Cyclones
Tropical cyclones are possibly the most destructive and worse disaster. The nomenclature of tropical storms naturally varies from one region of the world to another. Tropical storms with sustained winds of 64 knots are called hurricanes in the Atlantic and eastern Pacific; typhoons in the western north Pacific, willy-willy in Australia; Baguio in the Philippine islands; and, severe cyclones in South Asia. Tropical cyclones are seasonal phenomena and their greatest frequency is during periods of maximum sea surface temperatures, although other factors are also important. In the north Indian Ocean, this period is from May to June and from October to December. About sex cyclones reach tropical storm intensity in the north Indian Ocean each year. Large variability has been reported in the location of storms from decade to decade although no systematic patterns have emerged.
When a cyclone or depression approaches a country, a risk of serious loss or damage arises from severe winds, heavy rainfall, storm surges and river floods. The force exerted by the wind is proportional to the square of its speed. The total damage due to wind may, therefore, be expected to increase randomly with the more violent cyclones. Cyclonic storms and storms surges are much more common on the east coast of India than on the west coast.
Bangladesh has the worst record of cyclones and tidal surges. Cyclones and tidal surges are frequent in the months of October and November. These disasters destroy crops, damage infrastructure, houses and vital installations, and cause widespread health hazards for the people. They occur so frequently and in such magnitude in Bangladesh that they have multiplied the problems of poverty and seriously challenged the efforts of the country towards self-reliance.
The effective prediction of cyclones is very important. The intensity and development of a cyclone depend on many meteorological parameters. These parameters are derived from meteorological observations. The knowledge of these leads a forecaster to issue an effective forecast of a cyclonic storm, about its intensity, development and future movement.
