2011–12 South Pacific cyclone season

The 2011–12 South Pacific cyclone season was one of the least active South Pacific tropical cyclone seasons on record, with only three tropical cyclones occurring during the season. The season ran from November 1, 2011, to April 30, 2012, however, any tropical cyclones that form before June 30, 2012, would have fallen within the 2011–12 tropical cyclone year and would have counted towards the season total. The strongest and only severe tropical cyclone that occurred during the season was Severe Tropical Cyclone Jasmine, which tracked in from out of the South Pacific basin. Within the basin, tropical cyclones are monitored by the Regional Specialized Meteorological Center (RSMC) in Nadi, Fiji, and the Tropical Cyclone Warning Center (TCWC) in Wellington, New Zealand. RSMC Nadi attaches an F designation to tropical disturbances that form in or move into the South Pacific. The United States Joint Typhoon Warning Center (JTWC) issues unofficial warnings within the South Pacific, designating tropical storm-equivalent or greater tropical cyclones with a number and a P suffix. RSMC Nadi and TCWC Wellington both use the Australian Tropical Cyclone Intensity Scale, and measure windspeeds over a period of ten minutes, while the JTWC measures sustained winds over a period of one minute and uses the Saffir–Simpson hurricane scale.

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Seasonal forecasts Source/Record Region TropicalCyclone SevereTropicalCyclones RefRecords Average (1969–70 – 2010–11): 160°E – 120°W 9 4 Record high: 160°E – 120°W 1997–98: 16 1982–83:10 Record low: 160°E – 120°W 2003–04: 3 2008–09: 0 Predictions FMS 135°E – 120°W 5–8 4–5 NIWA October 135°E – 120°W 5–8 — NIWA February 135°E – 120°W 8–10 — Actual activity: 160°E – 120°W 3 1

Ahead of the season officially starting on November 1, the Fiji Meteorological Service (FMS) and New Zealand's National Institute of Water and Atmospheric Research (NIWA), both issued a tropical cyclone outlook that discussed the upcoming season. These outlooks took into account a variety of factors such as a developing weak to moderate La Niña event and what had happened in previous seasons such as 1971–72, 1974–75, 1976–77, 1983–84, 1985–86, 1985–86, 2000–01, 2005–06, 2007–08 and 2008–09. The Southwest Pacific tropical cyclone outlook issued by New Zealand's National Institute of Water and Atmospheric Research (NIWA) in conjunction with MetService and various other Pacific meteorological services, predicted that five to eight tropical cyclones would occur over the South Pacific Ocean between 135°E and 120°W. The outlook also predicted that one of these tropical cyclones would intensify further and become either a Category three, four or five severe tropical cyclone on the Australian tropical cyclone intensity scale.

In addition to contributing towards the Southwest Pacific tropical cyclone outlook, the FMS predicted that between five and eight tropical cyclones would occur within the basin, while four or five of these tropical cyclones were expected to intensify further and become either a category three, four or five severe tropical cyclone on the Australian scale. Both outlooks also predicted that the majority of systems would occur to the west of the International Dateline, which as a result meant that New Caledonia and Vanuatu had a high chance of being impacted by a tropical cyclone. It was also predicted that Fiji, Tonga and the Cook Islands had a moderate to high risk of being impacted by a tropical cyclone, while Niue, Wallis & Futuna, Samoa and the Solomon Islands all had a moderate risk. During February 2012, after two tropical cyclones had already occurred in the Australian region, NIWA updated its seasonal outlook and suggested that between 8 and 10 tropical cyclones would occur over the region during the season.

Seasonal summary

Despite predictions of between 5-8 tropical cyclones occurring within the South Pacific Basin, with only two tropical cyclones developing in the basin, while Jasmine moved in from the Australian region. The first tropical disturbance of the season developed on November 13, to the north-east of Fiji and moved south-eastwards before it weakened into an area of low pressure during November 17, as it affected Fiji.

On February 6, Cyclone Jasmine moved into RSMC Nadi's area of responsibility, and became the first named tropical cyclone since Tropical Cyclone Bune, the previous March, to exist in the South Pacific basin.

Systems

Tropical Disturbance 01F

On November 13, an area of low pressure located within the South Pacific convergence zone started to rapidly develop further. RSMC Nadi then declared the low-pressure area: Tropical Depression 01F later that day, while it was located about 400 km (250 mi) to the north of Suva, Fiji. During the next day, the disturbance moved towards the southwest and onto the main Fijian Islands before convection surrounding the system started to weaken due to land interaction. The disturbance remained over the Fijian Islands until November 16, before RSMC Nadi issued their final advisory on the system as 01F had dissipated. Within Fiji, torrential rainfall was experienced on November 14, over the whole of the Fijian islands, which lead to widespread flooding of low-lying areas, while strong winds prevailed over the Lau and Lomaiviti group of islands during the next day as the rain gradually eased.

