What is Monsoon Withdrawal?
Monsoon withdrawal is a gradual process where the rain-bearing southwesterly winds retreat from the subcontinent. This retreat is declared by the India Meteorological Department (IMD) when specific conditions are met, such as a reduction in rainfall,
a drop in humidity, and a change in wind direction from southwesterly to northwesterly over a region for a continuous period. The process typically starts from the northwesternmost parts of the country, around West Rajasthan, and slowly progresses eastward and southward over several weeks. While the headline suggests the withdrawal has begun, some forecasts indicate the formal process might only commence after mid-September, even as conditions become favourable. The normal date for the withdrawal to begin is around September 17.
The Forecast for North and Northwest India
For North and Northwest India, including regions like Rajasthan, Punjab, Haryana, and Delhi, the withdrawal signals the start of a drier and hotter period. Forecasts suggest that maximum temperatures in September are likely to be above normal for most of the country. Satellite imagery has already shown a significant reduction in cloud cover over these areas. However, this doesn't mean zero rain. The IMD has still forecast isolated to scattered rainfall for states like Himachal Pradesh and Uttarakhand in the first half of the month, with some predictions of heavy spells around September 10-13.
Central India: A Mixed and Murky Picture
Central India, encompassing states like Madhya Pradesh and Chhattisgarh, is expected to see a mixed bag of weather. A low-pressure area over the central parts of the country was responsible for rainfall in early September. The IMD has forecast fairly widespread rainfall over parts of Madhya Pradesh and Chhattisgarh through the second week of September. Overall for the month, rainfall is expected to be below normal for the country as a whole. This erratic pattern means some areas could still see significant rainfall while others begin to dry out as the monsoon trough shifts and weakens.
East, Northeast and Peninsular India: The Rains Linger
The withdrawal process reaches the southern and eastern parts of the country last. For September, rainfall is likely to continue over many of these regions. A cyclonic circulation forming over the Bay of Bengal around mid-September could bring a fresh spell of rain to East and Southeast Peninsular India. While rainfall activity is expected to be subdued over much of the peninsula in the first half of the month, the Northeast is expected to see continued spells of heavy rain. The overall forecast for September points to below-normal rainfall for the country as a whole, but some areas in the Northeast, East, and Southeast Peninsula may receive normal to above-normal rain.
The Bigger Picture: An Erratic Monsoon Season
This year's monsoon has been marked by uneven distribution. As of early September, the country as a whole was facing a rainfall deficit of around 14%. The South Peninsula and East and Northeast India were significantly below normal, while some states like Odisha recorded excess rain. This erratic behaviour is attributed to the strengthening El Niño conditions in the Pacific Ocean, which are associated with weaker monsoon rains in India. As the withdrawal proceeds, this pattern of some parts remaining wet while others are dry is expected to continue, capping a season of high variability.
