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Rainfall to Ease for Southeastern Australia – Long-Term Patterns Remain Wetter Than Average

December 10, 2024


The wet season of 2024 has started with a bang, bringing widespread rainfall across Australia. Approximately one-third of the country recorded more than double the average November rainfall, with significant falls across inland regions. While South Australia, NSW, and Victoria have seen persistent showers and storms, a welcome reprieve is on the way.


Above average rainfall has occurred across much of Australia during November 2024. Source: BoM

A Temporary Reprieve for the South


The shift is linked to the Southern Annular Mode (SAM) turning negative, which supports a drier pattern through an increase in westerly winds. In contrast, November's positive SAM phase resulted in an increase in easterly winds which assisted in bringing the wetter conditions.


In the short term, this shift will favour northern Australia, with showers and storms expected to persist across northern Queensland, the Northern Territory, and parts of Western Australia.


A positive SAM helped increase easterly winds over November. These winds have eased but will likely be a brief break only before returning later in the month. Source: BoM


Warmer Oceans, Wetter Outlooks


Despite the short-term reprieve, long-term patterns indicate a wetter-than-average summer for much of Australia. This outlook is driven by:


  1. Warmer Ocean Temperatures:

    • Sea surface temperatures (SSTs) are 2–3°C above average off northwest WA, providing a steady stream of moisture for recent inland showers and storms.

    • SSTs near the southern Queensland coast have reached 26°C, just shy of the 27°C threshold needed for tropical cyclone formation.

      Well above average sea surface temperatures are present around the country, particularly off the eastern Australian coastline and off the northwest WA coastline. Source: BoM

  2. Climate Patterns:

    • A negative Indian Ocean Dipole is adding to the elevated moisture levels.

    • The Pacific Ocean’s “cool neutral” conditions (a near-La Niña pattern) continue to support wetter conditions, though a full La Niña declaration remains uncertain.



Forecast rainfall for the next 10 days across ACCESS, EC and GFS showing rainfall favouring the northern areas of the country. Source: MetCentre.


Tropical Cyclone Concerns


The unusually warm ocean temperatures also raise concerns about tropical cyclones and this could result in:

  • More intense tropical cyclones: Warmer seas can fuel stronger systems.

  • Tropical cyclones moving further south: While not guaranteed, the warm waters create potential for tropical cyclones to survive at lower latitudes.


It’s important to note that tropical cyclone behaviour depends on many factors beyond ocean temperatures, so this is not a certainty, but a risk to monitor.


Too Early for Christmas Outlook


As we move towards the festive season - everyone is keen to know what Christmas and New Year's may bring. Unfortunately it's a little too early to reliably determine the weather patterns but a better indication should be gained by next week.


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