7)) defines a tornado as a "violently rotating column of air extending from a thunderstorm to the ground-. The objective of this study on tornadoes is to establish what causes these rapid-striking storms, how tornadoes form, the occurrence and distribution of tornadoes between the world and the United States, and lastly how tornadoes are measured. .
WHAT CAUSES A TORNADO.
The National Weather Service defines a tornado as " a violently rotating column of air in contact with the ground and pendant from a thunderstorm-. In other words, a thunderstorm is the first step in the creation of a tornado. Then, if other conditions are right, the thunderstorm could spin out one or more tornadoes.
The three key conditions required for thunderstorms to form are:.
Moisture in the lower to mid levels of the atmosphere,.
Unstable air. That is, air that will continue rising once it begins rising from near the ground,.
A lifting force. Something is needed to cause the air to begin rising. The most common lifting force is heating of air near the ground. As the air warms it becomes lighter and begins rising. Advancing masses of cool air, which force warm air upward, also trigger thunderstorms.
When all the conditions are present, humid air will rise high into the sky. The rising air is called an updraft. As air rises, it cools and the moisture in it begins condensing to form a cloud. When the lifting force is strong enough and the air contains enough moisture, the cloud can tower more than 50,000 feet in the air. The updraft can carry air upwards at more than 100mph. Raindrops and balls of ice also known as hail, form inside the thunderstorm. Positive and negative electrical charges become separated, creating the areas of different charges that lead to lighting and thunder (Williams, 2000). .
The strongest thunderstorms normally form in warm, humid air that's east or south of advancing cold air. A "low level jet- of warm, humid air blowing from the south only 3,000 to 5,000 feet above the ground helps feed the violent thunderstorms that can form tornadoes.
