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2020–21 South Pacific cyclone season
Season summary map
Seasonal boundaries
First system formed	December 8, 2020
Last system dissipated	Season ongoing
Strongest storm
Name	Yasa
• Maximum winds	250 km/h (155 mph) (10-minute sustained)
• Lowest pressure	899 hPa (mbar)
Seasonal statistics
Total disturbances	3
Total depressions	3
Tropical cyclones	2
Severe tropical cyclones	1
Total fatalities	None
Total damage	None
Related articles
2020–21 Australian region cyclone season 2020–21 South-West Indian Ocean cyclone season
South Pacific tropical cyclone seasons 2018–19, 2019–20, 2020–21, 2021–22, 2022–23

The 2020–21 South Pacific cyclone season is a currently ongoing period of the year when most tropical cyclones form within the South Pacific Ocean to the east of 160°E. The season officially started on November 1, 2020 and will end on April 30, 2021, however a tropical cyclone could form at any time between July 1, 2020 and June 30, 2021 and would count towards the season total. During the season, tropical cyclones will be officially monitored by the Fiji Meteorological Service (FMS), Australian Bureau of Meteorology (BoM), New Zealand's MetService. The United States Armed Forces through the Joint Typhoon Warning Center (JTWC) will also monitor the basin and issue unofficial warnings for American interests. RSMC Nadi attaches a number and an F suffix to tropical disturbances that form in or move into the basin while the JTWC designates significant tropical cyclones with a number and a P suffix. RSMC Nadi, TCWC Wellington and TCWC Brisbane all use the Australian Tropical Cyclone Intensity Scale and estimate windspeeds over a period of ten minutes, while the JTWC estimated sustained winds over a 1-minute period, which are subsequently compared to the Saffir–Simpson hurricane wind scale (SSHWS).

Seasonal forecasts

Ahead of the cyclone season formally starting, the Fiji Meteorological Service (FMS), Australian Bureau of Meteorology (BoM), New Zealand's MetService and National Institute of Water and Atmospheric Research (NIWA) and various other Pacific Meteorological services, all contributed towards the Island Climate Update tropical cyclone outlook that was released during October 2020. The outlook took into account the ENSO neutral conditions that had been observed across the Pacific and analog seasons, that had ENSO neutral and El Nino conditions occurring during the season. The outlook called for a near-average number of tropical cyclones for the 2020–21 season, with nine to twelve named tropical cyclones, predicted to occur between 135°E and 120°W, compared to an average of just over 10. At least four of the tropical cyclones were expected to intensify further and become severe tropical cyclones, while it was noted that a Category 5 severe tropical cyclone could occur during the season.

In addition to contributing towards the Island Climate Update outlook, the FMS and the BoM issued their own seasonal forecasts for the South Pacific region. The BoM issued two seasonal forecasts for the Southern Pacific Ocean, for their self-defined eastern and western regions of the South Pacific Ocean. They predicted that the Western region between 142.5°E and 165°E, had a 60% chance of seeing activity above its average of 4 tropical cyclones. The BoM also predicted that the Eastern Region between 165°E and 120°W, had a 45% chance of seeing activity above its average of 6 tropical cyclones. Within their outlook the FMS predicted that between four and six tropical cyclones would occur within the basin compared to an average of around 7. At least one of these tropical cyclones was expected to intensify further and become a Category 3 or higher severe tropical cyclone.

