Timeline of Events

Impact  
  • 2010 Australia’s third-wettest calendar year, wettest on record for the Murray-Darling Basin and Queensland
  • Australia’s wettest two-calendar year period (2010–2011)
  • Southwest Australia’s driest year on record
 
  • El Niño breaking down
  • Australia’s wettest 24-month period on record (April 2010–March 2012)
  • Australia’s third-wettest 12-month period (April 2010–March 2011)
  • Wettest ‘dry’ season on record for northern and central Australia (May–October)
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  • Above-average monthly rainfall for most of Australia (July 2010–March 2011)
  • Wettest second half of the year on record for Australia
  • Floods and landslips in northeast Tasmania (10–11 August)
  • Wettest September on record for Australia
  • Wettest spring on record for Australia, and all states except Tasmania and Victoria
  • Major flooding in northern Victoria (early September)
  • Second-wettest October on record for Australia
  • Floods in southeast Queensland (10–12 October) – Wivenhoe Dam spills for the first time since 2001
  • Floods in Riverina and southwest slopes New South Wales (13–16 October)
  • Record-high sea surface temperatures around the northern coasts of Australia (October–December)
  • Wet season second wettest on record for northern Australia, Queensland, and Western Australia (November 2010–April 2011)
  • Australian monsoon arrives earlier and is stronger than normal
  • Wettest December on record for Australia and Victoria
  • Wettest summer on record for Victoria, second-wettest for Western Australia and Australia as a whole
  • Widespread flooding on inland rivers , especially in New South Wales (early December)
  • Severe floods in the Gascoyne associated with a tropical depression (16–18 December)
  • Severe floods in southern and central Queensland (mid-December–January)
  • 2011 Australia’s second-wettest calendar year, wettest on record for Western Australia
  • Wettest January on record for Queensland and Victoria
  • Flooding in western and central Victoria and northern Tasmania (12–15 January)
  • Flooding in northeastern and western New South Wales and southeast Queensland, notably in Brisbane River catchment and severe flash floods in Toowoomba/Lockyer Valley.
  • Tropical cyclone Bianca brings rain and strong winds to the Kimberley and Pilbara (25–30 January)
  • Second-wettest February on record for Australia
  • Tropical cyclone Yasi strongest to hit Queensland coast since at least 1918 (3 February)
  • Severe thunderstorms associated with ex-tropical cyclone Anthony cause flash flooding in Victoria (4 February)
  • Tropical cyclone Carlos inundates Darwin (15–17 February)
  • Wettest March on record for northern Australia
  • Monsoonal burst causes flooding in eastern Kimberley (week ending 14 March)
  • Prolonged flooding across western Queensland
  • Flooding in northeastern Tasmania, southeast New South Wales, and Gippsland (20–24 March)
  • Flash flooding and river flooding in eastern Tasmania (10–13 April)
     
  • Increased vegetation following high rainfall in 2010 and 2011 fuels widespread grassfires in central Australia (August–November)
 
  • Rainfall above average for most of mainland Australia (October 2011–March 2012)
  • Australia’s record highest October rainfall total: 1494 mm at Bellenden Ker
  • Second-wettest November and spring on record for Western Australia
  • Extensive flooding through northeastern New South Wales west of the Great Divide (late November)
  • Sea surface temperatures around northern Australia above average (December 2011–February 2012)
  • Tropical cyclone Grant brings very heavy rain to the Top End (25–26 December)
  • Extended flooding in northern New South Wales (late January)
  • Severe flooding in inland southern Queensland and northeast New South Wales (early February–March)
  • Torrential rain in central and northeast Victoria cause flash flooding (late February)
  • Flooding in southern New South Wales and northern Victoria (record seven-day falls, 27 February–4 March)
  • Second-wettest March on record for New South Wales
  • Heavy rain exacerbates flooding from northern Victoria through southeast and western Queensland
  • Tropical cyclone Lua strongest to cross the Western Australian coast since Laurence in 2009 (17 March)
  • Australia’s rainfall 43 per cent below average for April
  • Monthly rainfall across the Murray-Darling Basin 63 per cent below average
Date Dec-09 Jan-10 Feb-10 Mar-10 Apr-10 May-10 Jun-10 Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 March-12 April 2012
Indicator
  • 2009–10 El Niño reaches its peak around late December
   
  • Pacific Ocean cools rapidly during autumn
  • Positive SAM (March 2010–February 2011 – record high values June, July, and November, second highest for August and October)
  • ENSO indicators neutral by late April
  • Climate models suggest increased chance of La Niña
  • First signs of La Niña apparent
  • Sea surface temperatures approach  La Niña thresholds
  • Bureau announces La Niña about to become established.
  • Climate models predict La Niñalikely to persist through the remainder of 2010
  • First indication of falling IOD index
  • Negative IOD event (late August–late November)
  • Monthly SOI second highest on record (+25.0), also the highest monthly value for any month since November 1973
  • IOD strongly negative (September–November)
  • Monthly SOI equal highest on record (+18.3) for October
  • Bureau seasonal outlooks indicate very high probability of above-average spring–summer rainfall for parts of Queensland and New South Wales
  • Climate models predict La Niña conditions into first quarter 2011
  • Negative IOD event decays
  • Monthly SOI highest on record (+27.1) for December
  • Monthly SOI third highest on record (+19.9) for January
  • 2010–11 La Niña reaches its peak
  • Unusually warm sea surface temperatures in the western Pacific Ocean
  • Monthly SOI highest on record (+22.3) for February
  • Climate models predict La Niña to decline to neutral by winter
  • Monthly SOI highest on record (+21.4) for March
  • Oceanic ENSO indicators decline but atmospheric indicators continue to indicate strong La Niña conditions (late March)
  • Climate models forecast neutral ENSO conditions by winter
  • Monthly SOI second highest on record (+25.1) for April
  • Sharp drop in SOI
  • 2010–11 La Niña ends
  • Pacific Ocean begins cooling
     
  • Model outlooks indicate re-emergence of La Niña likely
  • Brief, weakly positive IOD event during spring
  • 2011–12 La Niña declared mid-October, forecast not to be as strong as the 2010–11 La Niña
 
  • Monthly SOI equal second highest on record (+23.0) for December
  • 2011–12 La Niña reaches its peak
 
  • Most oceanic ENSO indicators return to neutral
  • 2011–12 La Niña ends late-March
  • Some climate models indicate that an El Niño may emerge later in 2012