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==Description==
[[File:High Pressure.jpg|thumb|left|The Australian High west of Tasmania]]
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 fronts and 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 clockwise. It remains almost stationary for an 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 High tends to keep the southern half of Australia mostly clear and dry.]]
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 the Bight (due to a positive [[Southern Annular Mode|SAM]] phase), it can
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. Conversely, the High may direct more rainfall in southeast Australia, as feeble westerly winds result in increase of easterly onshore winds that bring moist air from the Tasman Sea towards the east coast from [[Brisbane]] to [[Sydney]] (though regions west of the [[Great Dividing Range]] would remain dry).<ref name = BOM/><ref>[https://phys.org/news/2019-01-stubborn-high-pressure-australia-heatwaves.html The stubborn high-pressure system behind Australia's record heatwaves] by Steve Turton from [[The Conversation (website)|The Conversation]]. 25 January 2019. Retrieved 7 April 2022.</ref> The Australian High is one the drivers of the [[Southerly buster]], which occurs in the southeast coast.<ref>''Modelling coastally trapped wind surges over Southeastern Australia.'' Reid, Helen J. 1999. [[UNSW]] </ref>
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==Tasman High==
Between summer and autumn, the high over the Great Australian Bight may be linked, or would intertwine, with the Tasman High in the southern [[Tasman Sea]], between [[Tasmania]] and the [[South Island]] of [[New Zealand]], where it can become a [[blocking high]]. During such events, New Zealand and 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, including heavy rain events, and lack of warm days.<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> These blocking highs ward off low pressure systems out in the Tasman Sea and towards eastern Australia, whereby providing rainfall on the east coast of Australia (particularly during [[La Nina]] phases).<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==
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