"For my part", wrote the pirate and adventurer William Dampier as far back as 1687, "I know of no difference between a Hurricane among the Carribee Islands in the West Indies and a Tuffoon upon the coast of China or in the East Indies, but only in the name."
Dampier was quite right that there is no distinction, and he might have also added cyclone, another name used to describe the same lethal phenomenon, this time when it occurs in the Indian Ocean. They are all local names for that which meteorologists know by the generic term of tropical revolving storm.
Tropical storms develop over the warm waters near the Equator on the western sides of the world's great oceans - with the exception of the South Atlantic Ocean where, anomalously, these phenomena are unknown. As it moves further north into a cooler environment, or over land where its supply of moisture is cut off, a tropical storm gradually loses its energy and dissipates as quickly as it formed.
Apart from the obvious effects of the very strong winds, many deaths from a cyclone are caused by what is often referred to as a "tidal wave", but which is more properly called a storm surge. Hurricane-force winds over the open ocean bring wind-generated waves of quite spectacular heights.
The swell produced in this way propagates tangentially outwards from the storm in all directions; but whereas a cyclone typically advances some 500 miles in 24 hours, these storm-generated waves propagate much faster and may cover 800 miles in a day. Before satellites, aircraft or radar, the arrival of this massive swell was often the only warning for coastal-dwellers that a cyclone might be on the way.
But the worst effects come with a large and sudden rise in sea level, a "surge" which occurs as the "eye" of the storm approaches land. The surge is produced by a combination of the very low atmospheric pressure near the cyclone's centre, and the very strong winds which tend to "pile up" sea water against a coastline. The ultimate height of the surge depends on several factors, including tides, the shape of the seabed and the coastline in the vicinity, and the speed and angle at which the cyclone approaches the shore.
But typically a raised "dome" of water some 10 to 15 feet above the normal tide level, and some 40 to 50 miles across, might be expected, often, as we have seen in recent days in India, causing flooding and great loss of life.