Part 1 1.B)

A tropical cyclone needs two main ingredients: a cluster of thunderstorms and a warm body of water-at least 27 degrees Celsius-from which the storm gathers its energy. The warm, tropical ocean under a developing storm evaporates then condenses to form clouds, releasing heat throughout the process.

The heat energy combined with the rotation of the Earth gets the cyclone spinning and propels it forward. While the cyclone looks savage from the outside, its low-pressure centre, commonly known as the eye, is deceptively calm. This belies the danger of the dense wall of cloud that surrounds it, which is the deadliest part of a cyclone.

Here the strongest winds and greatest rainfall are found. The eye is usually 40 km in diameter, but can range in size from less than 10 km to over 100km-as is the case with

Yasi-depending on the size of the cyclone itself.

“The thing about Cyclone Yasi is its large diameter.” “We commonly get ‘midgets’ in Queensland-small diameter but still intense tropical cyclones. From time to time we get one of these very, very large one, but the midgets have been more common in recent years. It makes it more unusual for us again to see a large diameter system here.”