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The high is generally more affixed in the Bight and it is even known linked to the Bight's name. |
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{{short description|A semi-permanent high pressure system over Southern Australia}}
{{Use dmy dates|date=April 2022}}
{{Infobox weather type
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|image= High pressure Area Sep 08 2012.jpg
|imagesize=
|caption = The high featuring
|area of occurrence=*[[Great Australian Bight]],
*[[Central Australia|Central]], [[northeastern Australia|eastern]], and [[northern Australia]] (winter)
|season=All-year round
|effect= *[[Drought]] in the west and south (summer)
*Drier conditions, and at times drought, in the centre, [[northern Australia|north]] and [[eastern Australia|east]] (winter)
}}
The '''Australian High''', also known as the '''
In [[summer]], it typically sits over [[southern Australia]] as an '''Australian Bight High''',<ref>[https://globalsolochallenge.com/australian-bight-high-slows-down-gsc-front-runners-and-could-reshuffle-rankings/ Australian Bight High slows down GSC front runners and could reshuffle rankings] by Marco Nannini from Global Solo Challenge. Retrieved 12 July 2024.</ref> where it generally provides dry weather in the proximate region. In [[winter]] it normally moves north, therefore permitting [[cold front]]s and [[low pressure system]]s to relocate up from the Great Australian Bight and bring rainfall to most parts of southern Australia.<ref>[http://www.bom.gov.au/climate/about/?bookmark=strexample Sub-tropical Ridge Example]. Bureau of Meteorology. 2 April, 2008. Retrieved 31 May, 2023.</ref> The high is part of the [[subtropical ridge]] system and it is the reason why a [[deserts of Australia|large part of Australia]] is arid to semi-arid.<ref name = BOM>[http://www.bom.gov.au/climate/updates/articles/a025.shtml#:~:text=The%20subtropical%20ridge%20is%20a,on%20the%20climate%20of%20Australia. Subtropical ridge leaves us high and dry this June] [[Bureau of Meteorology]]. July 2017. Retrieved 31 May, 2023. </ref>
==Description==
[[File:High Pressure.jpg|thumb|left|The Australian High west of Tasmania over the [[Indian Ocean]]]]
The Australian High tends to follow the seasonal variation in [[position of the sun]]; it is strongest and most persistent during the southern hemisphere summer and weakest during winter when it shifts towards the interior of Australia, as the [[westerlies|westerly]] [[frontal system]]s becomes more active in the region around the Bight, thereby allowing [[Cold front|cold fronts]] and [[Low-pressure area|low-pressure systems]] to perforate the southern states.<ref name = prevention>[https://www.preventionweb.net/news/stalled-weather-how-stuck-air-pressure-systems-drive-floods-and-heatwaves STALLED WEATHER: HOW STUCK AIR PRESSURE SYSTEMS DRIVE FLOODS AND HEATWAVES] by Steve Turton from PreventionWeb.net. 3 March 2022</ref>
This high-pressure block exhibits anticyclonic behaviour, circulating the air anticlockwise. It remains almost stationary for a prolonged period over the Bight, hence obstructing the typical easterly procession of weather systems across southern Australia.<ref>[https://www.abc.net.au/news/2018-08-14/southern-annular-mode-and-how-it-affects-our-weather/10106134 Southern Annular Mode: The climate 'influencer' you may not have heard of] By Kate Doyle from [[ABC TV (Australian TV channel)|ABC]]. 14 August 2018. Retrieved 7 April 2022.</ref>
The High can stretch thousands of kilometers across the [[Bight (geography)|Bight]], and may move eastwards towards [[Tasmania]]. This area of high pressure is part of the great subtropical belt of anticyclones called the [[subtropical ridge]]. A [[cloud hole]] with an expansion as far as 1,000 kilometers (620 miles) has been observed, with tops of 1,040 [[millibar]]s. The high may be extensive enough to interconnect with the Tasman High over in the [[Tasman Sea]], just near [[New Zealand]].<ref>[https://www.farmonlineweather.com.au/news/high-pressure-systems-everything-you-need-to-know/527959#:~:text=High%20pressure%20systems%20are%20a,weather%20across%20an%20entire%20continent. High pressure systems: everything you need to know] by Ben Domensino from Weatherzone. 21 May 2018. Retrieved 22 April 2022.</ref>▼
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==Effects==
[[File:Australia.A2002231.0145.250m NASA Nullarbor.jpg|thumb|230px|The
The anticyclonic circulation produces a dry climate, bringing warm to hot weather in the southern Australian summer. The high influences the weather and climatic patterns of vast areas of [[Australia]]; The aridity of the [[deserts of Australia|Australian deserts]] and the summer [[drought in Australia|drought]] of southern Australia is due to the large-scale subsidence and sinking motion of air in the system.<ref>[https://www.weatherzone.com.au/news/extreme-heat-on-its-way-to-northwest-wa/536209 Extreme heat on its way to northwest WA] by Ben Domensino from [[Weatherzone]]. 12 February 2022. Retrieved 7 April 2022.</ref>
