A wetter than normal July to September period is considered likely for most of Australia, according to the Bureau of Meteorology’s latest three month outlook.

The parts of Australia not expected to receive higher than average rainfall, or lower than average rainfall, according to the outlook are Tasmania and parts of the tropical north and western WA coast.
The climate is being influenced by a developing negative Indian Ocean Dipole, a neutral-to-cool tropical Pacific, and warm sea surface temperatures around the coast of Australia
The Bureau says the chance of exceeding the median rainfall for July to September is more than 60pc over most of mainland Australia, except for parts of the tropical north and the western WA coastline.

The chance rises to more than 80pc over southern NSW and northern Victoria.

Such odds mean that for every ten years with similar climate patterns to those currently observed, about six to eight July to September periods would be expected to be wetter than average over these areas, while about two to four would be drier.

However, over tropical Australia it is seasonally dry at this time of year, with July-September median rainfall between 0 and 1 mm at many locations; even a small amount of rain would exceed the median in these areas.

The chance of receiving a wetter or drier than normal July to September is roughly equal (i.e. close to 50pc) over the western coastline of WA, parts of the northern NT, northern Queensland, and Tasmania.

A negative IOD during winter-spring increases the chances of above normal rainfall over southern Australia.

The tropical Pacific has remained ENSO-neutral since mid-2012.

The Bureau said the dynamical seasonal outlook model indicates an increased likelihood of La Niña forming during the next few months.

This has increased the chance of above normal rainfall for northern and eastern Australia. However, international climate models surveyed by the Bureau of Meteorology suggest ENSO-neutral is the most likely outcome over the coming season, with the Bureau model showing stronger odds than most of a weak La Niña.