October 2022 Southern Ocean cyclone

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October 2022 Southern Ocean cyclone
The cyclone on 16 October, soon before record peak intensity
Meteorological history
Formed9 October 2022 (ECMWF)
16 October 2022 (Geophysical Research Letters paper)
Dissipated20 October 2022 (ECMWF)
22 October 2022 (Geophysical Research Letters paper)
Extratropical cyclone
Lowest pressure≤900.7 hPa (mbar); ≤26.60 inHg
Overall effects
FatalitiesNone
DamageNone

The October 2022 Southern Ocean cyclone, also referred to as the Peter I storm[1] or EC2022[2] was the most intense extratropical cyclone on record. Forming as a weak depression near Tonga late on 9 October, the extratropical cyclone tracked slowly southeastward across the South Pacific, remaining weak. Starting on 14 October, the cyclone began rapid deepening as it moved towards Antarctica. Deepening rates peaked on 16 October, where the pressure fell as rapidly as 19 mbar (0.56 inHg) over a six-hour period. The storm peaked early on 17 October in the Bellingshausen Sea, with a minimum pressure of around 900 mbar (26.58 inHg). The cyclone moved slowly in a loop, rising in pressure over the next few days before dissipating on 20 October.

The cyclone's pressure has been estimated by the European Centre for Medium-Range Weather Forecasts (ECMWF) as 900.7 mbar (26.60 inHg) at 06:00 UTC on 17 October. An analysis paper published in Geophysical Research Letters in July 2023 got a minimum pressure of 899.91 mbar (26.574 inHg) at 03:00 UTC the same day. These pressures would make the extratropical cyclone the most intense since at least the start of the satellite era; for comparison, the most intense extratropical cyclone known over the North Atlantic was the Braer Storm in 1993, with a pressure of 914 mbar (27.0 inHg).

Background

The Southern Ocean is defined as the body of water that surrounds Antarctica, generally below 60° degrees south. The status of the Southern Ocean is disputed,[3] with it being an official ocean on the 2002 draft of Limits of Oceans and Seas by the International Hydrographic Organization.[4] However, the draft has not been published due to several naming disputes of different bodies of water, primarily the Sea of Japan.[5]

Extratropical cyclones in the Southern Ocean have been observed to be stronger than Northern Hemisphere cyclones at the same latitude. Cyclones in the Southern Ocean tend to have lowest pressures in mid-late September, when Antarctic sea ice is at is maximum. The lower pressures are likely caused by less friction against sea ice rather than ocean waves.[1] As there are limited weather stations in the region, pressures in the region are calculated using results from ECMWF models and ERA5 reanalysis data using 13 different variables including temperature, potential vorticity and 10 meter wind.[2]

Meteorological history

The cyclone's origins can be traced back to 9 October, when a weak extratropical cyclone formed near Tonga. The cyclone spent around a day moving slowly near the island before moving southeastward on 11 October. The cyclone started to deepen on 13 October and rapidly move across the Southeast Pacific. During this time, the isobars along the southeastern side of the cyclone elongated with additional development taking place on the eastern side. This caused an accelerated movement of the cyclone between 06:00 UTC and 12:00 UTC on 13 October. At this time, the associated warm front with this extratropical cyclone started to deepen and turn poleward. Explosive cyclogenesis occurred on the 16th, with the storm's central pressure falling as rapidly as 19 mbar (0.56 inHg) over a six-hour period. A paper in Geophysical Research Letters first identified the cyclone at 03:00 UTC on this date. The cyclone's peak intensity occurred early on 17 October near Peter I Island in the Bellingshausen Sea. The cyclone then executed a clockwise loop in the Bellingshausen Sea for three days while rising in pressure. The ECMWF concluded that the cyclone lost its identity on 20 October while the Geophysical Research Letters paper called a dissipation two days later in the southwestern Atlantic Ocean.[1][2]

The cyclone lasted roughly for ten days, much longer than typical cyclones in the North Pacific and North Atlantic, although some summer cyclones in the Arctic Ocean have been observed to last as long.[1]

