Experts from the Bureau of Meteorology believe ‘‘a whole family of tornadoes’’ hit the region early Sunday morning, with four separate twisters now reported.
Attention focused on serious property damage in Kiama in the immediate aftermath of the storm, but there are also tell-tale trails of destruction at Gerroa, Jamberoo and Albion Park Rail.
Andrew Treloar, the bureau’s manager of weather services NSW, toured the region yesterday and confirmed damage in Kiama and Gerroa was the result of tornado activity.
He said the Kiama tornado was likely a category F1, or moderate, on the six-tiered Fujita scale of tornado intensity, with F0 the least intense and F5 the most destructive.
‘‘The system down here [in Gerroa] was even stronger – in our preliminary assessment, at least an F2. There’s no doubt in my mind now that we’re seeing tornadoes.
‘‘There seems to have been a whole family of tornadoes spawned by this weather system.’’
The F2 rating is for ‘‘significant’’ tornadoes, with wind speeds of between 181 and 252km/h
Mr Treloar examined the pattern and extent of damage to the region with the bureau’s manager of severe weather services, Michael Logan.
The bureau’s interest in the tornado activity is scientific, and is also geared towards better calibrating its warning services so forecasters can relate what they see on their charts to what is happening on the ground.
Mr Treloar said the Kiama damage couldn’t be attributed to lesser phenomena such as a waterspout or a microburst – though these may have also occurred as part of wider extreme weather event.
The system that spawned the tornadoes registered in Sydney about midnight and is thought to have made landfall in Kiama soon after 3am Sunday.
The Kiama weather station, which is about a kilometre from the tornado’s path, recorded wind speeds of less than 90km/h, but speeds would have been far greater closer to the twister.
‘‘We’re thinking at least 125km/h, and there’s pockets where it would have been stronger than that,’’ Mr Treloar said.
Mr Treloar said tornadoes were ‘‘not uncommon’’ in Australia but often went under-reported – particularly when they hit unpopulated areas.
The bureau has yet to finalise its ratings for events at Kiama and Gerroa, and investigators had yet to visit Jamberoo and Albion Park Rail late yesterday afternoon when contacted by the Mercury.