• Storm chaser: tornado looming in US

    Touchdown: this tornado near El Reno, Oklahoma, in May 2013 grew into a four kilometre-wide monster. PIC: John Allen

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Storm chaser John Allen sees “mathematics in the atmosphere” as he hunts monster storms across the US. 

 

I CHASE storms because when I visualise things, I can see the mathematics in the atmosphere.  I’ve been pretty close to tornadoes and I can see the processes going on: the physics of severe thunderstorms.

Storm chasing isn’t the safest thing to do but if you pay attention to the way the storm evolves, and don’t forget you are under threat, you can hold a safe position: even if it requires driving at a reasonable rate to get out of there.

I’m a post-doctoral researcher at Columbia University in New York, having completed my PhD on the impacts of climate change on severe thunderstorms in Australia.

Until now, people haven’t really understood the likelihood of a severe thunderstorm in Australia and in a warmer world that changes quite a bit.

My research proved that the conditions favourable to severe thunderstorms in Australia were remarkably similar to those in America, where more research has been carried out.  In fact, conditions are similar worldwide.

If we know storm environments are similar worldwide, we can use modeling in places where there is no — or limited — data like South Africa, China and South America. 

We’re looking to develop tornado climatology for places that don’t have one, such as Bangladesh where a tornado will kill 1000 people.

I also showed that in a warmer world with increasing amounts of thermodynamic energy, more water in the atmosphere and changes in the jet streams, you get greater instability and more frequent thunderstorms.

By looking at the data, I found a link between El Nino and thunderstorms. My research was the first to show El Nino and La Nina had a very strong influence on severe thunderstorms.

With dry El Nino winds, everything shifts northwards towards Queensland.  In La Nina, things shift southwards and you get many severe thunderstorms over New South Wales, Victoria and South Australia.

‘Blissful ignorance is part of the problem.  In 2013, there were 64 tornadoes in Australia.  Most people wouldn’t know that.’

Nobody had put together a detailed and sizeable climatology for severe thunderstorms in Australia using modern techniques. There was a reasonable amount of research in America, but not in Australia. 

Blissful ignorance is part of the problem.  In 2013, there were 64 tornadoes in Australia.  Most people wouldn’t know that. 

Apart from preliminary data collected for insurance purposes, my work was the first study to use a long-term indirect climatology. 

There’s a set of weather conditions including relative warmth and vertical wind shear called an ‘environment’ that are generally present to create a severe thunderstorm.

There’s been work using data from balloons to analyse storm conditions.  We asked what happens if we look at reports from people on the ground in Australia?

We looked at reports of hail bigger than two centimetres, winds stronger than 90 kilometres an hour or any tornado, and we used those reports to identify the characteristic local environment of severe storms in Australia.

Modeling the impacts of climate change showed the average number of days per year in Melbourne on which there is an environment favourable for a thunderstorm increases by more than 20 per cent. The average number of severe thunderstorms in Sydney goes up by 40 per cent.

The Bureau of Meteorology may have to deal with more of these changes. For them, it means more staff to worry about thunderstorms over an extended summer season.

In Australia, severe weather forecasts are typically only available one or two days ahead.  There’s no formal process for extended forecasts.

President Obama recently asked us for a tornado seasonal forecast and we’re now working on how to estimate the number and location of tornadoes to respond. Two weeks ahead of time we can know the approximate area of a storm system that produces tornadoes.

In North America, there were 553 fatalities in 2011 from tornadoes. I went pretty close to one that killed 158 in Missouri but more storm chasers have died from road fatalities than from actual tornadoes.

‘We don’t fully understand severe thunderstorms:  we still don’t know about all the microphysics behind, for example, the formation of giant hailstones.’

There have been significant tornadoes and hail recorded in Australian capital cities causing at least a billion dollars of damage on several occasions. A hailstorm in Melbourne in 2010 caused $800million to $900 million damage.

I’m still putting together the figures for Australia, but around 100 people have died from tornadoes. The most who died in a single outbreak is four in 1897.

We don’t fully understand severe thunderstorms:  we still don’t know about all the microphysics behind, for example, the formation of giant hailstones.

But we know more about when a storm is likely to become stronger and more organised.

Then there is a whole social science on how people respond to warnings. Working out how to implement warnings so people don’t get killed is another thing altogether.

 

For his PhD, undertaken in the Department of Earth Sciences, John Allen developed a unique dataset on severe thunderstorms in Australia and investigated the environmental conditions favourable for their occurrence using observations and climate model simulations. He showed that global warming is likely to lead to increased frequency of favourable conditions for severe thunderstorms over the east coast of Australia.

My PhD is an irregular series in which The Citizen speaks with recent Melbourne University PhD graduates.  

 

 

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