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Cyclone Yasa

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Not to be confused with Cyclone Yasi.
Severe Tropical Cyclone Yasa
Current storm status
Category 5 severe tropical cyclone (Australian scale)
Current storm status
Category 4 tropical cyclone (1-min mean)
Satellite image
Forecast map
As of:19:30 FJT, December 15
07:30 UTC, December 15
Location:14°48′N 173°06′E / 14.8°N 173.1°E / 14.8; 173.1 (Severe Tropical Cyclone Yasa)
About 580 km (360 mi) NW of Nadi
Sustained winds:110 knots (205 km/h; 125 mph) (10-min mean)
135 knots (250 km/h; 155 mph) (1-min mean)
gusting to 135 knots (250 km/h; 155 mph)
Pressure:929 hPa (27.43 inHg)
Movement:NE at about 4 knots (5 km/h; 5 mph)
See latest official information.

Severe Tropical Cyclone Yasa is a currently active tropical cyclone. This system is the second tropical disturbance as well as the first named storm and severe tropical cyclone of the 2020–21 South Pacific cyclone season. The system was first noted as a tropical disturbance 02F developed out a tropical disturbance which formed east-northeast of Vanuatu on December 11. The disturbance organized enough to become a tropical depression at 0:00 UTC on December 12 according to the Fiji Meteorological Service, as the JTWC issued a TCFA. Later that day, the JTWC upgraded the system into Tropical Cyclone 05P. The FWS also assigned the system the name Yasa.

Meteorological history

Map plotting the storm's track and intensity, according to the Saffir–Simpson scale
Map key
Saffir–Simpson scale
  Tropical depression (≤38 mph, ≤62 km/h)
  Tropical storm (39–73 mph, 63–118 km/h)
  Category 1 (74–95 mph, 119–153 km/h)
  Category 2 (96–110 mph, 154–177 km/h)
  Category 3 (111–129 mph, 178–208 km/h)
  Category 4 (130–156 mph, 209–251 km/h)
  Category 5 (≥157 mph, ≥252 km/h)
  Unknown
Storm type
triangle Extratropical cyclone, remnant low, tropical disturbance, or monsoon depression

The area of low pressure that was to become Severe Tropical Cyclone Yasa was first noted by the United States Joint Typhoon Warning Center (JTWC) during December 10, while it was located about 655 km (405 mi) to the north of Port Vila in Vanuatu.[1] At this stage the disturbance had a broad and fully exposed low level circulation, with little to no atmospheric convection surrounding the system.[1] The system was also located within a marginally favorable environment for further development, with high levels of vertical wind shear, being of set by warm sea surface temperatures of around 29–30 °C (84–86 °F).[1] During that day, the system gradually organized further as it moved north-eastwards, towards a more favorable environment, before it was classified by the the Fiji Meteorological Service (FMS) as Tropical Disturbance 02F during December 11.[2] Throughout that day, the system continued to develop and started to interact with Tropical Depression 01F/04P, which was located to the south of 02F.

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.[3] At 00:00 UTC on 12 December, the Fiji Meteorological Service (FMS) upgraded the system to Tropical Depression 02F, and began issuing forecast track maps.[4] At the same time, the Joint Typhoon Warning Center (JTWC) issued a tropical cyclone formation alert for the system.[3] JTWC also noted a possible Fujiwhara Effect with 01F which briefly hampered the formation of the system.[5][6]

During December 12, the United States Joint Typhoon Warning Center (JTWC) initiated advisories on the system and classified it as Tropical Cyclone 05P.[7] Over the next day, the system absorbed Tropical Depression 01F and continued to consolidate, before the FMS reported that the system had become a Category 1 tropical cyclone, on the Australian tropical cyclone intensity scale and named it Yasa.[8] The following day, the JTWC upgraded the system into a Category-1 equivalent cyclone on the Saffir-Simpson scale.[9] Meanwhile, the Fiji Meteorological Service determined that Yasa had strengthened into a Category 2 cyclone on the Australian scale.[10] The cyclone continued to strengthen, becoming a Category 4 cyclone on the Australian scale according to the Fiji Meteorological Service, early on December 15.[11] The cyclone also developed an eye during this time.[12] By 15:00 UTC that day, it intensified into a Category 3-equivalent cyclone on the SSHWS and a Category 5 cyclone on the Australian scale.[13][14]

Current storm information

As of December 15, 07:30 UTC, Yasa is now located near 15°00′S 173°00′E / 15.0°S 173.0°E / -15.0; 173.0 (Yasa). It is currently moving north eastwards with the speed of 4 kn (5 km/h; 5 mph). The maximum 10 minutes sustained winds speed is 105 kn (195 km/h; 120 mph) and maximum 1 minute sustained winds is 105 kn (195 km/h; 120 mph) gusting up to 105 kn (195 km/h; 120 mph). Minimum barometric pressure is 941 hPa (27.79 inHg).

