By Aditi Srivastava, May 11, 2022 16:00
‘Asani’, meaning ‘wrath’, is a tropical cyclonic storm that originated in the Southern Andaman Sea last week. It later advanced towards West Bengal, Andhra Pradesh and Bhubaneswar. Its emergence in the Bay of Bengal has caused severe rainfall in Kolkata and other parts of the state until now. But, what exactly is a tropical cyclone? Let’s find out below.
What is a tropical cyclone?
Low pressure systems that originate over warm tropical waters are known as tropical cyclones. Sufficiently warm sea surface temperatures, atmospheric instability, high humidity in the lower to middle troposphere are some of the culprits behind these storms. Tropical cyclones are formed when the sea surface temperature is above 26.5 degrees Celsius. They can last for days, even weeks, and their paths can be highly irregular. When a cyclone passes over land or over cooler oceans, it dissipates. A tropical cyclone is known by various names depending on its location and strength. Some of these names are hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone.
How many types of cyclones are there?
Cyclone, a weather phenomenon, can be classified on the basis of wind speed. Based on this, there are four types of cyclones: Tropical cyclone, polar cyclone, mesocylcone and extra tropical cyclone.
Polar Cyclone: A polar cyclone is a large area of cold, rotating air that covers both the northern and southern hemispheres of the Earth. It is constantly present in the poles, but is stronger in the winter and weaker in the summer.
Mesocyclone: A tornado is often triggered by a mesocyclone, which is a rapidly rotating air mass within a thunderstorm.
Tropical cyclone: A tropical cyclone is a rapidly spinning storm that forms over tropical oceans and absorbs energy to develop further from there (oceans).
Extra tropical cyclone: Low-pressure areas called extra tropical cyclones, together with anti-cyclones from high-pressure areas, drive the weather throughout most of the globe. They are also called mid-latitude cyclones or wave cyclones.
Asani: The recent tropical cyclone in India
On May 9th, India's weather agency, the Indian Meteorological Department (IMD), predicted that cyclone Asani was expected to intensify into a "severe cyclonic storm" in the next 12 hours. Following that, the Kolkata Municipal Corporation (KMC) put its personnel and disaster management teams on high alert due to the emergence of cyclone Asani. In the days that followed, Kolkata experienced severe rainfall, and the cyclone has now shifted to Odisha.
The severe cyclonic storm, Asani, has weakened into a cyclonic storm according to the IMD. By Thursday, May 12, it is expected to become a depression (a low-pressure area that moves from west to east in the northern hemisphere). Today, IMD has also predicted extremely heavy showers over Andhra Pradesh and West Bengal. The government of Andhra Pradesh has set up 454 relief camps in seven districts that are expected to be hit by 'Asani' in the Bay of Bengal.