Context:

Cyclone Asna has formed over the Kutch coast in Gujarat and adjoining areas of Pakistan, according to the India Meteorological Department (IMD).

More on the news:

  • Cyclone Asna is the first cyclonic storm in the Arabian Sea in August since 1976.
  • The name “Asna,” meaning “the one to be acknowledged or praised,” was given by Pakistan.
  • According to the IMD, between 1891 and 2023, only three cyclonic storms formed in the Arabian Sea in August: 1976, 1964, and 1944.
  • A low-pressure area formed off north Andhra Pradesh and south Odisha in the Bay of Bengal, a precursor to cyclone development.

India Meteorological Department (IMD)

  • It is the national meteorological service of India and the principal government agency in all matters relating to meteorology and allied subjects. 
  • Headquartered in New Delhi.
  • The IMD was established in 1875.

About Cyclones 

  • A cyclone is a large system of winds that circulates around a center of low atmospheric pressure, moving in a counterclockwise direction north of the Equator and in a clockwise direction south of the Equator.
  • The term “Cyclone” comes from the Greek word “Cyclos,” meaning the coils of a snake, and was coined by Henry Peddington because tropical storms in the Bay of Bengal and the Arabian Sea resemble coiled serpents.
  • Cyclones are classified into two types: extra-tropical (or temperate) cyclones and tropical cyclones.

Types of Cyclones

Extra-Tropical Cyclones: 

  • Also known as temperate cyclones, these occur in temperate zones and high-latitude regions, sometimes originating in the Polar Regions.
  • They have cold air at their center and derive energy from the interaction between cold and warm air masses.
  • These cyclones are always associated with one or more fronts, which are boundaries between different air masses—warm and cold.
  • They can occur over both land and ocean.

Tropical Cyclones: 

  • Develop between the Tropics of Capricorn and Cancer over tropical or subtropical waters, where they organize into surface wind circulation.
  • They develop only over seas.

Conditions Needed for Tropical Cyclone Formation

  • Low Pressure Area: A low-pressure area must be present.
  • High Sea Temperatures: Sea temperatures need to be at least 27°C.
  • Converging Winds: Winds near the ocean surface must converge, forcing air to rise and form storm clouds.
  • Low Wind Shear: Winds should not vary greatly with height, allowing storm clouds to rise vertically.
  • Coriolis Force: The cyclone must be far enough from the equator for the Coriolis force to take effect.

Worldwide Terminology:

  • Typhoons: China Sea and Pacific Ocean
  • Hurricanes: West Indian islands, Caribbean Sea, and Atlantic Ocean
  • Tornadoes: Guinea lands of West Africa and southern USA
  • Willy-Willies: North-western Australia
  • Tropical Cyclones: Indian Ocean

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