The APEC Climate Center (APCC) commenced its Boreal Summer Intraseasonal Oscillation (BSISO) forecast for the year 2025 at its website from 1 May, 2025.

BSISO forecast plays an important role in predicting the beginning and the characteristics of the Asian summer monsoon. The Oscillation is a large-scale convection, with a period of 15 to 60 days. It originates over the Indian Ocean, gradually traveling eastward as well as north with a diverse structure. It affects the beginning of the Asian summer monsoon, circulation of atmosphere, and weather patterns. Also, BSISO forecast provides information that helps predict dry and wet seasons in Asia by tracing large scale zones of precipitation. It plays an important role in predicting hydrometeorological extreme weather phenomena. Users can therefore prepare for disasters like heavy rainfall, drought, and heat wave.

The NOAA un-interpolated OLR (Outgoing Longwave Radiation) data, which was input data of the APCC BSISO monitoring index, has been no longer provided since September 17, 2023. Therefore, the OLR input data has been changed to NOAA CPC blended data, and the BSISO service has commenced from May 2024.

APCC first provided BSISO forecast services at its website, in cooperation with the World Meteorological Organization (WMO), the Working Group on Numerical Experimentation (WGNE) and the Madden Julian Oscillation (MJO) Task Force on July 1, 2013.
 

BSISO Forecast Website :
https://www.apcc21.org/prediction/bsiso/intro?lang=en