Abstract
Although both the tropical cyclone (TC) peak seasons in 2016 and 1998 are in the decaying stage of a super El Niño, TC activities over the western North Pacific (WNP) exhibit vast differences. The TCs in 2016 feature more number, greater intensity and more distinct monthly variation of TC activity in contrast to those in 1998. The detailed comparison shows the warm sea surface temperature anomaly over the WNP in 2016 had a higher magnitude and a more eastward extension, compared with the case in 1998. Especially in August coincident with the enhanced Madden-Julian oscillation (MJO) westerly phase, more TCs clustered within the eastward-extending convective belt caused by the southwesterly surge. The mean longitude of TC genesis in 2016 shifted more eastward, favorable for the longer lifetime and greater intensity of the TCs. In terms of the extratropical influences, the cyclonic circulation anomaly associated with the Silk Road Pattern from the middle latitude penetrated southward and split the WNP subtropical high (WNPSH) into two components in August of 2016, causing the deep-tropospheric southerly steering flows in between and thus the TC northward-prone tracks. During the boreal autumn in 2016, the WNPSH was strengthened and stretched westward, producing the robust easterly steering flows that led to the successive TCs affecting the coastal areas of the East Asia.
