Comments on “A GCM Simulation of the Relationship between Tropical Storm Formation and ENSO”

This paper presents a simple exploratory analysis of observational data to isolate the impact of ENSO on tropical cyclone activity in the western North Pacific, thus disputing the claim by Wu and Lau (1992), in their investigation of the influence of ENSO events on the variability of tropical storm formation, that it is difficult to isolate the impact of ENSO-related SST anomalies on tropical storm activity by using observational data alone. Tropical cyclone activity from 1960-1991 is examined, indicating a clear trend in the time series of the total number of tropical storms and typhoons in the March-January typhoon season. In addition, superimposing the August SST in the eastern equatorial Pacific with the March-January average Southern Oscillation index shows a remarkable coherence; the correlation coefficient between these two variables in -0.76. Attention is given to observed relationships between ENSO and the number distribution of tropical cyclones in the western North Pacific, where there is found no overall relationship between tropical cyclone numbers in the western North Pacific and the ENSO cycle. It is concluded that, in view of the observations, Wu and Lau's attempt to elucidate the nature of the relationship between tropical storm formation and ENSO with their GCM has failed to provide an accurate description of the role of ENSO on the character (particularly the annual storm totals) of tropical cyclone activity in the western North Pacific.