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
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| [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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