A tornado is a violent, rotating column of air that stretches from a thunderstorm down to the ground. These incredible weather events are also known as twisters. A tornado is officially defined as a funnel of rotating air that has made contact with the surface of the Earth. Understanding how these storms build up helps us appreciate their power.
The Special Ingredients Needed for a Tornado
Tornado formation requires a special recipe that starts with a clash of air masses. The first element is warm, moist air that usually flows in near the ground, often from the south. This air is buoyant and contains water vapor, which fuels the thunderstorm.
This rising warm air meets cooler, drier air higher up in the atmosphere. When these layers meet, the atmosphere becomes unstable, meaning the air wants to move a lot.
The third ingredient is wind shear, which is a change in wind speed or direction at different heights. For example, the wind near the ground might be blowing slowly north, while the wind a mile up blows quickly east. This difference causes the air between the layers to start rolling horizontally.
The Giant Spinning Tube: How the Storm Builds Up
The rolling motion created by wind shear is the first step toward a tornado. Once this horizontal spinning air is created, the powerful updraft of the thunderstorm takes over. The updraft is the strong stream of warm, rising air feeding the storm, and it pulls on the rolling air.
The updraft tilts the horizontal spin into a vertical position. This creates a large, spinning core inside the thundercloud called a mesocyclone. Most tornadoes form inside these powerful storms, which are often the strongest kind of thunderstorms, known as supercells.
The mesocyclone draws air inward, causing the rotation to speed up, much like a figure skater pulling their arms in close. This rapidly spinning air stretches downward, forming a visible funnel cloud. A funnel cloud is only officially called a tornado once the rotation makes contact with the ground, kicking up dust and debris.
What to Do When a Tornado is Near
Knowing the signs of an approaching tornado is an important part of staying safe. Look for dark, often greenish skies, large balls of ice known as hail, or a loud sound that may resemble a roaring train. If you hear an official tornado warning on the radio or a siren, you need to act quickly and calmly.
The safest place to go is the lowest level of a building, such as a basement or a storm cellar. If your home does not have a basement, immediately go to an interior room on the lowest floor, away from all windows. Small rooms like a closet or bathroom are often the best choices because they offer more surrounding walls for protection.
Once in your safe spot, crouch down and use your arms to cover your head and neck. It is also a good idea to put on sturdy shoes and wear a bike helmet for extra protection against falling debris. Remember to listen carefully to adults and weather alerts, and stay in the safe place until officials give the all-clear.