Monsoon may be less than normal, 60 per cent chance of El Nino, says IMD

With development of El Nino conditions in the equatorial Pacific, southwest monsoon may be less than normal this year, says the forecast released by the India Meteorological Department (IMD) Thursday.

According to the Long Range Forecast for 2014, even though the El Nino-Southern Oscillation or ENSO conditions in the equatorial Pacific continue to be neutral but probability of warming trend in the sea surface temperatures (SSTs) over the equatorial Pacific, reaching to El Nino level during the southwest monsoon season is around 60 per cent, says IMD.

Private weather forecasting company Skymet had earlier predicted that there was a 40 per cent chance that rainfall in 2014 would be less than average and a 25 per cent chance that there would be a drought.

Read more on Skymet’s forecast for this year

El Nino may lead to rainfall deficit, drought in 2014

ENSO is an ocean-atmospheric phenomenon that occurs due to local warming of surface waters of  equatorial Pacific Ocean  which affects the atmospheric circulation and direction of winds worldwide. It is often accompanied by drought in India and heavy rainfall in the Pacific coast of Latin America.

What different models say

The press release issued by IMD also says that experimental forecast based on the coupled dynamical model forecasting system suggests that the monsoon rainfall during the 2014 monsoon season (June to September) averaged over the country as a whole is likely to be 95 per cent (with model error of ± 5per cent) of long period model average (LPMA). Monsoons are considered normal when seasonal rainfall is 96-104 per cent of LPMA.

The experimental five category probability forecasts for the 2014 monsoon season rainfall over the country as a whole using the experimental dynamical prediction system are 16 per cent (deficient), 17 per cent (below normal), 33 per cent (normal), 16 per cent (above normal) and 17 per cent (excess).

Indian Ocean Dipole (IOD), which is also known as Indian El Nino, is also known to influence Indian monsoon, but currently IOD is near neutral over equatorial Indian Ocean. Based on the recent forecasts from some coupled models, it is expected that neutral IOD conditions are likely to continue till the end of southwest monsoon season.

“As the extreme sea surface temperature conditions over Pacific and Indian Oceans, particularly ENSO conditions over Pacific (El Nino or La Nina), are known to have strong influence on the Indian summer monsoon, IMD is carefully monitoring the sea surface conditions over Pacific and Indian oceans,” the release states. IMD will issue updated forecasts in June 2014.

Other factors that influence monsoon

“We cannot attribute the below normal rainfall to El-Nino alone. There are five parameters which influence the monsoons. These include Sea Surface Temperature (SST) gradient between North Atlantic and North Pacific, Equatorial South Indian Ocean SST, East Asia Mean Sea Level Pressure, Northwest Europe Land Surface Air Temperature and Equatorial Pacific Warm Water Volume. All these factors together will cause below normal rainfall,” says B P Yadav, director, IMD.

http://www.downtoearth.org.in/news/monsoon-may-be-less-than-normal-60-per-cent-chance-of-el-nino-says-imd-44133

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