Southwest Monsoon - Onset over Kerala (Geography
Southwest Monsoon - Onset over Kerala (Geography)
Why In News:
The India Meteorological Department (IMD) has forecast that the Southwest monsoon is expected to set in over Kerala around June 4, 2026.
What is the Southwest Monsoon?
Origin: The Southwest (SW) monsoon originates over the South Indian Ocean and the Arabian Sea. It is driven by differential heating of the land and sea as the Indian subcontinent heats rapidly in summer, a low-pressure zone forms, pulling in moist winds from the ocean.
Two branches: (1) Arabian Sea branch hits Kerala and moves north along the west coast; (2) Bay of Bengal branch enters through the northeast and Gangetic plains.
Normal onset date: June 1 over Kerala (as per IMD's Long Period Average). The monsoon covers the entire country by July 15 on average.
Withdrawal: Withdrawal begins from northwest Rajasthan around September 17 and the country is fully clear of monsoon by December.
Significance: The SW monsoon accounts for about 75% of India's annual rainfall. It is critical for kharif crops (rice, cotton, soybean, maize), groundwater recharge, and filling of major reservoirs.
Key Facts for Prelims:
IMD (India Meteorological Department): Under the Ministry of Earth Sciences. HQ in New Delhi. Issues the Long-Range Forecast (LRF) for the monsoon season.
Normal Rainfall: Defined as 96-104% of the Long Period Average (LPA). The LPA for India as a whole is 87 cm (for the June-September period).
Mawsynram& Cherrapunji: Among the wettest places on Earth, located in Meghalaya - both receive the bulk of their rainfall from the SW monsoon's Bay of Bengal branch.