Brownie's weather: Australia should brace for powerful Spring storms
Icy southwesterly winds are sweeping across the southeast corner of the country today as the weather gradually clears in the wake of a wild Spring storm that ripped across southern Australia.
Northerly winds cracked 154km/hr on the alpine peaks of NSW ahead of the turbulent change.
You may recall earlier in the week the active front whipped up destructive gales over southwest Western Australia.
Generally speaking, weather systems in the mid-latitudes travel from west to east, but during the journey cold fronts can evolve, weakening or intensifying, tracking northeast or southeast.
The wild weather hit the southwest corner of WA with maximum force, whipping up localised squalls to 150km/hr, which peeled the roof off a block of flats.
As the front crossed the Great Australian Bight and slipped a little to the south, it lost part of its upper atmospheric support, in turn losing some of its power as it moved across South Australia before sweeping into Victoria.
In Melbourne, the strongest reported wind was 106km/hr, for just a few seconds at the head of Port Philip Bay. Nevertheless, the winds were strong enough for old gum trees to topple, damaging homes in parts of the Dandenong Ranges and the upper reaches of the Yarra Valley.
The thunderstorms that followed were the biggest September storms I have seen in 20 years. They evolved over central Victoria as an independent pool of very cold air in the middle atmosphere and moved into place at the right time, providing an ideal environment for storm development.
Furthermore, there was just the right amount of vertical wind shear that allowed severe thunderstorms to evolve and rip across Northern and Eastern pockets of Melbourne for just a few hours, sparking flash flooding and causing commuter chaos.
The western suburbs missed the stormy weather altogether.
There’s no doubt that Spring is a turbulent time of year, and over the coming weeks and months there’ll be more thunderstorms; most evolving near the boundary of strong and active cold fronts.
Summer thunderstorms don't need cold fronts to get them going. Warmer air can hold more water and in turn provide more energy to drive the convection, creating powerful storms which have the potential to dump hail as big as cricket balls. Some can drive destructive twisters with winds in excess of 200km/hr.
