No one knows exactly what causes tornados, but some scientists believe that when warm air meets cold air, a tornado may form. The reason for this is that the warm air is lighter than the cold air, so it rises up fast and meets different winds moving different directions. Under the right conditions, this can cause a tornado. Though there is still much mystery surrounding tornados, many people believe that when warm moist air meets cool dry air, tornados can result. Choose which pattern of organization is used in the paragraph