<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> A tropical cyclone is a rapidly rotating storm system characterized by a low - pressure center, a closed low - level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain . Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane (/ ˈhʌrɪkən, - keɪn /), typhoon (/ taɪˈfuːn /), tropical storm, cyclonic storm, tropical depression, and simply cyclone . A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean, and a typhoon occurs in the northwestern Pacific Ocean; while in the south Pacific or Indian Ocean, comparable storms are referred to simply as "tropical cyclones" or "severe cyclonic storms". </P> <P> "Tropical" refers to the geographical origin of these systems, which form almost exclusively over tropical seas . "Cyclone" refers to their winds moving in a circle, whirling round their central clear eye, with their winds blowing counterclockwise in the Northern Hemisphere and blowing clockwise in the Southern Hemisphere . The opposite direction of circulation is due to the Coriolis effect . Tropical cyclones typically form over large bodies of relatively warm water . They derive their energy through the evaporation of water from the ocean surface, which ultimately recondenses into clouds and rain when moist air rises and cools to saturation . This energy source differs from that of mid-latitude cyclonic storms, such as nor'easters and European windstorms, which are fueled primarily by horizontal temperature contrasts . Tropical cyclones are typically between 100 and 2,000 km (62 and 1,243 mi) in diameter . </P> <P> The strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth's rotation as air flows inwards toward the axis of rotation . As a result, they rarely form within 5 ° of the equator . Tropical cyclones are also almost completely absent from Earth's southwestern quartersphere, mainly because the shapes of the African and South American continents permit the Benguela and Humboldt Currents to cover ocean basins as far north as 5 _̊ N with excessively cool water . These powerful cold currents also produce much stronger vertical wind shear in the South Atlantic and Southeast Pacific, which typically prevent tropical depressions and minor storms there from developing into cyclones and prevent even the waters of the Brazil Current from being so hot as analogous western boundary currents or ocean gyres . Also, the African easterly jet and areas of atmospheric instability which gives rise to cyclones in the Atlantic Ocean and Caribbean Sea, along with the Asian monsoon and Western Pacific Warm Pool, are feature of the Northern Hemisphere and Australia . </P>

Why does tropical cyclone originated over the seas
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