Tropical Cyclone: Formation, Stages, Characteristics | UPSC Notes

By K Balaji|Updated : July 6th, 2022

A tropical cyclone is a rapidly rotating storm that develops in a tropical location and moves inland along the coast. Tropical Cyclone are irregular winds with a low-pressure centre. It is accompanied by strong winds, heavy precipitation, high ocean waves and coastal flooding or both resulting in catastrophic devastation. The sum of these risks may prove fatal to human life and property.

Origin and characteristics of Tropical Cyclone often give it a different name in different places such as hurricanes in the North Atlantic Ocean and eastern North Pacific region. Tropical cyclones are a very important part of UPSC GS 2. Several questions have been asked about the various environmental phenomena leading to tropical cyclones in various regions of the world and updates with respect to them.

Table of Content

What is a Tropical Cyclone?

Tropical cyclones are irregular wind patterns with constrained air circulation centred on a region of low pressure. The restricted air circulation is brought on by the warm air rising quickly. Its diameter can range from 20-1000 km.

  • The Tropical Cyclone rotate in a clockwise direction in the Southern Hemisphere and in a counterclockwise direction in the Northern Hemisphere.
  • They are often associated with large-scale destruction
  • Tropical cyclones appear around the equator at 5 ° – 30 °

Formation of Tropical Cyclone

There are several factors that contribute to the formation of a tropical cyclone, which are listed below:

  1. Ocean water at a temperature of 27° or above is the source of moisture that fuels the storm.
  2. A regular supply of warm and moist air gets further enhanced in the presence of Warm currents. The storm can be generated by the latent heat of condensation that is released by moisture condensation.
  3. The Coriolis force increases with latitude which is powerful enough to start a storm at 5° latitude.
  4. Numerous minor low-pressure areas are caused by regional changes in the water and your temperatures.
  5. The rising warm, humid air has the potential to quickly produce a strong cyclonic vortex. Deep into the tropical latitudes, upper trough post ferric cyclone remnants can be seen. As divergence dominates on the eastern side of the valleys, thunderstorms began to fall.
  6. Due to modest differences in wind streams vertically, cyclone formation processes are restricted to latitudes close to the equator of the sub-tropical air stream.
  7. Because wet air helps in the formation of multi-layer, aggressive clouds in the mid-troposphere, high humidity, between 50 and 60%, is necessary.

Formation of Tropical Cyclone

Stages of Tropical Cyclone

It is important to understand the stage-wise Formation of Tropical Cyclone

  • Origin: Numerous thunderstorms confirm over the ocean when favourable conditions are present. As a result, the wind gets lighter and warmer.
  • Early-stage: Due to its warmth, the air rises, and the moisture it contains leads to condensation. As a result, the latent heat of condensation raises the air’s temperature. The thunderstorm intensifies when there is too much moisture over the ocean. This results in the rapid movement of air from the surroundings towards the thunderstorm and a process of deflection taking place because of the Coriolis force developing in a circular air column.
  • Mature stage: The swirling winds alternate between calm and aggressive regions. It is followed by a heavy downpour. After some time, the air starts to lose moisture and begins to move back towards the non-aggressive regions. As a result, the cloud size decreases from the centre to the margins.

Characteristics of Tropical Cyclone

There are some notable characteristics of tropical cyclone that must be understood in a detailed manner.

Eye: A powerful spiraling wind that revolves around the centre of a cyclone distinguishes it as a mature tropical cyclone. At the centre of a powerful cyclone, there are light winds and the area is known as the “eye”. There is little to no precipitation in this area. It ranges in size from 8 km to 200 km across, but the majority being between 30 km to 60 km in diameter. The eye of a tropical cyclone is a low-pressure point.

Eyewall: The tropical cyclone’s eyewall, a nearly circular ring of deep convection surrounding the eye, has the strongest surface winds. The area near the eye wall has the strongest sustained winds. In this area, the wind blows the hardest and the rain is the heaviest.

Spiral Bands: Long, narrow rain bands formed by the tropical storm convection, travel in the same direction as the longitudinal airflow. Due to their appearance of spiralling into the centre of the tropical cyclone, spiral bands are so termed.

Characteristics of Tropical Cyclone

Longitudinal section of a Tropical Cyclone

The longitudinal section of a tropical cyclone is divided into the following layers:

  • The storm is generated by the bottom layer, which reaches depths of up to 3 km.
  • The intermediate layer which extends from 3 km to 7 km is where the primary cyclonic storm takes place.
  • The outflow layer is located above 7 km where the highest outflow is found.

Categories of Tropical Cyclone

  • Category One: The greatest winds in a category one tropical cyclone are gales, with typical bursts of 90 to 125 km/h over open, flat terrain.
  • Category Two: A category two cyclone is a violent storm with the wind that frequently gusts between 125 and 64 km/h over flat land.
  • Category Three: With normal gas of 165 to 2 24 km/h, category three storms are very destructive and have the strongest winds.
  • Category Four: Category four (strong tropical storm) winds often gust between 225 and two 79 km/h above open, flat land.
  • Category Five: With consistent wind speeds of 80 km/h and above, category five cyclones have the most destructive winds.

Regional Names for Tropical Cyclones

The Tropical Cyclone is called by different names in different locations.

  • Indian Ocean: Cyclones
  • Atlantic Region: Hurricanes
  • Western Pacific and the South China Sea: Typhoons
  • Western Australia: Willy-willies

Tropical Cyclone UPSC

The Tropical Cyclone UPSC topic is important in Geography Syllabus for UPSC. Questions on this topic have often been asked in UPSC Prelims and Mains. Candidates preparing for the upcoming UPSC Exam must choose the right UPSC Books to ensure that all related topics are covered properly.

Applicants must also prepare for current affairs as they are in news. Also, practice UPSC Previous Year Question Papers for better revision.

Download Tropical Cyclone UPSC Notes PDF

Tropical Cyclone UPSC Question

Question. Consider the following statements: [UPSC 2020 Prelims Exam]

  1. Jet streams occur in the northern hemisphere only.
  2. Only some cyclones develop an eye.
  3. The temperature inside the eye of a cyclone is nearly 10°C less than that of the surroundings.

Which of the statements given above is correct?

  1. 1 only
  2. Two and three only
  3. Two only
  4. One and three only

Answer- Option C: Two only.

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FAQs on Tropical Cyclone

  • tropical cyclone is an erratic wind pattern that involves confined air circulation around a low-pressure centre point. The quick upward movement of heated air causes restricted air circulation. It can be anywhere from 200 to 1000 km in diameter.

  • The eye of a mature tropical cyclone is characterized by a strong spirally revolving wind around the centre.

  • The strongest winds in a category five tropical cyclone are most destructive, with regular wind intensity of greater than two 80 km/h above broad flat land.

  • In the mature stage of a tropical cyclone, the whirling winds develop consecutive areas of calm and aggression. It is followed by intense rainfall. The air starts losing its moisture at one point and starts returning to the non-aggressive regions.

  • The longitudinal section of a tropical cyclone is divided into the following layers:

    • The bottom layer stretches up to 3 km and is responsible for generating the storm.
    • The primary cyclonic storm occurs in the middle layer, which ranges from 3 km to 7 km.
    • The outflow layer is located above 7 km at 12 km and higher, where the highest outflow is found.

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