Climate outlook for December to March
Climate outlook overview
- Drier than average for the second half of November for most areas, with summer likely to be drier in large areas of the east but wetter in the northwest.
- Above average daytime temperatures across most of Australia for summer.
- Minimum temperatures—mixed outlook for the remainder of November. December to February nights warmer than average almost nation-wide.
- Climate influences—a strong positive Indian Ocean Dipole (IOD) is likely to persist until early-to-mid summer, and a negative Southern Annular Mode (SAM) is likely for the remainder of November.
Drier than average likely for the remainder of 2019, but may start to ease in early 2020
- Rainfall is likely to be below average across most of the country for 11 to 24 November and 18 November to 1 December, although northwest Australia, southern Victoria and western Tasmania have a neutral to wetter than average outlook. For the remainder of November, the pattern of drier conditions in NSW and wetter in western Tasmania is consistent with a negative Southern Annular Mode.
- The drier outlook continues into December for most of Australia. The summer (December to February) outlook is more neutral, although much of eastern Australia remains likely to be drier than average while northwest WA is likely to be wetter than average.
- While outlooks for drier than average conditions may ease for some areas, several months of above average rainfall would be needed to see a recovery from current long-term rainfall deficiencies.
Warmer days likely for the rest of spring and summer
- Daytime temperatures for summer are likely to be warmer than average across Australia, with many areas having a greater than 80% chance of warmer than average days. However, the second half of November is likely to be cooler than average in southeast SA, most of Victoria and Tasmania.
- Nights are likely to be cooler than average for most areas for 11 to 24 November, but warmer in western WA, parts of southeast Queensland and northeast NSW.
- Cooler nights for the southeast and northeast continue in December for some areas, but December to February nights overall are forecast to be warmer than average almost nation-wide.
- The strong positive Indian Ocean Dipole (IOD) continues, with a latest weekly value of +2.0 °C (week ending 3 November 2019), well above the positive IOD threshold of +0.4 °C. Typically, a positive IOD means below average spring 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.
- IOD events typically have little influence on Australian climate from December to April, meaning the positive IOD's contribution to the drier outlook should start to reduce in summer. However, given the positive IOD is so strong, it is likely to take several weeks to decline, and could persist well into mid-summer.
- A negative phase of the Southern Annular Mode (SAM) is expected for the rest of November. A negative SAM in spring tends to bring drier conditions to parts of eastern Australia, but wetter conditions to western Tasmania. This rainfall pattern is seen in the outlook for the second half of November. A negative SAM also increases the chance of spring heatwaves occurring across southern and eastern Australia.
- While forecasts of the El Niño–Southern Oscillation (ENSO) briefly dip into El Niño territory, ENSO is expected to remain neutral until at least early 2020.
- 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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