What Causes Tornadoes?

A tornado occurs when two different air masses meet, most often a high pressure air mass and a low pressure air mass. The cool air meets with hot, moist tropical air and this results in strong thunder storms forming. For this is to occur, there needs to be the hotter air in the lower atmosphere and the cooler air in the upper atmosphere.

The place where these two air masses meet is known as the dry line. It’s at the dry line that most tornadoes are formed because the two separate air masses run into each other. As the warm air tries to rise, which is a common fact of heat, the cold air blocks it. This results in the warm air beginning to rotate horizontally between the two air masses because there is nowhere else for the pressure to go.

While this is going on, the sun is heating the air on Earth which is resulting in warmer air. As more warm air tries to push past the cold air, even more pressure is formed. Once enough warm air is created, it breaks through the cold air and starts spinning upward, the cold air sinking into the warm air. The warm air at this point begins to spin faster and faster in its column.

If the updraft is considerably strong, the height of this column can be as high as 10 miles and spin at speeds of at least 100 miles per hour. These winds, as they rotate, create storm clouds that spread out as far as ten miles. The thunderstorms that come from these clouds are known as supercells and can produce an inch of water in ten minutes. As these supercells grow, they can cluster and turn into mesocyclones. All tornadoes started out as mesocyclones, but not all mesocyclones become tornadoes.

Scientists are not entirely sure how the tornado makes the jump from the mesocyclone to the ground. Some believe that it lowers from the high pressure to the low pressure, thus touching ground. Others believe that it actually starts from the ground and rises up to meet with the mesocyclone. All that is known is that, when this mesocyclone occurs, there’s an increased chance that a tornado is soon to form.

Tornados need a lot of energy to form, however, so there needs to be a very strong thunderstorm already in an area. If area contains a lot of obstacles, such as rivers, mountains, and so on, this hinders the formation of tornados or makes them short lived.

Tornadoes are most likely to appear in areas of the United States known as “Tornado Alley.” These states include: Missouri, Indiana, Colorado, Texas, Nebraska, Kansas, Oklahoma, Illinois and Arkansas. However, tornadoes have been known to appear in other locations. In New York, a tornado landed right on top of an elementary school, so they do appear in other locations.