Sydney, October 2
While many believe that tornadoes are a rare occurrence, they are actually surprisingly common and have killed a number of people since the European occupation. Geoscience Australia says there have been more than 40 tornado-related deaths in Australia over the past 100 years. This is because Australia has the right environmental conditions that favor the formation of tornadoes, which have the fastest wind speeds of all types of natural hazards on Earth.
Tornadoes are born, they live, they die
Australia has large tracts of flat land – usually farmland – and it is on these large flat areas that tornadoes like to form. It is much the same in “Tornado Alley”, an expanse of the central United States where tornadoes are most frequent.
There are thunderstorms that develop over these areas of flat land because the warm, humid air collides with a cold, dry air front and that is exactly what it takes for a storm to arise. .
Sometimes a tube is seen coming out of a storm cloud and it is only once it hits the ground that it is a tornado.
How long do they live on the ground and how far do they travel influence the extent of the damage?
Most storms only last a few minutes, but at Tornado Alley in the United States, there were tornadoes up to 500m in diameter on the ground for four hours. This kind of tornado would cause monumental damage.
Some tornadoes land briefly and are quite narrow, perhaps barely 20m in diameter. They can run for a few meters and then die. Others can be a lot bigger and obviously if they land in a metropolitan area they can do a lot of damage very quickly – and they can behave very unpredictably.
Tornadoes can move up a street and pick a house on the street and reduce it to a heap of debris, leaving the other houses alone. Or the reverse can happen: all the houses on the street are destroyed except one.
Finally, tornadoes lack energy. If the base of the funnel loses contact with the ground, it dies. Most tornadoes occur in the mid-afternoon or early evening.
Just like other types of natural hazards, tornadoes can be classified according to their impact. We have a magnitude scale for tornadoes called the Enhanced Fujita Scale, which ranges from 0 to 5 (where 5 is the largest). It is too early to say what the recent New South Wales tornado measured on the Fujita Improved Scale, as damage investigations are not yet complete.
Australia has seen big tornadoes
The BOM has a national tornado database and a record of tornado counts over the past century and some were quite large. One of the most memorable tornadoes happened in December 2015, when a tornado swept through the Kurnell area in eastern Sydney. No one was killed but people were injured and the tornado caused a lot of damage. The wind speed reached 210 km / h. According to the nomenclature, this tornado was recorded as a 2 on the Fujita Enhanced Scale.
Typically, Australia receives tornadoes all over New South Wales and Victoria, as well as the southwestern part of Western Australia.
There is a separate spatial geography of where tornadoes occur in the world. This map from the National Oceanic and Atmospheric Administration in the United States shows these places in the world with the right conditions for tornadoes to form.
How do we quickly detect, monitor and prevent tornadoes?
The truth is that it is very difficult to give precise early warnings. Rather, meteorological services monitor the types of conditions that are conducive to the development of tornadoes, as tornadoes can form very quickly.
The Bureau of Meteorology uses Doppler radar to detect them in the short term. In this imagery, they show an unusual thing called a “hook echo”. This essentially shows inside the storm cloud system, where the winds are turning very quickly – a telltale sign that a tornado could be about to form.
But in Australia and the United States, we usually only know when a tornado is heading for the ground if tornado watchers report them.
Can we expect them to become more frequent with climate change?
Not sure. It is impossible for climate science to predict because these are phenomena of such small size. We have to rely on good planning and good observers.
What should I do if I am in a tornado?
In the United States, they have evacuation shelters in places such as restrooms in shopping malls or airports, which are reinforced with concrete. Residential houses tend to have a central shelter – sometimes in a basement or under a staircase.
But if you’re in a place that doesn’t have one and end up in a tornado, it’s basically a ‘duck and blanket’ case.
Find the most secure and reinforced part of the building, which is often the staircase, if the staircase is against a wall. You want to take refuge in the part of the building that is most likely to stand if the tornado comes overhead. The conversation
By Dale Dominey-Howes, Professor of Hazard and Disaster Risk Science, University of Sydney