Above Normal Rainfall during the Coming Monsoon Season

Long range Forecast of rainfall for the 2024 South West monsoon season released today by IMD

The country as a whole is likely to receive above normal rainfall during the south west monsoon from June to September 2024, according to Secretary, Ministry of Earth Sciences, Dr M. Ravichandran.

There will be 106% of the Long Period Average (LPA) with a model error of ± 5%. The LPA of the season rainfall over the country as a whole is 87 cm based on data of 1971-2020, informs Dr M. Ravichandran.

This forecast is based on both dynamical and statistical models, and it suggests above normal rainfall is likely over most part of the country except some areas of Northwest, East and Northeast India, where below normal rainfall is likely.

Dr M. Ravichandran believes that the expected La Nina, positive IOD and below normal snow cover over northern hemisphere would be favourable for rainfall during southwest monsoon season 2024.

Giving a detailed presentation DG, IMD, Dr Mrutyunjay Mohapatra has also pointed out that currently, moderate El Niño conditions are prevailing over the equatorial Pacific region and the Climate model forecasts indicate neutral condition by the beginning of monsoon season and La Niña conditions during second half of monsoon season.

He also informed the media that at present neutral Indian Ocean Dipole (IOD) conditions are prevailing and Climate model forecast indicate positive IOD conditions likely to develop during the monsoon season.

He added that since Sea Surface temperature conditions over the pacific and the Indian Ocean are known to have a strong influence on the Indian Monsoon, IMD is carefully monitoring the evolution of sea surface conditions over these ocean basins.

Dr Mohapatra further said that Northern hemisphere snow cover extent during the last three months (January to March 2024) was below normal which indicates above rainfall this monsoon season. Winter and spring snow cover extent over Northern Hemisphere as well as Eurasia has a generally inverse relationship with the subsequent monsoon season rainfall. He said, IMD will issue the updated forecasts for monsoon season rainfall in the last week of May 2024.

It may be noted that since 2003, India Meteorological Department (IMD) has been issuing the operational long-range forecast (LRF) for the southwest monsoon seasonal (June-September) rainfall averaged over the country as a whole in two stages. The first stage forecast is issued in April and the second stage or update forecast is issued by the end of May.

Since 2021, IMD has implemented a new strategy for issuing monthly and seasonal operational forecasts for the southwest monsoon rainfall over the country by modifying the existing two stage forecasting strategy. The new strategy uses both dynamical and statistical forecasting system. Multi-Model Ensemble (MME) forecasting system based on coupled global climate models (CGCMs) from different global climate prediction centres, including IMD’s Monsoon Mission Climate Forecast System (MMCFS) is used in dynamical forecast system.

In continuation to the above forecasts, monthly rainfall forecast is issued around the end of June, July and August respectively for the subsequent one month.

In addition, quantitative and probabilistic forecasts for the country as a whole and spatial distribution of probabilistic forecasts of rainfall for second half (August-September) of the season is issued around end of July along with forecast for August.

Summary of the Forecast of Rainfall during Southwest Monsoon Season, 2024 is as follows:

• The rainfall over the country as a whole during monsoon season (June to September) is very likely to be above normal (>106% of the Long Period Average (LPA)).

• Quantitatively, the seasonal rainfall over the country as a whole is likely to be 106% of LPA with a model error of ± 5%.

• The LPA of the season rainfall over the country as a whole is 87 cm based on data of 1971-2020.

• Currently, moderate El Niño conditions are prevailing over the equatorial Pacific region. Climate model forecasts indicate neutral condition by the beginning of monsoon season and La Niña conditions during second half of monsoon season.

• Currently, neutral Indian Ocean Dipole (IOD) conditions are prevailing. Climate model forecasts indicate positive IOD conditions likely to develop during the monsoon season.

• Northern hemisphere snow cover extent during the last three months (January to March 2024) was below normal. Winter and spring snow cover extent over Northern Hemisphere as well as Eurasia has a generally inverse relationship with the subsequent monsoon season rainfall.

• IMD will issue the updated forecasts for monsoon season rainfall in the last week of May 2024.