Introduction

Cyclones are large-scale air masses that rotate around a strong centre of low atmospheric pressure. They are characterized by inward spiralling winds that rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Cyclones can cause severe weather conditions, including heavy rainfall, thunderstorms, and strong winds, leading to significant damage to infrastructure and loss of life.

Causes of Cyclones

The formation of cyclones involves several meteorological and oceanographic factors. The primary causes include:

• Warm Ocean Waters: Cyclones derive their energy from warm ocean waters, typically above 26.5°C (79.7°F). This warmth provides the heat and moisture necessary for the development of a cyclone.
• Atmospheric Instability: Cyclones form in regions where the atmosphere is unstable. This instability occurs when there is a significant temperature difference between the surface and the upper atmosphere, causing rising warm air to be replaced by cooler air.
• Coriolis Effect: The rotation of the Earth affects the movement of air masses. The Coriolis effect causes the air to spiral, which is essential for the formation of cyclones. This effect is absent at the equator, which is why cyclones rarely form there.
• Low Pressure Area: The presence of a low-pressure area is crucial for the development of cyclones. As warm, moist air rises, it creates a vacuum effect, leading to the formation of a low-pressure zone.
• Wind Shear: Moderate wind shear (the change in wind speed and direction with altitude) helps in the organization of the storm. However, too much wind shear can disrupt the formation of cyclones.

Types of Cyclones

Cyclones are classified based on their location and characteristics. The primary types of cyclones include:

Tropical Cyclones:

• Definition: These are intense circular storms that originate over warm tropical oceans. They are characterized by strong winds, heavy rains, and thunderstorms.
• Regions: Tropical cyclones are known by different names in different regions. They are called hurricanes in the North Atlantic and Northeast Pacific, typhoons in the Northwest Pacific, and cyclones in the South Pacific and Indian Ocean.
• Formation: They form over warm ocean waters and develop an eye (a calm center), surrounded by a circular eyewall of intense winds and thunderstorms.

Extratropical Cyclones:

• Definition: These are large weather systems that occur in the mid-latitudes. Unlike tropical cyclones, they are not fuelled by warm ocean waters but by temperature contrasts between air masses.
• Regions: Extratropical cyclones primarily occur in the middle and high latitudes of both hemispheres.
• Formation: They develop along weather fronts where warm and cold air masses meet, leading to the formation of low-pressure systems.

Subtropical Cyclones:

• Definition: These cyclones have characteristics of both tropical and extratropical cyclones. They form over subtropical waters and can develop into tropical cyclones.
• Regions: They usually form in the subtropical regions, often between 20° and 35° latitude.
• Formation: Subtropical cyclones form over water that is cooler than what is typical for tropical cyclones, and they have a broader wind field with a less defined core.

Polar Lows:

• Definition: These are small, intense cyclones that form over the polar regions. They are also known as Arctic or Antarctic hurricanes.
• Regions: Polar lows occur in the Arctic and Antarctic regions.
• Formation: They develop over open seas in the polar regions, where cold air masses interact with relatively warmer waters, leading to the formation of low-pressure systems.