The 2008–09 South Pacific cyclone season was a below average tropical cyclone season, which featured six named tropical cyclones compared to an average of about nine. Ahead of the season officially starting on November 1, 2008, the Island Climate Update tropical cyclone outlook predicted that the season, would feature an average risk of tropical cyclones impacting the South Pacific between 160°E and 120°W. The first tropical disturbance of the season developed to the northeast of the Samoan Islands on December 1, however, it remained weak and was last noted during the next day.

Seasonal forecasts Ahead of the cyclone season formally starting on November 1, 2008, New Zealand's MetService and National Institute of Water and Atmospheric Research (NIWA), the Fiji Meteorological Service (FMS), as well as various other Pacific Meteorological services, all contributed towards the Island Climate Update tropical cyclone outlook that was released during September 2008. The outlook took into account the ENSO neutral conditions that had been observed across the Pacific, as well as analogue seasons that had a similar climate background. The outlook noted that on average eight to ten tropical cyclones occur between 135°E and 120°W during seasons, with neutral ENSO conditions. It was also predicted that there was a normal risk of tropical cyclones occurring over most of the Pacific and that the first named tropical cyclone would occur before the end of December. The outlook also assessed the risk of a tropical cyclone affecting a certain island nation or territory and noted that several tropical cyclones, usually occurred in the region between Vanuatu, New Caledonia, Fiji and Tonga. Most areas including Vanuatu, New Caledonia, Fiji, Tonga, Niue and Tuvalu, were thought to have an average risk of being impacted by one or more tropical cyclones. The Northern Cook Islands and the Tuamotu Islands were thought to have reduced risk, while it was thought unlikely that Pitcairn Island, Kiribati and the Marquesas would be impacted by a tropical cyclone.

During January 2009, a revised Island Climate Update tropical cyclone outlook was issued, which stated that La Niña conditions had redeveloped in the tropical Pacific and were expected to persist. As a result, they noted that on average six or seven tropical cyclones, could be expected to develop over the Pacific Ocean, during a season characterised by a weak La Niña. They also noted that the risk of a tropical cyclone impacting a certain island nation or territory had changed with an increased risk for areas to the west of the International Date Line. In particular, the Solomon Islands, Vanuatu, New Zealand, New Caledonia now had an increased risk, while Fiji had a variable risk of being affected by one or more tropical cyclones. The Northern Cook Islands, Tonga, Niue, Wallis and Futuna, Samoa and Tokelau were thought to have a reduced risk of being impacted, while other areas such as the Southern Cook Islands, Tuvalu and Papua New Guinea had an average risk of being affected by a tropical cyclone.

Season summary

During the season, a total of fifteen significant tropical disturbances were monitored and numbered by the Fiji Meteorological Service (FMS), within the South Pacific basin between 160°E and 120°W. Off these tropical disturbances, six became named tropical cyclones, while none developed into severe tropical cyclones for the first time since the 1994–95 season. The first tropical disturbance of the season developed on December 1, while the final system Tropical Disturbance 15F was last noted in the basin during April 10.

Notable systems include Tropical Depression 04F, which caused Fiji's second worst natural disaster at the time. Tropical Depression 08F, which intensified into Cyclone Hettie, was the first tropical cyclone to form during the season. Tropical Depression 10F brought heavy rains to Vanuatu and before making landfall on New Caledonia intensified into Tropical Cyclone Innis. After it made landfall, Innis became the first Tropical Depression to move into TCWC Brisbane's Area of responsibility since Cyclone Larry. Cyclones Joni and Ken both threatened the Southern Cook Islands however they only delivered minimal impacts. Cyclone Jasper then moved into the region early on March 24 at peak intensity, having developed inside TCWC Brisbane's area of responsibility two days earlier. The final named storm to develop during the season was Tropical Cyclone Lin, near the Lau Group of Fiji and Tonga.

Systems

Tropical Depression 02F

Early on December 3, RSMC Nadi reported that a Tropical Disturbance had formed near the Southern Cook Islands and was located in a moderately sheared environment and was moving towards the southeast. Deep Convection had been present around a well-defined cyclonic circulation for the previous 24 hours. Over the next day the disturbance gradually developed with RSMC Nadi upgrading it to a Tropical Depression later that day whilst it was moving between Niue and the Southern Cook Islands. Over the next couple of days the depression gradually weakened with convection which was located in the southern and eastern quadrants became sheared and the low level circulation centre became exposed as it moved into an area of cooler sea surface temperatures. Late on December 6 RSMC Nadi issued their final advisory on the depression as it moved into TCWC Wellingtons area of responsibility and was expected to become a mid latitude low-pressure system within 12 hours.

