The 2005–06 South Pacific cyclone season was an event in the annual cycle of tropical cyclone formation. It began on November 1, 2005, and ended on April 30, 2006. These dates conventionally delimit the period of each year when most tropical cyclones form in the southern Pacific Ocean east of 160°E. Additionally, the regional tropical cyclone operational plan defines a tropical cyclone year separately from a tropical cyclone season, and the "tropical cyclone year" runs from July 1, 2005, to June 30, 2006.

Tropical cyclones between 160°E and 120°W and north of 25°S are monitored by the Fiji Meteorological Service in Nadi. Those that move south of 25°S are monitored by the Tropical Cyclone Warning Centre in Wellington, New Zealand.

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Seasonal forecasts SourceRecord TropicalCyclone SevereTropical Cyclone Ref Record high: 1997–98:16 1982–83:10 Record low: 2003–04: 3 1994–95: 1 FMS 7–9 - Activity during the season: 5 3

During October 2005, both RSMC Nadi and New Zealand's National Institute of Water and Atmospheric Research issued seasonal forecasts which contained information on what was expected to occur during the 2005–06 tropical cyclone season. Both agencies expected that the season would see a near average amount of tropical cyclone activity due there being no El Niño or La Niña. As a result of these conditions RSMC Nadi predicted that between 7–9 tropical cyclones would develop while NIWA did not predict how many tropical cyclone there would be during the season. RSMC Nadi also reported that Fiji had a higher chance of being hit by a tropical cyclone this season than during recent previous seasons. NIWA also predicted that there was an average risk of a tropical cyclone coming within , of: Fiji, Tonga, Niue, Vanuatu, New Caledonia, Wallis and Futuna, the Southern Cook Islands, Samoa, and New Zealand.

Seasonal summary

Systems

Tropical Depression 03F

Formed on December 8 and dissipated on December 18, 2005.

Tropical Cyclone Tam

Tropical Depression 04F formed about to the north-northeast of Fiji on January 6, which moved slowly westward. Although the depression was located within an area of low wind shear, little intensification occurred, as a lack of low-level moisture hindered the development of deep convection. By January 9, shower and thunderstorm activity associated with the disturbance increased as it began to interact with the South Pacific Convergence Zone. Another tropical depression developed in the vicinity, but weakened. The following day, the RSMC Nadi upgraded Tropical Depression 04F to a tropical cyclone and gave it the name Tam, making it the first named storm of the 2005–06 season. Several hours later, the storm passed close to Niuafo'ou with winds of . By 0000 UTC on January 13, the JTWC classified Tam as Tropical Cyclone 06P. Tam strengthened further to attain winds of around 0600 UTC. However, with both wind shear and the forward motion of the storm continuing to increase, convection rapidly became dislocated from the center. Around 0000 UTC on January 14, Tam entered the area of responsibility of the Tropical Cyclone Warning Centre in Wellington, New Zealand as it moved quickly southward. Soon after, it transitioned into an extratropical cyclone, which dissipated early on January 15.

As Tam was developing, residents attempted to evacuate the island by plane, with the primary target of Fiji. Only a few flights took off before officials closed the airport, stranding numerous passengers. Late on January 11, RSMC Nadi placed Tonga and Futuna under a tropical cyclone alert and also placed Tonga and Wallis under a strong wind warning. On the next day RSMC Nadi placed northern Tonga and later Niue under a tropical cyclone gale warning. On January 11, Tropical Depression 04F produced a record of rain in a 24‑hour span on Rotuma. However, little damage resulted from the heavy precipitation. Cyclone Tam produced heavy rainfall in American Samoa which triggered damaging floods. Several buildings were flooded, and an estimated 70% of the island's crops were destroyed. Sustained winds of up to , with gusts reaching , tore a few roofs off unsecured homes. Scattered power outages were reported throughout the island. A few landslides were also reported as a result of the storm. Damage from the storm totaled $26,000 on the island. Relatively little damage was recorded in Futuna; there, the storm downed several trees and stranded a yacht on a reef. On Niuafo'ou, a weather station recorded sustained winds of with gusts of up to , along with a minimum pressure of 991 hPa (mbar). Minor damage, consisting of fallen branches and isolated power outages also occurred on Niue.

Tropical Depression 05F

Formed on January 10 and dissipated on January 13, 2006.

Tropical Cyclone Urmil

On January 13, Tropical Disturbance 06F formed over the open waters of the south Pacific Ocean, about 370 km (230 mi) west of American Samoa. Forming in the wake of Cyclone Tam, the disturbance rapidly organized within a favorable environment, including warm waters and moderate wind shear. RSMC Nadi upgraded 06F to Tropical Cyclone Urmil while the system was near Niuatoputapu, Tonga. At 0600 UTC on January 14, the JTWC classified Urmil as Tropical Cyclone 07P. The storm reached peak winds of 110 km/h (70 mph) according to both the RSMC Nadi and the JTWC, making it a high-end Category 2 cyclone on the Australian Scale. Stronger wind shear and faster forward motion caused the storm to become disorganized and devoid of convection. On January 15, Urmil transitioned into an extratropical cyclone, and was subsequently absorbed into the mid-latitude westerlies.

