Everything about Cyclones: Formation, Causes and Impact
Information collected by satellites suggests that cyclones form in low-pressure zones over warm intertropical seas. These are gigantic and deadly storms that cause havoc and damage.
Around 70 to 90 cyclones form every year around the globe.
Individuals wondering how cyclones are formed can read on to find answers. Further, you will find everything about its types, causes, occurrence, impact, hazard zones and preventive measures from this piece.
What Are Cyclones?
In meteorological terms, a cyclone is a wind system that rotates inwards (counter-clockwise in the Northern Hemisphere and clockwise in the Southern) around a strong low-pressure centre. Simply put, inward-spiralling winds that rotate about a low-pressure zone is known as a cyclone.
Generally, when winds rise above 118 kmph, it is known as a cyclone.
To understand the severity of this storm, one must learn in detail about cyclone formation and its categories.
How Are Cyclones Formed?
Check out the following section to understand the formation of a cyclone -
- Warm, moist air over the ocean rises due to less density. This air rises up and away from the ocean surface, leaving less air near the surface, creating a low-pressure zone.
- Due to the surrounding high-pressure areas, air flows into this low-pressure area and eventually warms up, forming a cycle.
- Now, this cycle makes the warm air above the ocean rise and cool the water below to generate clouds. With the constant heating and evaporating process, the entire cloud and wind system spins and grows.
- With more speed, cyclone eye formation takes place in the centre. This zone signifies the lowest air pressure and is calm and clear. The high-pressure air from above flows down into this region.
When the wind’s rotating speed reaches 63 kmph, it is called a tropical storm. However, when wind speed reaches 119 kmph, tropical cyclone formation takes place.
Now that you know how a cyclone is formed, let's look at the categories of a cyclone.
What Are the Different Categories of Cyclones?
The categories of a cyclone depend on wind strength. From the following table, you will be able to estimate the damage a cyclone may cause after landfall based on wind speed.
Wind Speed (in kmph)
Damage at Landfall
More than 250
What Are the Causes of a Cyclone?
After knowing the answer to your question, "how are cyclones formed?" you might also like to know about why a cyclone occurs or what causes it.
Here are the factors responsible for cyclone formation -
- Warm temperature at sea surfaces.
- Coriolis force impact area that forms a low-pressure zone.
- Atmospheric instability.
- Increased humidity in the lower to middle levels of the troposphere.
- Low vertical wind shear.
- Pre-existing low-level disturbance or focus.
Now that you know how cyclones are formed and what causes them, let's look at the types of cyclones that occurred in India over the years.
Cyclones that Occurred in India Till Now
With respect to the above table, the following list of cyclones have occurred in India over the past few years -
Severe cyclonic storm over the Bay of Bengal.
Very severe cyclonic storm originating from the Arabian Sea.
Severe cyclonic storm emerging from the Arabian Sea.
Super cyclonic storm formed in the Bay of Bengal.
Super cyclonic storm emerging from the Arabian Sea.
Extremely severe cyclonic storm originating in the Arabian Sea.
Severe cyclonic storms originate from the Arabian Sea.
Very severe cyclonic storm emerging from the Arabian Sea.
Extremely severe cyclonic storm originating from the Indian Ocean.
Severe cyclonic storm formed in the central Bay of Bengal
A very severe cyclonic storm emerged from the Bay of Bengal.
Impact of Cyclones in India
If you know how a cyclone is formed, you must know that it is often accompanied by strong winds, torrential rains and storm surge. These three elements cause have to a great extent as follows -
- Strong winds cause damages to infrastructure, uproots trees, and lead to other catastrophes.
- Torrential rainfall leads to unprecedented floods and damages to houses and buildings.
- Due to storm surge, seawater levels rise, and the coastal areas are exposed to floods.
- The rise in seawater level also erodes beaches and embankments.
- Severe cyclonic storms resulting in floods can damage vegetation and livestock.
- Due to the strong winds and flood conditions, the soil becomes infertile.
In addition to this, cyclonic storms result in the loss of human, plant and animal lives and affect the country's economy.
Next up, let's look at the cyclone-prone zones in India.
Cyclone Hazard Zones in India
As per the Indian Meteorological Department, 13 coastal regions and Union Territories in India are prone to a cyclone. This happens because of the long coastline of 8041 Km, which is exposed to nearly 10% of the world's tropical cyclones. For that cause, both the coasts of India experience cyclonic storms often.
Among both the coasts, some states are more vulnerable to cyclones than others. The most vulnerable states in India are as follows -
- West Bengal.
- Andhra Pradesh.
- Tamil Nadu.
- Puducherry (UT)
Individuals residing in and around the above areas can take some preventive measures to carry out damage control.
Preventive Measures to Combat Cyclones in India
The National Disaster Management Authority (NDMA) advises individuals to consider the following steps to stay safe during cyclones -
- It is necessary to stay indoors during a cyclonic storm and keep away from electrical mains.
- In extreme situations, one must prepare an emergency kit that is essential for survival.
- It is also vital to keep tabs on regular updates and rely on official warnings.
- In case your house is unsafe, it is advisable to shift before the onset of a cyclone.
Further, in collaboration with the NDMA, the Government carries out evacuation protocols for fishermen and the coastal dwellers before the cyclone makes landfall.
With a detailed knowledge of how cyclones are formed and their causes, one can take sufficient precautions and avoid the harsh consequences.