Seasonal rainfall likely to be normal in 2019

In a press release, the India Meteorological Department (IMD) has announced that the southwest monsoon rainfall over the country is likely to be normal for 2019. IMD issues operational forecast for the southwest monsoon season (June to September) rainfall for the country as a whole in two stages—one in April and the other in June. These forecasts are prepared using two state-of-the-art models namely Statistical Ensemble Forecasting system (SEFS) and Climate Forecasting System (CFS), developed under Monsoon Mission of the Ministry of Earth Sciences.

IMD’s SEFS model for the April forecast uses the following five predictors that require data up to March.

Forecast for the 2019 Southwest monsoon Season (June – September) rainfall over the country as a whole

Forecast based on the Monsoon Mission CFS Model

For generating the forecast for the 2019 southwest Monsoon season rainfall, global atmospheric and oceanic initial conditions up to March 2019 were used involving 47 ensemble members. The forecast based on the CFS model suggests that the monsoon rainfall during the 2019 monsoon season (June to September) averaged over the country as a whole is likely to be 94% ± 5% of the Long Period Average (LPA).

Forecast based on the Operational SEFS

• Quantitatively, the monsoon seasonal rainfall is likely to be 96% of the Long Period Average (LPA) with a model error of ±5%.
• The five category probability forecasts for the Seasonal (June to September) rainfall over the country as a whole is given below:

Forecast suggests that the 2019 Southwest monsoon rainfall is likely to be near normal. However, there is very less chance for the monsoon rainfall to be above normal or excess.

Overall, the country is expected to have well distributed rainfall scenario during the 2019 monsoon season, which will be beneficial to farmers in the country during the ensuing Kharif season.

Sea Surface Temperature (SST) Conditions in the equatorial Pacific & Indian Oceans

At present, weak El Niño conditions (SST anomalies between 0.5⁰ C & 1.0⁰ C) are prevailing over the equatorial Pacific Ocean. The latest forecasts from the Monsoon Mission CFS & other global climate models indicate such conditions are likely to persist during the monsoon season but with reduced intensity in the later part of the monsoon season. It is noted that El Niño predictions made in February/March generally have more uncertainties compared to the El Niño predictions made in June. Presently, neutral Indian Ocean Dipole (IOD) conditions are prevailing over the Indian Ocean. The latest forecasts from the models indicate positive IOD conditions development likely during the monsoon season. Positive IOD conditions tend to associate with the normal monsoon over India.

Summary of the Forecast Assessment

The sea surface temperature (SST) conditions over the Pacific (El Niño/La Niña) and Indian Oceans (Indian Ocean Dipole-IOD) which are known to have a strong influence on Indian monsoon are being continuously monitored. Overall, the country is expected to have well-distributed rainfall scenario during the 2019 monsoon season, which will be beneficial to farmers of the country during the ensuing kharif season. IMD will issue the second stage Monsoon-2019 Forecast during the first week of June 2019.