Multiple weather agencies have issued forecasts and warnings regarding Australia's climate from May through late 2024. The forecasts include the potential development of an El Niño event, predictions of drier and warmer conditions for much of the country, and immediate warnings for heavy rainfall and flash flooding in some regions.
Current Severe Weather Warning
The Bureau of Meteorology (BoM) issued a severe weather warning for parts of eastern Australia, including eastern Tasmania, central west New South Wales (NSW), and southern Queensland. The warning covers a period from Wednesday to Friday.
- Cause: A low-pressure system over South Australia, combined with moisture from the tropics and an upper-level trough, is driving the rainfall.
- Predictions: Heavy falls are expected, with accumulated totals of 25-100mm in southern Queensland, 50-100mm in NSW western slopes, 100-150mm along parts of the NSW coast, and 50-100mm in eastern Tasmania.
- Timeline: The low-pressure system is expected to move offshore on Friday.
Heavy falls are expected, with accumulated totals of 100-150mm along parts of the NSW coast.
Seasonal Forecast: May to July
Large parts of south-east Australia are forecast to experience drier and hotter conditions from May to July 2024.
- Rainfall: Much of Queensland and New South Wales are forecast to have below-average rainfall. Parts of northern and western Victoria, southern South Australia, and south-west Western Australia may also be dry.
- Temperatures: Almost the entire country is likely to experience above-average maximum temperatures. The bottom two-thirds of Australia have an increased chance of unusually high maximum temperatures.
- Caveats: The Bureau of Meteorology stated that forecasts at this time of year tend to be less reliable.
Seasonal Forecast: June to August
The Bureau of Meteorology (BOM) forecast unusually warm winter temperatures across Australia.
- Rainfall: Rainfall is likely to be below average for most of the country. The dry signal is expected to emerge in July and strengthen into August. South-west Western Australia and parts of south-eastern Australia are most likely to experience below-average rainfall. The forecast for June shows no strong signal.
- Temperatures: Both daytime and night-time temperatures are "very likely" to be warmer than average. There is a strong chance temperatures will fall into the top 20% of all records.
- Snow Season: The combination of drier and warmer conditions is noted as not favorable for the snow season.
Both daytime and night-time temperatures are "very likely" to be warmer than average.
El Niño Development Status
Multiple climate models from various agencies indicate a shift towards El Niño conditions.
- Current Status: The Bureau of Meteorology (BoM) reported "signs of El Niño development" in the tropical Pacific, with sea surface temperatures in the central tropical Pacific warming substantially. The World Meteorological Organization (WMO) noted an increasing chance of El Niño developing in the Pacific.
- Timeline: Most weather models indicate sea surface temperatures consistent with El Niño could be in place by July. The BoM expects to declare an El Niño event during winter if ocean and atmospheric thresholds are met.
- Potential Strength: Models reviewed by the BoM indicate the event will be at least moderate in strength, with the possibility of a strong event. The European Centre for Medium-Range Weather Forecasts (ECMWF) projects El Niño to reach between 1.3 and 3.1 degrees Celsius above average sea surface temperature. A "super" event, characterized by sea surface temperatures exceeding two degrees above average, is considered possible by some models but remains uncertain.
- Record Potential: The rate of warming in the Niño3.4 region is the fastest since 1943. The BOM's ACCESS-S model forecasts peak warming exceeding 3°C above normal, which would surpass the previous record of 2.65°C (November 1902).
Contributing Factors
- Indian Ocean Dipole (IOD): Some models suggest cooling ocean temperatures to Australia's north-west, which can lower rainfall chances. The BoM forecast the IOD to remain neutral through early spring, though other models predict a positive IOD.
- Climate Change: The Bureau of Meteorology stated that the climate change signal is strongly evident in temperature forecasts. The long-term drying trend in south-west Western Australia is considered a stronger influence than El Niño for that region. The WMO reported that the past decade was the warmest on record.
Expert Statements
- Climatologist Caitlin Minney (BoM) stated that a developing El Niño is likely one of the factors behind the dry forecast, and that the climate change signal is very strong in temperature forecasts.
- Climate scientist Dr. Peter van Rensch (Monash University) noted that El Niño's influence on Australian rainfall has historically been greatest in June, July, October, and November. He added that the strength of an El Niño does not necessarily correlate with strong impacts on Australia's rainfall.
- Weather and climate expert Ailie Gallant stated that the strength of the event will not be clear until around June due to the "autumn predictability barrier."
Caveats and Uncertainties
- The Bureau of Meteorology warned that forecasts at this time of year tend to be less reliable.
- The strength of an El Niño does not guarantee strong impacts on Australian rainfall.
- The location of the warmest waters in the Pacific (central vs. eastern) can influence the extent of effects on Australia.
- Despite the El Niño outlook, no region is forecast to have "unusually" dry conditions in the June to August period.
- El Niño is an observation of Pacific conditions, not a specific forecast for Australia; other oceanic drivers can influence local weather.