The country will receive above-normal rainfall, which will be 106% of the long-period average (LPA) – 890mm -- and central and southern India will be the wettest this year, the India Meteorological Department (IMD) said on Thursday in its second long-range forecast.
IMD has largely maintained its first long-range forecast but highlighted that the La Nina weather phenomenon will bring excess rainfall, especially in the second half, and the monsoon will be longer.
IMD categorises rainfall in the 96-104% LPA range as normal and rainfall between 104-110% of LPA as above normal.
The opposite of El Nino weather phenomenon, wherein warmer-than-usual Pacific waters trigger droughts in South Asia, La Nina brings heavy rainfall in South Asia. "There is 96% probability of excess rainfall and we are expecting an extended run for the monsoon. Once the monsoon arrives in Kerala in the next 4-5 days, it will make a speedy progress," said Laxman Singh Rathore, director general, IMD.
"Based on our assessments, we will sit down with the agriculture ministry and issue suitable advisories to farmers," Rathore said.
The Met department, in its revised forecast, also mentioned the region-specific rain forecast and forecast for rainfall in July and August. Central India and Southern Peninsula are likely to be the wettest with a forecast of 113% rainfall of the long-period average, which will be the maximum in the country.
The northwest of the country, covering Gujarat, Rajasthan, parts of Madhya Pradesh, Uttar Pradesh, Delhi-NCR and Haryana, is likely to receive 108% rainfall of the LPA while North-East will receive 94% rainfall of the LPA. Monthly rainfall over the country will be 107% of LPA in July and 104% of the LPA in August.
Senior Met officials said during the forecast release that El Nino has gone from a neutral to negative state and La Nina will come into play. "In general, Indian southwest monsoon is stronger than normal during La Nina years. There is a stronger association between La Nina and rainfall during the later half of the monsoon season, particularly with September rainfall," said D Sivanandan Pai, director, long-range forecasting division, IMD.
What they said in the past
IMD said during its first long-range forecast that there will be 94% probability of excess rainfall this monsoon
It said during the second long-range forecast that there will be 96% probability of excess rainfall this monsoon.
Between 1901 and 2015, there were 24 La Nina years.
In those 24 years, 16 years or 67% of them saw above-normal rainfall while seven years or 29% saw normal rainfall. Only one year saw below-normal rainfall
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