Climatological aspects of South Pacific tropical cyclones, based on analysis of the RSMC-Nadi (Fiji) regional archive

Abstract

This study analyses the regional cyclone archive for the tropical South Pacific (160° E-120°W, 0°-25° S) maintained by the designated Regional Specialized Meteorological Centre located at Nadi in the Fiji Islands. The historical cyclone record was examined over 4 decades from the 1969-1970 cyclone season to the 2007-2008 season. Cyclogenesis origins, minimum pressures, durations and track parameters (azimuth and length) of 291 individual storms were investigated. Temporal variability in separate cyclone parameters was highly variable but not necessarily matching on an interannual basis. Anomalous periods of cyclone behaviour can be detected in 1976, 1981, 1983, 1991, 1998, 2001-2002 and 2003. Strong and significant inter-relationships are indicated between storm longevity, track length and minimum sea-level pressure (MSLP) attained, and also between seasonally averaged measures of latitude of cyclone origin and the strength of the Southern Oscillation Index and Multivariate ENSO Index. Yet no overall long-term linear trends were detected in the data, with the exception of MSLP which showed a spurious decreasing trend-a problem already highlighted in other cyclone archives. These findings suggest that the South Pacific cyclone basin and the islands therein will continue to experience strong but irregular interannual fluctuations in cyclone and track characteristics. Such anomalies will remain a much more dominant feature of temporal patterns than possibly evolving changes in long-term average cyclone activity resulting from climate change. © Inter-Research 2010.