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Global Geological And Climatic Events

Cyclone Shakhti forms over Arabian Sea

Why in the News?

The India Meteorological Department (IMD) confirmed the formation of Cyclone Shakthi (named by Sri Lanka) over the northeast Arabian Sea.

About Cyclogenesis in the Arabian Sea:

  • Overview: Cyclogenesis is the formation and intensification of tropical cyclones under favourable oceanic and atmospheric conditions.
  • Seasonality: Most active during pre-monsoon (Apr–Jun) and post-monsoon (Oct–Dec) periods, when sea surface temperatures (SSTs) exceed 27 °C, moist convection intensifies, and the Coriolis effect induces rotation.
  • Formation Process: Warm moist air rises forming low pressure; latent heat of condensation deepens the system; upper-level outflow and low vertical wind shear sustain vertical growth, producing a warm eye with spiral rainbands.
  • Historical Pattern: The Arabian Sea was once less cyclone-prone than the Bay of Bengal due to cooler waters, dry winds, and high wind shear. Limited basin size and monsoon winds restricted cyclone growth.
  • Recent Change: Ocean warming and climate change have sharply increased cyclonic activity, making the region far more active in the last decade.
  • Rapid Intensification Trend: Short-term surges in wind speed (< 24 hrs) are now common, linked to warmer SSTs, Indian Ocean Dipole (IOD) shifts, and monsoon wind variability.
  • Oceanic–Climatic Drivers:
    • Indonesian Throughflow imports warm Pacific waters, raising SSTs.
    • Southern Ocean inflow brings cooler deep water, stabilising lower layers.
    • Dual cyclone seasons arise from monsoon wind reversal unique to the region.
  • Climate Change Impact:
    • IMD data show a 52 % rise in Arabian Sea cyclones in two decades, while Bay of Bengal activity slightly declined.
    • The Indian Ocean is among the fastest-warming oceans, increasing heat-moisture availability, altering global weather, and heightening coastal risks to life and infrastructure.

Recent Examples:

  • Tauktae (2021) – winds > 185 km/h, heavy damage along Gujarat–Konkan.
  • Biparjoy (2023) – lasted 13 days, fed by SSTs ~31 °C.
  • Tej (2023) – hit Oman & Yemen, showing cross-basin movement.
  • Shakthi (2025) – latest late-season, fast-intensifying cyclone.

Back2Basics: Tropical Cyclones

  • What is it: Large low-pressure systems over warm oceans, marked by rotating winds, heavy rain, and storm surges.
  • Conditions: Form when ocean temps >27°C, with moist rising air releasing latent heat to fuel convection.
  • Rotation: Driven by the Coriolis force – anticlockwise in Northern Hemisphere, clockwise in Southern.
  • Structure: Eye (calm), Eyewall (violent winds/rains), Rainbands (widespread showers).
  • Regional Names: Typhoons (Pacific), Hurricanes (Atlantic/Caribbean), Cyclones (Indian Ocean).
  • Drivers & Frequency: Common in Southeast Asia due to warm Pacific waters, El Niño/La Niña cycles, and climate change.
  • Impacts: Loss of life, property damage, flooding, soil salinisation, displacement, and disease outbreaks.
  • Climate Change Link: Global warming is making tropical cyclones stronger, less predictable, and more frequent, raising risks for coastal populations.

 

[UPSC 2020] Consider the following statements:

1. Jet streams occur in the Northern Hemisphere only.

2. Only some cyclones develop an eye.

3. The temperature inside the eye of a cyclone is nearly 10°C lesser than that of the surroundings.

Which of the statements given above is/are correct?

(a) 1 only (b) 2 and 3 only* (c) 2 only (d) 1 and 3 only

 

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