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Tropical cyclone constitutes one of the most destructive natural disasters that affects many countries around the globe and exacts tremendous annual losses in lives and property. Its impact is greatest over the coastal areas, which bear the brunt of the strong surface winds, squalls, induced tornadoes, and flooding from heavy rains, rather than strong winds, that cause the greatest loss in lives and destruction to property in coastal areas. |
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STRONG WINDS |
A squall is defined as an event in which the surface wind increases in magnitude above the mean by factors of 1.2 to 1.6 or higher and is maintained over a time interval of several minutes to one half hour. The spatial scales would be roughly 2 to 10 km. The increase in wind may occur suddenly or gradually. These development near landfall lead to unexpectedly large damage.
Tornadoes are tropical cyclone spawned which are to expected for about half of the storms of tropical storm intensity. These are heavily concentrated in the right front quadrant of the storm (relative to the track) in regions where the air has had a relatively short trajectory over land. These form in conjunction with strong convection.
Rainfall associated with tropical cyclones is both beneficial and harmful. Although the rains contribute to the water needs of the areas traversed by the cyclones, the rains are harmful when the amount is so large as to cause flooding.
The storm surge is an abnormal rise of water due to a tropical cyclone and it is an oceanic event responding to meteorological driving forces. Potentially disastrous surges occur along coasts with low-lying terrain that allows inland inundation, or across inland water bodies such as bays, estuaries, lakes and rivers. For riverine situations, the surge is sea water moving up the river. A fresh water flooding moving down a river due to rain generally occurs days after a storm event and is not considered a storm surge. For a typical storm, the surge affects about 160 km of coastline for a period of several hours. Larger storms that are moving slowly may impact considerably longer stretches of coastline.