Withdrawal of Monsoon

Withdrawal of Monsoon

Subject: Geography

Section: Physical Geography

Context: According to, the India Meteorological Department

Monsoon started withdrawing from India on Monday, eight days after the normal date of September 17.

Late withdrawal:

• The late retreat of the monsoon this year is the 13th consecutive delayed withdrawal.    Withdrawal of the monsoon from northwest India marks the beginning of its retreat from the Indian subcontinent. Any delay in the monsoon’s retreat means a longer rainy season, which can significantly impact agricultural production, particularly for northwest India where monsoon rainfall plays a crucial role in the Rabi crop production.

Conditions favourable for withdrawal of monsoon

The following major synoptic features are considered for the first withdrawal from the western parts of NW India.

i) Cessation of rainfall activity over the area for continuous 5 days.

ii) Establishment of anticyclone in the lower troposphere (850 hPa and below)

iii) Considerable reduction in moisture content as inferred from satellite water vapour imageries and tephigrams.

Concept:

Withdrawal or the retreat of the monsoon is a more gradual process.

• The withdrawal of the monsoon begins in northwestern states of India by early September. By mid-October, it withdraws completely from the northern half of the peninsula.
• The withdrawal from the southern half of the peninsula is fairly rapid.
• By early December, the monsoon has withdrawn from the rest of the country.
• The withdrawal, takes place progressively from north to south from the first week of December to the first week of January. By this time the rest of the country is already under the influence of the winter monsoon.
• The months of October and November are known for retreating monsoons. By the end of September, the southwest monsoon becomes weak as the low pressure trough of the Ganga plain starts moving southward in response to the southward march of the sun.
• The monsoon retreats from the western Rajasthan by the first week of September. It withdraws from Rajasthan, Gujarat, Western Ganga plain and the Central Highlands by the end of the month.
• The retreating southwest monsoon season is marked by clear skies and rise in temperature. The land is still moist.
• Owing to the conditions of high temperature and humidity, the weather becomes rather oppressive. This is commonly known as the ‘October heat’.
• In the second half of October, the mercury begins to fall rapidly, particularly in northern India. The weather in the retreating monsoon is dry in north India but it is associated with rain in the eastern part of the Peninsula.
• By the beginning of October, the low pressure covers northern parts of the Bay of Bengal and by early November, it moves over Karnataka and Tamil Nadu.