Cyclone Arnab Formed in Bay of Bengal: Key Insights

Cyclone Arnab Formed in Bay of Bengal: Key Insights

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Key takeaways

  • The IMD issued a Red Alert as Cyclone 'Arnab' strengthened into a Very Severe Cyclonic Storm (VSCS) over the Bay of Bengal.
  • The storm packed sustained wind speeds between 118 and 166 kmph (64-89 knots).
  • The name 'Arnab' means ocean in Bengali and was contributed by Bangladesh to the WMO/ESCAP panel matrix of 13 nations.
  • Formation requires Sea Surface Temperatures exceeding 26.5°C to 28°C and location beyond 5° latitude for sufficient Coriolis deflection.
  • Disaster relief groups like NDRF, APSDMA, and OSDMA are deployed to execute evacuations along the Andhra Pradesh and Odisha coasts.

Why in News

  • The India Meteorological Department (IMD) issued a Red Alert for Andhra Pradesh and Odisha because of Cyclone 'Arnab'.
  • The cyclonic storm grew stronger over the west-central Bay of Bengal and turned into a Very Severe Cyclonic Storm (VSCS).

What is Cyclone Arnab

  • It is an intense tropical storm that the IMD classified as a Very Severe Cyclonic Storm (VSCS).
  • The storm features a low-pressure central core along with organized spiral bands of heavy rain clouds.
  • It carries sustained surface winds blowing at speeds between 64 and 89 knots or 118 to 166 kmph.

Origin of Cyclone Arnab

  • The storm started as a simple atmospheric low-pressure system over the east-central and adjoining southeast Bay of Bengal.
  • It gained power step by step, changing from a depression to a deep depression before becoming a named cyclonic storm.
  • After forming, the storm moved in a west-northwest direction into the west-central Bay of Bengal.

How Cyclones Form (Cyclogenesis)

  • Thermal Engine: Cyclones need warm sea surfaces with temperatures above 26.5°C to 28°C, which release heat as moist air rises.
  • Coriolis Force: The storm needs planetary rotation force away from the equator, usually beyond 5° latitude, to spin counter-clockwise.
  • Low Vertical Wind Shear: Weak changes in wind speed at higher altitudes allow the rising cloud column to stay together without breaking.
  • Upper-Level Divergence: Strong outward airflow at the top of the storm pumps out rising air, which lowers pressure at the eye and pulls in strong surface winds.

Naming Convention for Cyclones

  • Regional Panel: The WMO/ESCAP Panel on Tropical Cyclones (PTC) names storms in the North Indian Ocean using recommendations from 13 member nations.
  • Sequential Registry: The panel picks names in order from a pre-approved alphabetical list created by member countries.
  • The name 'Arnab' means ocean in Bengali, and Bangladesh contributed this name to the official list.

Significance of Cyclone Arnab

  • Post-Monsoon Coastal Vulnerability: The storm shows how warm oceans in October and November build strong cyclones that threaten Andhra Pradesh and Odisha.
  • Cascading Inland Disruptions: Moving inland can cause heavy unseasonal rains, flash floods, and serious crop losses across northern India.
  • Zero-Casualty Disaster Governance: The crisis tests disaster management groups like APSDMA, OSDMA, and NDRF to evacuate people quickly and prevent loss of life.