Tropical Storms

• Tropical storms have high winds and torrential rain, and usually affect small islands and coastal regions.
• Tropical storms form between 5 - 30 degrees north or south of the equator in warm oceans
• Temperature

  Ocean temperatures must be above 27 degrees Celsius, as warm water provides the storm with energy. This is why storms form during late summer, when the ocean has had time to heat up
• Cause - Air pressure

  Must be in areas of unstable air pressure - usually where areas of high pressure and low pressure meet. This is so that warm air rises more readily and clouds can form (air must be humid for cloud formation).

  Warm air rises because it is less dense than cold air
• Cause - Wind shear

  Winds must be present for the swirling motion to form, but not too strong or the storm system will be ripped apart in the early stages
• Cause - Rotation

  Tropical storms only from around the equator, but tropical storms will not form on it. The Coriolis Effect is the effect of the Earth's rotation on weather events. The storm spins because the Earth is spinning, but there is no Coriolis Effect at the Equator.
• Tropical Storm Formation


  1. Warm, moist air rises, leaving an area of low pressure below

  2. Warm air from the surroundings moves into this low pressure area and rises too

  3. Warm air rises and eventually cools, causing the moist air to condense and form large thunderstorm clouds

  4. The whole system is spinning due to the Coriolis effect

  5. The constant additions of energy from the warm air causes the storm to spin faster and generate higher wind speeds
• Eye


  An area of extremely low pressure where cool, dry air descends. The weather within the eye is relatively calm and cloud free.
• Eyewall


  The most intense and powerful area of the storm, surrounding the eye. Warm, moist air rapidly rises here with extremely high winds and torrential rain
• Storm surge


  A large amount of sea water pushed on the coast by low pressure and high winds when the tropical storm reaches a coast
• What happens when the storm reaches land?

  When the storm reaches land, it no longer has a supply of energy (warm, moist air from the sea) and the eye eventually collapses and the storm dissipates.
• Explain the structure of a tropical storm

  A) Warm air fans outwards when it reaches the top

  B) Colder, dry air sinks down they eye - calm, cloudless

  C) Wrm air rising and rotating - heavy rain, strong winds

  
• Effect of climate change of distribution

  As the world's average temperature rises, more of the world's oceans could be above 27 degrees, allowing tropical storms to form in more areas.
• Effect of climate change on frequency

  Oceans will stay at 27 degrees celsius or higher for longer periods of time each year, so there is a longer window of time which tropical storms can form in
• Effect of climate change on intensity

  Higher sea surface temperatures are likely to result in more evaporation and increase cloud formation, releasing more energy. This could result in storms becoming more powerful
• Monitoring - detecting and recording warning signs of storm formation and movement

  Cloud formations and movements can be tracked using radar, satellites and aircrafts. Scientists also monitor areas where tropical storms usually form to see if one is on the way
• Predicting - using monitoring as well as historical trends and computer based modelling to predict where, when and duration of storm


  It is possible to predict the route and intensity of a tropical storm up to days in advance using monitoring and computer modelling. The population can be informed and warned, so can take action
• Protection - increasing the resistance of a population by physically designing things that withstand effects


  Sea walls built on coast lines to block storm surges.

  Storm drains constructed to divert water after high levels of rainfall to reduce flooding

  Power lines, doors etc reinforced to be resistant to high winds

  Houses built on higher ground or stilts to reduce flood risk
• Planning - having systems in place to prepare population in advance


  Hazard mapping - identifying areas most at risk

  Evacuation routes

  Raising awareness
• Tropical storms


  Intense low pressure weather systems with heavy rain and strong winds that spiral around the centre