IMD forecasts normal rainfall over India in 2020 southwest monsoon season
New Delhi, June 1, 2020
The India Meteorological Department (IMD) today forecast that the rainfall over the country as a whole for the 2020 southwest monsoon (June to September) is most likely to be normal, that is 96% to 104% of long period average (LPA).
Quantitatively, monsoon season rainfall for the country is likely to be 102% of the LPA, with a model error of +/-4%, it said in its Long Range Forecast Update for the 2020 southwest monsoon rainfall.
The LPA rainfall over the country as a whole for the period 1961-2010 is 88 cm.
Regionwise, the season rainfall is likely to be 107% of LPA over North-West India, 103% of LPA over Central India, 102% of LPA over South Peninsula and 96% of LPA over North-East India, all with a model error of +/- 8 %.
The monthly rainfall over the country as whole is likely to be 103% of its LPA during July and 97% of LPA during August, both with a model error of +/- 9 %, it said.
IMD had issued the first stage operational longrange forecasts for the southwest monsoon season rainfall over the country as a whole on April 15.
It said the operational forecasts have been prepared based on the state-of-the-art, indigenously developed statistical models.
The update forecast was prepared using a 6-parameter Statistical Ensemble Forecasting System (SEFS). The seasonal rainfall over the four broad geographical regions and monthly rainfall for the July and August over the country as a whole have been prepared using Principal Component Regression (PCR) models with different set of parameters.
Experimental forecast based on the Ministry’s Monsoon Mission Coupled Forecasting System (MMCFS) was also presented. The latest version of the high resolution MMCFS implemented at the Office of Climate Research and Services, IMD, Pune was used for this purpose, a press release from IMD said.
The release said that, currently, normal sea surface temperatures are observed across most of the equatorial Pacific Ocean. Many atmospheric variables over the region indicate ENSO Neutral to cool ENSO neutral conditions over the region. The latest forecasts from MMCFS and other global models together indicate cool ENSO neutral conditions are likely to prevail during most part of the monsoon season. However, a few other climate models indicate possibility of development of weak La Niña conditions in the later part of the season or thereafter.
At present, Neutral Indian Ocean Dipole (IOD) conditions are prevailing over the region. A positive (negative) IOD is associated with a stronger (weaker) than normal monsoon. The latest forecasts from global coupled models suggest that these neutral IOD conditions are likely to continue during the monsoon season.
The prevailing and predicted SST conditions over the Pacific and Indian Oceans are favourable for a normal monsoon season, it said.
The release said the latest experimental forecased based on the Monsoon Mission Coupled Forecasting System (MMCFS) suggested that there is high probability for the 2020 monsoon season rainfall to be above normal to excess (more than 104 % of LPA). Quantitatively, the 2020 monsoon rainfall is likely to be 107% of LPA with a model error of +/- 4%.
The category probability forecasts for the monsoon season over the country as a whole suggest a very low probability (only 5%) for monsoon rainfall to be deficient. On the other hand, they suggested a very high probability (41%) for the monsoon rainfall to be normal.
The probability for below normal was 15% and for above normal 25%, while it was 14% for excess rainfall, the release added.