'Rain bomb', mini tornadoes: Debunking Australia's greatest weather myths

We explore some of the most common atmospheric misconceptions. (ABC News: Isabella Ross) Link copiedShareShare articleWeather is widely considered one of the most discussed topics of conversation in the world, and since we all live in it everyone has an opinion on the subject. However, meteorologic rhetoric in Australia, including from the media, can at times be inaccurate, misconstrued or just completely fictitious. So, in no particular order, let's explore some of the most common atmospheric misconceptions that circulate when Australians are shooting the breeze. Precipitation types are differentiated in forecasts to give a better understanding of what weather to expect. The frozen forms are self-explanatory, like snow or hail, but it is liquid drops which create the most confusion. Firstly, the definition of drizzle is not related to the intensity of precipitation. More precisely, drizzle is the technical term for extremely small water droplets less than half a millimetre in diameter. Then comes the rain-showers conundrum, and the difference between the two refers to duration and extent, and not intensity or more specifically the type of cloud the droplets spawned in. Showers fall from cumuliform clouds. (ABC News: Andrew O'Connor) Showers fall from cumuliform clouds; the puffy looking clouds which are often separated by blue sky. Cumuliform clouds often bring no rain or only a brief light shower, but when they grow into towering cumulus congestus or cumulonimbus (thunderstorms), precipitation can be torrential. And when heavy showers and thunderstorms are frequent, 100 millimetres or more could fall in a day, but it is still classified as showers as long as precipitation does not simultaneously engulf an entire region. Rain on the other hand normally falls from stratiform cloud, which is when the entire sky is overcast and precipitation is falling over a broad region. But rain, like showers, can range from just a drop or two, through light, moderate, grading to heavy or torrential. It all depends on the weather system at play. For decades, tornadoes in Australia were regularly reported by the media as "mini tornadoes". The problem is, mini tornadoes do not exist. As the Bureau of Meteorology (BOM) eloquently puts it on their tornado page: "This has no meaning. A tornado is a tornado, regardless of size, intensity or where it occurs." Tornadoes, like cyclones, are rated on a scale up to five based on the speed of wind in the vortex, and with 30 and 80 twisters reported across Australia each year, their frequency is magnitudes above the three to four cyclones which make landfall on our shores. Mini cyclone also does the rounds occasionally, but again this term is completely fake. Put simply, there is no such thing as a mini cyclone or mini low, regardless of whether it is a tropical system, subtropical low, east coast low, polar low, or any other type of low. However, there is a similar sounding term "mesocyclone" used by meteorologists. "Meso" means intermediate, and "mesocyclone" is used to differentiate smaller scale circulations, like a rotating thunderstorm from larger scale synoptic scale systems. Who would have thought the Lord Mayor of Brisbane, Adrian Schrinner, would have such an impact on how weather is reported in Australia. During the devastating floods of early 2022 he described the deluge as a "rain bomb", and within 24 hours the term was repeated by the Queensland premier at the time, Annastacia Palaszczuk. "We were seeing an enormous amount of rain fall in a very short period of time and it felt like the sky was dropping a bomb of water on the city," Mr Schrinner said at the time. "I was simply trying to explain to residents how serious and unusual the situation was." The term "rain bomb" was used by Mr Schrinner in 2022. (ABC News) But the term's usage quickly evolved from a way to describe rainfall, to a phoney weather system. Before long, "rain bombs" were being predicted by social media amateur forecasters right across the country and the media could not get enough of the clickbait frenzy. Even the Climate Council caught the rain bomb fever titling their report on the 2022 floods: A Supercharged Climate Rain Bombs, Flooding and Destruction. This had meteorologists tearing their hair as genuine systems like East Coast Lows, Atmospheric Rivers, Northwest Cloudbands, Black Nor'easters where being falsely labelled as rain bombs. Even more frustrating was the time I was asked live on radio: "So how does a 'rain bomb' form?". That was like being asked: How you get to Spaghettiland?". The term survives to this day within various media organisations, possibly due to its likeness to similar but valid meteorological terms "bombing low" and "bomb cyclone". This one is slightly nuanced, but essentially a declaration of El Niño or its counterpart La Niña are observations not forecasts, and therefore cannot be wrong. El Niño is defined by meteorologists based off

'Rain bomb', mini tornadoes: Debunking Australia's greatest weather myths

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