Seasonal summary

On December 8, a disturbance formed near Fiji, starting the 2020–21 South Pacific Ocean cyclone season, it gradually intensified into a depression and attained a tropical storm status according to JTWC. It reached at the maximum 10 minutes sustained wind speed of 55 km/h (35 mph) and minimum pressure of 1000 mb (29.53 inHg). Another disturbance formed near the existing 01F and rapidly intensified into a depression. It hampered the system intensification due to a brief interaction with Tropical Depression 01F. Following the same day, another disturbance formed and intensified into a depression in the next day. 01F became a remnant low and got absorbed by Tropical Depression 02F. On December 13, 15:00 UTC, 02F intensified into a Category 1 tropical cyclone Yasa according to Australian scale. Yasa is currently intensifying and is now a Category 5 according to Australian scale. Following the same day, 03F intensified into Category 1 tropical cyclone Zazu, strengthening to Category 2. Yasa became the most powerful tropical cyclone of 2020 beating Goni with a minimum barometric pressure of 899 mb (26.55 inHg) and maximum wind speed of 250 km/h (155 mph). It was also the fourth most intense South Pacific tropical cyclone after Winston, Zoe, Pam. While Zazu dissipated into an extratropical cyclone.

Systems

Tropical Depression 01F

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. 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. 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. At 00:00 UTC on December 11, the JTWC upgraded the system to a tropical storm on the Saffir–Simpson hurricane wind scale. 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). 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). However, environmental conditions were only marginally conducive for intensification, with strong vertical wind shear inhibiting further development. 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 centre of circulation fully exposed. Due to the deteriorating structure of the system, the FMS ceased advisories on Tropical Depression 01F at this time. 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.

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.

Severe Tropical Cyclone Yasa

Severe Tropical Cyclone Yasa
Current storm status Category 3 severe tropical cyclone (Australian scale)
Current storm status Category 2 tropical cyclone (1-min mean)
Satellite image Forecast map
As of:	18:00 FJT, December 17 06:00 UTC, December 17
Location:	16°54′N 179°48′E / 16.9°N 179.8°E / 16.9; 179.8 (Severe Tropical Cyclone Yasa) About 500 km (310 mi) NW of Suva, Fiji
Sustained winds:	105 knots (195 km/h; 120 mph) (10-min mean) 85 knots (155 km/h; 100 mph) (1-min mean)
Pressure:	920 hPa (27.17 inHg)
Movement:	ESE at about 11 knots (20 km/h; 15 mph)
See latest official information.

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. 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. 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. At the same time, the Joint Typhoon Warning Center (JTWC) issued a tropical cyclone formation alert for the system. The JTWC also noted a Fujiwhara interaction with 01F, which briefly hampered the development of the system. 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. 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. Soon afterwards, the JTWC upgraded Yasa to a Category 1-equivalent cyclone on the Saffir–Simpson scale.

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. 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). 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. 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).

Current storm information

As of 06:00 UTC December 17 (18:00 FJT December 17), Severe Tropical Cyclone Yasa is located near 16°54′S 179°48′E / 16.9°S 179.8°E / -16.9; 179.8 (Yasa), about 500 km (310 mi) northwest of Suva, Fiji. Maximum 10-minute sustained winds are 120 kn (220 km/h; 140 mph), while maximum 1-minute sustained winds are 115 kn (215 km/h; 130 mph). The minimum central pressure is 920 hPa (27.17 inHg), and the system is moving east-south east at 11 kn (20 km/h; 15 mph).

For the latest official information see:

• FMS's Special Weather Bulletin for Cyclone Yasa
• FMS's Tropical Disturbance Advisories for Cyclone Yasa
• JTWC's Tropical Cyclone Warning Text for Tropical Cyclone 05P (Yasa)

Tropical Cyclone Zazu

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. 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). 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. Zazu continued to strengthen even as it began an extratropical transition, reaching Category 2 status on the Australian scale on December 15, despite struggling with the effects of westerly wind shear. During December 16, the system moved into MetService's area of responsibility, before they reclassified it as an extratropical low later that day.

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. 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. Zazu also brought wind gusts up to 120 km/h (75 mph) to the island nation of Tonga, but no significant damage was reported.

