Tropical cyclone

How they form and evolve

Tropical cyclones develop when sea surface temperatures of at least 26–27 °C provide the necessary heat and moisture to fuel the storm. Warm, moist air rises and cools, releasing latent heat through condensation. This process lowers surface pressure, drawing in more air and creating a self-sustaining cycle of rising warm air and inward-spiraling winds driven by the Coriolis effect.

As the system organizes, thunderstorms cluster around a central low-pressure zone. If conditions remain favorable—low vertical wind shear, sufficient moisture, and continued access to warm ocean water—the storm intensifies, forming the classic structure of a tropical cyclone: an eye at the center, surrounded by the eyewall where the strongest winds and heaviest rainfall occur.

When a tropical cyclone moves over cooler waters or land, it loses its energy source and begins to weaken. Some may transition into extratropical cyclones if they move into mid-latitudes.

Tropical vs. extratropical cyclones

While both are low-pressure systems with rotating winds, tropical cyclones differ in structure and energy source.

• Tropical cyclones have a warm core and derive their energy from the release of latent heat during condensation over warm oceans. Their most intense winds and rainfall are concentrated near the center, and they lack cold and warm fronts.
• Extratropical cyclones have a cold core, form along weather fronts, and are powered by temperature contrasts between air masses. They are generally larger but less compact than tropical cyclones.

Classification and regional names

The strength of tropical cyclones is often measured by maximum sustained wind speeds. In the Atlantic and Northeast Pacific, the Saffir-Simpson Hurricane Wind Scale categorizes them from Category 1 (least severe) to Category 5 (most severe).

The naming convention depends on where the storm occurs:

• Hurricanes in the North Atlantic, Northeast Pacific, and South Pacific
• Typhoons in the Northwest Pacific
• Cyclones in the Indian Ocean and South-West Pacific

Despite different names, the storms share the same physical structure and behavior.

Associated weather and environmental impact

Tropical cyclones bring destructive winds, torrential rainfall, coastal flooding, and storm surges that can devastate communities and infrastructure. Their impacts can extend far inland, causing landslides, river flooding, and power outages.

At the same time, they play a role in Earth’s climate system by redistributing heat from the tropics toward higher latitudes. Over the ocean, they can stir surface waters and occasionally trigger upwelling, which supports marine ecosystems.