Southern and southeastern Australia is currently experiencing one of the most potent cold fronts of the year so far. This powerful early spring weather system will blast through as a cold weather outbreak in the coming days, bringing a wide range of weather phenomena to the region, including rain, thunderstorms, destructive winds, bone-chilling wintery temperatures, low-level snowfall, and even the potential for a hazardous squall line.
Despite recently experiencing the warmest winter on record, cold wintery conditions are poised for a resurgence in the southern part of the country. The impact of the cold blast will be felt just when the tell-tale signs of spring have begun to appear, with states like Victoria experiencing several warm and mostly sunny days this week.
The satellite image below shows a large region of scattered clouds to the south and southwest of Australia, indicative of the extensive cold air mass en route from the Indian Ocean toward the southern parts of the Australian continent in the next few days.
(Himawari8 Sat Image, 6/9/23. Source – RAMBB, Colorado State University)
By Wednesday evening, this icy air mass had traversed southern Western Australia, bringing abnormally cold temperatures to the southern coastal areas, including the towns of Albany and Hopetoun, where the top temperatures for the day were 15 degrees Celsius (C), and Esperance, where it reached only 14 degrees C. Thursday will be another cold day in southern Western Australia before temperatures rise into the weekend.
The cold front has extended its reach to South Australia throughout Thursday. It will eventually envelop southeastern Australia, including Victoria, Tasmania, and New South Wales, from Thursday to Friday.
Weather forecast models now suggest a large temperature gradient will set up across South Australia, New South Wales, and Victoria, with a deepening, low-pressure system to form in response to very cold polar air moving NE behind the strong cold front.
South Australia becomes the focus for the impact of this cold weather outbreak on Thursday as the frontal band begins to push through early, bringing a band of showers and isolated thunderstorms, possibly tending to rain in the south of the state. A cold pool will develop due to widespread convective showers and isolated cold air thunderstorms (coldies) with small hail in the state’s agricultural areas.
Although the rain over the next few days will be welcome, especially in light of the climate outlook for Spring and Summer, this system could have some potential negative impacts on agriculture and primary producers. We will explain these potential negative impacts later in this article.
On Thursday night, the surface low will deepen rapidly with a vigorous low-level jetstream (a fast-moving ribbon of air in the low levels of the atmosphere) to wrap up the western side of the low, as shown in the image below. The focus at this time will be on the Gulf regions, Adelaide, and Mount Lofty Ranges in South Australia, with a short and narrow time period of damaging winds possible, with gusts potentially to 45-50 knots (83-92kph) for some isolated areas, and more widespread gusts to 30-35 knots (56-65kph) in the region.
GFS model 850hPa winds(5,000ft) showing low-level jetstream into gulf regions of SA
During Thursday night and into the early hours of Friday morning, the coldest air moves up in the lower levels with moisture wrapping around a tight kink or shortwave trough rotating up and around the main surface low, driving an expected increase in showers and damaging winds.
There will be some potential for snow at Mount Lofty and even more potential for snow for the higher terrain over the Mid-North. Locations including Mount Bryan, Hallett, Orroroo, Peterborough, and the Southern Flinders Ranges, including Mount Remarkable, look set to get a dusting of snow. Although snowfall in South Australia in Spring is a little unusual, it is not unheard of. A similar cold front event occurred in October 2012, and a significant cold weather outbreak occurred more recently in October 2020.
Possible impacts of this cold outbreak weather event on agriculture and primary producers in southern Australia
Damage to crops from wind
As mentioned, the cold weather outbreak will move through South Australia on Thursday and Thursday night. When it does, it is expected to bring strong to damaging winds in a narrow band that will potentially blow flowers off heads of canola crops.
Damage to crops from frost
Once the front moves through South Australia, a large high-pressure system is expected to move in behind it, leading to a rapid moderation of winds in the region. When this occurs, it is expected that cold air aloft, left over from the recent system, will sink down through the zone of high pressure, increasing the chance of moderate to heavy frost at the surface, especially across the Mid-North and Riverland areas of the state on Friday morning and possibly again on Saturday morning.
Impact on crops from possible heat forecast for the end of the month
The cold, dry air expected to be in place behind the frontal zone as it moves eastward throughout the weekend is then expected to shift westward around the new high-pressure zone, where it will heat up over inland Western Australia (dry air heats more quickly than moist air).
Such an outcome will contribute to hot conditions expected to move southeast by mid-month, potentially impacting the same areas experiencing this cold blast.
Broad impacts of this frontal system as it moves eastward
As the system progresses throughout Thursday and Friday, the impending collision between the eastward-moving cold air mass and the existing warmer air mass over eastern Australia is set to generate a dynamic array of weather conditions.
Showers are anticipated to develop across multiple regions on Thursday and Friday, including South Australia, Victoria, Tasmania, the Australian Capital Territory, New South Wales, and southern Queensland, gradually spreading from west to east each day.
Thunderstorms will likely affect parts of South Australia, New South Wales, Victoria, and Queensland on Thursday and Friday. There is also a chance of isolated storms in the Australian Capital Territory and Tasmania. Some of these storms may become severe, with the primary threats being damaging winds and large hail.
A squall line could form over western New South Wales on Thursday as the front advances across the state, raising the risk of damaging winds and lightning as it moves from west to east. With recent dry conditions, raised dust through the region could lead to dramatic scenes.
Blustery winds will accompany the cold front’s passage, with the possibility of damaging gusts, particularly in parts of Tasmania, Victoria, and New South Wales, predominantly in elevated areas.
Ahead of the front, lower pressure will increase wind and warm air, briefly elevating fire danger ratings in central and eastern Australia in an ominous fore-warning of the fire season on the horizon later this year.
Following the front, low temperatures risk livestock in some southern and southeastern Australian regions.
Snowfall is expected in elevated Tasmania, Victoria, and New South Wales. At the same time, some lower-elevation snowfall is likely in Tasmania, Victoria, and southern New South Wales. There is also a chance of snow falling in elevated areas of central New South Wales on either Friday or Saturday.
3-day Wind Accumulation from this weather event – windy.com
Although this weather system is significant, it should be noted that spring in Southern Australia is a time of great atmospheric dynamics, with larger temperature gradients typically in place from locations ahead to locations behind the frontal boundaries. Severe weather is almost always assured when these interactions come together similarly to the current event. It can bring weather that feels like we’re experiencing four seasons in one day, something the population of Southern Australia is all too familiar with.
But certainly, in the not-too-distant future, the cold blast we are currently experiencing will be replaced with warm to even hot conditions as the inland heat engine over the dry Australian interior begins to crank up again. The weather in the coming weeks will quickly remind us that spring is well and truly here, and summer is just around the corner.
Sources & Credits:
Weatherzone
Bureau of Meteorology
Colorado State University,
BSCH Stormcast
CSIRO
Windy
See also this recent article relating to Australian weather: