Tropical Cyclone A tropical cyclone is a powerful low-pressure system forming over warm tropical oceans. When winds hit 62 kmph (34 knots) and pressure drops sharply, it evolves into a vast spinning storm — stretching 150 to 800 km across and moving up to 500 km a day! The term cyclone comes from the Greek word ‘cyclos’ meaning "coiling of a snake" coined by Henry Piddington in the 19th century. Region-wise, it's known as: Cyclone - Indian Ocean Hurricane - Atlantic Ocean Typhoon - Pacific Ocean