A very good description of tropical cyclones and the events of tropical cyclone Tracy.
Cyclones in General
The word cyclone has two possible origins. The first one being from the mid 19th century when captain Henry Piddington referred to a storm as a cyclone. It is thought the Piddington got this word from the Greek word cyclos which means coils of a snake. The other possible origin is the word Cyclops. A Cyclops is a mythical Greek creature with only one eye. A cyclone also has one eye.
A cyclone is defined as an area of low atmospheric pressure with inward spiraling wind. In the northern hemisphere the wind rotates counter-clockwise but in the southern hemisphere the wind rotates clockwise. The word covers a wide variety of winds and should not be used by itself very often. Words like tropical or extratropical should be used with it.
All cyclones have a few common characteristics. The centre is the area of lowest atmospheric pressure, often called the eye. Also they all rotate clockwise in the southern hemisphere and anti-clockwise in the northern hemisphere. All cyclones can only be formed when the pressure in the centre of the cyclone compared to the pressure outside the cyclone is balanced with the Coriolis force.
Cyclones spin in different direction in different hemispheres because of the Coriolis Effect. The equator cannot have a cyclone on it as the coriolis parameter is exactly zero, therefore the cyclones perimeter would also be exactly zero therefore no cyclone has ever turned its rotating direction.
There are 6 main types of cyclones. One type is the tropical cyclone. It is fueled by the heat released when moist air rises and the water vapor in it condenses. These types of cyclones only exist near the equator. Most of them appear only near the Pacific Ocean, Indian Ocean and there are a lot of tropical cyclones in the north parts of the Atlantic Ocean.
Although tropical cyclones are very deadly and devastating, they play an important part in keeping the Earth wet. The areas that the cyclones hit are usually in need of rain or are in drought; therefore the water that a cyclone provides helps the native ecosystems.
Cyclones vary in sizes. A small cyclone has a radius of about 200km, but this doesn’t make them weak, some of the strongest cyclones have been midgets. Between 350 and 650 are average and a huge cyclone has a radius of over 900km, that’s more then 8 degrees of latitude!