Saturday, June 5, 1999 Published at 09:13 GMT 10:13 UK
Last year's floods devastated parts of Asia
By Helen Briggs of BBC Science
Scientists say they might soon be able to forecast monsoon rains like the ones that brought heavy flooding to Asia last year.
They hope to use the twin cyclones that appear in the South China Sea to predict when the summer monsoon will come.
The research could help farmers in East Asia plan when to plant their crops and give authorities warning of floods.
Monsoons, which bring rain to the region during the summer months, are starting now in many areas of the world.
But no-one knows precisely when they will strike and how much rain they will bring.
Clues to monsoon
Dr William Lau says there seems to be a set pattern of events that precedes the monsoon.
"What we found is that in the middle of May there is this very strong and pronounced twin cyclones that seems to be propagating from West to East or propagating eastward in the Indian Ocean that seems related to increased activities of the southern bay of Bengal just before the onset of the South China Sea monsoon," he said.
The scientists used satellite data to study wind patterns over the Indian Ocean and the South China Sea.
They found that prior to the summer monsoon, storms over the Indian Ocean increased. These were in the form of cyclones, each covering an area twice the size of Texas, which travelled together eastwards over the equator.
Just before the monsoon started, the cyclones split up. The researchers are now planning more experiments to see if they can use such weather systems to forecast monsoons.
If they succeed, the information will be of great value to people living in low lying areas who need warning of heavy flooding.