Monsoon begins packing up: India's rainy season is ending soon. What's ahead?

India's monsoon is entering its withdrawal phase. Here's how dry air, high pressure and changing winds signal the end of the rainy season.

In Short

• Northwest India to witness first monsoon retreat after September 19-20
• Dry air incursion will reduce moisture and rainfall in northwest and west India
• India faces 15% rainfall deficit; monsoon withdrawal gradual, ending by early October

The southwest monsoon is beginning to lose its momentum and is making arrangements to leave.

The first region that will bid farewell to the rainy season is the country’s northwest.

A massive incursion of dry air is expected to move into the region after September 19-20, sweeping away the remaining moisture and signalling the beginning of the season’s retreat.

For millions of people who have spent the past few months watching the skies, the change will be rather gradual and not instant.

HOW DOES MONSOON WITHDRAW?

The monsoon normally begins withdrawing from western Rajasthan around September 17. This year, the India Meteorological Department (IMD) has noted that conditions are becoming favourable for the process to start from some parts of west Rajasthan around September 19.

The withdrawal of the monsoon is also not something that occurs overnight. It slowly moves eastward and southward over the following weeks, with the monsoon usually leaving the country only after early October.

The IMD declares the first withdrawal only after September 1 and only when three clear signs present themselves; rainfall stops for five continuous days over the area, dry air takes hold, and a high-pressure system builds in the lower atmosphere.

Together, these changes replace the moist monsoon winds with drier northwesterly winds, marking the beginning of the season’s retreat.

DRY AIR ARRIVES NEXT WEEK

The massive dry-air incursion expected after September 19-20 will sweep away leftover moisture from northwest and west India.

As the drier air settles in, rainfall is expected to gradually lose its hold over Rajasthan, parts of Punjab, Haryana, Gujarat and neighbouring areas.

The shift will bring clearer skies and lower humidity, although temperatures may rise a little in the short term as cloud cover decreases.

However, the monsoon’s retreat does not mean rain will disappear from the rest of India.

A low-pressure area is likely to form over the Andaman Sea around the same time, as a result of a cyclonic circulation that was over Thailand but is now moving towards us.

This system could keep rains active over central and eastern India for a while longer, meaning full withdrawal from those regions may wait until after the end of September.

MONSOON SEASON SO FAR

As of September 17, India as a whole has received 15% less rainfall than the long-term average, according to official IMD figures.

Northwest India sits closer to a 10% shortfall, while southern and northeastern regions face steeper gaps.

What's more is that this rain deficit is unlikely to close fully in the remaining days. Meaning India will finish its rainy season facing less rain than it usually does.

For now, people in the northwest can expect the last few light showers in places before the dry air settles in. Elsewhere, scattered rain may continue for another week or two.

The monsoon’s departure is not just a mere change in the forecasts ahead, but also marks the slow turning of the seasons, as India moves away from its rain-filled months and towards the cooler, drier days of autumn.

- Ends