Cyclone intensification in the Kuroshio region and its relation to the sea surface temperature front and upper-level forcing

Abstract

The Northwest Pacific features strong sea surface temperature (SST) gradients providing favourable conditions for wintertime cyclone intensification in the midlatitudes. To estimate the relative contribution of the SST front to the evolution of cyclones and identify the mechanisms for cyclone intensification, we track individual cyclones and categorise them depending on their propagation relative to the SST front. We focus on cyclones remaining on either the cold or warm side of the SST front, as well as those crossing the SST front from the warm to the cold side. Cyclones crossing the SST front or remaining on its warm side propagate near the left exit region of the jet and are associated with higher precipitation, consistent with higher moisture availability and cyclone intensity. Comparing the different cyclone categories, there is no direct effect of the SST front on cyclone intensification. However, the SST front contributes to the climatological low-level baroclinicity, providing a conducive environment for cyclone intensification for the cyclones crossing the SST front. Compared with the Gulf Stream region, the land–sea contrast plays a less prominent role for the low-level baroclinicity in the Kuroshio region.