How are tropical cyclones different to mid-latitude cyclones?
To a first approximation a tropical cyclone is like a heat engine – it derives its energy from the heat that is released when water vapour that has been evaporated from the ocean surface (assisted by high winds and low pressure) condenses in the middle of the atmosphere. Mid-latitude cyclones (low pressure systems associated with fronts) primarily get their energy from horizontal gradients in temperature. Another important difference between the two is that tropical cyclones have their strongest winds near the surface while mid-latitude systems have their strongest winds many kilometres above the surface near the top of the atmosphere.
