CoachA tropical cyclone is a storm, hundreds of kilometres across, that forms over a warm tropical sea around a centre of low pressure, with winds spiralling in towards the centre and bands of thunderstorms. When its sustained winds reach knots, about , it is called a hurricane in the Atlantic and the eastern Pacific, a typhoon in the western Pacific, and simply a cyclone in the Indian Ocean and the South Pacific. Its calm, nearly cloudless centre is the eye; the ring of towering thunderstorms around it, where the winds are strongest, is the eyewall.
