An unusually stormy start to May has seen parts of south-east Queensland recording more rain than normally expected for the entire month.
May is generally considered a transition month, Bureau of Meteorology (BOM) forecaster Shane Kennedy said, with a few bursts of rain not out of the ordinary.
But Mr Kennedy said the quick succession of recent storms was unusual.
Yesterday’s storms were just the latest in a series of recent, wild weather events that have lashed the region with hail and lightning, causing power cuts and localised flooding.
Less than two weeks into the month, some areas have received up to four times as much rain as the average monthly total, and hailstones as big as 5 centimetres have been reported in some regions.
La Niña is not causing the higher rainfall. That weather system ended in late March after creating the wettest summer Australia had seen in half a decade.
Instead, the current weather is being caused by the remnants of La Niña — warmer oceans off the coast — combining with cooler troughs moving up from the south.
“Even though La Niña is over, we still have residual heat in the ocean,” Mr Kennedy said.
“We’ve had quite a few upper troughs in the atmosphere and that’s led to unstable conditions.
Flooding and downed trees
The combination of weather events — hail, lightning, and flooding — has surprised some locals used to milder weather at this time of year.
Farmer Douglas Wunsch’s sorghum crop at Warra, near Dalby on Queensland’s western Darling Downs, suffered hail damage on Tuesday night.
“I’ve never seen storms of this capacity …with hail … in May ever,” he said.
“You might get something through June that might thunder and carry on but that’s only pea-sized, soft hail.
“This was fair dinkum October storm hail.”
AgForce Grains president Brendan Taylor said the unusual storms had delivered welcome rain and a boost for winter crops in some areas.
“We haven’t had rain at this time of year for a number of years,” Mr Taylor said.
“The rain’s very beneficial but it’s unfortunate that some of these storms have been quite vicious.”
The State Emergency Service (SES), which had more than a dozen call-outs on Tuesday for flooding in the Toowoomba region and the Lockyer Valley, answered more calls for help on Wednesday.
“The amount of water that fell in such a short period of time [meant] there was a lot of runoff,” SES regional manager Bob Bundy said.
He said the weather was unusual for May.
“We thought the storm season had pretty much finished and we were looking at other things,” he said.
“It’s never over. You have to be prepared all the time.
“You never know where it’s going to fall.”
Storm clouds loaded with hail
The BOM said Wednesday’s storms brought more hail, including chunks as big as 5 centimetres, to a number of areas, including Toogoolawah.
Mr Kennedy said cooler weather moving north from southern Australia was creating the right conditions for hail to “survive the journey” from the storm clouds to the ground.
He said the storms had “front-loaded” May with much higher than average rainfall totals.
For example, in the 24 hours to 9:00am on Wednesday, Forestdale received 126mm, more than four times the monthly average of just 29mm.
Caloundra has received 225mm so far in May, twice as much as the long-term average of 105mm.
Redcliffe’s rainfall total is nearly double expectations, with 115mm of rain versus the May average of 64mm.
With 65mm of rain so far this May, Brisbane has already surpassed its average monthly total of just 60mm, but it is a long way short of its most recent May record of 269mm set in 2016.
Mr Kennedy said it was too soon to say if May would break any rainfall records, especially because calmer conditions were forecast for next week.