- A large body of air uniformly related to temperature and humidity
- The zone between cold and warm air masses
Warm Front
Warm air advances over cold air • Gradual lifting • Steady rainfall
Cold Front
Cold air advances under warm air • Steep lifting • Heavy rainfall
Stationary Front
Neither warm nor cold air advances • Boundary remains stationary
Occluded Front
Cold front catches warm front • Warm air is lifted completely off the ground
📌 Frontogenesis
Process of formation of a front
📌 Frontolysis
Dissipation of a front, as one air mass overrides the other
⚡ Quick Recall
Mid-latitude / Temperate cyclones form due to
frontogenesis — front formation is central to their development, unlike tropical cyclones.
| Key Feature | Details |
|---|
| Centre | Low pressure |
| Periphery | High pressure • Wind flows from periphery to centre |
| Direction | Northern Hemisphere → Anti-clockwise • Southern Hemisphere → Clockwise (Coriolis force) |
| Eye of the Cyclone | Centre – calm zone • No rainfall in the eye |
- High sea surface temperature
- Coriolis force must be present — absent at the equator → no cyclone at the equator
- Less variation in vertical air movement
- Low pressure area
📌 Absence of cyclones on the Equator
Coriolis force value is Zero there
⚠ Exam Trap
Cyclones need Coriolis force to spin, but Coriolis force is
zero at the equator — that's exactly why cyclones never form right on the equator, despite warm ocean waters there.
Tropical Cyclone
- Between Tropic of Cancer and Tropic of Capricorn
- Occurs only over sea surface
- More destructive
- Moves East to West
Temperate / Extra-Tropical Cyclone
- Between 35°–65° Latitudes (both hemispheres)
- Occurs on both sea and land surface
- Less destructive, generally
- Moves West to East
| Region | Name |
|---|
| South China Sea / Western Pacific | Typhoon |
| Indian Ocean | Cyclone |
| Australia / Madagascar | Willy-Willy |
| USA, Caribbean Islands / Atlantic Ocean | Hurricane |
📌 Funnel-shaped destructive storm in USA
Tornado
⚠ Exam Trap
Tropical Cyclones move
East to West (driven by Trade Winds); Temperate Cyclones move
West to East (driven by Westerlies) — an easily reversed fact.
- Opposite of a cyclone — a "weather-less" phenomenon
- Centre: High air pressure • Wind flows from centre to periphery
- Periphery: Low air pressure
- Direction – Northern Hemisphere: Clockwise
- Direction – Southern Hemisphere: Anti-clockwise
| Feature | Cyclone | Anti-Cyclone |
|---|
| Pressure | Low Pressure (LP) | High Pressure (HP) |
| Wind direction (NH) | Anti-clockwise | Clockwise |
| Wind direction (SH) | Clockwise | Anti-clockwise |
| Weather | Stormy, rainy, destructive | Clear, calm, fair weather |
| Wind flow | Periphery → Centre (inward) | Centre → Periphery (outward) |
| Centre | Eye – calm zone, no rain | High pressure core |
⚡ Quick Recall
Cyclone and Anti-Cyclone have exactly
opposite wind rotation in each hemisphere — if a cyclone spins anti-clockwise in the NH, the anti-cyclone spins clockwise there.
| Year | Cyclones in India |
|---|
| 2024 | Remal, Asna, Dana, Fengal |
| 2023 | Michaung, Tej, Biparjoy |
⚡ Quick Recall
Cyclone naming rotates among countries in the North Indian Ocean region (India, Pakistan, Bangladesh, Sri Lanka, Myanmar, Thailand, Oman, Iran, UAE, Qatar, Saudi Arabia, Yemen) — that's why names like Biparjoy (Bangladesh) or Remal (Oman) come from different countries.
| Name | Time | Affected Areas | Origin | Naming Country |
|---|
| Cyclone Asna | 27 Aug – 2 Sep, 2024 | Gujarat, Rajasthan, Madhya Pradesh | Arabian Sea | Pakistan |
| Cyclone Remal | 24–28 May, 2024 | West Bengal | Bay of Bengal | Oman |
| Cyclone Michaung | 1–6 Dec, 2023 | Andhra Pradesh, Tamil Nadu | Bay of Bengal | Myanmar |
| Cyclone Biparjoy | 6–9 June, 2023 | Gujarat, Maharashtra | Arabian Sea | Bangladesh |
| Cyclone Mocha | 9–15 May, 2023 | Odisha, West Bengal, Myanmar | Bay of Bengal | Yemen |
| Cyclone Tej | 21 Oct, 2023 | Mumbai, Pune (Maharashtra) | Arabian Sea | India |
| Cyclone Midhili | 17 Nov, 2023 | Odisha, West Bengal | Bay of Bengal | India |
| Cyclone Hamoon | 25 Oct, 2023 | Mizoram, Bangladesh | Bay of Bengal | Iran |
| Cyclone Asani | 8 May, 2022 | Andhra Pradesh, Odisha | Bay of Bengal | Sri Lanka |
| Cyclone Mandous | 6–10 Dec, 2022 | Tamil Nadu, Puducherry | Bay of Bengal | United Arab Emirates |
| Cyclone Sitrang | 22–25 Oct, 2022 | West Bengal, Tripura, Assam | Bay of Bengal | Thailand |
⚠ Exam Trap
All these are
Cyclones from the North Indian Ocean basin — none are "Typhoons" (Western Pacific term) or "Hurricanes" (Atlantic term), even though the underlying storm system is the same.