Twenty years of progress and achievement of the WMO tropical cyclone programme (1980-1999). Report no. TCP-43
Tropical cyclones are among the most devastating of all natural hazards. Their potential for wrecking havoc caused by their violent winds, torrential rainfall and associated storm surges, floods, tornadoes and mud-slides is aggravated by their severity, size, frequency of occurrence and the vulnerability of the extensive areas they affect. Every year several of them cause sudden-onset disasters of varying harshness, with loss of life, destruction of property and severe disruption of normal activities.
About 80 tropical cyclones form annually over tropical oceans. As they intensify, with warm temperatures and very low atmospheric surface pressure in the centre, or "eye" as it is called, and wind speeds exceeding 118 km/h - and in extreme cases 250 km/h - they are called hurricanes in the western hemisphere and South Pacific, typhoons in the western North Pacific and severe tropical cyclones, tropical cyclones or similar names in other areas.
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