Geography Quiz: Cyclones: Naming, Categories and Warnings

The Philippines lies in the western North Pacific, and every tropical cyclone of that basin, whether it strikes the Philippines, China or Japan, is called a typhoon.

A tropical cyclone runs on the latent heat released when water vapour condenses, so it needs a sea whose surface is at about 26.5 degrees Celsius or warmer, with that warm water reaching down about fifty metres, so that the churning of the sea does not cool the surface.

The India Meteorological Department puts a system in the highest class, super cyclonic storm, when the sustained wind at its centre reaches 222 km/h, which is 120 knots.

The eight countries of the WMO and ESCAP Panel on Tropical Cyclones agreed on a list of names for this basin and began using them in 2004, long after the Atlantic, where naming had been practice for decades.

The names themselves are contributed by the thirteen member countries of the panel, but the centre at New Delhi, which the India Meteorological Department runs, takes the next name from the list, announces it when a deep depression strengthens into a cyclonic storm, and issues advisories to all the member…

The warning comes in four stages, each tied to a number of hours before the adverse weather is expected on the coast.

The India Meteorological Department attaches a colour to the severity of the expected weather so that an administration can act without reading the whole bulletin.

A cyclone is a low pressure system, so air flows inwards towards the centre, and the Coriolis force deflects moving air to the left in the Southern Hemisphere, which turns that inflow into a clockwise spiral.

The eye is ten to fifty kilometres across, the air inside it sinks rather than rises, the wind is light and the sky can even be clear, while the atmospheric pressure there is the lowest in the whole system.

The Bay of Bengal gets about four cyclones for every one that forms in the Arabian Sea.

The Saffir-Simpson hurricane wind scale puts a storm of the Atlantic and the eastern Pacific in one of five categories by its sustained wind, from Category 1, which begins at about 119 km/h, to Category 5 at 252 km/h and above, and a storm of Category 3 or higher is…