Australian Weather

Today, 2:58AM UTC

If you don't like the weather, just wait five minutes. That's the classic old saying about Melbourne weather, and it definitely looks like it will apply for the next week or so. Persistent showers are streaming across the city today in a classic chilly southwesterly winter flow in the wake of a cold front and associated trough. Between the showers, large dollops of sunshine are on offer, until you pop out to grab a sandwich for lunch – you know the drill if you live in Melbourne – and rain hammers down for those crucial few minutes before quickly clearing again. How much rain has fallen/will fall? By midday Tuesday, nowhere in the greater Melbourne metro area had received more than 5 mm, while 1.2 mm had fallen in the city – most of it in a brief burst before 11 am. That has been the pattern for most of August to date. Rain has fallen on eight of the 16 days to date this month with just 12.6 mm accumulating overall in the gauge (with a little more in the city's east, as often happens with winter weather systems). Like we said, it's classic Melbourne weather: frequent showers which often don't amount to much overall. The same pattern looks likely to continue for the next seven days, with a few millimetres of rain expected on each day except Sunday, when there's just the slight chance of a light shower. Rain is likely to be heaviest on Thursday and Friday as a cold front crosses Victoria, with up to 10 mm possible on both days. What about the Victorian floods? Image: Vic weekly rainfall from Aug 9 to 15. Source: BoM. Interestingly, Melbourne dodged the heavy weekend rain that lashed Gippsland. You can see an indication of that on the Bom weekly rain chart above. The chart also shows that a large chunk of south Gippsland received between 50 mm and 100 mm of rain. That's the large, teal-coloured section. Gippsland resident Steve Mesaric told Weatherzone there was "loads of rain" that flowed down from the Strzelecki Ranges into low-lying paddocks, inundating them. A moderate flood warning remains in place for the La Trobe River, and several minor flood warnings are also in effect for other creeks and waterways. Please check our warnings page for the latest. Eastern parts of Victoria away from the mountains can expect rainfall totals similar to Melbourne's for the rest of the week, so with luck, there'll be nothing heavy enough to exacerbate the existing flood situation. Meanwhile, Melburnians should take an umbrella to work every day this week, just in case. Image: Or you could just ride a tram all day. Rain problem sorted! Source: @wimkantona via Pixabay. But as mentioned, you can also expect frequent patches of blue. Top temps should be a degree or so either side of 15°C all week, although it will start to feel colder as the wind picks up from midweek.

Today, 1:58AM UTC

New data reveals that a negative IOD is gaining strength in the Indian Ocean and La Niña is re-emerging in the Pacific Ocean, boosting the likelihood of heavy rain and flooding across Australia during the months ahead. The weather in Australia, and many other parts of the world, is strongly influenced by sea surface temperatures in the tropical Pacific and Indian Oceans. When the Pacific Ocean is in a La Niña pattern, cooler-than-normal water sits near the central and eastern equatorial Pacific Ocean and wetter-than-average water sits in the western tropical Pacific. This pattern of sea surface temperature anomalies drives moisture-laden winds towards Australia, which typically increases rainfall over large areas the country’s north and east. Image: Typical changes in sea surface temperatures and rainfall patterns during La Niña. A similar mechanism also occurs in the Indian Ocean, called the Indian Ocean Dipole (IOD). When the IOD is in a negative phase, abnormally cool water sits near eastern Africa and unusually warm water lies around Indonesia. This pattern of sea surface temperature anomalies sends more rain-bearing winds towards Australia from the northwest. A negative IOD typically enhances the frequency and strength of northwest cloudbands over Australia, which increases rainfall over parts of the country’s south and southeast. Image: Typical changes in sea surface temperatures and rainfall patterns during a negative IOD. New data out this week The Indian Ocean is currently in a negative IOD phase, which was officially declared earlier this month. However, new data came out at the start of this week showing that the IOD index had dipped to its lowest value since 2016. This means that the negative IOD is becoming entrenched to the northwest of Australia and is likely to enhance rainfall and flooding over our continent in the coming months. Image: Indian Ocean Dipole (IOD) weekly index values from the past 4.5 years. Likewise, the latest observations from the Pacific Ocean show that La Niña is now re-emerging after briefly weakening over the last couple of months. The graph below shows an index that monitors sea surface temperature anomalies in the central equatorial Pacific. Sustained negative values of this index represent periods of La Niña and as you can see, it has become more negative over the last five consecutive weeks. Image: NINO-3.4 weekly sea surface temperature anomaly values from the past 4.5 years. This latest data shows that both the Indian and Pacific Oceans are trending more towards a state that promotes rainfall and flooding over Australia. With most forecast models suggesting that this trend will continue over the coming months, large areas of Australia are expected to have a wetter-than-average spring, particularly over the eastern half of the country. Image: Seasonal rainfall outlook for spring from the Bureau of Meteorology.