The Bureau of Meteorology has said the violent storm that tore through the Geelong suburb of Waurn Ponds early Wednesday morning was a tornado, marking a rare weather event for Victoria.
There are around 60 tornadoes every year in Australia, most of them in NSW and Queensland, with only one or two recorded in Victoria each year.
The BOM released the preliminary findings of its investigation into the storms and thanked locals for helping meteorologists survey the storm's impact, even as they were trying to clean up their damaged properties.
The bureau's Victorian Weather Services Manager Peter Otto described the tornado as a "frightening event" for residents.
"A line of thunderstorms approached Geelong and intensified quite rapidly over about 10 minutes and within that line of thunderstorms some cells pitched off little tornadoes," Mr Otto said.
The State Emergency Service received more than 160 calls for help from residents in Geelong, Ballarat and Stawell during the storms, which hit Waurn Ponds hardest, severely damaging a number of homes.
"There's been impacts on their homes that will affect their lives for some time yet," Mr Otto said.
"It must have been terrifying for the poor residents there."
'Violent' wind gusts
The BOM team used a US system for categorising tornadoes called the Enhanced Fujita scale, or EF-scale, which rates the damage to trees and buildings to infer wind strengths.
The team found that winds reached between 150 and 160 kilometres per hour during the storm, confirming it was a tornado.
"So really quite a violent wind gust came across in a very short period of time in a very narrow corridor at night," Mr Otto said.
The BOM's Victorian Manager Andrew Tupper said it was likely a category 1, or EF1 intensity tornado.
"They are rare in Victoria, but with tornados we don't always observe them," Dr Tupper said.
"The difference with this tornado is that it went through a suburb of Geelong so that's unlucky when a tornado goes through such a built-up area."
Mr Otto said the storm formed in a corridor about 60 metres wide and 3 km long, making it consistent with a tornado.
"It's not uncommon for us to get strong storms in Victoria but it's very rare to get such a strong impact over a residential area."
The next phase of the BOM investigation will examine the warnings given before the storm hit.
Meanwhile, windy, rainy conditions have since settled across most of Victoria, but the Bureau is warning of the risk of flash flooding in East Gippsland at the weekend.
Between 20 to 40 millimetres of rain is forecast and some areas will get up to 70mls, including some areas devastated by bushfires earlier in the year which have increased the risk of localised flash flooding.ABC