Tropical Cyclone

A low-pressure system that originates over tropical oceans, called a typhoon, hurricane, or cyclone depending on the region, accompanied by strong winds and heavy rain.

Tropical Cyclone

Overview

A tropical cyclone is a low-pressure system that forms over the warm sea surface in tropical or subtropical oceans and is a representative weather phenomenon accompanied by strong winds and heavy rain near its center. Depending on the region, it is called a typhoon, hurricane, or cyclone; dozens occur worldwide every year and cause loss of life and property damage. Tropical cyclones form through energy exchange between the ocean and atmosphere, and their intensity and frequency are changing due to global warming.

Main Content

Occurrence Conditions

Several conditions must be met for a tropical cyclone to develop. First, the sea surface temperature must be about 26.5°C or higher. Warm seawater evaporates large amounts of water vapor, and when this water vapor condenses, it releases latent heat that heats the atmosphere. Second, atmospheric instability must be high, and the wind speed difference between upper and lower levels must be small. This is called vertical shear; when shear is strong, tropical cyclone development is suppressed. Third, because the Coriolis force produced by the Earth's rotation is required, tropical cyclones form at least about 5 degrees away from the equator. Fourth, abundant water vapor must be present in the atmosphere, and an existing disturbance must serve as the starting point.

Structure

A tropical cyclone has a distinct structure. At its center lies a calm region called the eye, which is surrounded by the eyewall. The eyewall is the area where the strongest winds and heaviest rainfall occur, with active updrafts. Outside the eyewall, spiral rainbands are arranged, and these bands also produce large amounts of rain. Tropical cyclones can reach hundreds of kilometers in size and extend vertically across the entire troposphere.

Classification

Tropical cyclones are classified according to the maximum wind speed near the center. According to the Korea Meteorological Administration, a maximum wind speed below 17 m/s is classified as a tropical depression, 17–24 m/s as a tropical storm, and 25 m/s or more as a typhoon. Typhoons are further subdivided by intensity into 'weak', 'moderate', 'strong', and 'super'. The U.S. Joint Typhoon Warning Center (JTWC) classifies hurricanes into categories 1 to 5 using the Saffir–Simpson scale, and a Category 5 storm is capable of destroying even high-rise buildings. In the North Indian Ocean, cyclones are classified by stage without a special regional name.

Regional Names

Tropical cyclones are given different names depending on the ocean basin in which they form. They are called 'typhoons' when they form in the northwestern Pacific, 'hurricanes' in the North Atlantic and northeastern Pacific, and 'cyclones' in the North Indian Ocean and the Southern Hemisphere. There are also older names such as 'baguio' in the Philippines and 'willy-willy' in Australia. These regional differences in name originate from historical and cultural backgrounds, while internationally, names designated by the World Meteorological Organization (WMO) are used.

Damage and Impacts

Tropical cyclones cause enormous damage through strong winds, torrential rain, and storm surges. Destruction of structures by wind, coastal flooding from storm surges, landslides, and floods can lead to casualties. Damage is especially severe in developing countries, where disaster prevention infrastructure is inadequate. On the other hand, tropical cyclones also have positive aspects: they help alleviate droughts and contribute to the global heat balance by transporting heat toward the polar regions.

Latest Trends

In 2024 and 2025, the intensity and characteristics of tropical cyclones are changing under the influence of climate change. Due to rising sea surface temperatures, tropical cyclones of stronger categories are becoming more frequent, and rapid intensification is also on the rise. In 2024, Hurricane Beryl in the North Atlantic rapidly developed into a Category 5 storm in early July, marking the earliest Category 5 on record. In addition, typhoon tracks in the Pacific are expected to change in 2025 in response to the transition between El Niño and La Niña. AI-based prediction models have been introduced, improving the accuracy of track and intensity forecasts, and real-time monitoring systems are being strengthened along with advances in satellite technology. Countries are responding by improving disaster prevention facilities as climate adaptation measures and establishing international cooperation frameworks.