Typhoons are among the most powerful and destructive weather phenomena on Earth. Often the terms typhoon and hurricane are used interchangeably, leading to some confusion. However, they are fundamentally the same weather event, known scientifically as tropical cyclones. The distinction in terminology simply depends on location. So, what exactly is a typhoon?
In essence, a typhoon is a mature tropical cyclone that develops in the northwestern part of the Pacific Ocean, specifically west of the International Date Line and north of the equator. To understand typhoons, it’s crucial to first grasp the broader term: tropical cyclone. Meteorologists use “tropical cyclone” as a general term to describe a rotating, organized system of clouds and thunderstorms. These storms originate over warm tropical or subtropical waters and are characterized by a closed, low-level circulation.
The intensity of a tropical cyclone dictates its classification. The weakest form is known as a tropical depression. When a tropical depression intensifies and achieves maximum sustained winds of 39 miles per hour, it graduates to a tropical storm. It’s only when these storms reach maximum sustained winds of 74 miles per hour or greater that they are further classified as either a hurricane, typhoon, or simply a tropical cyclone – again, depending on their geographic origin.
In the North Atlantic, the central North Pacific, and the eastern North Pacific, these intense tropical cyclones are termed “hurricanes.” However, in the Northwest Pacific, the identical weather phenomenon is designated a “typhoon.” Interestingly, in the South Pacific and the Indian Ocean, the term “tropical cyclone” is used generically, irrespective of the storm’s wind strength.
Several key ingredients must align for a typhoon or any tropical cyclone to form. These include a pre-existing weather disturbance, extensive warm tropical ocean waters, ample moisture in the lower to mid-levels of the atmosphere, and relatively light vertical wind shear. When these conditions persist, they can coalesce to create the formidable storms we recognize as typhoons, bringing with them violent winds, towering waves, torrential rainfall, and significant flooding. In situations where a developing weather system is predicted to bring tropical storm or hurricane-force winds to coastal areas within 24 to 48 hours but hasn’t fully met all cyclone criteria, it might be termed a “potential tropical cyclone,” particularly in the Atlantic and the central and eastern North Pacific basins.
The structure of a typhoon, like all tropical cyclones, is characterized by distinct features. The primary components are rainbands, the eye, and the eyewall. Air spirals inwards towards the center in a counter-clockwise direction in the Northern Hemisphere (and clockwise in the Southern Hemisphere), ascending and then diverging outwards at the upper levels. At the very heart of the storm lies the “eye,” a region of descending air, typically cloud-free and calm, offering a deceptive lull in the otherwise violent storm.
Understanding what a typhoon is, and how it relates to other tropical cyclones, is crucial for communities in affected regions. Preparedness and awareness are key to mitigating the impacts of these powerful weather systems.
