For the first time in its monsoon forecast history, IMD on Wednesday also released new monsoon onset and withdrawal dates, factoring in the likely impact of climate change, which has altered the way the south-west monsoon progresses over India. “The data we were using for monsoon onset and withdrawal was very old and based on only a few stations. El Nino years in India are linked to below normal monsoon rains and higher-than-normal frequency of heat waves. Last monsoon, weak El Nino conditions prevailed, which led to a delayed onset of monsoon rains, according to scientists. IOD is characterised by warmer sea surface temperature in the equatorial Indian Ocean; positive IOD conditions are usually associated with normal or above normal monsoon rains.

Source: Hindustan Times April 15, 2020 18:23 UTC