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Tropical Cyclones

What sequene of events occurs in the selected extreme natural event?

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

  • Before a tropical cyclone:


  • Hot temperatures in equatorial areas cause air to rise and sea water to evaporate- the evaporating water mixes with the rising air to form a rising cloud of warm, moist air.
  • This rising air begins to spin clockwise by the Coriolis effect on the earth's roatation.
  • The air continues to rise, and air from surrounding areas is sucked in below the rising air, adding more moist air.
  • Jet stream air currents cause the air to increase in speed as they suck the spiralling air further upwards and more air is added- the tropical cyclone is now formed.


  • As the cyclone grows and begins to move, it can begin to be tracked by satellites and radar, and radio broadcasts can issue warnings and begin emergency Civil Defence procedures- people are told to evacuate low- lying areas, to gather food and water supplies and to stay indoors.
  • People live in areas prone to the greatest effects of tropical cyclones.


During a tropical cyclone:
  • As the cyclone passes over a south- west pacific island, the island experiences rapidly increasing wind speeds. Followed by dark skies and heavy rainfall.
  • As the eye of the hurricane passes over head, clear skies with calm wind conditions occur. However, this is short lived, as the eye passes, high winds and torrential rainfall return, but from the opposite direction.
  • Wind and rain finally begin to decrease as the hurricane moves away from the island.
  • Flooding and erosion result from heavy rainfall and the rapid rise in sea level and wave height which accompanies the hurricane.


  • Emergency responses begin, in order to minimise loss of life, injury and damage to property. People most in danger are evacuated, medical facilities are set up and care is provided for those that require it; and vital services such as water and sewerage are reconnected. Edit Text



After a tropical cyclone:


  • After the hurricane passes, damage is assessed and the clean-up bgins.
  • Emergency aid arrives from other countries to aid the clean-up process eg: after Cyclone Kina, NZ donated tents for homeless people, food supplies, first aid equipment and helicopters and transport.



  • Longer- term recovery operations, such as repairing or reconstructing damaged houses, buildings, airports, wharves and roads and replanting export crops, begins.

This stage can take a long time and can be very expensive.

 the formation of a tropical cyclone