Cyclone Fengal

Cyclone Fengal

Cyclone Fengal, a tropical cyclone, recently made landfall over Puducherry, India. This event is significant in the context of seasonal cyclonic activity in the Bay of Bengal.

About Landfall

• Landfall refers to the event when the center of a tropical cyclone, or its eye, moves from over the water onto land.

• The India Meteorological Department (IMD) defines a tropical cyclone's landfall when the center of the storm moves over the coastline. The duration of the landfall varies depending on the storm’s size and the speed of the winds.

It is different from a direct hit, which occurs when the cyclone’s eyewall (core of high winds) comes ashore, but the center of the storm might remain offshore.

What Are Cyclones?

• Cyclones are powerful rotating storms characterized by a low-pressure center and high winds.

• The word Cyclone is derived from the Greek word Cyclos, meaning "the coils of a snake". The term was coined by Henry Peddington because tropical storms in the Bay of Bengal and the Arabian Sea often resemble coiled serpents in the sea.

Cyclones: Definition and Types

Cyclones are powerful, rotating storms that form around low-pressure areas. The term cyclone refers to the inward movement of air around this low-pressure zone, which leads to intense weather systems. The direction of the air circulation in cyclones depends on the hemisphere in which they occur:

• Northern Hemisphere: Air circulates anticlockwise around the low-pressure center.

• Southern Hemisphere: Air circulates clockwise around the low-pressure center.

Cyclones are often associated with severe weather conditions such as high winds, heavy rainfall, and storms. They can be classified into two main types:

Types of Cyclones

1. Tropical Cyclones

• Formation: Tropical cyclones form over warm ocean waters in tropical and subtropical regions. These are the most powerful type of cyclones.

• Characteristics:

  • Low pressure at the center.

  • High winds near the center of the storm.

  • Heavy rainfall.

  • Warm ocean temperatures fuel these storms by providing heat and moisture to the air, which rises, creating the low-pressure system.

• Impact: Tropical cyclones are capable of causing significant damage due to their strength, size, and the torrential rainfall they bring. They are typically accompanied by storm surges, flooding, and high winds.

• Example: Cyclones in the Bay of Bengal and the Arabian Sea, such as Cyclone Amphan (2020) and Cyclone Fani (2019).

2. Extra-Tropical Cyclones

• Also Known As: Wave cyclones, mid-latitude cyclones, or temperate cyclones.

• Formation: These cyclones develop in the mid and high latitudes, outside the tropics, and are often associated with the polar front.

• Characteristics:

  • Less intense than tropical cyclones.

  • They typically form where cold and warm air masses meet, often around the 50°–60° latitude.

  • Cold and warm fronts are significant features, leading to less direct and more complex weather patterns.

  • Temperature contrast between warm tropical air and cold polar air creates low-pressure systems.

• Impact: Extra-tropical cyclones tend to cause moderate weather disturbances, such as rain, snow, and windstorms. However, their intensity is usually lower than that of tropical cyclones.

• Example: Cyclones that form in the North Atlantic, North Pacific, and over parts of Europe, such as the Great Storm of 1987.

Cyclone Formation Process

• Tropical Cyclones form when:

  1. Warm ocean water (at least 26.5°C) provides energy to the storm.

  2. The Coriolis effect causes the system to rotate, initiating the cyclonic motion.

  3. Rising warm air from the ocean creates a low-pressure zone.

  4. The system strengthens as air continues to rush in from surrounding areas to replace the rising air, leading to the formation of a well-defined eye and eye-wall.

• Extra-Tropical Cyclones form when:

  1. A temperature contrast exists between warm and cold air masses.

  2. A disturbance, such as a low-pressure system, moves along the polar front.

  3. The system develops a warm and cold front, generating cyclonic circulation and complex weather patterns.

Cyclone Terminology

• Eye: The calm, clear center of a tropical cyclone, where the lowest pressure is found.

• Eye-wall: A ring of intense thunderstorms that surround the eye, containing the strongest winds.

• Storm Surge: A rise in sea level caused by the winds of a tropical cyclone, which can lead to coastal flooding.

• Cyclonic Circulation: The rotation of air around the low-pressure center, caused by the Coriolis effect.

Differences between Tropical and Extra-Tropical Cyclones

Cyclone Terminology Worldwide

Cyclones are known by different names in various regions of the world:

• Typhoons: In the China Sea and Pacific Ocean.

• Hurricanes: In the West Indies (Caribbean Sea) and Atlantic Ocean.

• Tornados: In West Africa and parts of the Southern USA.

• Willy-willies: In North-Western Australia.

• Tropical Cyclones: In the Indian Ocean.

Formation of a Cyclone

Cyclones generally form under the following conditions:

1. Warm Ocean Waters: Cyclones form over warm waters (at least 26.5°C), which provide the heat and moisture needed to fuel the storm.

2. Evaporation and Rising Air: Warm water causes evaporation, creating moist, warm air that rises from the ocean surface. This causes a decrease in air pressure at the surface, leading to the formation of a low-pressure system.

3. Cyclonic Circulation: The Earth’s rotation (the Coriolis effect) causes the rising air to start rotating around the low-pressure center, developing cyclonic circulation.

4. Eye Formation: As the wind system rotates faster, the storm's eye forms at the center, creating calm and clear weather within. The difference in temperature between the warm rising air and the cooler surroundings causes the air to rise and become buoyant.

5. Dissipation: A cyclone weakens and dissipates when it moves over cooler waters, encounters dry air, or makes landfall, disrupting its source of warm, moist air.

Cyclone Nomenclature

Cyclones are named for easier communication. The names are provided by an international committee of the World Meteorological Organization (WMO). Cyclones in the North Indian Ocean region (Bay of Bengal, Arabian Sea) are named by regional meteorological centers, including those in India, Bangladesh, Myanmar, Oman, Pakistan, and Sri Lanka. Each country contributes names to a rotating list, making it easier to communicate about storms.

India Meteorological Department (IMD)

• Established: In 1875, the India Meteorological Department (IMD) is the principal government agency for all meteorological matters in India.

• Role: IMD is under the Ministry of Earth Sciences (MoES) and is responsible for providing weather forecasts, cyclone warnings, and related services.

IMD plays a vital role in tracking and providing timely updates on cyclones, helping mitigate the impacts on vulnerable regions.

Cyclone Fengal: Key Takeaways

• Landfall over Puducherry: The landfall of Cyclone Fengal is a reminder of the powerful and dynamic nature of tropical cyclones.

• Preparedness: IMD's accurate forecasting and naming of cyclones play a crucial role in the preparedness and response efforts to minimize damage and loss of life.

This event underscores the importance of monitoring cyclonic activity in the Indian Ocean region and the role of agencies like the IMD in providing timely and critical information.