How do tropical storms form?

  • Hurricanes need a lot of heat to form, which is why they usually occur over tropical seas (at least 26°C).
  • The sun is close to the equator, providing energy to heat the ocean.
  • The warm ocean heats the air above it causing it to rise rapidly.
  • Water evaporates quickly from the hot surface of the ocean, so the rising air contains great amounts of water vapour.
  • The rising air starts to spin (anti-clockwise in the northern hemisphere)
  • The centre of the storm - the eye - is calm.
  • As the air rises it cools, condenses and forms towering cumulonimbus clouds.
  • The rapidly rising air creates an area of intense low pressure. The low pressure sucks in air, causing very strong winds.
  • Once the storm moves over land it starts to lose energy and fades.
Diagram of tropical storm forming at sea