The reason isn’t simply because El Nino is just one among many factors that influence rains over India during the season. The reason isn’t simply because El Nino is just one among many factors that influence rains over India during the season.
The first official forecast is at least a couple of weeks away, but predictions on the southwest monsoon’s performance — including by a private forecaster that has got it wrong in the past — have already begun.
These are based largely on indications that El Nino-like conditions could develop in the equatorial Pacific Ocean during the second half of the four-month season (June-September) that brings nearly 75 per cent of India’s annual rainfall.
Scientists, however, say that it’s too early to make any reliable claim about this year’s monsoon. The reason isn’t simply because El Nino is just one among many factors that influence rains over India during the season. Right now, it’s even not clear whether at all it would develop and when.
“Some models are indicating that an El Nino may emerge by July, but the confidence in that prediction is not very high at present,” said J Srinivasan of the Divecha Centre for Climate Change at the Indian Institute of Sciences, Bangalore.
El Nino refers to an abnormal warming of sea surface waters in the equatorial Pacific Ocean that is known to impact weather events worldwide. In India, it is associated with a suppressed rainfall during the monsoon season.
The Climate Prediction Centre of the National Oceanic and Atmospheric Administration of the United States, in its latest outlook, has said that the current “neutral” conditions were likely to continue till “at least the northern hemisphere spring (of) 2017”, even while there are “increasing chances” of El Nino developing towards the fall season. That would mean an El Nino cannot be expected before August-September or the monsoon’s second half.
The Australian Bureau of Meteorology, too, is pointing to only a “50 per cent chance of El Nino developing” this year, “during the second half of 2017”. Its latest outlook says that El Nino may emerge by the “end of autumn” (i.e. around September). The Japan Meteorological Agency also believes there is a 60 per cent chance that the current neutral conditions “will persist during the spring and summer”. That leaves only a 40 per cent probability of El Nino developing by August.
Even if there is an El Nino event, its impact on actual rainfall over India would not be evident till almost the end of the season.
But there are also other reasons why El Nino might not be a very good indicator to use at this point of time. Scientists warn that outlooks for El Nino in March and early April are not very reliable due to what is known as ‘Spring Predictability Barrier’.
It refers to the increased uncertainty in predicting the El Nino phenomenon during this time when sea surface temperatures are in a transitory phase. “Caution must be exercised (in reading El Nino signals), as models have lower accuracy at this time of the year,” says the outlook from the Australian agency.
That apart, establishing a direct one-on-one correlation between El Nino and the monsoon might itself be problematic. In the past, there have been quite a few El Nino years when the country received good monsoon rainfall. The India Meteorological Department, in fact, uses at least five major indicators to forecast the monsoon. El Nino is only one of them, albeit important.
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