Some aspects of the summer monsoon in South-East Asia May to September 1986

In this report the rainfall pattern, onset, low-frequency oscillations and tropical storm activities over the South China Sea during the 1986 northern hemisphere summer monsoon are documented. On the whole, South-East Asia experienced below normal rainfall from May to September 1986. The onset date of the monsoon over South-East Asia was found to fall within the range of onset dates determined by Orgill (1967). There was a distinct 20 to 40 day oscillation in the surface pressure, upper wind and rainfall in South-East Asia during the monsoon. This oscillation was found to be related to the active and break cycle of the monsoon. Tropical storm/typhoon occurrence was below average for all the months except for May.