1989–90 South Pacific cyclone season

The 1989–90 South Pacific cyclone season was a below-average season with only five tropical cyclones occurring within the South Pacific to the east of 160°E. The season officially ran from November 1, 1989, to April 30, 1990, with the first disturbance of the season forming on November 8 and the last disturbance dissipating on March 19. This is the period of the year when most tropical cyclones form within the South Pacific Ocean.

During the season at least 15 people were killed from tropical disturbances whilst overall damage was estimated at $196 million. The most damaging tropical disturbance was Cyclone Ofa, one of the strongest storms to affect Samoa in the 20th century, which caused at least $180 million in damage to multiple countries and left eight dead. Cyclone Nancy caused $14 million in damages to Queensland and NSW, Australia and killed four people. During the formative stages of Cyclone Peni, the system caused $1 million in damages to the Cook Islands. Cyclone Rae drowned three people in Fiji but caused only $1 million (1990 USD) of damages to crops and vegetation. As a result of the impacts caused by Ofa and Peni, the names were retired from the tropical cyclone naming lists.

During the season, tropical cyclones were monitored by the Tropical Cyclone Warning Centers (TCWC) in Nadi, Fiji, and in Wellington, New Zealand. Whilst tropical cyclones that moved to the west of 160°E were monitored as a part of the Australian region. Both the United States Joint Typhoon Warning Center (JTWC) and the Naval Western Oceanography Center (NWOC) issued unofficial warnings within the southern Pacific. The JTWC issued warnings between 160°E and the International Date Line whilst the NWOC issued warnings for tropical cyclones forming between the International Date Line and the coasts of the Americas. Both the JTWC and the NWOC designated tropical cyclones with a number and a P suffix with numbers assigned in order to tropical cyclones developing within the whole of the Southern Hemisphere. TCWC Nadi, TCWC Wellington and TCWC Brisbane all use the Australian Tropical Cyclone Intensity Scale and estimate wind speeds over a ten-minute period, while the JTWC estimates sustained winds over a one-minute period, which are subsequently compared to the Saffir–Simpson hurricane wind scale (SSHWS).