According to increasing hazard caused by high impact weather around the world, there is a growing need for reliable forecasts of high impact extreme event at subseasonal timescale. Boreal Summer intraseasonal Oscillation (BSISO) is well known as a potential source of S2S predictability as well as the main driver of subseasonal variability over the Asia-monsoon region. So BSISO impact on summer climate/weather over the region is also a budding research issue and it comes down to the needs of reliable BSISO forecast.

Since 2013, APEC Climate Center (APCC) has provided real-time BSISO information including forecast, monitoring and verification. Along with BSISO forecast, APCC has found the relationship between BSISO and high impact extreme events in order enhance the practical use of BSISO forecast by applying their relationship to the extreme event forecast.

In this study, we investigated how to apply and interpret the BSISO information to the tropical cyclone genesis over the western north Pacific (WNP). There was BSISO phase preference in the tropical cyclone genesis over the WNP region. During Jul.∼Oct., BSISO1 in phase 5,6,7 and BSISO2 in phase 8,1,2 could influence on the large-scale zonal wind related to monsoon trough and the trough could contribute to make favorable synoptic scale environment to tropical cyclone genesis over the WNP. In addition, we could identify the potential for practical use of BSISO in monitoring and predicting the extreme event about two weeks in advance by developing local Intreaseasonal Genesis Potential Index (ISGPI) for WNP region. It suggests the possibility for the good use of BSISO information in predicting TC genesis over the WNP region from the subseasonal forecast perspective.