India to have normal monsoon this year, IMD comes out with new onset and withdrawal dates for cities

Vishwa Mohan | TNN | Apr 15, 2020, 16:44 IST

NEW DELHI: In what could be a positive signal to farm sector, the India Meteorological Department (IMD) on Wednesday predicted ‘normal’ summer monsoon for the country during June-September period and released new reference dates for its onset/advance and withdrawal in cities across states.
“Quantitatively, the monsoon seasonal (June to September) rainfall is likely to be 100% of the Long Period Average (LPA) with a model error of ± 5%,”said Madhavan Rajeevan, secretary, ministry of earth sciences (MoES).
The LPA of the seasonal rainfall over the country as a whole for the period 1961-2010 is 88 cm. The monsoon rainfall has to be between 96-104% of the LPA to be considered as ‘normal’. If the IMD’s prediction goes well, which invariably be the case, 2020 would be the second consecutive year of very good rainfall during summer (southwest) monsoon.
Releasing this year’s southwest monsoon forecast, Rajeevan said there was quite high probability of 2020 being the year of good rainfall (normal to excess).
Though monsoon onset over Kerala, under IMD’s new reference dates, remains the same (June 1), its advance dates over states like Maharashtra, Gujarat, Madhya Pradesh, Chattisgarh, Telegana, Andhra Pradesh, Odisha, Jharkhand, Bihar and parts of Uttar Pradesh are now delayed by 3-7 days compared to existing normal dates.
“However, over extreme northwest India, the monsoon arrives now little earlier, on July 8 compared to the existing date of July 15,” said Rajeevan.
Accordingly, the monsoon arrival will now be four days late in Delhi (June 27 instead of June 23), three days late in Chennai (June 4 instead of June 1) and one day late in Mumbai and Kolkata (June 11 instead of June 10) while it will be five days early in Chandigarh (June 26 instead of July 1) and 15 days early in Jammu (June 28 instead of July 13).
Similarly, there are changes in the monsoon withdrawal dates, especially over northwest and central India.
“Monsoon withdrawal from northwest India will now be almost 7-14 days later from the existing dates. There is, however, no change in the final withdrawal date over south India (October 15),” said Rajeevan.
These changes are based on analysis of historical data on changing rainfall pattern across the country. While the normal dates of onset are revised based on data during 1961-2019, the normal dates of withdrawal are revised based on data during 1971-2019. The present normal monsoon onset and withdrawal dates are based on records of only a few stations during the period 1901-1940.
“These new dates are relevant for many applications like agriculture, water and power management,” said the MoES secretary.
The changes assume significance as onset and withdrawal dates are crucial for farmers, civic agencies, hydro-power plants and disaster management authorities in planning of their works in better ways during the monsoon season.
As far as onset of monsoon in 2020 is concerned, the IMD would be able to come out with its prediction by May 15. Since the forecast released on Wednesday is preliminary one (called first stage) which talks about status of the overall monsoon this year, the country’s national weather forecaster will come out with its updated forecast either in the last week of May or in first week of June as a part of its second stage forecast.
“Along with the updated forecast, separate forecasts for the monthly (July and August) rainfall over the country as a whole and seasonal (June-September) rainfall over the four broad geographical regions of India will also be issued,” said IMD director general, Mrutyunjay Mohapatra.
The IMD issues operational forecast for the southwest monsoon season (June to September) rainfall for the country as a whole in two stages. The first stage forecast is issued in April and the second stage forecast is issued in May/June.
Though the IMD’s first stage monsoon forecast on Wednesday gave only a broad picture, it will be quite important for farmers to plan in advance the kind of crop they should select for cultivation and arrange seeds and relevant farm inputs such as fertilisers and pesticides.
Keeping the first stage monsoon forecast in view, the agriculture ministry will on Thursday hold Kharif National Conference (through video conferencing) to firm up the field preparations for upcoming summer sowing season.
This year’s preparedness would be different as farmers will have to do it during the lockdown period which has now been extended till May 3.
During Kharif conference, all states will be sensitised to keep their support ready, keeping in view the monsoon forecast so that farmers can get proper supply of seeds and other farm inputs on time. India’s half of the foodgrain production comes from sowing in monsoon season.