La Niña takes hold

It's official; the Bureau of Meteorology has declared a La Niña pattern is established in the tropical Pacific, and that is big news for weather in Australia. Indicators in the Pacific Ocean and the atmosphere above it currently exceed La Niña thresholds. Long-range forecasts show there is a high chance La Niña will last until at least January 2021.

La Niña typically means wetter weather for much of eastern Australia, so it is no surprise that much of the south-eastern mainland away from the coast has high chances (above 80%) of a wetter than average October to December. That includes parts of northern and western Victoria. At the same time, days are likely to be warmer than average south of the Dividing Range and nights are very likely (greater than 80% chance) to be warmer than average across the state, and most of Australia.

Adding to the wet signal for the months ahead is a higher than normal chance of a negative Indian Ocean Dipole. A negative Indian Ocean Dipole is when warmer waters concentrate near Australia's north-west, generating extra cloud and favouring weather patterns that can bring more rainfall to south-eastern Australia. While some of the climate models anticipate a negative Indian Ocean Dipole pattern will last for a couple of months, others show a return to more neutral conditions in November. Indian Ocean Dipole events tend to break down when the monsoon arrives in the southern hemisphere around the end of spring. Last year was a notable exception when a strong positive Indian Ocean Dipole lasted until the last week of December, coinciding with a late arrival of the monsoon over northern Australia, and a very dry October and December for Victoria (eighth-driest and third-driest respectively). This year is looking quite the opposite.

Looking back on September, rainfall has been below average for most of the eastern half of Victoria and very much below average (in the bottom 10% of records) for Central and East Gippsland. Most of Western Victoria has had near average rainfall and parts of the south-west even had above average monthly totals. Despite snow down to low levels and a few very cold days in the last weekmaximum temperatures were 68 °C below average on 25 September in parts of the west and the North Eastaveraged over the month, days and nights have been warmer than usual across the state.

Recent Weather Updates

  • A wet start to the week | 27/11/2020  

    Thunderstorms affected most of Victoria on Sunday, with isolated severe thunderstorms about the south and west, including the northern suburbs of Melbourne.

  • State of the Climate 2020 | 20/11/2020  

    The Bureau of Meteorology and CSIRO released the latest State of the Climate report last week. The report draws on current climate research, encompassing observations, analyses and projections to describe year-to-year variability and longer-term chan

  • La Niña likely to last all summer | 13/11/2020  

    Parts of Victoria recorded some rainfall this week but the second half of November is looking drier than average for parts of the south and south-east.

  • Wet weather and warm nights likely to continue | 6/11/2020  

    October rainfall was higher than average for much of Victoria, with parts of the east and some pockets of the west very much wetter than average (in the wettest 10% of records).