Charts of the Past with Blair Trewin
BAMOS Sept 2017
32
Charts of the Past with Blair Trewin
23 June 1981
The winter of 1981 was a very wet winter in much of mainland southeastern Australia, especially in Victoria where it was the wettest winter on record. Repeated cutoff lows resulted in June, July and August all being substantially wetter than average. Although seasonal mean temperatures were close to the 1961-1990 average, the systems which occurred were still cold enough that most of the precipitation fell as snow on the higher parts of the Australian Alps; 1981 went on to have the highest peak snow depths on record at Spencers Creek in the NSW Snowy Mountains.
1981 also saw one of the most significant low-level snowfalls in parts of southern Australia. The system responsible for this reached Australia as an active cold front which crossed the southwest of Western Australia on 20 June. The front crossed South Australia the next day, by which time a cutoff low had formed south of South Australia. The cutoff low moved slowly to be centred west of Tasmania on the 22nd and near the southwest coast of Victoria on the 23rd, where it stayed nearstationary for two days before weakening in situ and being reabsorbed into the westerlies by the 27th.
The most significant low-level snowfalls occurred as a result of a pool of cold air on the west side of the low. Initially this affected South Australia, with snow on the 21st at Wilpena and Blinman in the Flinders Ranges. The snow extended further south the next day, falling to around 400 metres in the Mid-North and affecting centres such as Clare, Jamestown and Hallett, as well as the higher parts of the Mount Lofty Ranges. A notably cold day during this period was 6.4 ° C on the 22nd at Kimba on Eyre Peninsula, nearly 2 ° C below its next coldest day on record.
On the 23rd the focus of the snow moved to western Victoria. In southwestern parts of the state it was described as the most significant snowfall since 1910, with falls to near sea level in places. Donald and Terang received their first reported snowfalls on record, and St. Arnaud its first since 1901, whilst there were also falls in Maryborough and Stawell. Snow also fell to low levels in northeast Victoria. The cold pool weakened the next day, although snow still fell on the 24th on the higher parts of the NSW Central and Southern Tablelands. Unsurprisingly, there were some very low maximum temperatures on the 23rd; Mount Gambier( 7.2 ° C) and Warrnambool( 7.0 ° C) had their coldest days on record, whilst June records were set at Ballarat( 4.2 ° C), Hamilton( 6.0 ° C) and Ararat( 5.0 ° C), and Beechworth( 2.4 ° C) had its coldest June day since 1922. The cold air largely bypassed Tasmania with no abnormal conditions reported there.
Rainfall totals with the system were generally light to moderate, although there were locally heavier falls( near 50 mm) in the Adelaide Hills and at Cape Nelson in southwest Victoria. Heavier rains occurred in northeast Victoria and the Adelaide Hills on the 25th, bringing significant flooding in the latter region. On the higher alpine peaks this fell as snow, with the snow depth at Spencers Creek increasing from 61 cm to 162 cm in a week.
In Western Australia, the main impact of the event was frost, with very low minimum temperatures in the southern inland on both the 22nd and 23rd. The most extreme conditions were in the Goldfields and Interior. Menzies( −4.8 ° C) had its coldest night on record, while June records were set at sites including Yeelirrie( −5.0 ° C), Kalgoorlie( −3.0 ° C) and Giles( −1.6 ° C).
Synoptic chart for 1000 AEST, 23 June 1981