The 2009–10 South Pacific cyclone season began on December 3, 2009 with the formation of Tropical Disturbance 01F. This was 32 days after the season had officially begun on November 1, 2009 and ended on April 30, 2010. 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; the "tropical cyclone year" began on July 1, 2009 and will end on June 30, 2010. Tropical cyclones between 160°E and 120°W and north of 25°S are monitored by the Fiji Meteorological Service. Those that move south of 25°S are monitored by the Tropical Cyclone Warning Centre in Wellington, New Zealand. The first tropical disturbance of the season formed on December 3, about 1015 km (700 mi) to the north of Suva, Fiji.
RSMC Nadi released their seasonal prediction on October 21, 2009, and reported that the El Niño conditions for this season indicated that tropical cyclone activity would be near normal with eight to eleven tropical cyclones predicted to form within the South Pacific compared to an average of nine cyclones. They also reported that a slightly higher risk existed of a tropical cyclone affecting a country to the west of the International Date Line including Fiji while a near average risk of a tropical cyclone affecting an island to the east of the dateline was predicted. In March 2010, RSMC Nadi predicited that there would now be at least 10 Tropical cyclones, within the whole of the Southern Pacific.
New Zealand's National Institute of Water and Atmospheric Research (NIWA) also reported in their seasonal outlook that the conditions for this season indicated that tropical cyclone activity would be near normal with eight to eleven tropical cyclones predicted to form compared to an average of nine cyclones. They also reported that because of El Niño conditions that islands to the east of the International Date Line would face an increased risk of a tropical cyclone while the amount expected to move within 550 km (350 mi) of New Zealand was expected to remain about normal. On February 15, 2010, NIWA issued a seasonal forecast update and maintained their forecast of 8–11 named storms. They also reported that the Solomon Islands now faced an increased risk of a tropical cyclone affecting them.
The 2009–10 South Pacific cyclone season was near its climatological average, with eight tropical depressions intensifying into tropical cyclones within the South Pacific to the east of 160E, while one other system intensified into a tropical cyclone after it had left the basin. Tropical Cyclone Mick was the first tropical disturbance to grace the waters of the South Pacific Ocean during the season. Tropical Cyclone Mick originally developed as a Tropical Disturbance on December 3, and gradually developed before it was christened as Tropical Cyclone Mick late on December 12. During the next couple of days the disturbance, the system accelerated towards the southeast while gradually intensifying further before peaking on December 14, with 10-minute sustained windspeeds of 110 km/h, (65 mph) and 1-minute winds of 130 km/h, (80 mph). Later that day, Mick made landfall on Viti Levu to the northeast of Nadi and as a result of land interaction, Mick rapidly weakened and became an extratropical depression early the next day. On December 6, Tropical Disturbance 02F developed about 1000 km (620 mi) to the north of Suva, Fiji.
Late on December 3, RSMC Nadi reported that Tropical Disturbance 01F had developed out of a weak area of low pressure to the northeast of Fiji. Over the next few days the disturbance gradually developed before RSMC Nadi reported that it had intensified into a tropical depression late on December 11. During the next day the system intensified further with the JTWC starting to issue warnings declaring it as Tropical Cyclone 04P. Later that day RSMC Nadi reported that Mick had intensified into a category one tropical cyclone and named it as Mick, while it was located about 225 km, (140 mi) to the west of Rotuma. During the next day Tropical Cyclone Mick accelerated towards the southeast while gradually intensifying further, before during December 14, as Mick approached the Fijian island of Viti Levu, the cyclone developed an eye. RSMC Nadi then declared that Mick had peaked with 10 minute windspeeds of 110 km/h, (65 mph) while the JTWC reported that it had peaked with 1 minute winds of 130 km/h, (80 mph). Later that day, Mick made landfall on Viti Levu to the northeast of Nadi. As a result of land interaction, Tropical Cyclone Mick rapidly weakened and became an extratropical depression early the next day. The extratropical remnants of Tropical Cyclone Mick were tracked by RSMC Nadi and TCWC Wellington for another 2 days before they dissipated early on December 18 Just inside TCWC Wellington's area of responsibility.
At least 6 fatalities have been attributed to Mick.
Early on January 7, RSMC Nadi reported that an extratropical depression had formed about 770 km (480 mi), to the southwest of Papeete in French Polynesia and assigned it the designation of 03F. The depression dissipated on January 10.
Tropical Disturbance 04F formed on January 18 and strengthened to a Tropical Depression as it moved south-west through the Solomon Islands. On January 20 it crossed the 160°E meridian into the Australian Basin, where it developed into Tropical Cyclone Olga.
RSMC Nadi announced the formation of Tropical Depression 06F on January 27 near 14S 172W. This was only about 320 miles (510 km) NE of the position then being given for 05F and these may have developed from the same area of disturbed weather. Later the same day JTWC designated it as a Tropical Cyclone, and the RSMC allocated the name Nisha and it had dissipated on January 31.
Tropical Disturbance 07F formed on January 29 near 12S 177E. It was upgraded to a depression late on the 30th. On February 1, the JTWC designated 07F as 12P, and the RSMC upgraded it to Tropical Cyclone Oli. On February 3 it strengthened to become the first Severe Tropical Cyclone since Gene in early 2008.
At least one person was killed by large swells produced by the storm in French Polynesia.
