New Delhi, April 19: India’s weather agency today predicted normal rainfall this year in its first long-range forecast for the 2011 monsoon, but said sea surface temperatures in the Indian and Pacific oceans could influence updated forecasts.

The monsoon rainfall from June through September is likely to be 98 per cent of the long-period average over India, the India Meteorological Department said in a forecast that has predicted a 53 per cent probability of normal rainfall over the country as a whole.

The forecast does not compute the rainfall distribution in India’s four geographical zones — the southern peninsula, central India, northwest India, and northeast India. The IMD said it would predict the geographical distribution of rainfall only in June.

Senior IMD scientists said this early forecast is based on five weather parameters relating to the north Atlantic Ocean, the south Indian Ocean, the equatorial Pacific Ocean, and east Asia and northwestern Europe.

“Two of these parameters are favourable for the monsoon and three are neutral,” said D. Shivanand Pai, director of long-range forecasts at the IMD, Pune. “Over the next month, we’ll take into account more weather observations for a detailed updated forecast.”

India had experienced a normal monsoon — 102 per cent of the long-period average of 89cm — during 2010, with the season becoming wetter and wetter — a deficient monsoon in June, but in excess in September. Over the past decade, India has experienced three drought years — 2002 with 19 per cent deficient rainfall, 2004 with 13 per cent deficient rainfall and 2009 with rainfall deficiency touching 22 per cent.

IMD scientists said the distribution of rainfall during the 2011 monsoon season could depend on the predicted behaviour of the sea surface temperatures in the Indian and Pacific oceans during the coming months.

A phenomenon called La Nina favourable for a good monsoon — cooler-than-average sea surface temperatures in the Pacific Ocean — now appears to be weakening, with Pacific Ocean temperatures swinging towards average values.

A rise in sea surface temperatures of the Pacific — the El Nino phenomenon — has in the past been linked to poor monsoon performance. “But we know of only two years in weather history when La Nina quickly switched to El Nino — 1964 and 1971,” Pai said.

An independent monsoon forecasting exercise by Indian and foreign scientists has cautioned that the sea surface temperature features in the Indian Ocean appear to be evolving into a pattern that tends to weaken the Indian monsoon.

“This is expected to evolve only during the second half of the year — July onwards — and this has a concurrent effect on the monsoon,” Pai said. “As of now, we do not expect this to have much impact on the monsoon this year.”

The international South Asian monsoon forecasting exercise initiated by the IMD had also predicted below normal rainfall in parts of India’s northwest and the northeast, and excess rainfall in the southern peninsula.