Weather hazards

• extreme weather= weather that is not normal for an area and have negative impacts
• low pressure = created at the surface where air is rising. Low pressure is associated with rain and cloud.
• high pressure= Created at surface where air is sinking. Associated with clear skies.
• Coriolis effect= deflects wind to the right
• Hadley cell = transfers air and heat between the equator
• ferrel cell = returns cooler air towards the equator but moves warmer air towards the poles
• polar cell= the amount of solar insulation at the poles leads to cold air which sinks
• Conditions which cause tropical storms:


  -low latitude

  -between 5-30 degrees North and South of the equator

  -Originate over oceans with temperatures above 26 degrees

  -Between summer and autumn
• Why do these conditions cause tropical storms?


  -Being near the equator means temperatures are higher, so the sea and air are heated more quickly. Air pressure is low and air rises.

  -High ocean temperatures provides heat and moisture, warm air rises rapidly.

  -Summer and autumn are typically warmer seasons so there is low pressure.
• The sequence of tropical storm formation:

  1. Air is heated by warm water at ocean surface
  2. As air is warmed, it becomes less dense and rises creating low pressure.
  3. As the air rises the evaporated water from sea surface cools, and condenses into clouds.
  4. the Coriolis effect causes air to spin around a central storm eye
  5. the Cumolonimous clouds generate torrential rain
  6. Winds become stronger as air rises rapidly
  7. once the storm reaches land, the storm isn't fuelled by moisture so it loses its power.
• Case study: Typhoon Haiyan


  Primary effects:

  -6,000 killed, 40000 homes destroyed, 90% of the city Tacloban destroyed

  Secondary effects:

  -Agricultural land destroyed and rice price rose by 11%

  -water supplies contaminated by sewage , education was distrupted.
• What were the responses to Typhoon Haiyan?


  Immediate responses:

  -800,000 evacuated , government provided medical supplies

  Long term responses:

  -cyclone shelters were built, warning system put in place