Tornado strikes south of Bungendore as Canberra cops supercell storm

The trail of destruction left behind suggests the supercell storm that struck Forbes Creek south of Bungendore on Saturday was a tornado, on the same night Canberra had its highest daily rainfall for the month.

Weatherzone meteorologist Ben McBurney said it was one of a number of "very severe" supercell storms that moved around Canberra on Saturday after an earlier supercell at Canberra Airport in the afternoon.

"If you have tornadic damage it tends to be in all different directions; you see trees twisted around power poles," he said.

"It tends to be very localised across maybe a 100-metre wide path."

The extent of the damage indicated wind speeds of at least 100 km/h, Mr McBurney said, but the "weak tornado" was too localised for exact speeds to be calculated.

"The highest wind gusts at Canberra [the nearest weather station] were 70km/h from the afternoon storm, which is fairly strong but not really considered damaging," he said.


Mr McBurney said the conditions on Saturday across the ACT and southern NSW were favourable for tornadoes caused by strong vertical wind shear and high amounts of low level moisture.

"For vertical wind shear you need different wind directions at different levels," he said.

"You can imagine that creating turning in the atmosphere.

"At same time we had low lifting condensation levels … that generally encourages low storm bases and more likely conditions for a touch-down."

While Forbes Creek resident Rosemary Smith said she had never witnessed a similar storm in the 15 years she had lived in the area, Mc McBurney said tornadoes were not uncommon with about one a year reported in the region.

"Around the southern area of NSW they seem to get tornadoes more frequently than other parts of the state," he said.

"The area around Cooma and Canberra tends to get quite a few reports.

"Because its south, you're towards Antarctica so you tend to get stronger wind shear in general, but it's far enough north to get large amounts of moisture."

While storms on Saturday afternoon and evening in Canberra brought 28 millimetres of rain, the highest daily fall for the month, Mr McBurney said further south was "drenched" with the Bega, Merimbula and Narooma areas receiving 100 to 150 millimetres.

The rain was predicted to remain for Canberra on Monday, with a high of 24 degrees. The skies are expected to clear on Tuesday when a top of 29 degrees was predicted.

Wednesday had the potential for showers and a top of 29 before a cool change on Thursday when a maximum of 26 was expected.

Weatherzone is owned by Fairfax Media, publisher of the Canberra Times.