Tropical Depression 02F

Early on December 28, RSMC Nadi reported that Tropical Disturbance 02F had developed within an area of moderate windshear, about 140 km (90 mi) to the southeast of Alofi on the island of Niue. During the next day, the disturbance moved towards the east, before it developed into a tropical depression during the next day.

Tropical Disturbance 03F

On January 7, RSMC Nadi started to monitor a tropical disturbance that had developed about 240 km (150 mi), to the southeast of Lifuka, Tonga. Over the next 24 hours the disturbance persisted in a weekly sheered environment to the southeast of an upper-level outflow centre. However late the next day, RSMC Nadi reported that the disturbance was not expected to develop any further and issued their final advisory on the system, since convection had been irregularly surrounding the system during that day.

Tropical Depression 04F

On January 8, RSMC Nadi reported that Tropical Depression 04F had developed, about to the west of Papeete on the French Polynesian island of Tahiti. 04F had an exposed low level circulation centre and was situated to the east of a trough of low pressure and to the west of an area of enhanced convection. Over the next 24 hours, convection surrounding the system became increasingly displaced to the far east of the exposed low level circulation centre because of strong vertical wind shear. As a result, RSMC Nadi issued their final warning on 04F, late on January 9.

Tropical Disturbance 05F

Late on January 8, RSMC Nadi reported that Tropical Disturbance 05F had developed within a trough of low pressure, about 460 km (285 mi) to the southeast of Apia, Samoa. Over the next few days the disturbance did not develop any further, before RSMC Nadi issued their final advisory on the disturbance during January 10.

Tropical Depression 06F

On January 19, RSMC Nadi reported that Tropical Disturbance 06F, had developed along an active trough of low pressure to the north of Fiji. Over the next couple of days, the disturbance moved towards the south before it developed into a tropical depression and moved across Vanua Levu during January 21. Over the next few days the depression, remained near stationary over central parts of the country and caused widespread heavy rainfall and strong winds, over Fiji's Northern and Eastern divisions which lead to flooding. The depression was last noted on January 25, as it weakened and moved off Fiji and started to move towards the southeast.

Tropical Depression 07F

The RSMC Nadi reported that a tropical disturbance formed near Vanuatu on January 26, and strengthened into a tropical depression on January 29. But on February 1, 07F rapidly became disorganized, and as it began an extratropical transition, the RMSC Nadi issued their last advisory on the storm. On February 2, 07F completed its extratropical transition, and thus it was dropped from the RMSC Nadi's advisories.

Tropical Depression 08F

On January 25, RSMC Nadi reported that a shallow tropical depression, had developed over the northern Lau Islands, within a weak surface trough of low pressure. Over the next couple of days the depression moved southwards through the Lau and Lomaiviti islands and moved into an area of moderate to high vertical windshear. The depression was last noted by RSMC Nadi on January 28, as it moved out of the Fijian archipelago.

Tropical Depression 09F

On January 30, RSMC Nadi reported that a tropical depression had developed about 250 km (150 mi) to the northeast of Port Vila, in Vanuatu. On January 31, RSMC Nadi issued their last advisory on 09F, as the system rapidly became disorganized.

Between February 1 and 4, a convergence zone associated with the remnants of Tropical Depression 09F, affected Fiji and caused widespread rainfall over the islands.

Tropical Depression 10F

On February 2, the RSMC Nadi reported that a tropical depression had formed east of New Caledonia. For the 4 few days, 10F began to accelerate towards the southeast. However, late on February 6, the storm weakened below tropical disturbance intensity, and the RSMC Nadi issued their last advisory on the storm.

Tropical Cyclone Cyril

During February 5, Tropical Depression 11F developed about to the north-east of Nadi, Fiji.

On February 5, the FMS reported that a tropical disturbance had developed, about 310 km (190 mi) to the southeast of Nadi, Fiji. During that day the disturbance moved towards the northeast and passed through the Fijian islands, while convection surrounding the system increased and organized before it was declared a tropical depression early the next day. Later that day as the system started to move towards the southeast it rapidly consolidated further with the JTWC and the FMS both reporting that the depression had developed into a tropical cyclone, with the later naming it Cyril as it moved south-eastwards through the Tongan islands. Early on February 7 after Cyril had moved through Tonga, the JTWC reported that Cyril had peaked with 1-minute windspeeds of , which made it equivalent to a tropical storm.

The system subsequently reported later that day that Cyril had become a category 2 tropical cyclone, with 10-minute peak windspeeds of . Later that day as the system moved below 25S and out of RSMC Nadi's area of responsibility, Cyril weakened and became a category 1 tropical cyclone. During February 8, Cyril transitioned into an extratropical cyclone and became embedded in the westerlies, before the system was last noted by TCWC Wellington during the next day while located over to the northeast of Wellington, New Zealand. Within the Fijian Islands, Cyril caused heavy rain, high seas, strong and gusty winds, before it brought gale-force winds and torrential rain to Tonga. As a result, some flooding and minor damage to vegetation and plantations was reported in parts of the Vava'u group of islands with fruit bearing trees such as breadfruit and banana trees, severely affected.

Severe Tropical Cyclone Jasmine