Why do tornadoes happen in the us?

Answer 1

Although tornadoes can happen almost anywhere they are especially common in the U.S. Most of the activity is concentrated on the central plains. Here, warm moist air from the Gulf of Mexico collides with cool air from Canada and dry air from the Rockies. When this happens thunderstorms develop, feeding on the moisture from the Gulf. Then a second condition, called wind shear comes into play, tilting the convection of the storms, which allows them to become stronger and last longer as well as giving the rotation they need to produce tornadoes. Finally there is a layer of air called a cap the often forms over the plains that suppresses storm development. This allows instability to build until some storms break the cap. This cap only allows the strongest storms to develop and as a result they don't have to compete with weaker storms for energy.

Although conditions similar to these can occur elsewhere in the world they are rarely this ideal for tornado formation.

Answer 2

Tornadoes can occur anywhere in the world that gets thunderstorms but are most common in the central U.S. do to an ideal setup. Storm systems bring warm, moist air from the Gulf of Mexico into the U.S. and slam cool air from Canada and dry air from the Rockies into it. This creates thunderstorms. At the same time a layer of stable air called an inversion holds back storm development, allowing instability to build until storms break through and develop explosively. Finally differences in wind speed and direction at different altitudes sets the storms rotating. This rotation can then develop into tornadoes.

Similar conditions can occur elsewhere in the world, but not so frequently as in the central U.S.