Tropical Cyclone: Formation, Characteristics | Tropical Cyclone UPSC

By BYJU'S Exam Prep

Updated on: September 11th, 2023

Tropical Cyclones are powerful storms that form over tropical waters and move ashore, wreaking havoc on a global scale with their high winds, torrential rain, and storm surge. These are turbulent air currents that revolve tightly around a low-pressure point. In the Northern Hemisphere, the wind blows anticlockwise, whereas, in the Southern Hemisphere, it blows clockwise. Tropical cyclones play a significant role in shaping weather patterns, impacting the global climate system, and influencing regional economies and ecosystems.

Understanding the Tropical Cyclones is of great importance for aspirants as it comes under environmental studies in the UPSC exam. The topic covers various aspects such as the formation and structure of tropical cyclones, their classification, the factors influencing their development and intensification, and the measures to mitigate their impacts. Having a comprehensive understanding of tropical cyclones enables candidates to tackle questions related to climate change, extreme weather events, and disaster preparedness, which are crucial topics in the contemporary global scenario.

Tropical Cyclone

Tropical cyclones are ferocious storms that develop over tropical oceans and travel to the coast. It delivers widespread havoc brought by storm surges, extremely heavy rains, and powerful winds. A tropical cyclone’s diameter can range from 20-1000 km.

The Tropical Cyclone rotates 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° to 30°

Formation of Tropical Cyclone

Tropical cyclones are spherical, tightly packed winds. Its winds circle a low atmospheric pressure area in the center. The low-pressure center and the Earth’s rotation both have a significant role in the rotation of Tropical cyclone winds. There are several factors that contribute to the formation of a tropical cyclone, which are:

  • A large ocean/sea surface with a temperature of more than 27 °C
  • Creation of cyclonic vortex when the Coriolis force is present. The Coriolis force increases with latitude which is powerful enough to start a storm at 5° latitude.
  • Changes in vertical wind speed. Due to this, cyclone formation processes are restricted to latitudes close to the equator of the sub-tropical air stream.
  • A weak low-pressure area or cyclonic circulation at low levels already exists.
  • At the sea level system, a higher divergence should be present.

Stages of Tropical Cyclone Formation

Tropical cyclones form over tropical waters in the late summer (August to mid-November) and have a thermal origin. The Coriolis force causes the strong local convectional currents at certain areas to acquire a whirling motion. These cyclones advance after emerging until they locate a weak area in the trade wind belt. Below are the stage-wise Formation of Tropical Cyclones.

  • Stage 1: There is a small area of low pressure in the tropics that crosses the equator. The north side of this zone experiences northeast trade winds, whereas the south side experiences southeast winds (southeast trades).
  • Step 2: The creation of thunderstorms results from the air rising from the low-pressure area in small parcels as a result of the air being heated over the warm tropical ocean.
  • Step 3: A center of low pressure, or depression, forms at the surface as a result of a flow of extremely warm, moist, quickly rising air.
  • Step 4: These cloud clusters must go through a variety of trigger processes in order to develop into tropical cyclones, which at the very least serve as a trigger for inclement weather. The swirling winds alternate between calm and aggressive regions. It is followed by a heavy downpour.
  • Step 5: After some time, the air starts to lose moisture and begins to move back toward the non-aggressive regions. As a result, the cloud size decreases from the center to the margins.

Structures of Tropical Cyclone

There are some notable structural characteristics of tropical cyclones that must be understood in a detailed manner. These are:

  • Eye: A powerful spiraling wind that revolves around the center of a cyclone distinguishes it as a mature tropical cyclone. At the center 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. 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 spiraling into the center of the tropical cyclone, they are so named.

Tropical Cyclones Names in Different Countries

Using names for cyclones rather than numbers and technical words makes it simpler for people to recall. The Tropical Cyclone Warning Centers (TCWC) and regional specialized meteorological Centers (RSMCs) give names to cyclones that originate in all ocean basins worldwide (TCWCs). There are five TCWCs and six RSMCs worldwide, including the India Meteorological Department (IMD). The regional names of tropical cyclones in different regions are discussed below:

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

In the Philippines, a tropical cyclone is referred to as Baguio. The phrase first appeared following a storm in Baguio in 1911.

Categories of Tropical Cyclone

A non-frontal synoptic scale low-pressure system over tropical and subtropical waters with organized convection is referred to as a “tropical cyclone” in general. The categories of Tropical Cyclones include:

  • 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 a wind that frequently gusts between 125 and 64 km/h over flat land.
  • Category Three: With normal gas of 165 to 224 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 to 279 km/h above open, flat land.
  • Category Five: With consistent wind speeds of 280 km/h and above, category five cyclones have the most destructive winds.

Tropical Cyclone UPSC

Tropical Cyclone is an important topic in the UPSC Geography Syllabus. Questions on this topic have often been asked in both prelims and mains. Candidates preparing for the topic should refer to NCERT Books for UPSC to understand the basic concepts of the phenomena.

The candidates can practice the below-mentioned questions that have been curated by the experts. This will enable the candidates to perform exceptionally well in the upcoming exam.

Tropical Cyclone UPSC Questions

The aspirants eyeing the upcoming exam must possess a methodical and well-curated strategy in order to get ahead in the competition. Practicing the UPSC Previous Year’s Question Papers will lead to having conceptual clarity of the topics.

Question: Which of the following statements is true regarding tropical cyclones? (A) They originate over cold ocean waters, (B) They are characterized by high-pressure centers, (C) They can cause heavy rainfall, storm surges, and flooding, (D) They primarily occur in temperate regions.

Answer: (C) They can cause heavy rainfall, storm surges, and flooding.

Question: Which factors contribute to the formation and intensification of tropical cyclones? (A) Low humidity and dry air masses, (B) Cool ocean temperatures, (C) Presence of strong wind shear, (D) Warm ocean waters and low-pressure centers

Answer: (D) Warm ocean waters and low-pressure centers

Question: Compare the causes of and meteorological patterns surrounding tropical and temperate cyclones.

Question: Describe the formation of tropical cyclones. Why is India’s eastern coast more vulnerable to tropical cyclones than its western coast?

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