Facts for kids: What is a typhoon?

Typhoon Haiyan

Typhoon Haiyan from the Internatioal Space Station

A typhoon is a large storm system having a circular or spiral system of violent winds and heavy rain, typically hundreds of kilometers or miles in diameter.

They are caused by very low areas of air pressure over warm waters. The low pressure, atmospheric moisture, sufficient Coriolis force, and inward spiraling winds all play a role in the creation of a typhoon.

Warm ocean temperatures (over 26.5°C (79.7 °F)) result in increased evaporation from the surface, meaning increased humidity and clouds. As explained earlier in ‘What causes wind’ air moves from high pressure to low pressure regions. In this case, wind moves into the low pressure region above the warm water. The winds collide and join up, forced upwards to high altitude where they are spread outwards. The rising humid air plays a central role in generating the storm clouds associated with the typhoon. Finally, light winds outside of the typhoon help steer and grow the typhoon.

Some facts about typhoons:

  • Hurricanes, cyclones, and typhoons are all the same weather phenomenon
  • Typhoon is the name of the storms that occur in the Western Pacific
  • Hurricane is the name given to these storms in the Atlantic Ocean and Eastern Pacific
  • In the Indian Ocean, they are called Tropical Cyclones
  • Typhoons typically form between 5 to 15 degrees latitude north and south of the equator
  • Coriolis Force is needed to create the spin in the typhoon
  • Coriolis Force is too weak near the equator, so typhoons don’t form there
  • Due to the Coriolis force, winds in a typhoon spiral in the counter-clockwise direction in the northern hemisphere
  • The winds spiral in the clockwise direction in the southern hemisphere
  • To be classified as a hurricane, typhoon, or cyclone, a storm must reach wind speeds of at least 74 miles per hour (119 kilometers per hour)
  • If typhoon winds hit 150 miles per hour (241 kmph) — Typhoon Haiyan exceeded this — then it becomes a super typhoon

Short answer: Hurricanes, cyclones, and typhoons are all the same types of very powerful tropical storms. Typhoon is the name of the storms that occur in the Western Pacific, and are the result of warm ocean temperature, low air pressure and and inward spiraling winds.

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