2020–21 South Pacific cyclone season

Tropical depression (Australian scale)
Tropical storm (SSHWS)
Duration	December 8 – December 12
Peak intensity	55 km/h (35 mph) (10-min)  998 hPa (mbar)

During December 8, the FMS reported that Tropical Disturbance 01F had developed about 145 km (90 mi) to the northeast of Apia in Samoa.[5] At this stage, the system had a broad low level circulation and was located within a marginal environment for further development, with warm sea surface temperatures as well as moderate levels of vertical wind shear.[6] Over the next couple of days, the system gradually moved westwards before the FMS classified it as a tropical depression during December 11, while it was located about 280 km (175 mi) to the west of the Fijian Dependency of Rotuma.[7] At 00:00 UTC on December 11, the JTWC upgraded the system to a tropical storm on the Saffir–Simpson hurricane wind scale.[8] The depression continued to consolidate, with deep convection wrapping into the centre of the system from the northern semicircle, and by 12:00 UTC, one-minute sustained winds had increased to 75 km/h (45 mph).[9] A few hours later, the FMS estimated maximum 10-minute sustained winds to be at 55 km/h (34 mph), with a minimum central atmospheric pressure of 998 hPa (29.47 inHg).[10] However, environmental conditions were only marginally conducive for intensification, with strong vertical wind shear inhibiting further development.[9] By 00:00 UTC on December 12, both the JTWC and the FMS reported that the shear had displaced the system's deep convection to the northeast, leaving the center of circulation fully exposed.[11][12] Due to the deteriorating structure of the system, the FMS ceased advisories on Tropical Depression 01F at this time.[12] The storm then weakened and degenerated into a low pressure system later on December 12. Because of the Fujiwhara effect, the remnant was absorbed by Tropical Depression 02F shortly afterward, which would later become Severe Tropical Cyclone Yasa.[13]

01F caused heavy rain in American Samoa, with a peak rainfall total of 62 mm (2.44 in) recorded at the Pago Pago International Airport.[14]

Category 5 severe tropical cyclone (Australian scale)
Category 5 tropical cyclone (SSHWS)
Duration	December 11 – December 19
Peak intensity	250 km/h (155 mph) (10-min)  899 hPa (mbar)

Tropical Disturbance 02F was first noted by the FMS during December 11, while it was located about 800 km (495 mi) to the northeast of Port Villa in Vanuatu.[7] Environmental conditions were very favourable for tropical cyclogenesis, with radial outflow in the upper troposphere, low vertical wind shear, and sea surface temperatures near 30 °C (86 °F). Convective rainbands began to develop around the system as it tracked slowly eastwards, wrapping into the low-level circulation centre.[15] At 00:00 UTC on December 12, the Fiji Meteorological Service (FMS) upgraded the system to Tropical Depression 02F, and began issuing forecast track maps.[16] At the same time, the Joint Typhoon Warning Center (JTWC) issued a tropical cyclone formation alert for the system.[15] The JTWC also noted a Fujiwhara interaction with 01F, which briefly hampered the development of the system.[17][18] At 15:00 UTC December 12, the JTWC determined the system had strengthened into Tropical Cyclone 05P and was now producing winds up to gale force, while it absorbed the remnant of Tropical Depression 01F.[19] About a day later, on December 13, the FMS determined that the depression had further strengthened to Category 1 status, as convection continued wrapping into the center, with the storm acquiring the name Yasa.[20] Soon afterwards, the JTWC upgraded Yasa to a Category 1-equivalent cyclone on the Saffir–Simpson scale.[21]

The storm continued to intensify and soon became a Category 3 on the Australian scale. Just about 12 hours later on December 14, Yasa rapidly intensified to Category 4 status on the Australian scale as a defined eye began to clear on infrared satellite imagery.[22] The storm continued rapidly intensifying and strengthened to a Category 5 tropical cyclone on the Australian scale, the highest rating possible, whilst completing its loop, with a central pressure of 929 mbar and wind speeds of 110 knots (125 mph).[23] This was the earliest date a Category 5 South Pacific tropical cyclone formed on record and only the second Category 5 South Pacific tropical cyclone recorded in the month of December. Yasa continued its rapid intensification trend and further intensified to the equivalent of a high-end Category 4 tropical cyclone on the Saffir–Simpson scale (SSHWS), developing a well-defined and very clear eye, while continuing to become more symmetrical.[24] By 00:00 UTC on December 16, Yasa had intensified into a Category 5-equivalent tropical cyclone on the SSHWS, with 1-minute sustained winds of 260 km/h (160 mph). At 18:00 UTC, Yasa's maximum 10-minute sustained winds increased to 250 km/h (155 mph), with a minimum atmospheric pressure of 899 hPa (26.55 inHg),[25] making the system one of the most intense tropical cyclones ever recorded in the Southern Hemisphere. After making landfall, Yasa moved into an area of unfavourable conditions, causing the storm to rapidly weaken, with Yasa weakening into a Category 3 severe tropical cyclone later that day. Yasa continued its weakening trend as it turned southward, dropping to Category 1 tropical cyclone status late on December 18. Late on December 19, Yasa transitioned into an extratropical storm, and the FMS issued their final advisory on the storm. Afterward, Yasa's extratropical remnant moved southward and then eastward, before dissipating on December 24, to the northeast of New Zealand.

