Tornadoes occur in most parts of the world. However they are most frequent over the continental plains of the USA.
Tornadoes are typically identified as a funnel of spiraling air descending from the base of clouds to the earth. The tornado is usually narrow, about 1/2 km wide and rarely does it move more than 20 km.Like hurricanes the precise mechanism of how the funnel forms in not understood.
Tropical Storms start within 8º and 15º north and south of the equator where surface sea temperatures reach 27ºC. The air above the warm sea is heated and rises. This causes low pressure.
The weather system generates heat which powers the storm, causing wind speeds to increase. This causes the Tropical Storm to sustain itself. Tropical storms rely on plenty of warm, moist air from the sea - this is why they die out over land.The central part of the tropical storm is known as the eye. The eye is usually between 30-50km across. It is an area of calm, with light winds and no rain. It contains descending air. Large cumulonimbus clouds surround the eye. These are caused by moist air condensing as it rises. Wind speeds average 160km per hour around the eye
Tornadoes and hurricanes appear to be similar in their general structure. Both are characterized by extremely strong horizontal winds swirling around the center, strong upward motion dominating the circulation with some downward motion in the center. The tangential winds far exceed the radial inflow or the vertical motion, and can cause much damage. Hurricanes always rotate counterclockwise in the northern hemisphere (clockwise in the southern), the direction of their rotation being determined by the Earth's rotation. This is almost always true of tornadoes too, although on rare occasions "anticyclonic" tornadoes spinning in the opposite direction do occur (tornadic circulation is determined by the local winds). This is where the similarities end.