Influence of ENSO on formation of tropical cloud clusters and their development into tropical cyclones in the western North Pacific

This study analyzes the influence of El Nino-Southern Oscillation (ENSO) on the activity of tropical cloud clusters (TCCs) in the western North Pacific (WNP). A TCC must have at least one embedded mesoscale convective system and it must persist for more than 24hours. In all, 2,248 TCCs were identified during July-October 1981-2009. While more (less) TCCs form in the eastern (western) part of the WNP during El Nino years than during normal years, the converse is true during La Nina years. The ratio of tropical cyclone (TC) numbers to TCC numbers (genesis productivity) was 27.3%, higher than found in previous study. TC genesis productivity does not correlate with the Oceanic Nino Index even in subregions of the WNP. The influence of ENSO on TC numbers in each subregion of the WNP was mainly due to changes in TCC number, not changes in TC genesis productivity.