Pressure estimates

A weather station on Thurston Island recorded an elevated pressure of 897 mbar (26.5 inHg), a sea-level pressure of 923 mbar (27.3 inHg).[6] The Servicio Meteorológico Nacional of Argentina marked the cyclone of having a pressure of 905 mbar (26.7 inHg) on 17 October at 12:00 UTC.[7] The analysis of data from the ERA5 model by the ECMWF estimates that the cyclone's central pressure reached a minimum of 900.7 mbar (26.60 inHg) along the edge of the Bellingshausen Sea near Peter I Island at around 06:00 UTC on 17 October. They note that the storm originating in the tropics might have helped the pressure of the cyclone get so low.[1] A subsequent analysis published in Geophysical Research Letters in July 2023 estimated a minimum central pressure of 899.91 mbar (26.574 inHg) at 03:00 UTC 17 October.[2]

Forecasts

In the week preceding the event, ECMWF high-resolution forecast models were "remarkably consistent" in the forecast of a very deep low-pressure system in the Bellingshausen Sea. Minimum pressures were generally in the range of 895–910 mbar (26.4–26.9 inHg).[1] Model runs from the Global Forecast System and various ensemble models also had a consensus of a sub 910 mbar (27 inHg) system.[6]

Records and findings

Most intense extratropical cyclones in the Southern Ocean
Rank Date Pressure Location
1 October 2022 889.91 mbar (26.279 inHg) 69°S 98°W / 69°S 98°W / -69; -98
2 September 2018 910.8 mbar (26.90 inHg) 70°S 115°W / 70°S 115°W / -70; -115
3 September 2022 912.11 mbar (26.935 inHg) 71°S 169°W / 71°S 169°W / -71; -169
4 August 1983 913.54 mbar (26.977 inHg) 70°S 151°W / 70°S 151°W / -70; -151
5 March 2002 914.58 mbar (27.008 inHg) 70°S 127°W / 70°S 127°W / -70; -127
Source:[2]

At peak, the cyclone reached a minimum pressure of around 900 mbar (26.58 inHg), the lowest pressure of an extratropical cyclone since at least the start of the satellite era in 1980. The deepening rate of the cyclone was greater than 93.4% of other extreme cyclones.[2] Research from the Geophysical Research Letters article shows that amount of extreme extratropical cyclones, especially in the Amundsen and Bellingshausen Seas, has significantly increased between 1980 and 2022. Additionally, the southwest Pacific Ocean and the South Atlantic has seen a decrease in extreme cyclones.[2] At least five cyclone in the Southern Ocean have had pressure equal to or less than 914 mbar (27.0 inHg), the same pressure as the Braer Storm.[2][8]

See also

References

  1. ^ a b c d e f Hewson, Tim; Day, Jonathan; Hersbach, Hans (January 2023). "The deepest extratropical cyclone of modern times?". Newsletter. European Centre for Medium-Range Weather Forecasts. Retrieved 4 October 2023.
  2. ^ a b c d e f g h Lin, Peiyi; Zhong, Rui; Yang, Qinghua; Clem, Kyle R.; Chen, Dake (28 July 2023). "A Record-Breaking Cyclone Over the Southern Ocean in 2022". Geophysical Research Letters. 50 (14). Bibcode:2023GeoRL..5004012L. doi:10.1029/2023GL104012. Cite error: The named reference "GRL" was defined multiple times with different content (see the help page).
  3. ^ Rosenberg, Matt (10 April 2020). "The New Fifth Ocean". ThoughtCo. Retrieved 7 October 2023.
  4. ^ "IHO Publication S-23, Limits of Oceans and Seas, Draft 4th Edition". International Hydrographic Organization. 2002. Archived from the original on 2 February 2014. Retrieved 7 October 2023.
  5. ^ "IHO Special Publication 23". Korean Hydrographic and Oceanographic Administration. Archived from the original on 1 February 2014. Retrieved 7 October 2023.
  6. ^ a b "Record 900 hPa extratropical cyclone surprises meteorologists!". Yourweather.co.uk | Meteored. 19 October 2022. Retrieved 26 November 2022.
  7. ^ "Pronóstico para la Navegación Marítima en la METAREA-6". Servicio Meteorológico Nacional (in Spanish). 17 October 2022. Archived from the original on 17 October 2022. Retrieved 31 March 2023.
  8. ^ Odell, Luke; Knippertz, Peter; Pickering, Steven; Parkes, Ben; Roberts, Alexander (April 2013). "The Braer storm revisited" (PDF). Weather. 68 (4): 105–111. Bibcode:2013Wthr...68..105O. doi:10.1002/wea.2097. S2CID 120025537. Retrieved 10 October 2023.
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