tornado and typhoon

A tornado is a violently rotating column of air which is in contact with both a cumulonimbus (or, in rare cases, cumulus) cloud base and the surface of the earth. Tornadoes can come in many shapes, but are typically in the form of a visible condensation funnel, with the narrow end touching the earth. Often, a cloud of debris encircles the lower portion of the funnel.
Most have winds of 110 mph (175 km/h) or less, are approximately 250 feet (75 meters) across, and travel a few miles (several kilometers) before dissipating. However, some tornadoes can have winds of more than 300 mph (480 km/h), be more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 kilometers).[1][2][3]
They have been observed on every continent except Antarctica; a significant percentage of the world's tornadoes occur in the United States.[4] This is mostly due to the unique geography of the country, which allows the conditions which breed strong, long-lived storms to occur many times a year. Other areas which commonly experience tornadoes include Australia, south-central Canada, northwestern Europe, south-central and eastern Asia, east-central South America, and Southern Africa.[5].
A tropical cyclone is a storm system fueled by the heat released when moist air rises and the water vapor in it condenses. The term describes the storm's origin in the tropics and its cyclonic nature, which means that its circulation is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. Tropical cyclones are distinguished from other cyclonic windstorms such as nor'easters, European windstorms, and polar lows by the heat mechanism that fuels them, which makes them "warm core" storm systems.
Depending on their location and strength, there are various terms by which tropical cyclones are known, such as hurricane, typhoon, tropical storm, cyclonic storm and tropical depression.
Tropical cyclones can produce extremely strong winds, tornadoes, torrential rain, high waves, and storm surges. The heavy rains and storm surges can produce extensive flooding. Although their effects on human populations can be devastating, tropical cyclones also can have beneficial effects by relieving drought conditions. They carry heat away from the tropics, an important mechanism of the global atmospheric circulation that maintains equilibrium in the earth's troposphere.

Tornadp's meaning:
http://en.wikipedia.org/wiki/Tornado
Typhoon's meaning
http://en.wikipedia.org/wiki/Typhoon

tornado 是龍捲風, typhoon 是颱風。