During the 1990-91 season a total of eleven tropical cyclones affected the South Pacific and southeast Indian Ocean basins, of which five reached hurricane intensity (ten-minute mean wind speed in excess of 120 km h- 1). There was a total of 64 cyclone days spanning the period late November to mid-May, including 16 hurricane days. Sina and Joy caused damage costing US55 million, accounting for over 95 per cent of the total cyclone damage in the basin. Eight lives were lost; six of these were associated with Joy and two with Fifi. Key features of the broadscale circulation included: a more active than normal westerly monsoon in the Australian region; a weaker than normal South Pacific convergence zone (SPCZ) and an anomalously weak long wave trough over eastern Asia (with fewer cross-equatorial surges over western Indonesia and the Indian Ocean). The Madden-Julian oscillations (MJO) were weaker and less regularly defined than in the preceding two seasons. The Southern Oscillation Index (SOI) was generally negative but small. Sea-surface temperatures (SST) remained above average in the equatorial central Pacific and warm SST anomalies, although generally small, persisted in the tropical Indian Ocean.
Bannister et al. (1993) studied this question.