In winter, when the high remains stationary in southern Australia (in a positive [[Southern Annular Mode|SAM]] phase), it can block or replace [[cold front]]s from the Bight, thereby allowing warm weather to the southeast.<ref>[https://www.weatherzone.com.au/news/sydneys-record-15-day-spell-of-20-degree-winter-days/534824 Sydney's record 15-day spell of 20 degree winter days] by Ben Domensino from Weatherzone. 23 August 2021</ref> However, when the high remains fixed south of [[Western Australia]], it can drive in polar air towards the continent, whereby increasing snowfall and rain in the southeast, particularly areas that lie west of the Great Dividing Range (due to the [[Southeast Australian foehn|foehn effect]]).<ref>[https://www.abc.net.au/news/2022-06-09/blocked-weather-high-pressure-system-linking-snow-to-record-heat/101134306 Australian snow, rain and heat linked by blocked weather systems, climatologist says] By Ben Deacon from ABC Weather. 9 June 2022.</ref> Conversely, a large high stationed below [[South Australia]] can bring persistent rainfall to the east coast of Australia, whilst proving clear conditions to [[Tasmania]].<ref>[https://www.weatherzone.com.au/news/unrelenting-high-pressure-dominating-australias-weather/1889387 Unrelenting high pressure dominating Australia’s weather] by Ben Domensino from Weatherzone. 7 May 2024. Retrieved 9 May 2024.</ref>
In the western part of the high, hot dry northerly winds from the dry centre push through South Australia and Victoria, ensuing heatwave conditions in these regions. The Australian High is one the drivers of the [[Southerly buster]], which occurs in the southeast coast in the summer.<ref>''Modelling coastally trapped wind surges over Southeastern Australia.'' Reid, Helen J. 1999. [[UNSW]]</ref> In winter, when the high pressure system is broad over the [[Australia]]n landmass, widespread [[frost]] may occur.<ref>[https://www.abc.net.au/news/2023-05-27/widespread-frost-outbreak-forecast-australia-bom/102399008 Frost expected across nearly every state and territory in Australia this weekend] By Tyne Logan from [[ABC News (Australia)|ABC News]]. 27 May 2023.</ref>
===Effects on Asia===
During the southern winter, the Australian High is one of the driving forces behind the [[Monsoon of South Asia|South Asian Monsoon]]. [[Trade winds|Easterly]] winds blow from the center of the high towards [[Asia]], and are deflected in a southwest direction towards [[India]] after crossing the [[equator]] due to the [[Coriolis force|Coriolis effect]].
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Between summer and autumn, the high over southern Australia may be linked, or would intertwine, with the Tasman High in the southern [[Tasman Sea]]. When the high stalls in the Tasman Sea and becomes a [[blocking high]], New Zealand and [[climate of Tasmania|Tasmania]] will generally experience warm and generally dry weather, whilst the east coast of Australia (particularly southern Queensland and New South Wales) will experience moist onshore flows, particularly during a [[La Niña]] phase.<ref>[http://www.bom.gov.au/climate/current/statements/scs64.pdf Special Climate Statement—record warmth in the Tasman Sea, New Zealand and Tasmania] Bureau of Meteorology. 27 March 2018</ref> In [[2021 Eastern Australian floods|March 2021]], and also in [[2022 eastern Australia floods|February and March 2022]], a stubborn blocking high in the Tasman caused heavy rain and flooding over large parts of Southeast Queensland and coastal New South Wales.<ref name = prevention/><ref>[https://docs.niwa.co.nz/library/public/NIWAsts71.pdf THE CLIMATE AND WEATHER OF NELSON AND TASMAN] 2nd edition G. R. Macara </ref><ref>[https://www.stuff.co.nz/national/weather-news/124327154/weather-blocking-high-expected-to-keep-much-of-country-warm-mostly-dry-for-last-days-of-summer Weather: Blocking high expected to keep much of country warm, mostly dry for last days of summer] by Michael Daly from [[Stuff (website)|Stuff]]. February 23 2021.</ref>
==See also==
*[[Climate of Australia]]
*[[Brickfielder]]
==References==
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[[Category:Regional climate effects]]
[[Category:Southern Ocean]]
[[Category:Indian Ocean]]
[[Category:Tasman Sea]]
[[Category:Great Australian Bight]]
[[Category:Coastline of Western Australia]]
[[Category:Coastline of South Australia]]
[[Category:Coastline of Tasmania]]
[[Category:Coastline of Victoria (state)]]
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