Below-normal September rain, warmer nights: what IMD's El Nino outlook means for India
India's monsoon is heading into its final weeks under the shadow of a strong El Nino. In its outlook for September issued on 31 August, the India Meteorological Department (IMD) said rainfall over the country as a whole is most likely to be below normal, that is, less than 91 per cent of the month's long-period average of 167.9 mm, Sangri Times reported. The forecast extends a below-normal expectation the IMD had first signalled for August-September at the end of July, and it carries direct implications for kharif crops now in their grain-filling stage and for reservoir levels heading into the rabi season.
The numbers
The IMD's April seasonal forecast had projected the June-September monsoon at about 90 per cent of the long-period average, with a model error of four percentage points, DD News reported at the time, placing the season in the below-normal category from the outset. July brought a partial recovery from a weak June, according to a Blitz India analysis of the 31 July update, but the department then forecast August at below 94 per cent of its 254.9 mm average and August-September combined below normal against a 422.8 mm average.
For September itself, the picture is uneven. Large parts of the country are expected to fall short, but northwest, northeast, east, east-central and southeast peninsular India are projected to receive normal to above-normal rain, the IMD said. This week's rain across the northern plains and central India fits that regional pattern.
Why El Nino matters
El Nino, the periodic warming of the central and eastern equatorial Pacific, is historically associated with weaker Indian monsoons because it shifts the tropical circulation that feeds moisture into the subcontinent. The IMD said strong El Nino conditions are currently prevailing, with sea surface temperatures above normal across the central and eastern Pacific. The Indian Ocean Dipole, which can offset El Nino when in its positive phase, is neutral and expected to remain so through September, though the department noted that some international models suggest a transition to positive later in the season.
Warmer days and nights
The department also expects above-normal maximum and minimum temperatures over most of the country in September. The exceptions are northwest, west-central and northeast India, where minimum temperatures are likely to be normal to below normal. Warmer nights in a month that normally marks the transition to autumn raise electricity demand for cooling and add stress to standing crops.
What the IMD is advising
The outlook recommends timely water conservation, efficient management of stored water and agricultural contingency planning. Blitz India's analysis identified four practical measures for state governments: scheduling reservoir releases carefully, ensuring assured power for irrigation pumps, issuing crop-specific advisories through extension networks and preparing crop insurance machinery for possible claims.
Withdrawal still to come
Monsoon withdrawal from western Rajasthan, the first step in the retreat, is not attempted before 1 September and requires the cessation of rainfall over the region for five consecutive days along with a build-up of anticyclonic flow, according to the IMD's criteria. With a fresh rain spell forecast for Rajasthan this weekend, the start of withdrawal is unlikely before the middle of the month. The IMD will confirm the date on its monsoon information page once the criteria are met.