October 2022 Southern Ocean cyclone

The cyclone on 16 October, soon before record peak intensity
Meteorological history
Formed	9 October 2022 (ECMWF) 16 October 2022 (Geophysical Research Letters paper)
Dissipated	20 October 2022 (ECMWF) 22 October 2022 (Geophysical Research Letters paper)
Extratropical cyclone
Lowest pressure	≤900.7hPa (mbar); ≤26.60 inHg
Overall effects
Fatalities	None
Damage	None

TheOctober 2022 Southern Ocean cyclone, also referred to as thePeter I storm^[1] orEC2022^[2] was the most intenseextratropical cyclone on record. Forming as a weak depression nearTonga late on 9 October, the extratropical cyclone tracked slowly southeastward across theSouth Pacific, remaining weak. Starting on 14 October, the cyclone beganrapid deepening as it moved towardsAntarctica. 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 theBellingshausen 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 theEuropean Centre for Medium-Range Weather Forecasts (ECMWF) as 900.7 mbar (26.60 inHg) at 06:00UTC on 17 October. An analysis paper published inGeophysical 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 theBraer Storm in 1993, with a pressure of 914 mbar (27.0 inHg).

TheSouthern Ocean is defined as the body of water that surrounds Antarctica, generally below60° degrees south. The status of the Southern Ocean is disputed,^[3] with it being an official ocean on the 2002 draft ofLimits of Oceans and Seas by theInternational Hydrographic Organization.^[4] However, the draft has not been published due to several naming disputes of different bodies of water, primarily theSea of Japan.^[5]

Extratropical cyclones in the Southern Ocean have been observed to be stronger thanNorthern Hemisphere cyclones at the same latitude. Cyclones in the Southern Ocean tend to have the lowest pressures in mid-late September, whenAntarctic sea ice is at its maximum. The lower pressures are likely caused by less friction against sea ice rather than ocean waves.^[1] As there are limitedweather stations in the region, pressures in the region are calculated using results from ECMWF models andERA5 reanalysis data using 13 different variables including temperature,potential vorticity and 10 meter wind.^[2]

The cyclone's origins can be traced back to 9 October, when a weak extratropical cyclone formed nearTonga. 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, theisobars along the southeastern side of the cyclone elongated withadditional 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 associatedwarm 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 inGeophysical Research Letters first identified the cyclone at 03:00 UTC on this date. The cyclone's peak intensity occurred early on 17 October nearPeter 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 theGeophysical Research Letters paper called a dissipation two days later in the southwesternAtlantic 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 theArctic Ocean have been observed to last as long.^[1]

A weather station onThurston Island recorded an elevated pressure of 897 mbar (26.5 inHg), a sea-level pressure of 923 mbar (27.3 inHg).^[6]TheServicio Meteorológico Nacional ofArgentina 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 thetropics might have helped the pressure of the cyclone get so low.^[1] A subsequent analysis published inGeophysical Research Letters in July 2023 estimated a minimum central pressure of 899.91 mbar (26.574 inHg) at 03:00 UTC 17 October.^[2]

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 theGlobal Forecast System and variousensemble models also had a consensus of a sub 910 mbar (27 inHg) system.^[6]

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 theGeophysical Research Letters article shows that amount of extreme extratropical cyclones, especially in theAmundsen 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 cyclones 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]

• Weather of 2022
• List of weather records
• List of notable non-tropical pressures over the North Atlantic
• Perfect storm
• Storm Dennis – 920 mbar (27 inHg) extratropical cyclone nearIceland
• Typhoon Tip – Strongesttropical cyclone on record with a pressure of 870 mbar (26 inHg)
• October 2021 Northeast Pacific bomb cyclone andNovember 2024 Northeast Pacific bomb cyclone – StrongestPacific Northwest windstorms, both with pressures of 942 mbar (27.8 inHg)
• 1993 Storm of the Century – Extreme winter storm in March 1993
• November 2014 Bering Sea cyclone – Strongest extratropical cyclone in the Northern Pacific with a pressure of 920 mbar (27 inHg)
• November 2011 Bering Sea cyclone – Similar strength to the November 2014 cyclone
• January 2013 Northwest Pacific cyclone – 936 mbar (27.6 inHg) extratropical cyclone off the coast of Japan in January 2013

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• Meteorological events in 2022
• History of Antarctica
• Climate of Antarctica
• 2022 in Antarctica
• Southern Ocean
• Extratropical cyclones

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