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Late entry yet normal rain prediction

Patna, June 10: The foray of monsoon into Assam and northeastern states today prompted the Patna Met office to claim that Bihar is likely to receive normal rainfall this year.

In quantitative terms, the state is likely to receive 99 (±) 8 per cent of the long period average rainfall this year, which is 1024mm for June, July, August and September. On the contrary, the season rainfall for the country as a whole is likely to be 93 per cent of the long period average with a model error of (±) 4 per cent.

Monsoon is expected to be “marginally delayed” in Bihar. The rain-bearing winds are expected to enter the state around June 16 against it normal onset of June 11-13.

The evening monsoon bulletin of IMD today stated that monsoon had advanced into some parts of west-central Bay of Bengal, remaining parts of east-central and northeast Bay of Bengal, some parts of north-west Bay of Bengal, entire Nagaland, Manipur, Mizoram, Tripura, Assam, Meghalaya, Arunachal Pradesh and some parts of sub-Himalayan Bengal.

Meanwhile, the India Meteorological Department (IMD) continues to remain firm on its prediction that there is more than 70 per cent chance of the El Niño weather phenomenon influencing monsoon in India this year. El Niño — a Spanish word for Christ Child — is an abnormal warming of water in the equatorial Pacific Ocean every three to five years and it can last up to 18 months. This has been commonly associated in the past with poor rainfall in South Asia.

Severe cases of El Niño (see chart), as in the 1997-98 and its related impact had caused deaths of hundreds of people and caused billions of dollars in damages in an estimated 15 countries, especially in the Panama Canal region and the east coast of Africa.

Ashish Sen, director, Patna meteorological centre, claimed that occurrence of El Niño does not necessarily mean that it would lead to drought conditions in Bihar. Based on data on sea surface temperature in the equatorial Pacific Ocean and monsoon rainfall in India between 1881 and 2013, Sen has recently studied the correlation between El Niño and drought conditions in India and particularly Bihar.

“I have assessed that eastern parts of the country, including states like Bihar, Jharkhand and Bengal, were comparatively well-off with regard to monsoon rainfall even during major drought years across the country owing to the El Niño impact. This is basically because of the fact that monsoon rainfall in eastern India is largely influenced by local weather factors over the Bay of Bengal as well,” said Sen.

The Met chief added that monsoon depressions — severe low-pressure conditions over the Bay of Bengal are the biggest factors influencing monsoon rainfall in eastern India.

“Normally, 10 to 11 depressions form over the bay during the monsoon months. According to the present conditions, the sea surface temperature in the bay looks favourable. Thus, we expect that normal number of depressions would form during the monsoon months, which, in turn, would keep the total rainfall at around 99 per cent even if the country as a whole receives deficient rainfall due to El Niño,” said Sen.

Pradhan Parthsarthy, secretary, Bihar chapter of India Meteorological Society and professor at Central University of Bihar, who has also studied El Niño, also claimed that formation of monsoon depressions would be crucial to avert drought conditions in the state for the third consecutive year.

The state received 30 per cent deficient rainfall in the 2013 monsoon, making it the lowest rainfall in the past decade. The monsoon rainfall in 2012 was 20 per cent deficient.