Storm names

Within the Southern Pacific a tropical depression is judged to have reached tropical cyclone intensity should it reach winds of 65 km/h (40 mph), and it is evident that gales are occurring at least halfway around the center. With tropical depressions intensifying into a tropical cyclone between the Equator and 25°S and between 160°E - 120°W named by the FMS. However, if a tropical depression intensify to the south of 25°S between 160°E and 120°W it will be named by MetService in conjunction with the FMS. Should a tropical cyclone move out of the basin and into the Australian region it will retain its original name. The next 10 names on the naming list are listed here below.

Season effects

This table lists all the storms that developed in the South Pacific to the east of 160th meridian during the 2020–21 season. It includes their intensity on the Australian tropical cyclone intensity scale, duration, name, landfalls, deaths, and damages. All meteorological data is taken from the warning centers while damage estimates are in 2021 USD.

See also

• List of Southern Hemisphere cyclone seasons
• Tropical cyclones in 2020
• Atlantic hurricane seasons: 2020, 2021
• Pacific hurricane seasons: 2020, 2021
• Pacific typhoon seasons: 2020, 2021
• North Indian Ocean cyclone seasons: 2020, 2021
• 2020–21 South-West Indian Ocean cyclone season
• 2020–21 Australian region cyclone season

References

1. ^ Climate Services Division (October 26, 2010). Tropical Cyclone Guidance for Season 2010/11 for the Fiji and the Southwest Pacific (PDF) (Report). Fiji Meteorological Service. Archived from the original (PDF) on February 27, 2012. Retrieved October 17, 2016.
2. ^ 2020/21 RSMC Nadi Tropical Cyclone Outlook (PDF) (Report). Fiji Meteorological Service. October 15, 2020. Archived (PDF) from the original on October 20, 2020. Retrieved October 20, 2020.
3. ^ Southwest Pacific Tropical Cyclone Outlook - October 2020 (Report). National Institute of Water and Atmospheric Research. October 20, 2020. Archived from the original on October 20, 2020. Retrieved October 20, 2020.
4. ^ "South Pacific Tropical Cyclone Outlook for 2020 to 2021". Australian Bureau of Meteorology. October 20, 2020. Retrieved October 20, 2020.
5. Tropical Disturbance Summary December 8, 2020 09z (Report). Fiji Meteorological Service. December 8, 2020. Archived from the original on December 13, 2020. Retrieved December 13, 2020.
6. Significant Tropical Weather Advisory December 8, 2020 11z (Report). United States Joint Typhoon Warning Center. December 8, 2020. Archived from the original on December 13, 2020.
7. ^ Tropical Disturbance Summary December 11, 2020 09z (Report). Fiji Meteorological Service. December 11, 2020. Archived from the original on December 13, 2020. Retrieved December 13, 2020. Cite error: The named reference "TDS Dec 11 00z" was defined multiple times with different content (see the help page).
8. "Tropical Cyclone 04P Warning #1 (00Z)". Joint Typhoon Warning Center. Naval Meteorology and Oceanography Command. 11 December 2020. Archived from the original on 11 December 2020. Retrieved 11 December 2020.
9. ^ "Tropical Cyclone 04P Warning #3 (12Z)". Joint Typhoon Warning Center. Naval Meteorology and Oceanography Command. 11 December 2020. Archived from the original on 11 December 2020. Retrieved 11 December 2020.
10. ^ "Tropical Disturbance Summary (18Z)". Fiji Meteorological Service. 11 December 2020. Archived from the original on 12 December 2020. Retrieved 12 December 2020.
11. "Tropical Cyclone 04P Warning #5 (00Z)". Joint Typhoon Warning Center. Naval Meteorology and Oceanography Command. 12 December 2020. Archived from the original on 12 December 2020. Retrieved 12 December 2020.