Upon being designated Tropical Disturbance 06F, tropical cyclone alerts and strong wind warnings were issued for Niue, Tonga, the Cook Islands, and French Polynesia. A flood advisory and small craft advisory were issued for Samoa. Early on January 14, 06F passed close to Tafahi and Niuatoputapu, produced heavy rains and near gale-force winds over the islands. The highest winds in Tonga were recorded on Niuatoputapu; sustained winds reached 35 km/h (25 mph) with gusts to 65 km/h (40 mph). The winds caused minor damages, mainly limited to vegetation. Some fruit trees were damaged, mainly banana trees. The rains from Urmil exaggerated flooding produced by Cyclone Tam just a few days earlier.

Tropical Depression 07F

The seventh depression of the season developed on January 15 as Urmil was dissipating. A weak system, 07F formed out of a slow moving tropical disturbance about north of Fiji. The system peaked in intensity with winds of later that day. On January 16, the low dissipated about west-northwest of Fiji.

Severe Tropical Cyclone Jim

Cyclone Jim originated in the Australian region, and moved into Fiji's area of responsibility on January 30. Jim gradually turned south-southeastward and became extratropical on February 1. The extratropical remnants of Jim (08F) lingered around and then moved northwest.

Despite being well to the west of that country, Cyclone Jim was blamed for extensive flooding in Fiji, with the western coast of the island of Viti Levu – including the city of Lautoka – inundated by floodwaters on January 29. No fatalities were reported in any of the areas affected by the cyclone.

Tropical Depression 10F

The tenth depression of the season formed on February 2 about southwest of Niue. High wind shear prevented significant strengthening, with winds peaking at and a minimum pressure of 998 hPa (mbar). Tracking erratically in a southerly direction, the depression slowly weakened as convection was displaced by wind shear. Tropical Depression 10F was last monitored on February 4 about southeast of Tongatapu.

Tropical Depression 11F

Formed on February 8 and dissipated on February 10, 2006.

Severe Tropical Cyclone Vaianu

Late on February 9, Tropical Depression 12F developed within a convergence zone about northeast of Vanua Levu. The depression tracked southeastward, although further development was initially inhibited by wind shear. During the next day, the depression turned towards the southeast and moved into a more favorable environment for intensification, with a ridge to its southeast. On February 11, it strengthened into a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale, and was named Vaianu. JTWC also designated the system as Tropical Cyclone 12P. On February 11, the system significantly organized, and at 1200 UTC that day, RSMC Nadi reported that the depression had intensified into a Category 1 tropical cyclone on the Australian tropical cyclone intensity scale; it was assigned the name Vaianu. Vaianu continued to strengthen, and passed west of Tonga. The JTWC reported that the cyclone peaked in intensity at 1200 UTC on February 13, with maximum sustained 1-minute winds of 140 km/h (85 mph). RSMC Nadi assessed the storm as having peaked slightly later, with 10-minute winds of 130 km/h (80 mph), which made it a Category 3 severe tropical cyclone. The storm held its strength for some time as it moved southward between Ono-i-Lau and Tongatapu. Beginning to accelerate, Vaianu entered the area of responsibility of the Tropical Cyclone Warning Centre in Wellington, New Zealand. It curved southeastward and slowly deteriorated due to increasing wind shear and colder sea surface temperatures. The JTWC downgraded it to a tropical storm on February 15, and by the next day it was undergoing extratropical transition. At 0600 UTC, the JTWC classified it as extratropical, but it remained a powerful storm system for several days as it tracked over the open ocean.

RSMC Nadi issued a tropical cyclone alert for Tonga, including a gale warning for the Vavau, Haapai, and Nomuka islands and a tropical cyclone warning for southern Tonga. Businesses in Nuku'alofa closed as the storm passed by. At Fuaʻamotu International Airport, sustained winds blew at , with gusts to . Rainfall there totaled . The storm caused power outages across its path that took up a week to fully restore. On Tongatapu and Eua, the storm inflicted extensive crop damage, and it is estimated that 70% of the banana crop was destroyed. In Nuku'alofa, the capital of Tonga, flooding of low-lying areas reportedly shut down the city for two days. The high winds brought down trees and dispersed debris throughout the region, while schools were forced to close. RSMC Nadi also placed the Lau Islands under a strong wind warning, and a damaging swell warning was declared for Fiji.

Tropical Depression 13F

Formed on February 19 and dissipated on February 26, 2006.

Severe Tropical Cyclone Wati

Tropical Depression 16F formed on March 17 and strengthened into Tropical Cyclone Wati on March 19 north of New Caledonia. It moved westwards and slowly strengthened into a Category 3 cyclone on the Australian scale before coming to a near standstill over the Coral Sea. After remaining stationary for most of March 22, Wati took a southeasterly course on March 23, gaining speed and continuing that course on March 24. A cyclone watch was issued for Lord Howe Island and a cyclone warning was issued for Norfolk Island. Wati passed between the two islands and became extratropical on March 25.

The remains of Wati brought heavy rain and strong winds to the North Island of New Zealand on March 26, with gusts of 140 km/h reported at Cape Reinga.

Other systems