Vietnamese weather stations can only provide accurate forecasts for 24 hours at a time, the country's top meteorological official admitted at a conference in Hanoi Wednesday.
Bui Minh Tang, director of the National Center for Hydro-Meteorological Forecasting, said forecasts for any period beyond that are only for "reference" purposes.
Most attendees agreed this weakness had led to wrong predictions about some recent storms, including the latest one, Vicente, the fourth of this year.
"The storm [Vicente] changed direction five times, sometimes very suddenly," he said.
"It was really a big challenge for meteorologists."
Vicente made landfall over China in late July, bringing torrential rains in northern Vietnam that killed 12 people and caused damage worth VND50 billion (US$2.4 million).
Tang said Vietnam can only provide general weather forecasts, not specific forecasts for storms over the country and the East Sea.
"Vietnam's storm forecasts mostly depend on international agencies."