Context
The India Meteorological Department (IMD) has forecast that the Southwest Monsoon is likely to arrive in Kerala around May 26, with a possible variation of four days. This is ahead of the climatological normal onset date of June 1 — making it an early arrival year.
1. Key Data Trends & Observations
- Early Onset Trend: The standard calendar date for the monsoon’s arrival over mainland India (Kerala) is June 1. An onset on May 26 indicates an accelerated atmospheric pipeline moving up from the Southern Hemisphere.
- The Andaman Pipeline: The monsoon typically establishes itself over the Andaman and Nicobar Islands and the Bay of Bengal before embarking on a roughly 10-day journey to the Kerala coast.
- The Disconnect Between Onset and Quantum: An early onset does not automatically correlate with high volume or well-distributed rainfall. Total seasonal volume depends on sustained cross-equatorial pressure gradients throughout June–September.
- Disruptive Factors: The steady advance of the monsoon branch can be actively impeded or deflected by synoptic features, such as a fermenting tropical cyclone in the Arabian Sea or the Bay of Bengal during late May.
2. About the Southwest Monsoon: Core Geographical Concepts
- The Southwest Monsoon originates from the South Indian Ocean as the South-East Trade Winds, which after crossing the equator deflect rightward (due to the Coriolis Effect) and become the South-West Monsoon over India
- It enters India via two branches:
- Arabian Sea Branch → hits the Western Ghats first → Kerala, Karnataka, Goa, Maharashtra
- Bay of Bengal Branch → enters through Myanmar and Northeast India → advances westward
- The Inter-Tropical Convergence Zone (ITCZ) — a low-pressure belt — shifts northward in summer, pulling the monsoon winds deep into the subcontinent
- Kerala is the first landfall point because it lies at the south-western tip of the peninsula, directly in the path of the Arabian Sea Branch
3. The El Niño Warning
Global climate agencies are closely monitoring the possible development of El Niño conditions in the Pacific Ocean. An El Niño event is generally linked to weaker monsoon rainfall, rising temperatures, and drier conditions across India. The IMD has already projected below-normal rainfall for the June-to-September monsoon season at 92% of the Long Period Average (LPA).
4. Key concepts to remember:
| Term | What It Means |
| El Niño | Unusual warming of central/eastern Pacific Ocean surface waters; weakens Indian monsoon |
| La Niña | Cooling of Pacific waters; generally strengthens Indian monsoon |
| LPA (Long Period Average) | This is the benchmark check used to calculate whether a monsoon is “normal,” “above normal,” or “below normal.” It represents the average rainfall recorded over a historical window of 50 years. |
| Normal Rainfall | 96–104% of LPA |
| Below Normal | 90–96% of LPA |
Consider the following statements regarding the Southwest Monsoon in India:
1. The Southwest Monsoon originates as South-East Trade Winds in the Southern Hemisphere.
2. Kerala is the first landfall point of the monsoon because it lies directly in the path of the Arabian Sea Branch.
3. El Niño conditions are generally associated with stronger monsoon rainfall over India.
Which of the statements given above is/are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: A. 1 and 2 only
Explanation:
• Statement 1 is correct: The Southwest Monsoon originates as South-East Trade Winds over the South Indian Ocean and, after crossing the equator, deflects due to the Coriolis Effect.
• Statement 2 is correct: Kerala is the first landfall point because it lies at the southwestern tip of India along the Arabian Sea Branch.
• Statement 3 is incorrect: El Niño usually weakens the Indian monsoon and is associated with below-normal rainfall.
