Thunder and lightning

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Tags: centenary-edition, environment, thunderstorms, weather

Joshua Soderholm gathers data with a theodolite

There is no denying South-east Queensland and storms are a match made in heaven, and on a field trip to Kooralbyn, near Beaudesert, in October, it was startling to see just how quickly this destructive relationship could unfold.

During the 2009 summer storm season, a team of UQ researchers set up a site at the country setting to collect real-time data for better storm warnings in the region.

The project, headed by Associate Professor Hamish McGowan and Bachelor of Science Honours student Joshua Soderholm, marked the first time the researchers – from the School of Geography, Planning and Environmental Management – placed themselves in the field before, during and after a storm hit.

The project aims to provide a greater understanding of the relationship between the pre-storm atmosphere and a storm’s evolution, direct impact areas and the weather it would produce.

“We collected a very wide set across as many storm days as possible, thereby allowing us to develop a climatology of thunderstorm events. We were then able to better understand the relationship between pre-storm conditions and the ensuing thunderstorm weather,” Mr Soderholm said.

As I travelled to Kooralbyn on October 13, the temperature was already about 26 degrees and the wind was howling through the dry terrain.

If you view a storm like a theatre production, the opening number had been forecast for late afternoon.

Mr Soderholm prepares to launch a radiosonde

“It’s a bit of a waiting game,” Dr McGowan says as we arrived on site.

“I’m still reasonably hopeful and optimistic. It’s a shame that the wind wasn’t more round in the north east rather than the north west to bring that moisture in.”

From about 8am, the team had been busy releasing radiosondes – small instrument packages attached to large helium-filled balloons – every two hours.

The technology aims to provide information on the ambient atmosphere in terms of temperature, humidity and wind speed and direction.

“If nothing is kicking off by 3.30pm then we can call it quits,” Dr McGowan says as he surveys the sky.

At about noon, the latest in a series of radiosondes is released – a big red balloon fading into the distance.

While the balloon becomes less visible, the monitor on the ground beeps to alert the team to new information on the developing weather conditions.

Every 20 seconds the optical telescope makes a measurement of the balloon’s position and the information is scanned into the computer for download.

Looking at the data on the computer screen, Mr Soderholm is excited by the balloon’s quick ascent into the atmosphere.

“It’s blowing up to 40 knots at 500 metres now,” he says.

“It’s gone over 1000 metres now.”

A quick scan of the surrounding environment and it appears the clouds are starting to thicken.

Associate Professor Hamish McGowan

“Fingers crossed, it’s only 1.15pm, hopefully by 3pm things will be a bit more organised and we’ll see some deeper convection,” Dr McGowan says.

“We should be getting pretty impressive storms under typical conditions but at present things are still relatively dry.

“That’s what you look for on thunderstorm days, conditionally unstable atmospheres that remain stable as long as it’s dry but as soon as it becomes moist it becomes unstable and remains so.”

Time continues and more data is collected. The sky is beginning to blacken as the clouds become thicker. Before we know it, the conditions have drastically changed and it is obvious that a storm is on the horizon.

Droplets of water begin to bucket down as the sound of rolling thunder echoes in the distance.

While we take cover, Dr McGowan and Mr Soderholm are busy releasing another radiosonde into the atmosphere. The red balloon is immediately whisked up into the turbulence.

Mr Soderholm interrupts the conversation excitedly to report that the radiosonde is caught in the storm’s updraft and is hovering at 8400 metres – “we’ve never tracked it this high before,” he says.

As the storm passes, a quick glimpse at the radar shows a series of severe cells rolling in from the west towards Brisbane, the bayside and the Sunshine Coast.

My ears remain pricked as talk of another storm passing through the Beaudesert area gains momentum.

“We’re measuring the structure of the lower atmosphere from the surface to about 6000 metres,” Dr McGowan adds, peering into a theodolite (a kind of telescope).

The research will hopefully allow the team to better identify what conditions are needed to predict the type of developing storms.

“For example, whether or not you are going to have a big super-cell thunderstorm or whether you are going to have a squall come through, a line of storms, that often passes through South-east Queensland in the spring.

“The more and more people that decide to reside in South-east Queensland, the greater the potential for severe impact on those urban environments in those communities.”

It’s about 4pm and the build-up for another storm begins to gain momentum just north of the research location.

It’s amazing to see how selective the storm path can be. Even though we can see the storm, it appears on the radar to be just shy of our location.

The storm’s ferocity is evident by the cloud dimensions and its increasing speed. Soon the panorama of black clouds is but a distant sight, closing the curtain on our storm-chasing adventure. At least until next time…

By Eliza Plant. Video by Jeremy Patten

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