A certain pocket of the country including small areas of north-west India, Bihar, Assam, northern West Bengal, Meghalaya, Ladakh and western part south peninsula may get ‘below normal’ rainfall during the four-month season. In north-west India, parts of Himachal Pradesh, Haryana and western Uttar Pradesh may fall in this forecast category.
The prediction, however, shows there is no shortage of rains for farming operations as the entire ‘monsoon core zone’ which consists of the rainfed agriculture regions in the country is most likely to get ‘above normal’ rainfall. The monsoon onset over Kerala is expected around Thursday. Its gradual progress will kick off the ‘Kharif’ sowing operation which is mostly dependent on rains.
“Quantitatively, the monsoon seasonal rainfall over the country as a whole is likely to be 101% of the Long Period Average (LPA) with a model error of ± 4%,” said the IMD director general, Mrutyunjay Mohapatra, while releasing its second stage long range forecast.
At first stage in mid-April, the IMD had predicted it to be 98% of the LPA with a model error of +/- 5%. The LPA of the season rainfall over the country as a whole for the period 1961-2010 is 88 cm. The 2021 monsoon will be third consecutive year of good rainfall, hinting at possibility of new record food-grain outputs like 2019 and 2020.
The IMD for the first time released maps of ‘monsoon core zone’, specifically showing state-wise distribution of rainfall as probabilistic forecast, using the Multi-Model Ensemble (MME) forecasting system. Under the new strategy, it issued monthly (June) and seasonal (June to September) operational forecasts for the southwest monsoon rainfall over the country.
“Climate models with the highest forecast skills over the Indian monsoon region including Monsoon Mission Climate Forecasting System (MMCFS) have been used to prepare the MME forecast,” said Mohapatra.
Considered the most advanced and comprehensive system to arrive at monsoon forecast, the MME system makes it possible to forecast “spatial distribution” of seasonal rainfall with the probabilistic “regionally averaged rainfall forecasts” of ‘monsoon core zone’ for better regional level planning of farming and other activities.
Asked about the slightly delayed monsoon (normal date is June 1), Mohapatra said, “All the criteria have, so far, not met. We are constantly monitoring the system. Conditions are gradually becoming favourable and we are expecting the onset around June 3.”