The onset of the southwest monsoon (June to September), which accounts for 70 per cent of India’s annual rainfall, is likely to be May 30, with a model error of four days either way, according to a statement released by the India Meteorological Department (IMD) here on Thursday.
“The southwest monsoon is likely to set over Kerala on May 30 with a model error of ± 4 days…it signals the arrival of monsoon over the Indian subcontinent and represents beginning of rainy season over the region,” said the statement.
Importantly, the agency noted that the El Nino weather condition – a heating of ocean water in the eastern and central Pacific Ocean – is strengthening. Several international Met agencies in the U.S., Australia and Japan, have forecast a 70 per cent probability of an El Nino event in 2015.
The phenomenon is a cause for concern since it could lead to a second consecutive season of below-normal rainfall leading to drought conditions.
“El Nino conditions are concerning, they have been prevailing since March and is likely to strengthen during the monsoon and post-monsoon season. We will update the analysis for our forecast in June,” said an IMD official.
Devolving El Nino
While its prediction for the date of the monsoon onset – May 27 with the same margin of error - is similar to the Met Department’s, private weather forecasting agency Skymet disputed the assertion of an evolving El Nino.
The agency had earlier predicted that rainfall in 2015 would be 102 per cent of the Long Period Average (LPA) with an 82 per cent probability of normal-to-above-normal showers. It varied with IMD’s forecast of the southwest monsoon being below normal at 93 per cent of LPA, the average rainfall India received between 1951 and 2000 which stands at 89 cm.
“Analysing drought patterns through this and the last century, the year after the phenomenon is established has no drought. Last year, rainfall was 12 per cent below the LPA, it’s classified as a mild meteorological drought but the Government denied it. Our contention is that the El Nino episode is devolving this year,” said Jatin Singh, CEO, Skymet.
History & technology
Historically, there have only been four consecutive droughts since 1873 – 1904-05, 1965-66 and 1986-87-88. In India, the El Nino phenomenon had led to drought conditions in 2002, 2004 and 2009.
“But 2003, 2005 and 2010 received normal rain. This is why we believe the episode is tapering off and there is a 97 per cent probability 2015 will not be a drought year,” he added.
Skymet collates its information through 2,500 weather stations and satellite data and its computing model comprising 124 programs predicts no impact on the coming monsoon.
“The monsoon will be decent through June and will climb across the country. Our El Nino theorising is converging with our computing. The region is cooling off over the next 5-6 months,” said Singh.
Both agencies agreed that Indian Ocean Dipole (IOD) conditions, which also impact the monsoon in conjunction with the El Nino, were neutral.