# Q1D · Discuss in detail how a cyclone is formed with a neat sketch.

Subject: Disaster Management

Exam: TEE

Reader: https://deep-learning-study-room.vercel.app/dm/#tee/papers/paper-2023-05-04/q1d

Canonical: https://deep-learning-study-room.vercel.app/read/dm/tee/papers/paper-2023-05-04--q1d/

Actual older TEE paper · 100 marks · Q1 compulsory; any four of Q2–Q7

### Q1D. Discuss in detail how a cyclone is formed with a neat sketch. [5 marks]

#### Answer

**Definition.** A cyclone is an atmospheric circulation around a low-pressure centre. A tropical cyclone is an organised rotating storm over warm tropical or subtropical waters, with strong winds, rain and potentially storm surge.

Swipe across the diagram to read its labels ↔

![Tropical cyclone: structure and hazards](https://deep-learning-study-room.vercel.app/dm/fig/cyclone.035d3a6b0d.svg)

Diagram: Tropical cyclone: structure and hazards. Labels: Tropical cyclone: structure and hazards | Tropical cyclone: structure and hazards | Eye: relatively calm centre | Eyewall: strongest winds | Rainbands: heavy showers | Main hazards | Strong wind + storm surge + rainfall flooding | Schematic plan view; not a map or a forecast.

Warm moist air feeds the storm. The eyewall surrounds the relatively calm eye in a mature intense tropical cyclone.

1. Warm ocean water supplies moisture and energy by evaporation. Typical favourable sea-surface temperatures are around 26–27°C or higher over adequate depth.
2. Warm moist air rises; condensation releases latent heat, supporting further rising motion.
3. Air flows towards the low-pressure centre. Earth’s rotation helps organise the circulation; systems do not usually form right at the equator.
4. With favourable conditions such as sufficient moisture and limited disruptive vertical wind shear, the system organises and intensifies.
5. A mature system may develop an eye surrounded by an eyewall. It weakens when it loses favourable ocean energy or encounters hostile atmospheric conditions.

| Part | Meaning |
| --- | --- |
| Eye | Relatively calm central region with descending air in a well-developed cyclone. |
| Eyewall | Ring of intense convection; strongest winds and heavy rainfall are commonly found here. |
| Rainbands | Spiral bands of clouds and rain around the centre. |
| Track | The path followed by the storm; forecasts have uncertainty. |

**Definition.** The principal tropical-cyclone hazards are strong winds, heavy rainfall and storm surge. Their combined effects can create cascading damage.

| Hazard | Mechanism | Damage |
| --- | --- | --- |
| Wind | Strong pressure gradients drive fast winds. | Roof damage, flying debris, fallen trees and power lines. |
| Rain | Intense rainfall produces runoff. | River/urban flooding and landslides. |
| Storm surge | Wind pushes sea water towards shore; low pressure adds a smaller contribution. | Coastal inundation, saltwater intrusion and erosion. |

**Storm tide** combines astronomical tide and storm surge; waves and river flooding can compound impacts further. A tsunami is a different process, usually generated by sudden displacement of the water column.

## Names and classifications without mixing systems

Hurricane is the regional name used in the Atlantic and northeast Pacific; typhoon in the northwest Pacific; tropical cyclone or cyclonic storm is used in the Indian Ocean context. A tornado is a small-scale rotating column connected to a thunderstorm and is **not** a South American synonym for tropical cyclone. A mesocyclone is a rotating thunderstorm updraft. Polar and extratropical cyclones occur in different environments and should not be described as identical warm-ocean systems.

In the Northern Hemisphere, cyclonic circulation is anticlockwise; in the Southern Hemisphere, clockwise. India’s Bay of Bengal and Arabian Sea coasts both face serious cyclone risk. Not every Indian cyclone is moderate.

## Wind categories need their own units and definitions

The PPT shows both a Saffir–Simpson hurricane image and a gust-based five-category table. They are not interchangeable with IMD’s North Indian Ocean classification. Use the named system supplied in a question; do not mix gust speed with sustained wind speed. The key M2 concepts are formation, hazards, warnings and mitigation.

#### Real case · Phailin, 2013

India reported pre-emptive evacuation of more than one million people before Cyclone Phailin. This is a real example of warning linked to action. For a formation question, keep the physical process separate; for management, explain how evacuation reduces exposed people’s immediate risk.

[Case reference ↗](https://www.pib.gov.in/newsite/erelcontent.aspx?lang=2&reg=48&relid=105888)