Shanghai's weather forecasters yesterday admitted they found it difficult to predict violent weather during the summer, such as the arrival of thunder or hail storms, and the situation would not improve in the short term.

Earlier, Qiao Lin, director of the Beijing Meteorological Observatory, said that on the Chinese mainland the accuracy rate of violent weather forecast was only 20 percent, "slightly lower than those of developed countries," when responding to people's complaints about an inaccurate forecast of a thunderstorm in the capital on Saturday.

The observatory had forecast rainstorms from Friday night to Saturday, but no rain fell. Qiao said that was because the rain belt had weakened and unexpectedly moved south.

Experts with the Shanghai Meteorological Bureau said that the problem of accurately predicting stormy weather was a long-term problem.

"Making forecasts about severe weather is one of the biggest difficulties of the whole weather forecast," said the bureau's Ding Ruoyang.

"We have so many factors to consider for the complicated weather phenomena, such as a convective weather phenomenon's strength and the specific area it would hit. Errors are inevitable," Ding said.

Ding said that in developed countries, the accuracy of violent weather was also around 20 percent, but they had a stricter standard. "As far as I am concerned, some developed countries wouldn't allow any error in the forecast, or they counted it as an inaccurate forecast, but we allow errors to some extent, such as in the calculation of rainfall," Ding said.

The Shanghai bureau said it expected that improved satellite technology would help in the long term with the ability to observe the whole process of the formation of thunder clouds allowing forecasts to be more timely and accurate.

"But it will take a very long time to make improvements," Ding said.