2013 to be normal monsoon year: IMD

Monsoon arrival date to be announced on May 15

By Soma Basu
Published: Friday 26 April 2013


Monsoon this year is most likely to be normal for the country as a whole, according to the India Meteorological Department (IMD), which released its Long Range Forecast for 2013 monsoon on Friday.

Union minister for science and technology, Jaipal Reddy, released the forecast and said that it is good news for the farmers that the monsoons would be normal this year. “As a politician contesting elections, I should be happy about the forecast as rainfall will directly affect the crop productivity which has a great impact on the country’s economy,” he added.

According to the forecast, southwest monsoon seasonal rainfall for the country as a whole is most likely to be normal—96-104 per cent of Long Period Average (LPA), with the highest probability of 46 per cent. The probability (27 per cent) of seasonal rainfall to be below normal (90-96 per cent of LPA) is also higher than its climatological value. However, the probability for the seasonal rainfall being deficient (below 90 per cent of LPA) or excess (above 110 per cent of LPA) is relatively low (10 per cent and 3 per cent respectively).

Quantitatively, the monsoon seasonal rainfall is likely to be 98 per cent of the LPA with a model error of ± 5 per cent. IMD will forecast monsoon’s arrival date on May 15. LPA of the season rainfall over the country as a whole for the period 1951-2000 is 89 cm. The Earth System Science Organization and IMD will issue the updated forecasts in June, 2013 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 geographical regions of India will also be issued.

Respite for drought-hit south India

Though the regional forecast is yet to be out, L S Rathore, director general of IMD, said that the trends show that this year, drought hit southern-region of the country will have some respite. He indicated that the areas adjacent to Pakistan may suffer from drought like situation. “But since those areas are not dependant on rainfall for agriculture, there is hardly anything to worry about,” he said.

The press note also says that borderline El Niño conditions were observed across the equatorial Pacific for a brief period between July and September 2012. Subsequently, El Niño–Southern Oscillation (ENSO) neutral conditions returned during October 2012 and have continued through early part of April, 2013. The latest forecasts from a majority of the dynamical and statistical models favour (about 60 per cent probability) ENSO neutral conditions to continue during the 2013 monsoon season. If ENSO neutral conditions prevail during the summer monsoon season, as most models indicate, there is little scope for typical ENSO impacts on the rainfall activity over the country.

El Nino/La Nina-Southern Oscillation or ENSO is an ocean-atmospheric phenomenon that occurs in a cycle. La Nina, which is one part of the cycle, is signified by a decrease of 3-5°C in sea surface temperature across the Equatorial Pacific Ocean and it is favourable for monsoons in India. El Nino, which is La Nina’s counter-phenomenon, is often accompanied by drought in India and heavy rainfall in the Pacific coast of Latin America.

In addition to the ENSO events, many other factors such as the Indian Ocean sea surface temperatures also influence monsoon’s performance. Recent forecasts from some coupled models suggest possibility of the development of a weak negative Indian Ocean Dipole event during northern hemisphere (NH) summer and to have a maximum peak during NH autumn which may not have much impact on the Indian monsoon. IOD, also known as the Indian Nino, is an irregular oscillation of sea-surface temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean.

As the extreme sea surface temperature conditions over the 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, said Rathore.

Click here to see rainfall data of 100 years (.pdf)

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