Tropical Depression 04F

On January 4, the FMS reported that Tropical Depression 04F had developed within a low to moderate area of vertical windshear, about to the northeast of Port Vila in Vanuatu. At this stage the system's low to mid-level circulation centre was poorly organised and exposed while atmospheric convection was displaced to the north of the system.

Over the next couple of days the depression moved towards the southeast, before on January 8 as it started to bring heavy rainfall to Fiji. RSMC Nadi then issued their final advisory on it later that day, as it was now an extratropical depression. However, late the next day RSMC Nadi started to reissue advisories on the depression and immediately passed primary warning responsibility for it to the Tropical Cyclone Warning Center in Wellington, who issued warnings on the depression until early on January 12 when they issued their last advisory.

Floods and mudslides caused by the depression killed at least eleven people in Fiji. Several towns and rural areas on Viti Levu were flooded.

Tropical Depression 05F

On January 11, RSMC Nadi reported that a tropical depression had formed to the south of the Solomon Islands and was just inside TCWC Brisbane's area of responsibility, and started issuing Tropical Disturbance Summaries on it. As the depression moved into RSMC Nadi's area of responsibility it was designated as 05F. Nadi reported at this time that whilst the depression had a low to moderate chance of forming into a tropical cyclone within 48 hours, there was an upper trough of low pressure that could provide an opportunity for the depression to either rapidly or explosively develop. Despite fair conditions, it dissipated without ever becoming a cyclone.

Tropical Depression 06F

Late on January 19, RSMC Nadi reported that a tropical disturbance had formed in a monsoonal trough of low pressure about 940 km to the north west of Papeete, in French Polynesia. Convection was confined to the northeast of the low level circulation and was disorganised. Late the next day whilst the disturbance was moving to the east and into an area of higher vertical wind shear, RSMC Nadi upgraded the disturbance to a tropical depression despite its low level circulation centre being exposed and lying to the west of the deep convection. During the next morning as it interacted with another disturbance to the northwest the depression reached its peak wind speeds of Over the next couple of days th depression moved towards the south before late on January 23 RSMC Nadi issued their final advisory on the depression as it was expected to become a hybrid system within 24 hours.

Tropical Depression 07F

On January 23, RSMC Nadi reported that a Tropical Depression had formed, to the southwest of American Samoa. Later that day as the Depression moved towards the east they downgraded the Depression to a Tropical Disturbance as the Low Level Circulation Center was exposed and located in an environment of moderate to strong vertical wind shear. During the morning of January 24 the Tropical Disturbance was reupgraded to a Tropical Depression and assigned the Tropical Depression the designation of 07F. Later that day the tropical depression reached its peak wind speeds of . Early the next day RSMC Nadi released their final Tropical Disturbance Summary as the Tropical Depression had lost all tropical characteristics.

Tropical Cyclone Hettie

On January 24, RSMC Nadi reported that Tropical Disturbance 08F had developed within the monsoon trough and an area of minimal vertical windshear to the north of the Fijian dependency Rotuma. During the next day the disturbance moved towards the southeast and developed into a tropical depression while it was located near Rotuma. Over the next 3 days, the depression continued to move south-eastwards between Fiji and Tonga while intensifying slowly against stronger vertical windshear. before RSMC Nadi and the JTWC reported that the depression had developed into a tropical cyclone during January 28.

Cyclone Hettie did not directly affect any inhabited land areas.

Tropical Depression 09F

On February 1, RSMC Nadi reported that Tropical Depression 09F had developed within the monsoon trough about to the northeast of Port Vila, Vanuatu.

Late on February 1, a Tropical disturbance formed about to the west of Vanuatu and was embedded in a monsoonal trough. It quickly organized itself and thus later that day, it was upgraded to Tropical Depression 09F. At this time the Low Level Circulation Center was exposed as strong vertical wind shear and deep convection was displaced to the north of Low Level Circulation Center. The next morning the JTWC reported that deep convection, was located over the western boundary, of the depression's low level circulation center. Strong shear also still existed over the system, with deep convection still being displaced to the north of the system. The next morning RSMC Nadi reported that the Low Level Circulation Center was obscured with indications of good inflow bands flowing into the depression from the north and west.

Early on February 5, RSMC Nadi issued its final advisory on the depression, as the systems low level circulation centre had become sheared and exposed.

Tropical Cyclone Innis