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Tropical Cyclones

What processes produce the selected extreme natural event? How often does it occur?

Home | Extreme Natural Events in the South- west pacific | What Processes produce the ENE and how oftn does it occur? | Sequence of events during and ENE | The affect of an ENE on the land | The affect of and ENE on economic and social activities | increase/ decrease the likelihood or effects of and ENE | Case Study: TROPCIAL CYCLONE LARRY | Case Study: Tropical Cyclone Namu
Processes of a Tropical cyclone:
Cyclones start when strong clusters of winds drift over warm ocean waters.
The warm air from the storm and ocean surface combine and begin rising. This creates low pressure at the surface. Winds start blowing in the opposie direction causing the storm to start spinning.
Rising warm air causes pressure to decrease at higher altitudes. Air rises faster and faster to fill this low pressure, which is drawing more and more air off the warm water and sucking cooler, drier air downwards. As the storm moves over the
ocean it picks up more warm, moist air. Wind speeds start to increase as more air is sucked into the low pressure centre.

How often do Tropical Cyclones occur?

In the northern hemisphere, tropical cyclones occur mainly between June and November in the North Atlantic, the North Pacific and the North Indian Ocean. In the southern hemisphere, they occur mainly between November and April in the South Indian Ocean, the South Pacific Ocean and in the seas around northern Australia. 


The region shaded red is where tropical cyclones occur.