The word cyclone was coined by an East India Company official in Calcutta
Henry Piddington, a British East India Company official, wrote 40 papers on tropical storms from Calcutta between 1836 and 1855 and gave them a name from the Greek for circle. A cyclone is exactly that: a vast wheel of air spinning around low pressure, one way in the north and the other way in the south.
Winds in a cyclone spiral inward toward a centre of low pressure. Seen from above, northern cyclones turn against the clock and southern ones with it, the reverse of an anticyclone. The centre, called the eye in a mature tropical storm, has the lowest pressure in the region. Near it, the push of air toward low pressure must roughly balance the Coriolis effect caused by Earth's rotation, or the system would collapse inward. One consequence: in the north, the strongest surface winds lie on the eastern side of a cyclone heading north, and on the northern side of one heading west.
Cyclones come in several kinds. Extratropical ones, the familiar mid-latitude storms, start as ripples in broad zones of temperature contrast. As the circulation tightens, fronts form: cold fronts to the west bring narrow bands of thunderstorms, while warm fronts to the east arrive behind layered rain and fog. Late in life the cold air undercuts the warm, the storm occludes, and it becomes cold-cored. Over a lifespan of 2 to 6 days the subtropical jet stream steers its path.
Tropical cyclones are different beasts, warm-cored and powered by latent heat released in intense thunderstorms. Storms can switch between tropical, subtropical and extratropical forms. Over land, small warm-cored mesocyclones can spawn tornadoes, and occasionally waterspouts, though those usually arise from unstable air with little wind shear.
Names depend on the ocean. In the Atlantic and northeastern Pacific the storm is a hurricane, after Huracan, an ancient Central American wind god; in the northwestern Pacific it is a typhoon; in the Indian Ocean and South Pacific it keeps the name cyclone. Formation and strengthening are called cyclogenesis, the building of high pressure is anticyclogenesis, and cyclones have been seen on Mars, Jupiter and Neptune as well.
Source: Cyclone
