A COMPLEX weather system led to the formation of a series of hail storms that dumped enormous hail stones across Western Australia, South Australia and Victoria last week.
It comes hot on the tail of a series of storms in Queensland that included the largest recorded hail stone in Australian history, measuring in at a whopping 16cm in diameter at Yarlboroo, near Mackay on October 19.
Bureau of Meteorology meteorologist Dean Narramore said the system last week was a cold front that then developed into a low pressure system over the Great Australian Bight as it interacted with tropical moisture from the north.
It deepened dramatically as it moved over SA and Victoria on Thursday, bringing the hail, heavy rainfall and destructive winds.
There were reports of crop damage across WA, SA and Victoria following the hail, with some paddocks expected to have 30 per cent yield loss.
WA agronomist Michael Lamond, SLR Research and Development, said there were patches hard hit by hail, but said wind was just as problematic.
"In particular in the canola we have seen some issues with the wind," Mr Lamond said.
"Overall, the damage has been patchy but there are certainly individual farms that have been hit hard."
He said the damage extended from Miling and Wongan Hills in the mid-north down into areas such as Corrigin in the heart of the wheat belt.
In South Australia, Garry Hansen, Murray Bridge, said there were patchy strips of heavy hail throughout his area.
"People have taken footage from the air and you can see clearly where the crops have been hit," Mr Hansen said.
He said he had heard of reports of damage in parts of the lower Eyre Peninsula, the Yorke Peninsula and the Barossa Valley as well as in his own area.
Due to crop maturity he said in the Murray Bridge region the canola was worst hit.
"It is a little riper while the wheat still has plenty of green in it so it was not so rigid when the hail stones hit."
Further east west Wimmera farmer John Bennett said there had been damage in areas around Kaniva.
"To the west of Kaniva there were big storms at Dinyarrak and to the east Tarranginnie was hard hit," Mr Bennett said.
He said his own crops had been damaged in places.
"We've had some pretty bad damage at an initial glance, we'll get the insurance assessor in and take a closer look, but at this stage it looks like some could have 30pc damage, with the barley seeming to fare worst of all."
Further south, Goroke farmer Steve Rich said there had been storms through the area.
"Areas like Ozenkadnook got some storms with some really big stones," he said.
Joshua Soderholm, BOM thunderstorm research scientist, said multi-day storm events were not uncommon, citing similar weather in January 2020.
He said giant hail, in excess of 5cm in diameter, needed very specific conditions to form.
"It requires warm, humid near the surface and cool air with strong winds in the upper levels of the atmosphere and for hail to grow to an exceptionally large size, larger than 10cm, it needs to spend longer growing," Dr Soderholm said.
"This occurs with just the right balance of the aforementioned conditions and when the parent hailstorm evolves in such a way that hail can grow for a longer time," he said.
He said the areas that received big hail often did not have heavy rain associated with the hail.
"Strong winds inside a thunderstorm will blow raindrops further than the comparatively heavy hailstones - we call this precipitation sorting.
"As a result, the heaviest rain often falls from a different portion of a thunderstorm than the largest hail."
Got your own severe weather pictures? Send them to gregor.heard@austcommunitymedia.com.au
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