The boreal summer intraseasonal oscillation (BSISO) is one of the dominant phenomena of summertime atmospheric variability in the tropics. The BSISO influences summer monsoon onsets and interacts with a wide range of atmospheric circulation patterns and associated weather. As the occurrence of and concern over extreme events rises, high-quality BSISO forecasts will become increasingly important.

The BSISO forecast service is now available at http://www.apcc21.org/eng/service/bsiso/fore/ japcc030601.jsp, with contributions from four operation centers in cooperation with the WMO Commission for Atmospheric Sciences (CAS)/World Climate Research Program (WCRP) Working Group on Numerical Experimentation (WGNE) Madden Julian Oscillation (MJO) Task Force. The APCC BSISO forecasts are displayed in phase space using newly developed indices that represent BSISO activity with northward propagation over the off-equatorial monsoon domain.

From observations, the Changma onset may be influenced by the BSISO, which showed a northward propagating component about 20 days before the onset. Moreover, the development of strong and long Changma activity may be related to the summertime subtropical anticyclonic circulation over the western North Pacific and small convective anomalies to the north on an intraseasonal time scale.

1. INTRODUCTION

2. DATA AND METHODOLOGY

2.1 Data

2.2 Methodology

3. RESEARCH RESULTS

3.1 Construction of the BSISO real-time forecast system

3.2 Relationship between the BSISO and EASM

4. CONCLUDING REMARKS