Twenty-three tropical cyclones formed in the South Pacific and southeast Indian Ocean during the 1997-98 tropical cyclone season. Of these, fifteen formed in the South Pacific east of 160°E, making the season for this region the biggest in terms of cyclone number and intensity in twenty years. Ten of these cyclones formed east of the date-line, an area used to little cyclone activity. Cyclone numbers in the Australian region were slightly less than average. The season was characterised by strong El Niño conditions, which peaked in the early months and had begun to decline by the end. Cyclone occurrences were linked to active phases of the 30 to 60-day intraseasonal oscillation.
Chappel et al. (Thu,) studied this question.