12. ^ "Tropical Depression 01F Disturbance Advisory #4 (00Z)". Fiji Meteorological Service. 12 December 2020. Archived from the original on 12 December 2020. Retrieved 12 December 2020.
13. "Final Warning, Remnant of Tropical Cyclone 04P". Joint Typhoon Warning Centre. Retrieved December 12, 2020.{{cite web}}: CS1 maint: url-status (link)
14. Mary Gilbert (December 13, 2020). "Tropical Cyclone Yasa 1st of the season for South Pacific". yahoo.com. Yahoo! Entertainment, AccuWeather. Retrieved December 14, 2020.
15. ^ "Tropical Cyclone Formation Alert (TD 02F) (0330Z)". Joint Typhoon Warning Center. Naval Meteorology and Oceanography Command. 12 December 2020. Archived from the original on 12 December 2020. Retrieved 12 December 2020.
16. "Tropical Depression 02F Disturbance Advisory #1 (00Z)". Fiji Meteorological Service. 12 December 2020. Archived from the original on 12 December 2020. Retrieved 12 December 2020.
17. "Tropical Cyclone Formation Alert (Invest 91P)". Retrieved December 12, 2020.{{cite web}}: CS1 maint: url-status (link)
18. "Bulletin No. 06, Tropical Cyclone 04P". Retrieved December 12, 2020.{{cite web}}: CS1 maint: url-status (link)
19. "Tropical Cyclone 05P (Five) Warning #01". Joint Typhoon Warning Center. December 12, 2020. Archived from the original on December 12, 2020.
20. "Tropical Cyclone Yasa Disturbance Advisory 5 (13Z)". Fiji Meteorological Service. December 13, 2020. Archived from the original on December 13, 2020.
21. "TROPICAL CYCLONE 05P (YASA) WARNING NR 012". metoc.navy.mil. Joint Typhoon Warning Center. December 15, 2020. Retrieved December 15, 2020.
22. "Severe Tropical Cyclone Yasa Disturbance Advisoru Number 8 (00Z)". Fiji Meteorological Service. Archived from the original on December 15, 2020.
23. "Fiji Meteorological Service". www.met.gov.fj. Retrieved 2020-12-15.
24. "Tropical Cyclone 05P (Yasa) Warning #14". Joint Typhoon Warning Center. December 15, 2020. Archived from the original on December 15, 2020.
25. "Tropical Cyclone 06P Warning #1 (12Z)". Joint Typhoon Warning Center. Naval Meteorology and Oceanography Command. 13 December 2020. Archived from the original on 13 December 2020. Retrieved 13 December 2020.
26. "Tropical Cyclone Zazu, Storm Warning 054 (00Z)". Fiji Meteorological Service. December 15, 2020. Archived from the original on December 16, 2020. Retrieved December 16, 2020.
27. Tropical Cyclone Potential Bulletin December 16, 2020 23z (Report). New Zealand MetService. December 16, 2020. Archived from the original on December 16, 2020. Retrieved December 16, 2020.
28. "Category 2 Cyclone Zazu Update: Yellow Alert for Niue". Television Niue. 2020-12-15. Retrieved 2020-12-18.
29. "Niue's only wharf slammed by massive waves whipped up by Cyclone Zazu". TVNZ. Retrieved 2020-12-18.
30. "Tonga hit by Cyclone Zazu as second system strengthens". Tonga hit by Cyclone Zazu as second system strengthens. Retrieved 2020-12-18.
31. RA V Tropical Cyclone Committee (2024). Tropical Cyclone Operational Plan for the South-East Indian Ocean and the Southern Pacific Ocean 2024 (PDF) (Report). World Meteorological Organization. Retrieved October 14, 2024.

External links

• World Meteorological Organization
• Australian Bureau of Meteorology
• Fiji Meteorological Service
• New Zealand MetService
• Joint Typhoon Warning Center

v t e Tropical cyclones of the 2020–21 South Pacific cyclone season
	TD01F 5Yasa 2Zazu TD04F 3Ana TD06F 1Bina 2Lucas TD09F DI10F DI11F 5Niran TD13F
Category

• 2020–21 South Pacific cyclone season
• South Pacific cyclone seasons
• Southern Hemisphere tropical cyclone seasons