For the latest official information see:

Preparations and impact

Fiji

Yasa strengthening on approach to Fiji and Vanuatu, early on December 14

During December 11, the FMS issued a gale warning for Rotuma, as Tropical Depression 01F was expected to impact the Fijian dependency, with wind gusts of up to 60 km/h (35 mph).[15] They also noted that the system was expected, to produce very rough to high seas, heavy rain and sea flooding of low lying coastal areas.[15] This warning was subsequently expanded during the following day to include Tropical Depression 02F and an associated convergence zone.[16] The warning was cancelled during December 13, after 02F had merged with 01F and developed into a tropical cyclone.[17] As the storm made its approach, a strong wind warning was issued for Rotuma and a flash flood warning was put in place for Vanua Levu.[18] On December 15, a heavy rain warning was issued for the Yasawa and Mamanuca islands, eastern Viti Levu, Vanua Levu, Taveuni, and other smaller islands nearby.[19][20] On December 16, shipping services was halted and the Ministry of Fisheries strongly advised fishermen to refrain from travelling out to sea.[21][22] The Ministry of Education, Heritage and Arts ordered the closure of all schools as schools would be used for evacuation centres.[23] Prime Minister Frank Bainimarama urged all Fijians to prepare for the cyclone.[24]

Vanuatu

As the storm began to impact the country, a strong wind warning was put in effect for central and southern coastal Vanuatu.[18]

See also

References

  1. ^ a b c Significant Tropical Weather Advisory December 10, 2020 06z (Report). United States Joint Typhoon Warning Center. December 10, 2020. Archived from the original on December 14, 2020.
  2. ^ 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.
  3. ^ a b "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.
  4. ^ "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.
  5. ^ "Tropical Cyclone Formation Alert (Invest 91P)". Retrieved December 12, 2020.{{cite web}}: CS1 maint: url-status (link)
  6. ^ "Bulletin No. 06, Tropical Cyclone 04P". Retrieved December 12, 2020.{{cite web}}: CS1 maint: url-status (link)
  7. ^ Tropical Cyclone 05P Warning Number 1 December 12, 2020 15z (Report). United States Joint Typhoon Warning Center. December 12, 2020. Archived from the original on December 15, 2020.
  8. ^ Tropical Cyclone Naming Bulletin December 13, 2020 12z (Report). Fiji Meteorological Service. December 13, 2020. Archived from the original on December 14, 2020. Retrieved December 14, 2020.
  9. ^ "TROPICAL CYCLONE 05P (YASA) WARNING NR 009". Joint Typhoon Warning Center. December 14, 2020. Retrieved December 14, 2020.
  10. ^ "HURRICANE WARNING 041 ISSUED FROM RSMC NADI Dec 141412 UTC". met.gov.fj. Fiji Meteorological Service. December 14, 2020. Retrieved December 14, 2020.
  11. ^ "HURRICANE WARNING 045 ISSUED FROM RSMC NADI Dec 150107 UTC". met.gov.fj. Fiji Meteorological Service. December 15, 2020. Retrieved December 15, 2020.
  12. ^ "TROPICAL CYCLONE 05P (YASA) WARNING NR 012". metoc.navy.mil. Joint Typhoon Warning Center. December 15, 2020. Retrieved December 15, 2020.
  13. ^ "TROPICAL CYCLONE 05P (YASA) WARNING NR 013". metoc.navy.mil. Joint Typhoon Warning Center. December 15, 2020. Retrieved December 15, 2020.
  14. ^ "HURRICANE WARNING 049 ISSUED FROM RSMC NADI Dec 151427 UTC". met.gov.fj. Fiji Meteorological Service. December 15, 2020. Retrieved December 15, 2020.
  15. ^ a b Special Weather Bulletin for Fiji and Rotuma Number 1 December 11, 2020 09z (Report). Fiji Meteorological Service. December 11, 2020. Archived from the original on December 15, 2020. Retrieved December 15, 2020.
  16. ^ Special Weather Bulletin for Fiji and Rotuma Number 10 December 12, 2020 19z (Report). Fiji Meteorological Service. December 11, 2020.
  17. ^ Special Weather Bulletin for Fiji and Rotuma Number 20 December 13, 2020 12z (Report). Fiji Meteorological Service. December 13, 2020. Archived from the original on December 15, 2020. Retrieved December 15, 2020.
  18. ^ a b ECHO (December 14, 2020). "Vanuatu, Fiji - Tropical Cyclone YASA (Fiji NEws, Radio New Zealand, NZ Herald, VMGD, MET Fiji, JTWC, GDACS)". reliefweb.int. ReliefWeb. Retrieved December 14, 2020.
  19. ^ Timoci Vula (December 15, 2020). "Weather watch: TC Yasa moves East at 5 knots; heavy rain alert remains". fijitimes.com. The Fiji Times. Retrieved December 15, 2020.
  20. ^ Vijay Narayan, Naveel Krishant (December 15, 2020). "Warnings issued for most parts of Fiji as TC Yasa expected to loop and head towards us". fijivillage.com. Fijivillage. Retrieved December 15, 2020.
  21. ^ "Shipping companies urged to take heed of advisory". Fiji Broadcasting Corporation. Retrieved December 15, 2020.{{cite web}}: CS1 maint: url-status (link)
  22. ^ "Fijians to adhere to all public advisories". Fiji Broadcasting Corporation. Retrieved December 15, 2020.{{cite web}}: CS1 maint: url-status (link)
  23. ^ "Schools to close, external exams to continue". Fiji Broadcasting Corporation. Retrieved December 15, 2020.{{cite web}}: CS1 maint: url-status (link)
  24. ^ "Bainimarama urges Fijians to prepare for TC Yasa". Fiji Broadcasting Corporation. Retrieved December 15, 2020.{{cite web}}: CS1 maint: url-status (link)
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