tornado watch means that weather conditions are favorable for tornado development — stay alert and be ready to act quickly. A tornado warning means that a tornado has been spotted by a weather observer or detected by radar — take cover immediately. When a tornado warning is issued, go to the lowest floor of a sturdy building and move to an interior room away from windows. A basement is the safest place. If there is no basement, go to a hallway, bathroom, or closet in the center of the building.

If you are outdoors when a tornado strikes, do not try to outrun it in a car. Cars can be thrown by strong tornadoes. Instead, get out of the car and lie flat in a low ditch, covering your head with your hands. Stay away from trees, power lines, and anything that can become airborne debris. After a tornado passes, watch out for downed power lines, broken gas lines, and structural damage before entering any building. Tornadoes can strike with very little warning, so knowing what to do in advance could save your life.

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