A strong high pressure system south of the Great Australian Bight dropped temperatures below zero across inland New South Wales, Victoria and South Australia overnight, with the Bureau of Meteorology issuing sheep graziers warnings in two states on Thursday morning.
The Bureau's national warnings summary at 9:15am AEST carried no severe weather warning, no severe thunderstorm warning, no fire weather warning and no heatwave warning anywhere in Australia. The two sheep graziers warnings are the only land-based warnings in the country.
In South Australia, warning IDS20242 was issued at 3:15am CST for the Flinders and Mid North forecast districts. "Sheep graziers are warned that cold temperatures and easterly winds are expected during Thursday," the Bureau said, adding that there is a risk of losses of lambs and sheep exposed to those conditions. In New South Wales, IDN29000 was issued at 4:48am EST for the Snowy Mountains district on the same grounds, with south-westerly winds. Both were due for reissue by 11am local time.
Goulburn Airport fell to minus 5.9C at 6:11am, the coldest reading in the country. The Bureau's climate statistics for the station give a September mean minimum of 3.0C across 35 years of record, which puts Thursday morning 8.9C below the September average. Canberra recorded minus 2.7C at 4:40am against a September mean minimum of 3.1C.
Thredbo Top Station reached minus 5.1C, Mount Ginini minus 4.2C, Perisher Valley minus 3.9C and Braidwood minus 3.6C. In Victoria, Mount Hotham fell to minus 4.5C at 4:51am, Falls Creek to minus 4.0C and Mount Buller to minus 3.0C, with Rutherglen at minus 0.4C on the plains. South Australian minima included minus 1.2C at both Keith West and Wudinna Airport, minus 0.9C at Kyancutta and minus 0.5C at Naracoorte.
The pressure readings are the clearest measure of how firmly the system is sitting over the south-east. Pallamana and Mount Gambier in South Australia both recorded 1039.8 hPa at 8:40am CST, with Dartmoor in Victoria at 1039.5 hPa and Adelaide's West Terrace at 1038.8 hPa. The Bureau's published extremes tables do not carry a national mean sea level pressure record, so no record claim can be made against those figures.
The Bureau's Victorian state forecast, issued at 4am EST, described "a strong high pressure system south of the Bight" directing a cool south to south-westerly airstream across the state, with the high extending a ridge over Victoria on Thursday before crossing Bass Strait on Friday. The New South Wales forecast has a second high drifting across the state's south later in the week and entering the Tasman Sea by the weekend, with what the Bureau calls generally stable weather patterns.
Wind gusts stayed well under warning thresholds. The strongest readings in the country were 83 km/h at Cape Byron at 3:44am and 82 km/h at Wilsons Promontory at 12:45am, against the 90 km/h damaging wind criterion. Rainfall was close to nil, with the heaviest fall in the observation tables 7.2mm at Ernabella in South Australia.
The eastern flank of the high is still driving swell up the New South Wales coast. The hazardous surf warning was reissued at 4:52am EST for the Coffs, Macquarie, Hunter, Sydney, Illawarra and Batemans coasts on Thursday, adding the Byron Coast on Friday, and runs until midnight Friday. The Sydney Coast waters forecast has southerly swell of 2.5 to 3 metres on Thursday, easing to 2 to 2.5 metres on Friday and 1.5 to 2 metres on Saturday.
Tasmania has the strongest marine product in the country. A gale warning is current for the South East Coast on both Thursday and Friday, with westerly winds of 25 to 30 knots reaching 35 knots offshore and south-westerly swell of 5 to 7 metres easing to 4 to 6 metres.
The final flood warning for the Murray River at Barham, issued on Tuesday afternoon, remains listed on state summaries but states that no further flooding is expected. The river was at 5.48 metres and steady, below the 5.50 metre minor flood level.
The Bureau expects patchy morning frost to continue on the New South Wales ranges and southern slopes on Friday, and areas of morning fog and patchy frost across Victoria, before temperatures climb above average on Saturday as the high moves into the Tasman. The next routine state forecasts are issued at 4:30pm EST Thursday, with the sheep graziers warnings reviewed at 11am local time.