Tropical Depression 09F formed on February 6 near 8ºS 166ºW, about 375 miles (604 km) east of Tokelau. On the 7th, the JTWC designated it as Tropical Cyclone 14P, and on the 8th RSMC upgraded it to become Tropical Cyclone Pat. By the 10th it reached Severe Tropical Cyclone strength as it moved towards the southern Cook Islands, and a hurricane warning was then issued for Aitutaki and its neighbours. The eye of the cyclone was reported to have passed right over Aitutaki, with continuous winds estimated locally at 100 knots for 4 hours. There was extensive damage to housing and a hospital, and the Cook Island government declared a State of Disaster.
Tropical Depression 10F formed on February 9 near 13S 172W, in the vicinity of Samoa. Late on February 11, RSMC Nadi upgraded the storm to a category 1 cyclone and named it Rene. It continued to strengthen as it moved south of American Samoa, and reached Category 4 on February 14. In American Samoa roads were damaged by landslides caused by the cyclone's heavy rain, and substantial damage was caused to crops. It had weakened to category 3 when it passed through the Vava'u island group of Tonga, and on February 15 the eye was reported to have passed over the Tongan capital Nuku'alofa. The main island of Tongatapu was left without power and water.
On February 17, RSMC Nadi commenced reporting on an unnumbered tropical disturbance located near 8.6ºS 162.0ºW, about 120 miles (190 km) north-northwest of Rakahanga in the Cook Islands. RSMC Nadi reported that the disturbance was moving west while the JTWC reported that the disturbance was moving east. Eventually, they both agreed on which direction it was moving and RSMC Nadi upgraded the disturbance to Tropical Depression 11F. It soon weakened, but remained identifiable until February 22 when it was again classified as a Tropical Depression. On February 26 it was at last upgraded to Tropical Cyclone Sarah and Tropical Storm by JTWC, being then about 90 miles (140 km) north of Palmerston Island.
Tropical Disturbance 13F formed on March 9 at 12.0ºS 167.0ºE, about 80 miles (130 km) north of Hiw Island, Vanuatu. The next day it was classified as a Tropical Depression. On March 12, 13F was upgraded to Tropical Cyclone Ului. By early on the 13th, it was a category 2 cyclone. Later that day, Ului strengthened into a category 3, making it a severe tropical cyclone. The storm continued to strengthen throughout the day and that night it became a category 5. Ului became the first category 5 South Pacific cyclone since Severe Tropical Cyclone Percy in February 2005. On March 14, Ului exited the Pacific Region and entered the Australian Region.
Shortly after the first advisory on Tropical Disturbance 13F was issued on March 9, the FMS began monitoring a new disturbance, designated 14F, further east. The following day, deep convection began to develop around the disturbance's low-level circulation, prompting the JTWC to begin monitoring it for possible cyclonic development. Later on March 10, the FMS upgraded the system to a tropical depression as it continued to become better organized. Located within an environment characterized by low wind shear, further intensification was anticipated as convection continued to develop over the expanding system. Around 1500 UTC on March 11, the JTWC issued their first advisory on the cyclone, classifying it as Tropical Storm 19P. Several hours later, the FMS upgraded the system to a Category 1 cyclone and gave it the name Tomas. Rapid intensification was expected to take place over the following 48 hours as sea surface temperatures ahead of the storm averaged 30 °C(86 °F), well-above the threshold for tropical cyclone development. Throughout the day on March 12, Tomas steadily intensified, and early the next day, the JTWC upgraded the storm to a Category 1 equivalent hurricane with winds of 120 km/h (75 mph).
Convective banding substantially increased on March 13, allowing Tomas to become the fourth severe tropical cyclone of the season early the next morning. Around the same time, the JTWC assessed the storm to have attained winds of 155 km/h (100 mph), ranking it as a Category 2 cyclone. By the afternoon of March 14, Tomas had developed a banding-eye feature surrounded by deep convection. At this point, the FMS assessed the storm to have winds of 150 km/h (90 mph) and a pressure of 950 hPa (mbar). The JTWC also noted further intensification, upgrading Tomas to a Category 3 equivalent storm. Tomas intensified on the night of March 14 and became a Category 4 severe tropical cyclone(according to the Fiji
Meteorological Service) with winds up to 170 km/h and gusts up to 215 km/h blowing roofs off some houses and damaging buildings around the eastern side of Vanua Levu.
Throughout Fiji, Cyclone Tomas wrought widespread damage, killing two people and leaving $83.4 million in losses. One person was killed on Vanua Levu after being swept out to sea by large swells while trying to rescue her two sisters, a niece and a nephew near Namilamila Bay.
Early on March 30, RSMC Nadi reported that a Depression had formed about 445 km, (275 mi) to the southeast of Port Vila in Vanuatu. The depression dissipated completely
on April 5.
The following weak tropical disturbances and depressions were also monitored by RSMC Nadi, however these systems were either short lived or did not develop significantly. During December 6, Tropical Disturbance 02F developed within a trough of low pressure about 1000 km (620 mi), to the north of Suva, Fiji. Over the next few days, the disturbance moved towards the southeast and remained weak, before it was last noted on December 11 as 01F developed into a tropical depression. Depression 03F, developed on January 7, about 770 km (480 mi) to the southwest of Pappette on the French Polynesian island of Tahiti.
This table lists all the storms that developed in the South Pacific to the east of longitude 160°E during the 2009–2010 season. It includes their intensity on the Australian Tropical cyclone intensity scale, duration, name, landfalls, deaths, and damages. All data is taken from RSMC Nadi and or TCWC Wellington. The Damage figures are all 2010 USD