Bombing low drops more than a month’s worth of rain over Sydney in just one day, Australia

Sydney, Australia recorded 142.6 mm (5.6 inches) of rain on June 1 and 2, 2024, surpassing its June average of 132 mm (5.2 inches) in just one day and marking its second wettest June day on record.

Sydney has been inundated with more than a month’s rain in less than 24 hours over the weekend, causing flash floods in parts of the city. The rain was driven by a rapidly deepening low pressure system over the Tasman Sea.

According to Weatherzone, the low formed on Saturday and intensified so quickly that its central pressure dropped by 19 hPa during the 24 hours ending at 16:00 LT on Sunday.

“At Sydney’s latitude, this rate of pressure change was enough to classify the system as a ‘bombing low’, which is the name given to mid-latitude low pressure system that deepens rapidly in a process called explosive bombogenesis,” Weatherzones Ben Domasino noted.

This was the second bombing low pressure system near Australia in one week after another low deepened by 30 hPa in 24 hours over the Great Australian Bight from May 29 into May 30.

Dean Narramore, the senior meteorologist at the Australian Bureau of Meteorology, said the heaviest rainfall on Saturday was around Sydney, with 171 mm (6.7 inches) of rainfall in Rose Bay, 159 mm (6.2 inches) in Little Bay, and 142.6 mm (5.6 inches) in the city itself.

“A lot of our eastern suburbs of Sydney saw a month’s worth of rain in just 12 to 18 hours,” Narramore said.

The rain was largely localized to eastern Sydney, with western suburbs of Penrith and Richmond receiving between 20 mm (0.78 inches) and 30 mm (1.18 inches), while falls in the Hunter region ranged between 25 mm (0.98 inches) and 50 mm (1.96 inches).

Other impacts of this system included maximum wave heights off Sydney reaching 9.6 m (31.5 feet) by midday on Sunday. Additionally, Mallacoota experienced its wettest winter day on record, receiving 112 mm (4.4 inches) of rain in the 24 hours ending at 09:00 LT on Monday, surpassing all previous records since record-keeping there began in the 1970s.

As of 09:00 LT on June 4, the total rainfall in Sydney since the start of the year reached 1 020 mm (40 inches), marking only the 14^th instance in 166 years of records that the city has received over 1 000 mm (39 inches) of rain by this point in the year.

Typically, Sydney would reach 1 000 mm of accumulated rainfall in October and average just over 1 200 mm (47.2 inches) annually.

References:

¹ Sydney drenched by month’s worth of rain in less than a day – The Guardian – June 2, 2024

² The ‘bombing low’ behind Sydney’s weekend deluge – Weatherzone – June 3, 2024

³ Sydney hits one metre of rain four months ahead of schedule – Weatherzone – June 4, 2024

Featured image: Bomb cyclone over Tasman Sea on June 2, 2024. Credit: JMA/Himawari-9, Zoom Earth, The Watchers