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. The most damaging tropical disturbance was Cyclone Ofa, one of the strongest storms to affect Samoa in the 20th century, which caused at least in damage to multiple countries and left eight dead. Cyclone Nancy caused in damages to Queensland and NSW, Australia and killed four people. During the formative stages of Cyclone Peni, the system caused in damages to the Cook Islands. Cyclone Rae drowned three people in Fiji but caused only 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 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 and the Naval Western Oceanography Center 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.
On December 19, the remnants of Tropical Cyclone Felicity, moved into the basin with 10-minute sustained windspeeds of 75 km/h, which would have made it a category 1 tropical cyclone on the Australian scale. However, because it did not have the "classical characteristics of a tropical cyclone", it was treated as a tropical depression by the BoM and the FMS. Over the next couple of days, in response to an upper level trough of low pressure weakening, the depression slowly weakened further, while accelerating to towards the southeast. Felicity was absorbed by a short-wave trough of low pressure to the north of New Zealand before it was last noted during December 22.
On January 20, TCWC Nadi started to monitor a shallow area of low pressure that had developed within a trough of low pressure, about to the Northwest of Noumea in New Caledonia. The depression was last noted on January 25, as it moved into TCWC Wellington's area of responsibility. There were no reports of any damage associated with this depression within New Caledonia, which was largely due to its small and not so intense nature of the system.
On January 27, a shallow tropical depression formed within the South Pacific Convergence Zone, about to the southeast of Funafuti, Tuvalu. Over the next two days the system developed little and remained slow moving, near the Tuvaluan atoll of Funafuti. During January 30, the depression moved towards the north-east and started to organize, as pressures near the systems center rapidly falling. During the next day the system subsequently started to curve south-eastwards and away from Tuvalu, before the NWOC initiated advisories on the system and designated it as Tropical Cyclone 13P. Late on January 31, TCWC Nadi named the tropical depression Ofa, after it had developed into a category 1 tropical cyclone on the Australian scale. Over the few days the system moved towards the south-southeast and intensified further. Ofa subsequently passed about to the west of the Western Samoan Island of Savai'i between 10:00 and 18:00 UTC during February 3. Early the next day as the system started to accelerate towards the south-southeast towards the island nation of Niue, the NWOC estimated that Ofa had peaked with 1-minute sustained wind speeds of 215 km/h, which made it equivalent to a category 4 hurricane on the SSHWS. Later that day TCWC Nadi also estimated that the system had peaked with 10-minute sustained wind speeds of 185 km/h as a category 4 severe tropical cyclone,. During February 5, the system passed about to the west of Niue, as it started to weaken and started to transition into an extratropical cyclone. The system completed this transition during February 8, before the remnants were last noted during February 10 after they had performed a small clockwise loop. Cyclone Ofa affected seven different island nations and caused gales or much stronger winds in six of those countries which resulted in damage ranging from moderate to very severe. Storm tide from the cyclone which is the combined effect of storm surge and high tide caused havoc in several countries and was the major cause of destruction. Overall the system killed at least eight people while it was estimated that the overall damage would amount to over with damage totals of at least and in Western and American Samoa.
Tropical Cyclone Nancy
Late on January 30, TCWC Nadi started to issue warnings on a tropical depression, that was intensifying as it moved southeastwards and approached 160°E and the South Pacific tropical cyclone basin. The system subsequently moved into the basin early the next day and was named Nancy by TCWC Nadi, after it had become a category 1 tropical cyclone. During that day the system re-curved and started to move towards the south-southwest, as it was steered around the southern extension of an upper level trough of low pressure. The system subsequently moved out of the basin during February 1, as it intensified into a category 2 tropical cyclone. While the system was in the basin the JTWC estimated that Nancy had peak 1-minute sustained winds of 215 km/h, which made it equivalent to a category 1 hurricane on the SSHWS. The system subsequently re-entered the basin as an extratropical cyclone on February 6, before it dissipated to the west of New Zealand on February 8. There was no damage associated with Nancy while it was in the basin, however it later caused 5 deaths, when it affected the Australian states of Queensland and New South Wales.
Samoa Depression
On February 6, the FMS reported that a depression had developed, within the South Pacific Convergence Zone near the islands of Tuvalu. Over the next few days the system was steered towards the southeast by a north-westerly steering flow on the eastern side of an upper level trough of low pressure. As the depression moved towards the southeast it passed in between Western Samoa and the northern islands of Tonga before it came very close to Niue during February 8. Despite marginal gale-force winds being present in the depressions eastern quadrant, strong north-westerlies prevented the depression, from strengthening into a tropical cyclone. The depression was subsequently last noted during February 9, as it was absorbed into the Westerlies. The only damage that could be attributed to the depression is a number of houses that were destroyed on the Tuvaluan atoll of Vaitupu on February 6, however it is possible that the houses were destroyed by the strong and squally north-westerlies that were prevailing over the northern islands of Tuvalu at that time. As Tuvalu, Western Samoa, American Samoa, Tonga, Niue had all been affected by Cyclone Ofa a few days earlier; any damage would have been difficult to assess.
Severe Tropical Cyclone Peni
Tropical Cyclone Hilda
During March 7, Tropical Cyclone Hilda moved into the basin from the Australian region, as a category 2 tropical cyclone while it was located about to the northeast of Noumea, New Caledonia. During that day, the system passed about to the south-west of New Caledonia, as it moved south-southwestwards and degenerated into an extratropical depression. Over the next couple of days, the system moved through the Tasman Sea and passed near New Zealand's South Island, before it was absorbed into a high-latitude trough of low pressure.
Tropical Cyclone Rae
On March 16, TCWC Nadi started to monitor a shallow tropical depression that had developed within the South Pacific Convergence Zone, about to the west of the Tuvaluan Islands. The system initially moved slowly towards the south — southeast and passed about to the east of the Fijian Dependency of Rotuma during March 18. Over the next 24 hours the system moved southwards before it turned towards the southwest during March 19, as it approached and started to affect the Fijian Islands. At this time the depression appeared disorganised in satellite imagery, with estimated sustained windspeeds of between in a broad area to the north and east of the depression center. During the next day the depression passed about to the west of the Yasawa group of islands as it continued to move towards the southwest.
Other systems
The following depressions were also monitored by TCWC Nadi, however these systems were either short lived or did not develop significantly. Between November 8–10 and December 14–17, TCWC Nadi monitored 2 depressions that had developed near the Southern Cook Islands and the Samoan Islands. On March 15, the precursor shallow tropical depression to Cyclone Ivor developed within the South Pacific convergence zone, about to the northeast of Port Villa in Vanuatu. During that day, the low moved towards the southwest and moved into the Australian region where it developed into Tropical Cyclone Ivor during March 16.
Season effects
This table lists all the storms that developed in the South Pacific basin during the 1989–90 season. It includes their intensity on the Australian Tropical cyclone intensity scale, duration, name, areas affected, deaths, and damages.
