Climate outlook for May to August
Climate outlook overview
- Early May is looking drier than average, with the week of 4 to 10 May likely to bring reduced rainfall for most of Australia.
- May to July overall is likely to be wetter than average for most of the southern two-thirds of Australia. However, parts of the tropical north, and areas east of the Great Dividing Range have roughly equal chances of being wetter or drier than average.
- May to July days are likely to be warmer than average across northern, eastern and far southwest Australia while nights are very likely to be warmer than average nationwide.
- A warmer than average eastern Indian Ocean is currently the main influence on Australia's climate, increasing the moisture available to weather systems as they sweep across the country.
Above average May to July rain likely for southern two-thirds of Australia
- The week of 4 to 10 May is likely to be drier than average for most of Australia (mostly 60–70% chance in eastern parts, greater than 70% chance further west), with no wetter or drier signal for the southwest, northeast and eastern coast. The drier signal extends through to the following week of 11 to 17 May across parts of the southeast and far north.
- However, the three months from May to July are likely to be wetter than average for most of the southern two-thirds of Australia (mostly 60–75% chance, greater than 75% chance for the Pilbara, extending into southeast WA and western SA). The likelihood of a wetter or drier May to July is roughly equal across the tropical north, areas east of the Great Dividing Range, and eastern Tasmania.
- Similarly, winter (June to August) is also likely to be wetter than average for most of Australia (mostly 65–80% chance, with higher chances in central and inland southeast Australia).
- It should be noted that May marks the official start of the northern Australian dry season. This means tropical northern Australia typically has very low rainfall totals, and only a small amount of rainfall is needed to exceed the median.
Warmer May to July days for north and east
- May to July days are likely to be warmer than average in northern, eastern and far southwest Australia (greater than 80% chance for the tropical north, mostly 60–80% in other parts). Elsewhere, days have roughly equal chances of being warmer or cooler than average for the three months. However, for the month of May, days are likely to be cooler in southeast Australia (60–70% chance).
- May to July night-time temperatures are very likely to be warmer than average for most of Australia (70–80% chance for southeast Australia, greater than 80% chance elsewhere).
- A warmer than average eastern Indian Ocean is increasing the likelihood of northwest cloudbands interacting with rain-bearing fronts and troughs as they sweep across the country during late autumn and early winter.
- While the Indian Ocean Dipole (IOD) is currently neutral, the outlook suggests a negative IOD could develop later in the outlook period. Caution should be exercised with using IOD forecasts issued during autumn, as they are less accurate than forecasts made at other times of the year. However, all other international models surveyed by the Bureau also indicate a negative IOD could form during 2020. Negative IOD events typically increase the likelihood of above average winter-spring rainfall across southern Australia.
- The El Niño–Southern Oscillation (ENSO) is most likely to remain neutral over winter, but may cool towards La Niña levels by late winter or early spring. As the chance of La Niña currently remains less than 50%, our ENSO Outlook remains at INACTIVE.
- In the shorter-term, higher pressure systems are expected to dominate much of Australia in early May, resulting in the dry outlook for 4 to 10 May.
- The Southern Annular Mode (SAM) has recently been weakly negative, but it is likely to return to neutral for the next three weeks. At this time of the year, SAM has little influence on Australian rainfall.
- Australia's temperature and rainfall variability are also influenced by global warming caused by human activities. Australia's climate has warmed by around 1.4 °C since 1910, while southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.
- The Bureau's climate model uses the physics of our oceans, ice and land surface combined with millions of observations from satellites and on land and sea. As a result, it includes the influence of climate change and natural climate drivers like ENSO, IOD, the MJO and SAM in its outlooks.
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