Climatology of Tropical and Transitional Extratropical Cyclones in the New Zealand Region

While tropical cyclones (TCs) that affect New Zealand (NZ) have usually completed or are in the process of completing extratropical transition, they retain the ability to inflict the same damage that was possible prior to their transition. This region, therefore, can be affected by the rapid onset of strong gale or storm force winds, extensive flooding, large storm surges, and severe coastal erosion. This study will provide a comprehensive analysis of tropical cyclones in the NZ region, including those that have transitioned to extratropical status, using the United States Joint Typhoon Warning Center (JTWC) “best track” database. Various NZ-centered domains were created to objectively categorize the cyclones. Cyclones that entered the latitude/longitude box [30S– 60S ; 150E – 180E] were classified as cyclones in the NZ region. Those that crossed a 300-mile radius of the NZ coastline were categorized as ‘affecting' NZ, and were considered as well as cyclones that made landfall. Metrics for these cyclones, such as their interannual variability of seasonal cycle characteristics (monthly maximum wind speeds, TC intensity, mean season start and end times and length, most vulnerable regions, and birthplace) will be calculated for each of the above domains. A wavelet analysis is performed to determine possible relationships between the 41-year (1970-2010) time series of TCs in the NZ region and major climate system oscillation modes.