The Heat Engine
Hurricanes, typhoons and cyclones are one kind of storm: a heat engine fuelled by warm seawater and spun by Earth's rotation. This interactive film explains how they form, why they spin, what the Saffir–Simpson categories mean, and why storm surge is often the deadliest part, with storms from Bhola and Katrina to Typhoon Gay in Chumphon.
The heat engine
In one week, two hurricanes hit North America. Both ran on the same fuel: warm seawater.
Hurricane, typhoon, cyclone
The same kind of storm gets a different name in each ocean.
A warm ocean
The fuel tank is the top fifty metres of the tropical sea.
The right weather
Warm water is not enough. Four more things must line up.
A chimney of rising air
Air spirals in at the sea surface, rises in the eyewall, and pours out at the top.
Two hundred times our power grid
Almost all of a hurricane’s energy goes into heat, not wind.
The Coriolis effect
Earth’s rotation turns inflowing air into a whirl, in opposite directions north and south.
The eye and the wall
The calmest place in the storm sits right next to the most violent.
Category 1 to 5
The Saffir–Simpson scale ranks hurricanes by wind alone.
Rapid intensification
Over very warm water, a storm can gain strength frighteningly fast.
Storm surge
In many of history’s worst storms, the killer was the sea itself.
The deadliest storms
The worst tropical cyclone disasters were floods from the sea.
Storms in the Gulf of Thailand
Over land a storm loses its fuel. The coast takes the hardest blow.
What climate change does to storms
Not necessarily more storms, but stronger and wetter ones.
Reading the forecast
Now you know what the numbers in the news mean.
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