Climate outlook for summer (December to February)
Issued 19 November 2015
Climate outlook overview
- December temperatures are likely to be warmer than average for southern Australia, while rainfall is likely to be above average across southeast Queensland and northeast NSW, parts of the interior and southwestern Australia.
- The summer outlook indicates below-average rainfall is likely across the northwest and Cape York Peninsula, and wetter across parts of the east. The daytime temperature outlook is patchy, with warmer days likely in parts of the west and north, while parts of the southeast are likely to be cooler. Overnight temperatures are likely to be warmer across most of the country except the southeast.
- Current climate influences include a combination of a strong El Niño in the Pacific, a decaying positive Indian Ocean Dipole, and very warm Indian Ocean temperatures. (See the climate influences section for more information).
Mostly neutral outlook for summer, drier in the northwest, wetter for parts of the far east
- December is likely to be wetter than average across southeast Queensland and northeast NSW, parts of the interior and southwestern Australia.
- Across most of Australia, the chances of a wetter or drier summer are roughly equal. However, summer is likely to be drier than average across northwest Australia and the Cape York Peninsula, while wetter than average conditions are favoured across southeast Queensland and northeast NSW.
- Current climate influences include a combination of a strong El Niño in the Pacific, a decaying positive Indian Ocean Dipole, and very warm Indian Ocean temperatures.
- Historical outlook accuracy for summer rainfall is moderate to high over most of WA, and moderate over the eastern mainland. Elsewhere, accuracy is low to very low.
Warmer start to summer for southern Australia
- The December outlook shows maximum and minimum temperatures are likely to be warmer across southern Australia and the far north of Australia.
- Summer daytime temperatures are likely to be warmer than average across some areas of WA, the northern tropics, and the far southeast mainland. Summer temperatures are likely to be cooler in parts of the southeast (see map).
- Overnight temperatures for summer are likely to be warmer than normal across much of the country except in parts of the northwest and eastern Australia, which have an equal chance of warmer or cooler nights.
- Current climate influences include a combination of a strong El Niño in the Pacific, a decaying positive Indian Ocean Dipole, and warm temperatures in the Indian Ocean outside the tropics.
- Maximum temperature accuracy is moderate over western and eastern parts of Australia, and low across central regions and western Tasmania. Minimum temperature accuracy is moderate over most of Australia.
Climate influences
- A strong El Niño continues in the tropical Pacific Ocean, and is very likely to persist into early 2016. The El Niño influence on Australian rainfall is variable at this time of year, with both wetter and drier summers observed in the past depending on how quickly the El Niño event breaks down. However, on average an El Niño summer brings lower than normal rainfall across northern Queensland with a later start to the wet season, and a slight drying influence across the southeast. Conversely, inland WA often sees an increased chance of rainfall at this time of year under El Niño.
- A positive Indian Ocean Dipole (IOD) and a strong El Niño in place have meant September and October have both been drier than average, which means the Australian landscape is not well buffered with moisture in the lead up to summer.
- Typically an IOD event decays in November or early December as the monsoon trough shifts south over the tropical Indian Ocean, changing the wind patterns. Once this occurs, the two dominating climate drivers are expected to be El Niño in the Pacific Ocean and the warm waters across the central and southern Indian Ocean. These competing climate drivers may ease the outlook back towards an above-average rainfall outlook.
- Bureau climatologists continually monitor the climate for any significant developments, with information on El Niño/La Niña and IOD events available fortnightly via the ENSO Wrap-Up. For a summary of Pacific and Indian Ocean outlooks, please see the Climate Model Summary.
