Wednesday, October 27, 2021

Tornado rips through western NSW – what are tornadoes and what do we need to know?

A tornado has swept through central western New South Wales, with the Bureau of Meteorology reporting damage to homes, power lines and trees around the Clear Creek area, northeast of Bathurst.

But while many people think of tornadoes in Australia as a rare occurrence, they are actually surprisingly common, and have killed quite a few people since 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 any natural hazard type on Earth.

The oldest known photograph of a tornado in Australia was taken in Marong, Victoria, in 1911.
Sea Hosken/Museum Victoria

Read more: Tornadoes in Australia? They’re More Common Than You Think

Tornadoes are born, live, die

Australia has wide areas of flat land – usually agricultural land – and it is on these large, flat areas that tornadoes like to form. It is very similar in “Tornado Alley”, a section of the central United States where tornadoes occur most often.

You develop thunderstorms in these areas of flat land because warm, moist air collides in front of cool, dry air, and that’s exactly what triggers storm births.

How does a tornado form?

You sometimes see a tube coming out of a thunderstorm and it only touches the ground once that it’s a tornado.

How long they stay on the ground and how far they travel affects the scale of the damage.

Most storms last only a few minutes, but Tornado Alley in the US has had tornadoes up to 500 meters in diameter on land for up to four hours. A tornado like that would cause monumental damage.

Read more: Explainer: why are tornadoes so destructive?

Some tornadoes touch down briefly and are quite narrow, perhaps just 20 meters across. They can run a few meters and then die. Others can be very large and obviously if they touch in a metropolitan area they can do a lot of damage very quickly – and they can behave very unexpectedly.

Tornadoes can move across a street and lift a house on the street and lower it into a pile of rubble, leaving other homes alone. Or vice versa – every house on the street is demolished but one.

Eventually, the tornado runs out of energy. If the base of the funnel loses contact with the ground, it dies. Most tornadoes occur in the mid-afternoon to early evening hours.

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 goes from 0-5 (where 5 is greatest). It is too early to say what the recent NSW tornado measured on the Enhanced Fujita scale as damage surveys have not yet been completed.

Tornado rips through western NSW - what are tornadoes and what do we need to know?
Tornadoes are classified into six categories from 0 to 5, with 5 being the most destructive.

Australia has had some major tornadoes

The BoM has a national tornado database and records of tornado accounts over the past century and some were quite large. One of the most memorable tornadoes occurred in December 2015, where a tornado ripped through the Kurnell area of ​​eastern Sydney. No one died but people were injured and the tornado caused a lot of damage. The wind speed reached up to 210 kmph. According to the BoM, this tornado was recorded as 2 on the Enhanced Fujita scale.

Generally, tornadoes occur in Australia along with NSW and Victoria, as well as in the south-western part of Western Australia.

Where tornadoes occur around the world, there is a different spatial geography. This map from the National Oceanic and Atmospheric Administration in the US shows locations around the world that have the right conditions to allow tornadoes to form.

Tornado rips through western NSW - what are tornadoes and what do we need to know?
A global map of tornado areas.

How do we detect, monitor and give early warning to tornadoes?

The truth is that it is very difficult to give accurate early warnings. Rather, weather services monitor the types of conditions that are right for tornadoes to develop because tornadoes can form very quickly.

The Bureau of Meteorology uses Doppler radar to detect them in the short term. In that imaging, they show an unusual thing called a “hook echo.” It’s basically looking inside a thundercloud system, where the winds are moving really fast – a telltale sign that a tornado is about to form.

Tornado rips through western NSW - what are tornadoes and what do we need to know?
A tornado in Melbourne in 2015.
Chris Stone / Underground / You

But in Australia and the US, we usually only know when a tornado is approaching land, if tornado spotters report them.

Can we expect them to be more frequent with climate change? We have no idea. It is impossible for climatology to predict because they are events of such a small size. We need to have good planning and rely on the best spotters.

Read more: Climate change’s role in eastern Australia’s wild storms

What should I do if I am in a tornado?

In the US they have evacuation shelters in places like malls or toilets in airports, which have been reinforced with concrete. Residential homes have a central shelter—sometimes in the basement or under the stairs.

We don’t usually have that happen in Australia, but if you end up in a tornado, it’s basically a matter of “duck and cover”.

Find the most secure, reinforced part of the building—which is often the ladder, if the ladder is on top of a wall. You want to take shelter in the part of the building you are most likely to stay on if a tornado hits your head.

This article is republished from – The Conversation – Read the – original article.

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