Tropical Cyclones
Published on 31 Jan 2025
Tropical cyclones, also known as hurricanes or typhoons, are powerful and destructive weather systems characterized by intense low-pressure centers. Typically forming over warm ocean waters, they unleash strong winds, heavy rainfall, and storm surges, posing significant threats to coastal regions
Features of Tropical Cyclones
Location: 8-200 North and south pole
Eye: A central, nearly calm region with clear skies at the cyclone's center, surrounded by the eyewall.
Eyewall: A ring of intense thunderstorms surrounding the eye, where the strongest winds and heaviest rainfall occur.
Spiral bands: Bands of thunderstorms spiralling outward from the center, bringing additional rain and wind.
Low Pressure: A well-defined area of low pressure at the center, characterized by descending air and clear skies (the eye).
Movement: Typically move across the ocean, following prevailing winds and steering by high-level atmospheric features.
Conditions required for formation of tropical cyclones
Warm ocean waters: Sea surface temperatures of at least 26.5 degrees Celsius (80 degrees Fahrenheit) are necessary to provide the heat and moisture needed to fuel the cyclone's development.
Coriolis effect: Coriolis effect, caused by the Earth's rotation, is crucial for the cyclone's rotation. This effect is minimal at the equator and increases towards the poles, providing the necessary spin for cyclone formation.
Low vertical wind shear: Low wind shear is necessary to allow the cyclone to maintain its structure and prevent disruption to the vertical development of the storm
Pre-existing disturbance: A pre-existing weather disturbance, such as a cluster of thunderstorms, serves as a starting point for cyclone development.
Upper level divergence: When there is upper-level divergence, it helps draw air away from the storm's center, allowing the warm, moist air near the surface to rise more freely.
High incidence of cyclones in South China Sea, Bay of Bengal and Gulf of Mexico
Warm Sea Surface Temperatures: The South China Sea, Bay of Bengal, and Gulf of Mexico have favourable sea surface temperatures for sustaining tropical cyclones
Atmospheric conditions: Presence of low vertical wind shear and high atmospheric moisture suitable for cyclogenesis
Geographical and topographic factors: Warm waters and relatively flat coastal areas provide an environment where cyclones can form and move over vast expanses of water without significant land barriers to weaken them.
Nature of water bodies: Gulf of Mexico, Bay of Bengal and South China Sea are semi enclosed in nature increasing the water temperature than surrounding oceans. Thus, favouring formation of cyclones
Monsoon Winds: In the South China Sea, the southwest monsoon brings warm and moist air, creating conditions conducive to cyclone formation. In the Bay of Bengal, both the southwest and northeast monsoons contribute to the cyclogenesis.
Climate patterns: Events and phenomena such as ENSO affecting ocean currents and temperature of Pacific and Indian ocean
Climate Change: Rising sea surface temperatures associated with climate change can potentially contribute to the increased intensity of tropical cyclones.
Cyclones on Bay of Bengal and Arabian Sea variations
The Bay of Bengal and the Arabian Sea are both prone to tropical cyclone activity, but there are some differences in their characteristics and the factors that influence their development.
Differences between Tropical and Temperate cyclone