6.6 Cyclones

Under the right conditions, storms grow into the most powerful weather systems on Earth — the cyclone, a vast spinning engine of cloud, wind and rain born over warm seas.

How a cyclone is born

The Cyclone Cycle A cyclone forms over warm ocean water through a self-feeding cycle:

  1. The warm sea heats the moist air above it, which rises.
  2. As it rises, the water vapour condenses into raindrops — and condensation releases heat (the heat the water took up when it evaporated).
  3. That released heat warms the air further, so it rises even more, deepening the low pressure below.
  4. Air from all around rushes in to fill the low, and it too rises — repeating the cycle.
  5. The Earth’s rotation makes all this in-rushing air spin.

The result is a huge low-pressure area with very high-speed winds revolving around it — a spinning system of clouds, winds and rain called a cyclone.

The Eye of the Cyclone At the centre of a cyclone is the region of lowest pressure, called the eye. Strangely, the eye is calm — but the ring of cloud around it brings the strongest winds and heaviest rain. As a cyclone moves from ocean toward land it whips up even higher wind speeds than ordinary thunderstorms. Once it reaches land, its supply of warm, moist air is cut off, and it gradually weakens.

The damage a cyclone does

A Trail of Destruction Cyclones can be devastating — the Amphan cyclone (2020) had peak winds of 270 km/h. Their strong winds push ocean water ashore as a storm surge, a wall of water 3–12 metres high that floods coastal (and even inland) areas. Heavy rain overflows rivers and triggers landslides; seawater contaminates drinking water and leaves salt that makes farmland less fertile; fallen trees block roads, and power outages can last days, crippling emergency services.

Staying safe

Forecasts Save Lives The best protection is warning in advance. The India Meteorological Department (IMD) constantly monitors cyclones and issues alerts. Thanks to weather satellites, we can now track a cyclone and predict its path, greatly reducing its toll. If you live in a cyclone-prone area: follow weather updates, keep an emergency kit ready, and move quickly to a designated cyclone shelter when warned.

One Idea, the Whole Chapter Notice how a single thread runs through everything: pressure differences. They make a sea breeze, lift a roof, and spin a cyclone — all the same physics, scaled up. And the charge that lights a cyclone’s lightning is the very static electricity from Chapter 5. Science, joined up.