The data used for this study includes radar and satellite images, vertical sounding and rainfall data, weather maps, and NCEP climate forecast system reanalysis (NCEP CFSR) data. Most of CCs occur in the eastern or the southeastern part of low-level cyclones (or troughs) propagating toward or along the northwestern flank of the western Pacific subtropical high (WPSH). The formation region of CCs is characterized by low-level convergence and transport of warm and moist air.
CCs generally move together with low-level cyclones (or troughs) or move along the fronts. HPSs within clusters show squall line movement or merge with each other. CCs consist of several line of convective rainfall embedded in continuous area of stratiform precipitation. Low-level convergence plays a crucial role in maintaining strong convection.