Climate outlook for January to April

Issued 5 December 2019

Climate outlook overview

Drier than average January to March 2020 likely for eastern Australia, but wetter for parts of Western Australia.
January to March 2020 daytime temperatures are very likely to be above average across Australia.
January to March 2020 nights very likely to be warmer than average apart from the southeast.
Climate influences—the currently strong positive Indian Ocean Dipole (IOD) will weaken, while a negative Southern Annular Mode (SAM) may influence the first half of January before returning to neutral levels.

While the remainder of December is likely to be drier than average for most locations other than Tasmania, the rainfall outlook for January to March 2020 suggests drier conditions are likely in the east, and wetter than average conditions are possible in parts of WA. Eastern Australia is most likely to be drier than average in January, with chances of dry reducing somewhat in February.
Much of WA is forecast to receive average to above average rainfall for January to March, with northern WA predicted to have the highest chance of above average rain. The far north of the NT and northern Cape York Peninsula in Queensand is predicted to have average to above average rainfall throughout the outlook period.
While outlooks for drier than average conditions may ease for some areas heading into 2020, several months of above average rainfall would be needed to see a recovery from current long-term rainfall deficiencies.

Daytime temperatures for January to March 2020 are very likely to be warmer than average for Australia, except for western Tasmania and parts of the northwest. The chances of above-average daytime temperatures reduces slightly for much of Australia during February.
Warmer nights are likely for most of the country for January to March. However, Tasmania and southern Victoria have roughly equal chances of warmer or cooler than average nights.

The strong positive Indian Ocean Dipole (IOD) currently influencing Australia's weather will ease over the season, returning to neutral levels by February. Typically, a positive IOD means below average rainfall for much of central and southern Australia, and warmer than average temperatures for the southern two thirds of Australia. This is broadly consistent with the current outlook.
It is very unusual for the IOD to persist into January, as it normally breaks down when the monsoon moves into the southern hemisphere in late spring or early summer.
The late retreat of the monsoon from India and its slow movement south, plus a forecast weaking of the Madden-Julian Oscillation pattern, which can trigger enhanced monsoon development, means the Australian monsoon could potentially be several weeks late.
A negative phase of the Southern Annular Mode (SAM) is expected to continue into early January. A negative SAM in summer tends to bring drier conditions to parts of eastern Australia, but wetter conditions to western Tasmania.
While tropical Pacific Ocean temperatures are likely to stay warmer than average, the El Niño–Southern Oscillation (ENSO) is expected to remain neutral until at least early 2020, and therefore will have a reduced influence on Australian climate.
In addition to the natural drivers such as ENSO and the IOD, Australian climate patterns are being influenced by the long-term increasing trend in global air and ocean temperatures.

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