Australia to Experience a Massive Rainband Stretching Over 3,000 Kilometres
Australia is set to experience a massive rainband stretching over 3,000 kilometres next week. The rainband will bring soaking rains from the Pilbara and Kimberley, across the outback to the eastern seaboard. The upcoming drenching follows well-above-average rain already this June across southern states, essentially nullifying the forecast of a dry winter. Ski resorts are also rejoicing after a slow start to winter, with numerous snowfalls setting up a solid base for the upcoming school holidays.
A Season’s Rain to Fall Next Week
This winter is defying the odds which were strongly weighted to produce below-average rain. During the past 48 hours, rain has fallen across the whole of south-east Australia, including more than 15 millimetres for much of South Australia and northern Victoria, including 48mm in Adelaide and up to about 100mm on the Mount Lofty Ranges. This week’s good falls follow heavy rain earlier in June, leading to the wettest start to winter in decades for some towns in the Murray Basin. In Shepparton, the monthly total has exceeded 100mm for the first time in a winter calendar month since 1991.
Showers will continue along Australia’s southern coastline and ranges through the weekend, but the real surprise will arrive next week. From Monday, a river of tropical moisture will stream south along a jetstream from the warm tropical waters north of Western Australia and lead to the formation of a north-west cloudband. This mammoth mass of cloud and rain will gradually shift east across central Australia early in the week and reach the south-east states from Wednesday.
From Thursday, the cloudband’s movement is less certain, although rain should continue through much of the interior and east. The system should deliver anywhere from 10 to 100mm across a wide swathe of north-west, central and south-east Australia with falls on the higher end of the range enough to easily surpass the winter average in just a few days for the outback. Towards the end of the week, even more rain is likely. A low-pressure system may develop well north of the usual winter storm track to produce further heavy falls as far north as tropical Queensland.
Deviation from El Niño
Through autumn all the boxes were ticked for a dry season, including a developing El Niño, a potential positive Indian Ocean Dipole (IOD), and the climate change-driven reduction in cool season rains. However, the most important factors behind the welcome deviation from the forecast are:
1. The positive IOD has not developed. While El Niño steals the headlines, in the cooler months when westerly winds dominate it’s the ocean to our west which can have a greater influence on our weather patterns and the failure of a positive IOD to form has allowed cloud bands to spread east over the country.
2. The winter storm track (the position of rain-producing low-pressure systems) has shifted well north, a rare occurrence in recent years.
Snow Season Improving by the Day
Another positive of the northward shift in the winter storm track is the slow start to this year’s snow season is improving rapidly. Mount Hotham Resort reported a natural snow depth of 54 centimetres on Friday, 21cm above the average for this time of year. Snow will continue falling across the Alps during the next five days, bringing another 30 to 40cm and establishing a deep cover in time for the upcoming school holidays.
Australia is set to experience a massive rainband stretching over 3,000 kilometres next week. The rainband will bring soaking rains from the Pilbara and Kimberley, across the outback to the eastern seaboard. This comes after well-above-average rain already this June across southern states, essentially nullifying the forecast of a dry winter. The positive IOD has not developed, and the winter storm track has shifted well north, a rare occurrence in recent years. Ski resorts are also rejoicing after a slow start to winter, with numerous snowfalls setting up a solid base for the upcoming school holidays.