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Context

The India Meteorological Department (IMD) confirmed the formation of Cyclone ‘Shakhti’ over the northeast Arabian Sea.

What are Cyclones?

Cyclones are large, powerful, and rotating storm systems that have a low-pressure center. The direction of this rotation is determined by the Earth’s rotation (the Coriolis effect).

• In the Northern Hemisphere, air circulates in an anti-clockwise direction.
• In the Southern Hemisphere, it circulates in a clockwise direction.

There are two main types of cyclones:

Tropical Cyclones

These are intense storms that form over warm tropical oceans, like Cyclone Shakhti. They are known as Hurricanes in the Atlantic, Typhoons in the Pacific, and Cyclones in the Indian Ocean.

Extra-Tropical Cyclones (or Temperate Cyclones)

These form in the mid-latitudes (between 30° and 60°) and are driven by the difference between cold and warm air masses. Western Disturbances that bring winter rain to northwest India are an example of these cyclones.

How Tropical Cyclones Form?

Specific conditions are necessary for their formation and intensification:

• Warm Sea Surface: A large and continuous supply of warm ocean water with a temperature of 27°C or higher is required.
• Coriolis Force: Spinning of the Earth is required to initiate the cyclonic rotation. This force is negligible at the equator, which is why cyclones do not form there.
• Low Vertical Wind Shear: Difference in wind speed and direction between the upper and lower atmosphere must be minimal, allowing the storm structure to grow vertically.
• Pre-existing Low-Pressure Area: A weak, low-pressure system is needed to act as the seed for the cyclone.
• Upper-Level Divergence: Air flowing away from the top of the storm allows the air from the bottom to rise and fuels the system's growth.

How are Cyclones Named?

The naming of cyclones is a coordinated international process managed by the World Meteorological Organization (WMO) to avoid confusion and aid in disaster risk communication.

• For the North Indian Ocean region (including the Arabian Sea and Bay of Bengal), a panel of 13 member countries prepares a list of names.
• The members are: Bangladesh, India, Iran, Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, the UAE, and Yemen.
• The names are used successively from the combined list. For example, Cyclone ‘Shakhti’ was a name contributed by Sri Lanka.

Cyclones in India

Tropical cyclones in the Bay of Bengal and Arabian Sea strike the coastal states of Tamil Nadu, Andhra Pradesh, West Bengal, Odisha, and Gujarat. Three main elements cause destruction:

• Strong Winds/Squall: Causes structural damage to buildings, installations, and communication systems.
• Torrential Rains and Inland Flooding: Leads to large-scale soil erosion, and weakening of embankments.
• Storm Surge: Floods low-lying coastal areas with seawater, destroying crops, reducing soil fertility, and causing loss of life.

Why is the Arabian Sea becoming a cyclone hotspot?

The Arabian Sea is transforming from a relatively calm basin into a major threat zone, altering India's cyclone risk map. This shift is a direct result of global warming.

Cyclone Management in India

Institutional framework

National Disaster Management Authority (NDMA): The apex body, headed by the Prime Minister, sets national policies and guidelines for disaster management. It is responsible for the National Cyclone Risk Mitigation Project (NCRMP) and coordinates with state and district authorities.

India Meteorological Department (IMD): Nodal agency for issuing cyclone early warnings. It monitors tropical cyclones in the Bay of Bengal and the Arabian Sea and provides forecasts and location-specific bulletins to coastal states.

National Disaster Response Force (NDRF): A specialist force deployed for search and rescue operations in affected areas. The NDMA proactively deploys NDRF battalions based on cyclone vulnerability profiles.

State and District Authorities: State Disaster Management Authorities (SDMAs) and District Disaster Management Authorities (DDMAs) are responsible for implementing the national plan at the local level. They conduct evacuations, coordinate relief efforts, and manage shelters.

Indian National Centre for Ocean Information Services (INCOIS): Provides a Storm Surge Early Warning System (SSEWS) for coastal communities and assists the IMD with data. 

Multi-stage management process

Pre-disaster: Mitigation and preparedness

• Early Warning Systems (EWS):
• The IMD's four-stage warning system uses color codes to indicate cyclone severity:
• Green (All is well): No advisory is issued.
• Yellow (Alert): For severe weather lasting several days.
• Orange (Warning): Indicating harsh weather and advising preparedness.
• Red (Take Action): Calling for extreme caution and readiness for drastic action.
• The GEMINI (GAGAN Enabled Mariner's Instrument for Navigation and Information) device provides satellite-based cyclone and tsunami warnings to fishermen.
• Structural measures:
• Cyclone shelters: Construction of multi-purpose shelters in vulnerable areas provides safe refuge during a cyclone.
• Coastal protection: Creation of natural barriers, like mangrove plantations, and building saline embankments to protect against storm surges and coastal erosion.
• Resilient infrastructure: Building cyclone-resistant infrastructure, such as power systems, roads, and bridges, as part of the NCRMP.

During the disaster: Response

• Coordination: Activation of Emergency Operation Centers (EOCs) at national, state, and district levels to coordinate the emergency response.
• Evacuation: Timely and systematic evacuation of coastal communities to designated shelters.
• Rescue and Relief: NDRF teams, along with local authorities, conduct search and rescue operations and provide immediate relief supplies, including food, water, and medical aid. 

Post-disaster: Recovery and reconstruction

• Damage Assessment: Surveying damage to infrastructure, property, and livelihoods to guide recovery efforts.
• Relief and Rehabilitation: Distributing relief materials and providing financial support to the affected population. The NDRF maintains an emergency reserve of relief equipment.
• Restoration of Services: Clearing debris and restoring critical services like power, communication, and water supply.
• Long-term Reconstruction: Rebuilding damaged infrastructure with an emphasis on creating disaster-resilient structures.
• Review and Improvement: Analyzing the response to past cyclones, such as Cyclone Fani in 2019, allows states like Odisha to continuously refine their disaster management strategies. 

Conclusion

India must continuously upgrade its forecasting technology and disaster response protocols to manage the increasing frequency and intensity of severe cyclones emerging from the rapidly warming Arabian Sea.

Source: DOWNTOEARTH