A large, rotating storm system characterized by a low-pressure center, strong winds, and heavy rainfall is known globally as a tropical cyclone. This weather phenomenon forms over warm tropical or subtropical waters and draws energy from the evaporation of ocean water, which then condenses into towering thunderstorms. The system must possess a closed, low-level atmospheric circulation to be classified as this type of storm. To sustain this circulation, the storm requires ocean temperatures of at least 80°F (26.5°C) extending to a significant depth.
The Primary Global Synonyms
While the overarching scientific term is tropical cyclone, the name used depends entirely on the storm’s geographic location. These three main terms describe the same meteorological event but are determined by the ocean basin where the storm originates. The distinction is purely a matter of geographical convention established by international meteorological organizations. For a storm to earn one of these primary names, its maximum sustained surface winds must reach or exceed 74 miles per hour (119 kilometers per hour).
Before reaching this intensity, the system is classified as a tropical storm when sustained winds reach 39 mph (63 km/h). This is the threshold at which the storm is officially given a sequential name from a predetermined list. Naming these systems helps avoid confusion, especially when multiple storms are active within the same ocean region.
Defining the Geographic Basins
The term used to describe the storm is dependent on the ocean basin and established boundaries, such as the International Date Line (180 degrees longitude).
Hurricanes
Storms forming in the North Atlantic Ocean, the Caribbean Sea, the Gulf of Mexico, and the Northeast Pacific Ocean are designated as hurricanes. This classification extends across the Pacific until the storm reaches the International Date Line.
Typhoons
The name changes to typhoon for storms that form in the Northwest Pacific Ocean, specifically west of the International Date Line. This region, which includes the waters around East Asia and Southeast Asia, is the most active basin globally for these storm systems.
Cyclones
The third designation, cyclone, is applied to storms that develop in the Indian Ocean (including the Arabian Sea and the Bay of Bengal) and the South Pacific Ocean west of the International Date Line. For example, a storm moving from the Central Pacific into the Northwest Pacific would change its designation from a hurricane to a typhoon.
Localized and Lesser-Known Terminology
Beyond the three global terms, various regions use localized or specific terminology for these phenomena. In the Indian Ocean, for example, a storm may be classified as a Severe Cyclonic Storm or a Very Severe Cyclonic Storm depending on its wind speed. This offers a more precise description than the generic term “cyclone.”
The term Baguio is a localized name used in the Philippines to refer to any tropical cyclone that enters their area of responsibility, regardless of its strength. Historically, the informal term Willy-Willy was sometimes used in Northwestern Australia to refer to a tropical cyclone.