The climatological relationship between tropical cyclones in the southwest pacific and the Madden–Julian Oscillation

The focus of this study is the climatological relationship between southwest Pacific Tropical Cyclone ( TC ) activity and the Madden–Julian Oscillation ( MJO ) on the interannual time‐scale. It investigates TC seasonal characteristics (e.g. cyclogenesis, track morphology, ex‐tropical transition, and intensity) as modulated by the phase and intensity of the MJO . The approach is novel as in addition to the focus on the intraseasonal variability of TCs there is also a focus on the interannual variability of TCs even though the MJO is an intraseasonal phenomenon. Links between the MJO , the Southern Annular Mode ( SAM ) and TC variability are also investigated. Using the MJO phases defined by Wheeler and Hendon (2004), southwest Pacific TC frequency exhibited a statistically significant decrease during MJO phases 2 and 3, and an increase during phases 6 and 7; and during the positive phase of the SAM , an increased frequency of TCs undergoing extratropical transition was observed. In summary, the results show a clear intraseasonal climatological relationship between specific phases of the MJO with respect to a decreased (increased) frequency of TCs during the paired MJO phases 2–3 (6–7); as well as the existence of a statistically significant relationship between the MJO and SAM with respect to the extratropical transition ( ETT ) of TCs . During positive phases of the SAM , coincident with weak interannual MJO phases 4–5 and 6–7, there are statistically significant greater frequency percentages of TCs undergoing ETT .