The Telltale Signs of Retreat
The withdrawal of the monsoon isn't like flipping a switch. The India Meteorological Department (IMD) watches for a specific set of criteria before making an official declaration. First, rainfall must cease over northwest India for five consecutive days.
Second, and most critically, an 'anticyclone'—a large-scale circulation of winds around a high-pressure area—needs to establish itself in the lower atmosphere over the region. This high-pressure system pushes moisture away, leading to the third condition: a significant drop in humidity, which is visible through satellite imagery. Recent satellite images have shown a dramatic reduction in cloud cover over northwest and central India, sparking conversations about the monsoon's departure. While these are strong indicators, the official process is yet to begin.
Is the Withdrawal On Schedule?
Normally, the monsoon begins its withdrawal from the extreme western parts of Rajasthan around September 17. However, forecasts suggest the process may start around that time or slightly later this year. Weather models indicate that conditions will become increasingly favourable for a retreat in the second half of the month, with a prominent anticyclone expected to form over northwest India around September 21. This year's monsoon has been erratic, influenced by a strong El Niño, which typically leads to suppressed rainfall. After one of the hottest and driest Augusts on record, September is also forecast to have below-normal rainfall for the country as a whole.
A Month of Contrasting Weather
The monsoon's withdrawal from the northwest does not mean an end to rain for the rest of the country. The process is a gradual, staggered retreat that takes over a month to complete. While northwest India turns drier, other regions can expect a very different September. In fact, the same weather patterns steering the withdrawal can pull moisture into other areas. The IMD has forecast continued rainfall, with some heavy spells, for parts of east, northeast, and east-central India. Meanwhile, a press release from the IMD on September 7th indicated that subdued rainfall activity is likely to continue over Peninsular India for the next week. This creates a complex picture: dry, clearer skies in the west and north, while the east and northeast continue to experience wet conditions.
Impact on Farming and Water Security
September's weather is critical for the Kharif crops, which are in their final maturing stage. The overall monsoon rainfall this season has been deficient, leaving a 14% deficit as of early September. A dry end to the season in key agricultural belts could add stress to crops that have already faced an erratic season, potentially impacting yields. For farmers in the northwest, the cessation of rain is a welcome sign that allows for harvesting. However, the below-normal rainfall forecast for September raises concerns about soil moisture for the upcoming Rabi (winter) crop sowing season. Reservoir levels, which are crucial for irrigation and drinking water, are also under scrutiny after a season of uneven rainfall distribution.
What to Expect Where You Are
For those in Rajasthan, Punjab, Haryana, and Delhi, the coming weeks will likely bring a noticeable drop in humidity and clearer skies as the monsoon retreats. Conversely, states like Uttarakhand and Uttar Pradesh may still see spells of heavy rain in the near term before conditions dry out. Eastern states such as West Bengal, Jharkhand, and Odisha, along with the northeastern states, should brace for more wet days. For southern states in the peninsula, the immediate forecast suggests a period of subdued rainfall. The key is to remember that the monsoon's exit is a regional and phased process. The 'October Heat'—a period of rising temperatures and humidity after the rains retreat but before winter sets in—is another phenomenon to watch for, particularly in north and central India.
