Historical Variability of Southwest Pacific Tropical Cyclone Counts Since 1855

Tropical cyclones (TCs) represent a significant threat to people and places of the southwest Pacific (0 degrees-35 degrees S, 135 degrees E-120 degrees W). TC modeling is hindered by exceptionally short TC records (typically from 1970/1982 to present) because the brevity of TC data does not allow us to appropriately quantify TC-related risk and/or identify long-term trends/variability. Therefore, in this paper, we derive a series of statistical hindcast models to reconstruct TC counts in the western (135 degrees E-160 degrees E) and eastern southwest Pacific (160 degrees E-120 degrees W) regions to 1855. Reanalysis data representing Indo-Pacific sea surface temperature variability and genesis parameters required for tropical cyclogenesis were identified and trained on post-1970 TC observations and applied to the pre-1970 period. By hindcasting up to an additional 115 TC seasons, using four separate hindcasts, this study offers a unique perspective on historical TC variability and reiterates the need to place the recent downward trend in TC counts within the context of long-term variability.