Cyclones, weather phenomena characterized by rapid inward air circulation and violent storms, have made their impact felt across the globe. The Indian Meteorological Department (IMD) classifies cyclones based on their intensity. The naming of cyclones is a global endeavor, with different countries suggesting names.
Cyclone Mocha: An Extremely Severe Cyclonic Storm
Recently, Cyclone Mocha that made landfall in Myanmar was categorized as an ‘Extremely Severe Cyclonic Storm’ by the IMD and as a super cyclone by Zoom Earth, a global weather website. It emerged from the Bay of Bengal and reached a wind speed of 277 kmph, outpacing previous cyclones Amphan, Tauktae, and Gonu. This makes it the most potent cyclone since 1982 in both the Arabian Sea and the Bay of Bengal in all seasons.
The Inspiration Behind the Name ‘Mocha’
The cyclone got its name, Mocha, from Yemen. This name references a Red Sea port city renowned for coffee production, which also inspired the name of the popular beverage, café Mocha.
Understanding the Nature of Cyclones
Cyclones are a type of weather system marked by the inward circulation of air around a low-pressure area. Their direction of circulation varies depending on the hemisphere they occur in, with anticlockwise rotation in the Northern hemisphere and clockwise in the Southern hemisphere. The term cyclone comes from the Greek word ‘Cyclos,’ which means ‘the coils of a snake.’
Types of Cyclones
Cyclones are broadly categorized into two types: Tropical Cyclones and Extra Tropical cyclones. The World Meteorological Organisation (WMO) describes Tropical Cyclones as weather systems with winds that exceed ‘Gale Force’ and develop within the Tropics of Capricorn and Cancer. Extra Tropical cyclones are also known as Temperate cyclones, middle latitude cyclones, Frontal cyclones, or Wave Cyclones and principally occur in temperate zones and high latitude regions.
The Formation of Cyclones
Several specific conditions favor the formation and intensification of tropical storms. A significant factor is a large sea surface with a temperature higher than 27° C. Additionally, the Coriolis force, small variations in the vertical wind speed, a pre-existing weak low-pressure area, or low-level cyclonic circulation, and upper divergence above the sea level system also contribute to cyclone formation.
Classification of Low-Pressure Systems
The IMD has set criteria for classifying low-pressure systems based on their potential for causing damage in the Bay of Bengal and the Arabian Sea. These standards have been recognized by the WMO.
Naming of Cyclones
Cyclones worldwide are named by regional specialized meteorological centres (RSMCs) and Tropical Cyclone Warning Centres (TCWCs). The India Meteorological Department (IMD) is one of the six RSMCs in the world. The decision to name cyclones in the region was made by a group of nations under WMO/ESCAP, which includes Bangladesh, India, Maldives, Myanmar, Oman, Pakistan, Sri Lanka, Thailand, Iran, Qatar, Saudi Arabia, United Arab Emirates, and Yemen.
Occurrence of Cyclones in India
India experiences two cyclone seasons annually, from March to May and October to December. However, isolated instances of cyclones also occur in June and September. The North Indian Ocean region, comprising the Bay of Bengal and the Arabian Sea, typically witnesses cyclonic developments during the pre-monsoon and post-monsoon periods. Cyclones of severe intensity usually occur in May-June and October-November, impacting the Indian coasts.
Examination Questions on Cyclones
The topic of cyclones also features prominently in the UPSC Civil Services Examination. Past questions have focused on reasons why cyclones do not originate in certain regions and the naming process for tropical cyclones across the world. There have also been queries on India Meteorological Department’s colour-coded weather warnings for cyclone-prone areas.