Southwest Monsoon Withdraws From India

Relevance: GS1 - Important Geophysical phenomena; Geographical Features & Their Location

(Source: The Hindu, 20/10/2023)

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Why in the news?

• Recently, the India Meteorological Department (IMD) announced that the southwest monsoon has ended, and the northeast monsoon, or the 'retreating monsoon,' is expected to arrive.

The Retreating Monsoon Season in India

• Retreating Monsoon Months: The South-West Monsoon starts retreating from northern India in early October. Hence, the months of October and November are known for the retreating monsoon.
• Temperature: During this phase, temperatures decrease significantly, and the skies become clearer. As the monsoon moves southward, the pressure gradient weakens, and local pressure conditions play a crucial role in influencing wind patterns.
• Emerging Cyclones: During this season, cyclones and depressions in the Bay of Bengal can cause heavy rainfall. It may lead to flooding and landslides in some areas. The retreating monsoon also marks the beginning of the winter season in India. The temperatures gradually decrease across the country.
• Rainfall: The Retreating Monsoon season is critical for many parts of India as it is the main source of rainfall for the southern peninsula. This particularly includes Tamil Nadu, Puducherry, and coastal Andhra Pradesh.
• Varied Rainfall Patterns: The retreating monsoon delivers varying amounts of rainfall to different regions of India, with some areas experiencing heavy precipitation while others receive meager rainfall.

• Agriculture and other related activities rely heavily on the retreating monsoon season. It is the time for harvesting crops and preparing for the winter season.

(Retreating Monsoon)

What is the forecast of IMD?

• Northeast Monsoon Forecast: The IMD predicted a 'normal' northeast monsoon for the period from October to December. They anticipate 'normal to above-normal rainfall' in significant parts of north-west India and the southern peninsula.

  • Tamil Nadu, Kerala, Karnataka, and parts of Andhra Pradesh heavily rely on the northeast monsoon, even though it constitutes only 11% of India's annual rainfall.
• Yearly Monsoon Variability: Historical records show considerable year-to-year variability. In 2015, Chennai faced heavy rainfall, while the northeast monsoon was weak in 2019, resulting in a severe water shortage.
• Low-Pressure Areas and Cyclone Potential: The IMD has reported the development of two low-pressure areas, which could be precursors to cyclones. These developments are observed in the Arabian Sea and the Bay of Bengal. The extent of their potential intensification remains uncertain.

Monsoon Withdrawal and Recent Rainfall Statistics

• The 2023 southwest monsoon season was the weakest in five years, and also marked by erratic distribution of rains.
• June received 9% below normal rainfall.
• July brought torrential downpour and floods across man regions in northern India.
• August was the driest month on record in 100 years, with 36% below normal rainfall.
• September saw some recovery with showers 13% above normal, but the four-month monsoon season ended with 6% below normal rainfall.
  • The southwest monsoon began its withdrawal from Rajasthan on September 25, nearly a week behind its normal date of September 17.
  • Though monsoon withdrawal begins from Rajasthan, it takes nearly until early to mid-October for it to fully withdraw and be replaced by the northeast monsoon.

• India officially considers rainfall from June 1 to September 30 as monsoon rainfall.

• As of September 30, India received 94% of the expected rain during the monsoon months, slightly below the forecasted 96%.
  • This shortfall was due in part to the El Nino causing dry conditions in August, but September brought unexpected rains.

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