With serious bushfires affecting the Western Downs in Qld and cyclone activity around our coasts, maybe you have been wondering what is happening with our weather patterns? What is the forecast for the next few weeks?
Large areas of western Queensland are hot and dry, hence the bushfire risk, but tropical lows recently developed across northern Australian waters with two - TC Freddy in the West and TC Gabrielle in the Coral Sea - becoming tropical cyclones. The Bureau of Meteorology (BOM) indicates that while the current La Niña event continues to ease, “the atmosphere has been slower to respond and remains La Niña-like” (BOM 14/2/2023). Consequently, monsoon conditions are expected to continue, resulting in above-average rainfall for many parts of northern Australia. The BOM issues interesting weekly climate updates which explain what is happening - they indicate a transition coming around late February. Here are the key climate drivers that BOM monitors for Australia's climate:
SSTs sea surface temperatures have weakened since their peak during spring 2022 but are still warmer than average to the south and south-east of Australia resulting in greater evaporation, humidity, cloudiness, and rainfall. All models anticipate SSTs in the central Pacific will return to neutral ENSO (El Nino Southern Oscillation) levels during late February, with neutral conditions (neither La Niña nor El Niño) anticipated until at least mid-autumn.
SAM Southern Annular Mode refers to the north-south movement of the strong westerly winds that blow almost continuously in the mid- to high-latitudes of the southern hemisphere. These westerly winds are associated with storms and cold fronts that move from west to east. The SAM is currently strongly positive, indicating increased summer rain, but is anticipated to ease over the coming weeks and then remain neutral.
MJO Madden–Julian Oscillation is a feature of the tropical atmosphere, an eastward moving 'pulse' of cloud and rainfall near the equator that typically recurs every 30 to 60 days. A strong MJO pulse is currently over the western Pacific bringing monsoonal conditions and above-average rainfall across northern Australia. This MJO pulse is forecast to move into the eastern Pacific in late February.
IOD Indian Ocean Dipole is the difference between SSTs of the tropical western and eastern Indian Ocean. The IOD has three phases: positive, neutral, and negative. A positive IOD results in suppressed rainfall and conversely a negative IOD results in enhanced rainfall in the Australian region. Currently the IOD is neutral and is having little influence on Australian climate.
The BOM also notes that climate change continues to influence Australian and global climates. Australia's climate has warmed by around 1.47 °C over the period 1910–2021. There has also been a trend towards a greater proportion of rainfall from high intensity short duration rainfall events, especially across northern Australia.
Contributed by Dr Iraphne Childs
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