- The India Meteorological Department (IMD) has said monsoon rains are expected to be normal in 2019- 96% of the Long-term average (LPA). The IMD defines normal rainfall as between 96% and 104% of the Long Period Average (LPA). LPA (50year average) of monsoon rains in India is 89 cm.
- The IMD issues its first monsoon forecast in April. Then in June, updates are issued. It contains details on how the monsoon will perform in various geographical regions.
- IMD’s prediction is contradictory to what Skymet, India’s only private weather forecaster has predicted. Skymet has said that it expects the 2019 monsoon rains to be “below normal”.
- IMD’s optimistic assessment of monsoon rains is based on global climate models which has projected a ‘weakening El Nino.’ El Nino refers to the large-scale ocean-atmosphere climate interaction linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific.
- A temperature rise greater than 1 degree C for three consecutive months, is considered a ‘strong’ El Nino. A 0.5C -1C rise is called ‘weak El Nino conditions. At present, the El Nino is 0.9 C.
- A strong El Nino results in reduction and uneven distribution of rainfall across the Indian sub-continent. This is because the trade winds coming from South America which normally blow westward towards Asia during Southwest Monsoon gets weakened due to the warming of the Pacific Ocean. Therefore, moisture and heat content gets limited and this leads to poor rainfall in the region.
