Mini-tornadoes, weather bombs, gales, hurricanes – these are all words or terms that we frequently see or hear in the news media – but they are often used incorrectly.
We’ve gone through a few of the more common media mistakes to explain why some of these terms are used inappropriately.
Firstly, there is no such technical description for a tornado. It’s either a tornado, or its not. The term is frequently used in the media – and by the public – to describe a sudden damaging wind gust and often is connected to a trampoline being lifted or a piece of roofing iron coming off – and more often than not, there was never a tornado in the first place.
To know if it’s a tornado or not we need either eyewitness reports or photos/videos (like we did with the Albany tornado) or, after it’s occured, we need to see the damage. Seeing the destruction will show if the buildings or trees have been damaged by just a strong gust (where it’s blown with the wind in a perfectly straight line) or if it’s more messy (such as with a tornado) in which things can be scattered and twisted and thrown at different angles.
The origin of the term Mini-tornado is hard to find, but a quick search in Google search engines from various countries shows that it’s not unique to New Zealand – although it does seem to be used in our mainstream media more than the mainstream media of other countries.
More often than not a ‘mini-tornado’ was never a tornado in the first place – and was simply a wind burst which came without warning, often associated with the weather we have over the country at the moment – short, sharp squalls then sunny.
This is another term used incorrectly all the time. A weather bomb, believe it or not, IS actually a technical term! It relates to a sudden drop in air pressure associated with a low pressure system. For it to qualify as a ‘bomb’ the air pressure literally has to drop 24 hPa (millibars) in 24 hours. That is a huge drop – and on a 24 hour weather map it would show a shallow low at hour 1 and a cyclone-looking storm by the 24th hour. We don’t get many of these in New Zealand but they do happen from time to time. When they do hit they almost always cause damage.
Journalists sometimes describe ANY severe weather event, even just a localised weather event, as a weather bomb – but as you can see, when we DO get one, it’s unlikely to be isolated to one town.
Gale force winds are when the winds reach 62km/h for a minimum of 10 minutes – not just a strong gust. When we warn of gales it means the wind will frequently be at this speed and over. Many places today have strong winds but only a handful have sustained winds at 62km/h. Gales occur more often on the mountains and over the sea where there is less resistance – allowing the wind to blow freely and strongly.
We don’t get hurricanes in New Zealand – apart from the rugby team! Hurricanes occur only in the northern Hemisphere and only form east of the International Date Line in the Pacific or, more commonly reported, in the Atlantic heading towards America. But we do get hurricane force winds in New Zealand. They can also be referred to as Severe Gales. Hurricane force winds are winds sustained at 120km/h for 10 minutes – although in America they only measure them at 120km/h sustained for 1 minute. When we get hurricane force winds you know we have something nasty moving over or near us!
Cyclones are the same as hurricanes – except them form int he Southern Hemisphere and spin cyclonic (as opposed to hurricanes that spin anticyclonic).
Homepage image / Franz Krippner
on 17/05/2011 8:25am
Thanks very much for an excellent article here, but there is one small correction that needs to be made.
All cyclones, hurricanes and typhoons are all low pressure systems, as such they all spin ‘cyclonically’, wherever they are on earth. There are no hurricanes that spin ‘anti-cyclonically’, anywhere on earth.
It just so happens that, due to the direction the earth is spinning, all cyclonic systems (lows, typhoons, hurricanes and cyclones) spin clockwise in the southern hemisphere and anti-clockwise in the northern hemisphere. Conversely, all anti-cyclones spin anti-clockwise in the southern hemisphere and clockwise in the northern hemisphere.
If a weather system is spinning ‘cyclonically’, that means it is spinning clockwise south of the equator or anti-clockwise north of the equator.
on 17/05/2011 5:38am
great article. good to see some media stating the facts around misused terms. Hope this was sent to all media around the country
on 17/05/2011 5:50am
Hi there – yes it was sent to at least 70% of the media.
on 17/05/2011 5:19am
Try using the term ‘Sediment’ rather than silt – most ‘silt’ is clay, while silt sits between clay and sand (then cobbles and boulders) in terms of particle size. Care needs to be taken when describing a ‘slip’ as it may be a slide, fall, or flow – combinations of these, plus a host of other factors give us more than 80 distinct types of slope failure… the latter phrase is more accurate.
Adding back some of the complexity is not a bad thing, we tend to oversimplify complex issues.
on 17/05/2011 2:26am
Good to see you writing on this. It’s one of my bug-bears.
A good example was the ‘mini tornado’ in Nelson on the weekend. More than likely a squall associated with the admittedly decent thunderstorm.
Other misused or over used terms:
– ‘Wild’ or ‘extreme’ for a decent bit of weather
– ‘Freezing’ for waters off Auckland
– ‘Partly overcast’. It is or it ain’t.
I could go on.
on 17/05/2011 2:23am
How about proper weather forcast for once without all the crap terms. Your weather forcasts have been of the chart for last 3 days for Auckland,