Category 2 tropical cyclone (Australian scale)
Tropical storm (SSHWS)
Duration	December 11 – December 16
Peak intensity	95 km/h (60 mph) (10-min)  980 hPa (mbar)

During December 11, the FMS reported that Tropical Disturbance 03F had developed about 480 km (300 mi) to the northeast of the island nation of Niue.[7] Deep convection near the system was initially only fragmented; however, environmental conditions were assessed as being conducive for development, with low vertical wind shear, good upper-level outflow and sea surface temperatures near 29 °C (84 °F).[10] The system's organisation improved steadily over the next few days, and at 12:00 UTC on December 13, the Joint Typhoon Warning Center (JTWC) upgraded the depression to a tropical storm on the Saffir-Simpson hurricane wind scale.[26] Zazu continued to strengthen even as it began extratropical transition, reaching Category 2 status on the Australian scale on December 15, despite struggling with the effects of westerly wind shear.[27] During December 16, the system moved into MetService's area of responsibility, before they reclassified it as an extratropical low later that day.[28] Zazu's extratropical remnant continued southward for another day, before turning eastward on December 18, and dissipating a day later.

Yellow cyclone alerts (the third-highest level) were issued for the island of Niue on December 15, while residents were taken to higher grounds by officials.[29] Zazu brought heavy surf which severely damaged the wharf on Niue which was recently rebuilt while bringing rainy conditions to the island that same day.[30] Zazu also brought wind gusts up to 120 km/h (75 mph) to the island nation of Tonga, but no significant damage was reported.[31]

Tropical depression (Australian scale)
Duration	January 22 – January 28
Peak intensity	Winds not specified  999 hPa (mbar)

During January 22, the FMS reported that Tropical Disturbance 04F had developed about 700 km (435 mi) to the northwest of Noumea in New Caledonia.[32] At this stage, the system was poorly organised and lied under the western edge of an upper-level ridge of high pressure in a low to moderate area of vertical windshear. Early on January 27, the storm strengthened into a tropical depression.[33] The FMS ceased advisories on the system, late on January 28.[34]

Category 3 severe tropical cyclone (Australian scale)
Category 1 tropical cyclone (SSHWS)
Duration	January 26 – February 1
Peak intensity	120 km/h (75 mph) (10-min)  970 hPa (mbar)

During January 26, the FMS reported that Tropical Disturbance 05F had developed within the South Pacific convergence zone about 220 km (135 mi) to the northeast of Port Vila in Vanuatu.[35][36] During that day, the system moved eastwards and developed into a tropical depression, within an area of low to moderate vertical wind shear.[37] Over the next couple of days, the system moved eastwards and gradually developed further, as atmospheric convection started to wrap into the systems low level circulation center.[38] During January 29, the FMS reported that the depression had developed into a Category 1 tropical cyclone on the Australian scale and named it Ana.[39][40] At this time, the system was located about 350 km (215 mi) to the northwest of Nadi in Fiji and had started to be steered south-southeastwards towards Fiji, by a ridge of high pressure to the northeast of the system.[40] The United States Joint Typhoon Warning Center subsquently initiated advisories, on the newly named system and designated it as Tropical Cyclone 15P.[36]

