A striking early-summer event of a convective rainband persistent along the warm Kuroshio in the East China Sea

A narrow, well-defined rainband persisted over the East China Sea on 19–20 May 2010, well separated from the Baiu/Meiyu front to its north. The rainband formed along the Kuroshio, leading us to the hypothesis that its high sea-surface temperature (SST) helped organise and maintain convective precipitation within the warm, moist surface southerlies. This hypothesis is verified through a pair of experiments with a regional atmospheric model. An experiment where high-resolution SST is prescribed as the lower-boundary condition is successful in reproducing the observed rainband. The reproduction is, however, unsuccessful in the other experiment where the narrow band of SST maxima along the Kuroshio has been artificially eliminated by smoothing. These experiments demonstrate that the high SST along the Kuroshio was of critical importance in organising the convective rainband separated from the Baiu/Meiyu front, thus presenting evidence that a mid-latitude western boundary current can influence the overlying atmosphere. Additional experiments suggest that the orography of Taiwan can also contribute positively to the organisation of the rainband by enhancing the convergence of the surface southerlies over the warm Kuroshio.