US-based International Research Institute for Climate and Society has predicted there’s higher probability of El Niño occurring during the peak of monsoon season, which is not in sync with the near-normal monsoon forecast by the India Meteorological Department (IMD) earlier in April.
According to early April conditions over the Pacific, the probability of the onset of El Niño during the monsoon months of June-September was below 50%, but things have changed in the last two weeks. According to the new forecast, there is over 55% likelihood of El Niño appearing during the months of May-July and close to 70% chance during July-September.
Other international agencies such as US-based National Oceanic and Atmospheric Administration (NOAA) and the Australian Bureau of Meteorology (ABM) have predicted a probability close to 50% only. But these are based on early April conditions.The ABM will release its next update on 26 April, while NOAA will give its next briefing on 11 May.
El Niño is a weather phenomenon caused by unusual warming in the Pacific Ocean, resulting in atmospheric changes, potentially leading to poor southwest monsoon in India.
Earlier this month, IMD forecast a near-normal monsoon for 2017 based on the low probability of El Niño. According to IMD, there was close to 50% probability of El Niño prevailing for the period of July-September, which was reduced to around 40% at the beginning of April.
The ENSO (El Niño-Southern Oscillation) forecast is worrying for the IMD which predicted normal monsoon at 96% of the long-period average. Though it has predicted that this year El Niño would be accompanied by a positive Indian Ocean Dipole (IOD) which would neutralize the negative impact of the El Niño, data from past years suggests that IOD has been known to be moody and has shifted directions in a matter of weeks.
The IOD is an irregular oscillation of sea-surface temperature in which the western Indian Ocean becomes alternately warmer and colder than the eastern part of the ocean.
According to IMD officials, it is too early to provide accurate forecast and the picture will become clearer in its second-stage forecast which arrives in early June.
Data from previous 16 years shows that IMD’s first monsoon forecast was mostly at a large variance from actual rainfall values. (bit.ly/2qaer63). This year, IMD has only issued a 38% probability of the monsoon being “near normal” instead of the usual break-up of probabilities for different rainfall scenarios such as deficit, below normal, above normal, normal and excess.