New Delhi, June 2: A government laboratory today predicted poor rainfall in June and July, filling gaps in the official monsoon forecast and fuelling concerns about crop yields.

Scientists at the Centre for Mathematical Modelling and Computer Simulation in Bangalore said rainfall would be 34 per cent below normal in June and 12 per cent below normal in July, a crucial month for agriculture.

However, the scientists clarified that they are not challenging the official forecast of the Indian Meteorological Department, saying their prediction is based on an experimental model.

“We’re not trying to replicate what the official agency is doing,” said Prashant Goswami, a senior scientist at the centre. “But this is an effort to develop better, more useful forecasts of the rainfall.”

The Met department forecasts rainfall for the entire monsoon season, from June through September. Scientists at the Bangalore centre used a different technique ? the general circulation models (GCM) ? that can predict the behaviour of rainfall during each of the four months and for specific regions.

They have also predicted 13 per cent excess rain in August, which may compensate for the deficit in the first half of the season.

However, the scientists added, July being an important month for crops such as rice, sugarcane, soybean and jute, “a 12 per cent deficit can be significant”.

“It is experimental work. I don’t think a GCM-based forecast for rainfall will be ready for operational use for another three years,” said Madhavan Rajeevan, head of the monsoon forecasting division at the Met department in Pune.

However, the Karnataka government had last year taken the centre’s predictions into account for agricultural planning.

“It took forecasts for 27 districts, monitored actual rain performance there and provided us feedback,” Goswami said.

The centre’s forecasts proved “quite successful” in 17 among 27 districts, but “failed miserably” in the other 10 districts, he added.

According to the Met department’s forecast, rainfall this year is expected to be 98 per cent of normal.

The onset of monsoon has been delayed this year, but the department said it has no relation to rainfall.