tropical storms

• Global atmospheric circulation


  The movement of air across the planet occurs in a specific pattern
• Global atmospheric circulation


  1. Air rises at the equator, leading to low pressure and rainfall

  2. Air travels to the north and south, becomes cold and falls to create high pressure and dry conditions at around 30° north and south of the equator

  3. Air rises again at around 60° north and south and descends again around 90° north and south
• Global atmospheric circulation creates winds across the planet and leads to areas of high rainfall, like the tropical rainforests, and areas of dry air, like deserts
• Tropical storm


  A very powerful low-pressure weather system which results in strong winds (over 120 km/h) and heavy rainfall (up to 250 mm in one day)
• Names of tropical storms in different regions

  • Hurricanes (US and Caribbean)
  • Cyclones (South Asia)
  • Typhoons (East Asia)
  • Willy-willies (Australia)
• Tropical storms


  • Between 482-644 kilometres wide and 6-8 kilometres high
  • Move forward at speeds of 16-24 km/h, but can travel as fast as 65 km/h
  • Coriolis force caused by the rotation of the Earth causes the tropical storm to spin
• Eye of a tropical storm

  The central part of the tropical storm, usually 32-48 km across, an area of light wind speeds and no rain, containing descending air
• Tropical storms


  • Large towering cumulonimbus clouds surround the eye, caused by warm moist air condensing as it rises, leading to very heavy rainfall and wind speeds of up to 320 km/h
• How tropical storms develop

  1. Form between approximately 5° and 30° latitude, initially move westward due to easterly winds

  2. Air above the warm ocean is heated, once the ocean water reaches at least 27°C, the warm air rises quickly, causing an area of very low pressure

  3. As the air continues to rise quickly it draws more warm moist air up from above the ocean leading to strong winds

  4. The rapidly rising warm air spirals upwards, cools, condenses and large cumulonimbus clouds form

  5. In the centre of the storm, cold air sinks forming the eye of the storm-here, conditions are calm and dry
• Storm expands up to 644 km
• Climate change


  Could lead to more locations being affected by tropical storms, warmer seas could cause the source areas to extend further north and south of the equator
• It's unclear whether climate change will increase or decrease the number of hurricanes, but climate models predict that their intensity may increase
• Factors that may increase the impact of tropical storms due to climate change


  • Warmer ocean surface temperatures and higher sea levels
  • Wind speeds potentially increasing 2-11 per cent
  • Rainfall rates during these storms are projected to increase by about 20 per cent
• Sea level rise is likely to make tropical storms more damaging with increases in coastal flooding and subsequent storm damage along coasts
• Low-lying coastal communities where the population density is high and the income level low are most at risk, more people living in coastal communities in the future will mean that more people will be affected
• Tropical storm forecasting centres


  Use satellite images, various weather instruments and computer-based prediction modelling to detect and track tropical storms, issue warnings to local authorities and the public
• Tropical storm forecasting


  Reinforced aircraft, fitted with various scientific instruments, fly through and over tropical storms to collect data, which can be used to help track and predict the path of a tropical storm