During January 30, Ana continued to move south-southeastwards and passed through the northern Yasawa Islands into the Bligh Waters, where it became slow-moving and intensified into a category 2 tropical cyclone.[41] The system subsequently continued to develop with an eye feature appearing on both radar and microwave imagery, before it made landfall on Viti Levu near Rakiraki at around 18:00 UTC (06:00 FST, January 31).[41][42][43] While located over Viti Levu, Ana moved south-southeastwards over the Central Division, where it passed in between Navua and Fiji's capital city: Suva.[41] The JTWC subsequently reported that the system had peaked with 1-minute sustained winds of 120 km/h (75 mph), which made it equivalent to a Category 1 hurricane on the Saffir-Simpson hurricane wind scale.[44] During January 31, Ana emerged into the Kadavu Passage and passed near or over Kadavu, before the FMS reported that the system had peaked as a Category 3 severe tropical cyclone, with 10-minute sustained winds of 120 km/h (75 mph).[44][45] During February 1, the system rapidly weakened into a subtropical low, as its low-level circulation center became exposed and moved south-eastwards into an area of high vertical wind shear.[46][47][48] Over the next few days, Ana moved south-eastwards over the South Pacific Ocean as a subtropical low, before it was last noted during February 3.[44]

Tropical depression (Australian scale)
Duration	January 27 – January 28
Peak intensity	Winds not specified  996 hPa (mbar)

During January 27, the FMS reported that Tropical Disturbance 06F had developed near the Lau Island of Nayau, about 250 km (155 mi) to the east of Suva, Fiji.[49] At this stage, the system was poorly organised and located to the south of a ridge of high pressure, in an area of moderate to high vertical wind shear.[49] Later that day the system developed into a tropical depression and caused gale-force winds over the Lau Islands, before it was last noted by the FMS during the next day as it moved out of the tropics.[50] Strong winds and heavy rainfall associated with the depression affected Tonga on January 29.[51]

Category 1 tropical cyclone (Australian scale)
Tropical storm (SSHWS)
Duration	January 29 – January 31
Peak intensity	65 km/h (40 mph) (10-min)  995 hPa (mbar)

During January 29, the FMS reported that Tropical Disturbance 07F had developed about 700 km (435 mi) to the north-northeast of Port Vila in Vanuatu.[52] On the evening of January 31, the depression intensified further to Tropical Cyclone Bina. However, Bina soon became very disorganized and was downgraded to a tropical depression on the morning of February 1.[53] It further weakened to an area of low pressure on the same day as it became even more disorganized.

Despite not being classified as a tropical cyclone at landfall, Bina extended the heavy rains and gale winds associated with Cyclone Ana which struck the islands hours before.[54] The Prime Minister Frank Bainimarama urged the public to continue being aware and be cautious of continued flash floods.[55]

Category 2 tropical cyclone (Australian scale)
Category 1 tropical cyclone (SSHWS)
Duration	February 1 (Entered basin) – February 3
Peak intensity	110 km/h (70 mph) (10-min)  975 hPa (mbar)

On the afternoon of February 1, Tropical Cyclone Lucas moved into the basin from the Australian region as a Category 2 tropical cyclone, to the northwest of Port Vila in Vanuatu.[56] Lucas maintained a steady southwestward heading during its time in the basin,[57] and gradually weakened under increasing vertical wind shear. Lucas's LLC became exposed as it weakened to a Category 1 cyclone on the Australian scale and began to undergo subtropical transition just north of New Caledonia on February 2, at which time the JTWC ceased warnings on the storm.[58] Shortly after, Lucas made landfall in New Caledonia at 18:00 UTC that day as a Category 2 tropical cyclone.[59]

In the Loyalty Islands, numerous homes, telecommunication systems, and electrical lines were damaged.[60] An estimated 6,338 people lost power in the country during the cyclone's passing.[61] Drinking water was contaminated and communication was cut off for over 36 hours.[62][63]

Tropical depression (Australian scale)
Duration	February 7 – Present
Peak intensity	55 km/h (35 mph) (10-min)  996 hPa (mbar)

On February 7, a weak tropical disturbance formed near the Lau Island of Cikobia, to the north of Nadi, Fiji.[64] The JTWC issued a TCFA on the disturbance at 15:00 UTC the next day, designating it as Invest 92P.[65]

For the latest official information see:

• FMS's Special Weather Bulletin for Tropical Depression (09F)
• FMS's Tropical Disturbance Advisory for Tropical Depression (09F)
• FMS's Forecast Track Map for Tropical Depression (09F)
• JTWC's Tropical Cyclone Formation Alert for Invest (92P)

If a tropical cyclone enters the South Pacific basin from the Australian region basin (west of 160°E), it will retain the name assigned to it by the Australian Bureau of Meteorology. The following storms were named in this manner:

• Lucas (named by BOM)