Does late monsoon mean less rainfall?

All eyes are set on the monsoon season that is due to arrive soon in the country. This year it will be normal, says the India Meteorological Department. The statement may have come as a big relief to different sectors that rely on seasonal rains, but the government’s weather forecast agency also said that monsoon, that hits Kerala first and on the 1st of June, will be delayed by three days.What does delay in monsoon from June 1 to June 4 mean?The IMD statement says the monsoon onset over Kerala is likely to be on June 4 with a model error of plus-minus four days. The prediction is obviously a three-day delay from the normal onset date.In practical terms, this is not much of a delay. We have seen in the past that monsoon has got delayed by as long as seven days.Southwest monsoon, which is the summer monsoon, normally sets in Kerala on June 1 with a standard deviation of about seven days.If you look at past data, last year the IMD predicted that monsoon would arrive on May 27. It arrived on May 29. In 2019, IMD predicted that monsoon would arrive on June 6, but it arrived on June 8. Such variations happen.Onset of monsoon in Kerala is considered the arrival of the four-month rainy season in India, though monsoon arrives in Andaman Nicobar Islands two weeks earlier.Will monsoon be weak this year?The India Meteorological Department has been issuing operational forecasts for the date of monsoon onset over Kerala. It has been doing so since 2005. Past records show that its forecast dates of monsoon onset were correct, except in 2015 when it was way off the mark.In 2019 monsoon arrived at the Kerala coast as late as on June 9. Its late arrival has no bearing on its progress or on its quantitative and spatial distribution. Spatial distribution is the geographical distribution of rains. There are other variables which impact the distribution of rainfall.In 2019 there was above normal rainfall even though monsoon arrived seven days late. So there are other factors which guide the overall rainfall, but delay cannot be seen as a signal of a weak monsoon. What is IMD’s spatial distribution forecast?IMD has not made the specific forecast yet. It is expected to release the precise forecast on monthly and spatial distribution of rainfall later this month, hopefully on May 31 just before the arrival of the monsoon in Kerala.IMD made a geographical distribution forecast in April which merely said that monsoon will be normal to below. Normal rainfall was predicted over parts of Northwest India, central parts of Gujarat and Maharashtra and the Northeast region in summer season. It said that over many parts of the Peninsula region and adjoining East Central, east and northeast area, and some parts of northwest India, monsoon will be normal. What is the link between El Niño and monsoon?El Niño is the unusual warming of surface waters in the eastern Pacific Ocean. It is generally linked to a weak monsoon. But it has not always led to the weak monsoon. Past examples show that there was normal to above rainfall in 40 per cent of the El Nino years. IMD data shows that out of 15 El Nino years between 1951 and 2022, there were six years with normal to above normal rainfall.If this is an El Niño year, temperatures will be high in many parts of the world. It will also impact monsoon. But it cannot be said with certainty that it's going to be a weak monsoon this year. It's a threat and we will have to wait and watch. A private weather forecast agency predicted monsoon to be below normal this year, while IMD says it will be normal. Whom should we believe?The Indian Meteorological Department is a national forecaster and the only nodal agency in the country which is accepted globally. The World Meteorological Organization recognizes the IMD. It has a perfected infrastructure methodology and assessment expertise. We should go by the IMD forecasts.The private forecast agencies use data from different sources. Unfortunately, some of them don't even give credit to their sources.IMD DG Mrutyunjay Mahapatra recently asked people to believe in IMD saying its forecast is not only judicious, reasonable and timely, but also has accountability. Audio Production: Shantanu Nanoti