Monsoon normal this year, forecasts IMD

Amid the coronavirus gloom, there's finally some good news. The India Meteorological Department (IMD) has announced that it expects monsoon rainfall to be normal this year.

"Southwest monsoon seasonal (June to September) rainfall over the country as a whole is likely to be normal (96-104 per cent)," the IMD said in its first stage Long Range Forecast (LRF) for monsoons.

Secretary of Ministry of Earth Sciences M. Rajeevan released the IMD’s LRF for the 2020 Southwest Monsoon Season Rainfall in the presence of IMD Director General M. Mohapatra.

The IMD also issued the ‘New Normal Dates of Onset/Progress and Withdrawal of Southwest Monsoon Over India’.

Monsoons are expected to hit Kerala's Thiruvananthapuram on June 1.

In states like Maharashtra, Gujarat, Madhya Pradesh, Chattisgarh, Telegana, Andhra Pradesh, Odisha, Jharkhand, Bihar and parts of Uttar Pradesh, monsoon will be delayed by three-seven days compared to the 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.

Monsoons are expected to withdraw in south India on October 15.

Rajeevan said that quantitatively, the monsoon seasonal (June to September) rainfall is likely to be 100 per cent of the Long Period Average (LPA) with a model error of 5 per cent.

The LPA of the season rainfall over the country as a whole for the period 1961-2010 is 88 cm.

"Good news is that it is estimated that the deficient rainfall will be 9 per cent. This forecast is based on the statistical model, it suggests that we will have a normal monsoon," he said.

He said the IMD will issue the updated forecasts in the last week of May/first week of June 2020 as a part of the second stage forecast.

Rajeevan pointed out that Neutral El Nino Southern Oscillation (ENSO) conditions are prevailing over the Pacific Ocean and Neutral Indian Ocean Dipole (IOD) conditions are prevailing over the Indian Ocean. Some climate model forecasts indicate these conditions are likely to persist during the ensuing monsoon season.

As sea surface temperature (SST) conditions over the Pacific and Indian Oceans are known to have strong influence on Indian monsoon, IMD is carefully monitoring the evolution of sea surface conditions over the Pacific and the Indian oceans.

La Nina, or cooler-than-usual sea surface temperatures in the east-central Pacific Ocean, is typically associated with better monsoon rains and colder winters in India while El Nino is associated with below-normal rainfall in the country.

The southwest monsoon season, that replenishes the country's farm-dependent economy, first hits the southern tip of Kerala usually in the first week of June and retreats from Rajasthan by September.

Summary of the Forecast for the 2020 Southwest Monsoon Rainfall:

Southwest monsoon seasonal (June to September) rainfall over the country as a whole is likely to be normal (96-104 per cent).

Quantitatively, the monsoon seasonal (June to September) rainfall is likely to be 100 per cent of the Long Period Average (LPA) with a model error of ± per cent The LPA of the season rainfall over the country as a whole for the period 1961-2010 is 88 cm.

Neutral El Nino Southern Oscillation (ENSO) conditions are prevailing over the Pacific Ocean and Neutral Indian Ocean Dipole (IOD) conditions are prevailing over the Indian Ocean. Some climate model forecasts indicate these conditions are likely to persist during the ensuing monsoon season. However, a few other global climate models indicate possibility of development of weak La Nina conditions over the Pacific Ocean during the second half of the season.

As sea surface temperature (SST) conditions over the Pacific and Indian Oceans are known to have strong influence on Indian monsoon, IMD is carefully monitoring the evolution of sea surface conditions over the Pacific and the Indian oceans.

The IMD will issue the updated forecasts in the last week of May/first week of June2020 as a part of the 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..