A tropical cyclone is a fast rotating storm system with a low-pressure core, a closed low-level atmospheric circulation, high winds, and a spiral arrangement of thunderstorms causing heavy rain and/or squalls. A tropical cyclone is known by many names depending on its location and severity, including hurricane (/hrkn, -ken/), typhoon (/tafun/), tropical storm, cyclonic storm, tropical depression, or simply cyclone. A hurricane is a tropical cyclone that forms in the Atlantic Ocean and the northeastern Pacific Ocean, whereas typhoon forms in the northwestern Pacific Ocean; equivalent storms in the south Pacific or the Indian Ocean are simply called “tropical cyclones” or “strong cyclonic storms.”

The term “tropical” alludes to the genesis of these systems, which virtually exclusively arise over tropical oceans. The term “cyclone” alludes to their winds whirling in a circle around their center clear eye, with the Northern Hemisphere’s winds flowing counterclockwise and the Southern Hemisphere’s winds blowing clockwise. The Coriolis effect causes circulation to flow in the opposite direction. Tropical cyclones usually develop over huge areas of water that are relatively warm. They get their energy by evaporating water from the ocean surface, which eventually condenses as clouds and rain when wet air rises and cools to saturation. Mid-latitude cyclonic storms, such as nor’easters and European windstorms, are largely driven by horizontal temperature differences. Tropical cyclones generally have a diameter of 100 to 2,000 kilometers (60 to 1,240 miles). Tropical cyclones hit several parts of the world every year, including the Gulf Coast of North America, Australia, India, and Bangladesh.

The conservation of angular momentum given by the Earth’s rotation as air rushes inwards toward the axis of rotation causes the powerful spinning winds of a tropical storm. As a result, they almost never develop within 5 degrees of the equator. Due to very severe wind shear and a small Intertropical Convergence Zone, tropical cyclones are practically unheard of in the South Atlantic. Cyclones in the Atlantic Ocean and the Caribbean Sea are caused by the African easterly jet and regions of atmospheric instability, whereas cyclones in Australia are caused by the Asian monsoon and the Western Pacific Warm Pool.

Warm ocean waters are the major source of energy for severe storms. As a result, these storms are generally fiercest over or near water and diminish quickly over land. In comparison to interior locations, this makes coastal regions more vulnerable to tropical cyclones. Strong winds and rain, high waves (due to winds), storm surges (due to wind and severe pressure changes), and the possibility for tornado spawning can all cause coastal devastation. Tropical cyclones suck in air from a broad region and concentrate the water content of that air (moisture in the atmosphere and moisture evaporated from water) into precipitation over a much smaller area. After the rain, this replenishment of moisture-bearing air can result in multi-hour or multi-day extremely heavy rain up to 40 kilometers (25 miles) from the shore, considerably beyond the quantity of water that the local atmosphere can store at any given moment. As a result, river floods, overland flooding, and a general overload of local water management infrastructure across a broad region may occur. Tropical cyclones may have a role in alleviating drought conditions, notwithstanding their destructive impacts on human populations. However, this assertion is debatable. They also transfer heat and energy away from the tropics and towards temperate latitudes, which plays a key role in global climate regulation.

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