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* Monsoon seen below average in some parts of Pakistan, S. Lanka
* Rains could be above average in Nepal and Bhutan
* El Nino phenomenon unlikely to influence monsoon-WMO expert
By Gopal Sharma
KATHMANDU, April 19 (Reuters) - India and its south Asian neighbours are set to avoid widespread drought for a fourth straight year, thanks to a normal monsoon in 2013, a global weather forum said on Friday, raising the prospect of bumper grain supplies to squeeze world food prices.
The June to September monsoon is vital for 55 percent of India's farmland, which has no irrigation facilities. For one of the world's largest agricultural producers, the rains can make the difference between being an exporter or importer of staples such as rice and sugar.
"This year's monsoon, as a whole, is most likely to be within the normal range," said D.S. Pai, lead forecaster of the Indian weather office, releasing the consensus forecast of the South Asian Climate Outlook Forum, a group of weather experts.
Forecasting the monsoon is difficult and India itself only makes two official attempts, one due on April 26 and another in June, when the rains should have covered half the country. It is working with many of the world's experts to improve accuracy.
The India Meteorological Department (IMD) has found it hard to predict extremes of weather and has twice gone wrong since 2005. Added to that, the monsoon can be patchy and last year, even though overall rains were ample, many areas had drought.
Agriculture accounts for about 15 percent of Asia's third-largest economy, with more than 800 million Indians living in rural areas. Ample harvests can also help keep a lid on food inflation, which is around a stubborn nine percent.
Forecasting has become a big event and private forecaster Skymet issued a party-style invitation for its predictions on Wednesday, which said rains would be average.
In March, Pai told Reuters that India was set for average rains in 2013.
The rains could be less than average in some parts of Pakistan and Sri Lanka, the forum said, while Nepal and Bhutan could get heavier showers.
"The more likely scenario is for below normal rainfall over some areas of northwestern and southern parts of south Asia, and for above normal rainfall in some areas along Himalayan region," Pai said, reading from the consensus statement.
Following bumper harvests in recent years, India is exporting wheat to keep the grain from rotting in overflowing bins.
World grain prices touched record highs late last summer after a bruising year that featured a historic U.S. drought, dryness in Eastern Europe and a third spike in global food prices in four years.
The next few months will be crucial as weather conditions in the United States, the world's top wheat exporter, will determine its harvest.
The El Nino weather phenomenon was unlikely to influence monsoon rains in the first half of the June-September season, the weather group said.
El Nino, an abnormal warming of waters in the equatorial tropical Pacific, is associated with poor rains or a drought-like situation in southeast Asia and Australia.
"El Nino is going to be neutral and continue to remain so," said Rupa Kumar Kolli, head of the climate applications and service division of the World Meteorological Organisation.
India's weather office rates as normal rainfall between 96 and 104 percent of a 50-year average of 89 centimetres during the entire four-month season. The last drought with rains below this range was in 2009 and before that, in 2004.
Last year, a late revival of the monsoon in the second half of the June to September rainy season helped India escape widespread drought, and the season ended with rainfall at 92 percent of the long period average.
But seven states in the country's south and west, including key sugar producer Maharashtra and cotton-producing Gujarat, had very low rainfall and are still battling acute drought that has hammered farmers' incomes and made this year's rains critical. (Additional reporting by Ratnajyoti Dutta in NEW DELHI; Writing by Jo Winterbottom; Editing by Clarence Fernandez)