In two weeks, the India Meteorological Department (IMD) will release its first rain forecast for this year’s monsoon season, and, as of now, a key indicator does not seem to be very favourable for good rainfall.
Latest bulletins from weather agencies across the world show that a mild El Niño currently prevailing in the equatorial Pacific Ocean was likely to continue till the monsoon, and possibly the rest of the year as well. El Niño, a reference to the periodic warming of the sea-surface temperatures in equatorial Pacific Ocean off the coast of South America, is known to suppress monsoon rainfall over the Indian sub-continent.
“Equatorial sea surface temperatures (SSTs) are above average across most of the Pacific Ocean. The pattern of anomalous convection and winds are consistent with El Niño. Weak El Niño conditions are likely to continue through the Northern Hemisphere spring (March to May) 2019 (approximately 80 % chance) and summer (June-September) 2019 (approximately 60% chance),” the Climate Prediction Centre of the National Oceanic and Atmospheric Administration (NOAA) of the United States said in its latest monthly bulletin.
The latest outlook is consistent with what it had said in March but stronger than its February forecast in which it had said there was only a 55 per cent chance that El Niño would continue till the spring and less than 50 per cent chance that it will extend till the summer.
The Australian Bureau of Meteorology’s outlook for El Niño has remained at ‘alert’ level, meaning that there was about 70 per cent probability of a full El Niño developing this year.
“Tropical Pacific sea surface temperatures have remained close to El Niño thresholds for the past five weeks. The atmosphere has responded to the surface warmth at times, but is yet to show a consistent El Niño-like response. All but one of the eight surveyed climate models predict sea surface temperatures (SSTs) will remain above El Niño thresholds for April and June, with six of the models maintaining SSTs values above the threshold during August,” it has said in its bulletin issued on Tuesday.
Like every year, IMD will make its first seasonal forecast of the monsoon rainfall sometime during the middle of this month. The forecast is awaited because of monsoon’s impact on agriculture, wider economy, and even on drinking water and power situation.
“The conditions are not ideal right now for good rainfall. But it is still too early to say anything definitive. We will have to wait and see how the indicators evolve,” head of Climate Research and Services at IMD, D S Pai, said.
The forecasts made about El Niño by climate models in March and April are considered not very reliable, as they have unusually large uncertainties. Scientists call it—Spring Barrier. It is not fully understood but one reason for low accuracy of forecasts during this period is believed to be the fact that this is a transition time for oceans during which SSTs turn warmer to cooler or the other way around.
Raghu Murtugudde of University of Maryland, College Park, US, said though an El Nino event did appear very possible, a clearer picture would emerge only in subsequent weeks. He said if the sub-surface warming in the equatorial Pacific Ocean was not neutralised by an easterly wind event, it was likely that current forecasts would hold. “If instead a westerly wind event occurs, it will greatly strengthen chances of an El Niño. That would not be good news for Indian monsoon then,” he said.