Cyclones

CYCLONES ARE METEOROLOGICAL systems consisting of areas of low pressure where the winds in the Northern Hemisphere and Southern Hemisphere rotate counter-clockwise and clockwise, respectively. The biggest storms around the world, such as cyclones, are intensifying. It is reported that the number of category four and five tropical cyclones, which are very intense, have increased over time. One reason for this is the impact of global warming, in particular, the effect of increased sea-surface temperature. Cyclones are often subdivided into other types, which include tropical cyclones and extra-tropical cyclones. Other types of cyclones include polar, polar low, subtropical, and mesoscale cyclones.

Tropical cyclones are low-pressure systems consisting of large rotating systems of clouds and winds, which occur over tropical and subtropical waters. They also have thunderstorm activity and cyclonic surface wind circulation. Depending on their location and strength, there are various terms by which tropicai [Page 297]cyclones are known, such as hurricane, typhoon, tropical storm, cyclonic storm, and tropical depression. These cyclones have no fronts and the center of the storm is warmer than the surrounding air. They are known as tropical storms if the wind reaches 56 ft. (17 m.) per second and hurricanes if the winds reach 108 ft. (33 m.) per second. Hurricanes occur in the North Atlantic Ocean and the northeast Pacific Ocean, east of the dateline. There are several environmental conditions favoring tropical cyclones, such as warm ocean waters, winds that do not vary greatly with height, and a minimum distance of 311 mi. (500 km.) from the equator. There are seven tropical cyclone basins where storms occur on a regular basis. These are the Atlantic basin, Northeast Pacific and Northwest Pacific basins, North Indian basin, South-west Indian basin, Southeast Indian/Australian basin, and Australian/Southwest Pacific basin.

The number of category four and five tropical cyclones, which are very intense, has increased over time. One reason for this is the impact of increased sea surface temperatures due to global warming.

Extratropical cyclones, sometimes called mid-latitude cyclones, are storms that form outside the tropics, sometimes as a tropical storm or hurricane changes, such that they have neither tropical nor polar characteristics. They form where cold and warm air masses come into contact with each other, and are formed in middle or high latitudes, in frontal zones. The center of the storm is generally colder than the surrounding air.

A subtropical cyclone is a non-frontal low-pressure system that has characteristics of both tropical and extratropical cyclones. Compared with tropical systems, they have a broad zone of maximum winds located further from the center. They also have a less symmetric wind field and distribution of convection. [Page 298]They can be formed in a wide band of latitude, from the equator to 50 degrees both North and South. A subtropical cyclone is known as a depression if the winds reach wind speed of 38 mi. (62 km.) per hour or less and as a storm if the speed reaches 39 mi. (63 km.) per hour or more. Many times, these subtropical storms transform into true tropical cyclones.

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