Consistent with Tuesday’s La Niña declaration, the Bureau of Meteorology’s Summer Outlook shows eastern Australia is likely to be wetter than average, with an increased risk of tropical cyclones, heavy rainfall and widespread flooding.
There are no strong swings to either wetter or drier conditions in South Australia, while parts of Western Australia are likely to see average to slightly above average rainfall.
The Bureau’s Head of Operational Climate Services, Dr Andrew Watkins said several climate drivers are likely to create continuing wet conditions for parts of eastern Australia this summer.
“Over winter and spring we saw a negative Indian Ocean Dipole, a pattern of ocean temperature patterns in the oceans to our west that was favourable to rainfall over Australia, and a dominant influence on our climate. While this event is approaching its end, warmer waters to the north-west of Australia may persist, and continue to increase the chance of rainfall.”
“The big driver looking at the months ahead is La Niña, which is now established in the Pacific Ocean for the second year in a row. La Niña describes a pattern of ocean temperatures that sees warmer waters in the western Pacific, which in turn drives increased atmospheric moisture and rainfall, including heavy rainfall, over Australia. This pattern is likely to continue through until at least the end of January.”
“December is likely to see our typical summer weather systems pushed further south than normal, meaning more humid air coming off the Tasman Sea, and into NSW and eastern Victoria.
Even though this will be a wetter summer for many, Dr Watkins said the outlook was an important reminder for the community to always be vigilant for the potential risks of severe weather.
“Spring has been wetter than normal and, as a result, soil moisture is high, water storages are full, and we’ve seen flooding in some areas. Any additional rain on our already wet landscape will increase the flood risk for eastern Australia this summer.”
Bushfire risk may not be as high this summer as in some recent years, but bushfires happen every summer in Australia and even short periods of hot and windy weather will raise the fire risk.
“This year we need to be extra careful about grass and crop fires, particularly across inland areas and in the southwest of the country where we have had good growth over winter and spring” Dr Watkins said.
Summer days are likely to be warmer than average across most of Australia, except in the south-east. Minimum temperatures are likely to be above average across most of the country, so we’re in for some warmer nights. [KB1]
“The risk of heatwave is about average this year, and it’s important to remember that heatwaves are Australia’s most deadly natural hazard. Warm nights after hot days in particular make heat stress a significant health risk,” Dr Watkins said.
La Nina also means we’re expecting an average to above average number of tropical cyclones and lows. We’ve already seen our first tropical cyclone of the season, roughly three weeks earlier than normal. The Australian region experiences an average of 9 to 11 tropical cyclones each year, with four typically crossing the coast. Even when cyclones remain well off-shore coastal impacts can still be felt.
