The Bureau of Meteorology has released weather data for the next three to four months for the tropical north.
La Niña is currently active across the tropical Pacific Ocean.
La Niña is typically associated with above-average rainfall across much of eastern Australia during spring and into early summer. Model outlooks suggest the La Niña will peak around December or January, and is likely to persist until at least the end of the 2020-21 Australian summer.
For the November, December, January (NDJ) and the DJF (December, January, February) periods, both daytime and overnight temperatures are likely to be warmer than average along the coast.
The Indian Ocean Dipole (IOD) is neutral. Most models indicate that the IOD will remain neutral over the coming months.Waters to the north of Australia have warmed over the past month, which may also enhance rainfall over the continent.
The Southern Annular Mode (SAM) is expected to be positive in the coming weeks, with generally positive values expected over the 2020-21 summer. The current La Niña and strong polar vortex favour a positive SAM. This typically enhances the wet signal of La Niña in parts of eastern Australia, although western Tasmania is often drier.
Australia’s temperature and rainfall variability are also influenced by global warming caused by human activities. Australia’s climate has warmed by around 1.4 °C since 1910 while recent decades; have seen increased rainfall during the northern wet season (October–April), with more high intensity and short duration rainfall events.
The Bureau’s climate model uses the physics of our atmosphere, oceans, ice, and land surface combined with millions of observations from satellites and on land and sea. As a result, it incorporates the influence of climate change and natural climate drivers like ENSO, IOD, the MJO, and SAM in its outlooks.
- December to February is likely to be wetter than average for nearly all of Australia (with a greater than 70% chance in most areas), except western Tasmania where there is increased chance of drier than average conditions. A similar outlook exists for December though the likelihood of above average rainfall is not as high (greater than 60% chance in most areas).
- The fortnight of 16-29 November 2020 is likely to be wetter than average for north-east WA and adjacent NT (with a greater than 75% chance), while drier than average conditions are more likely along the Gulf coastlines, northern Queensland, western Tasmania and parts of eastern Victoria and south-west WA. Roughly equal chances of wetter or drier conditions are forecast for most of the remainder of Australia.
- While the outlooks indicate wetter than average conditions, southern parts of Australia are entering into their drier season, so rainfall is not likely to be sufficient to relieve long-term rainfall deficits.
- Warmer days for much of the south-east, as well as the far north and far west during December to February; warmer nights very likely for all of Australia
- For the fortnight 16-29 November, average daytime temperatures are likely to be above the long-term average for almost all of Australia (greater than 75% chance), except for far west WA and the Kimberley region where roughly equal chances of warmer or cooler days are more likely. On average, nights during this period are very likely to be warmer than the long-term average across almost all of Australia (greater than 80% chance), except for inland of Queensland’s North Tropical Coast where roughly equal chances of warmer or cooler nights are more likely.
- The average maximum temperature for December to February is likely to be higher than the long-term average for Victoria, Tasmania, the far west of WA, the northern coastlines of NT and Queensland, and parts of eastern SA, southern Queensland and western NSW. However, it is likely to be cooler than the long-term average for south coast WA, north-east WA, and north-west NT.
- The average minimum temperature is very likely (greater than 80% chance) to be higher than the long-term average across Australia during December to February, apart from around south-east WA where there is a closer to 60% chance.
Tropical Cyclone Outlook
- The Bureau of Meteorology has released its Severe Weather Outlook, www.youtube.com/watch?v=KtdFJggSIUU&feature=youtu.be through till April 2021, showing an increased risk of flooding for eastern Australia and tropical cyclones in the north, with roughly average potential for heatwaves and severe thunderstorms.
- While recent decades have seen a decline in the number of tropical cyclones in our region, Bureau climatologist, Greg Browning, says this summer is likely to buck that trend.
“On average Australia sees 9 to 11 tropical cyclones each year, with four crossing the coast. With La Nina this year we are expecting to see slightly more tropical cyclones than average, and the first one may arrive earlier than normal,” Mr Browning said.
“Every northern wet season has had at least one tropical cyclone cross the Australian coast, so we can never be complacent. We know that cyclones can develop at any time throughout the tropical cyclone season, which runs from November to April,” he said.
“This means that communities right across northern Australia need to stay be prepared now, and stay informed from the very start of the tropical cyclone season in October, right though until April.”
- Now, more than ever, it’s vital to heed the Bureau’s warning to know your weather, and to know your risk.
Summary of the Tropical Cyclone Seasonal Outlook
- La Nina is likely to bring more rain than usual, with an increased risk of widespread flooding
- Likely to see more tropical lows and cyclones than normal
- Earlier start to the wet season across the north
- Average numbers of severe thunderstorms
- About Tropical Cyclones – http://www.bom.gov.au/cyclone/tropical-cyclone-knowledge-centre/
- Tropical cyclone warnings and information: www.bom.gov.au/cyclone
- National Tropical Cyclone Outlook: www.bom.gov.au/climate/cyclones/australia/