Can you get sunburnt on a cloudy day? Do highs always bring sunny weather? Are typhoons the same as cyclones? We get asked many questions about the weather and our planet, so we thought we’d address some of them with 10 NZ Weather MythBusters!
Sunburn only occurs in summer. MYTH. You can get sunburnt any time of the year, but in summer UV rays are stronger and it’s the UV (ultra violet) damage to your skin that leads to burns. In NZ we often hear of people being sunburnt on a sunny winter’s afternoon just sitting at home outside.
Cloud always prevents sunburn. MYTH. While to some degree clouds can limit UV rays it’s very important to understand you can still get badly sunburnt on a cloudy day because it depends on how thick the clouds actually are and how much UV gets through. For example, if it’s pouring with rain all day you won’t likely get sunburnt! But if it’s only high cloud, or small/thin clouds, then the UV rays will easily penetrate through to your skin and still be able to burn you, even if it looks mostly cloudy. Many people in summer can get sunburnt on “cloudy” days.
“Fine” always means sunny weather. MYTH. Fine usually means ‘settled and pleasant’ – it may be calm and dry but can also be quite cloudy. Whereas a sunny day with strong winds isn’t considered “fine”. WeatherWatch.co.nz doesn’t actually use the word fine in our forecasting due to the confusion with how some people interpret it. But MetService has actually written a blog about this very topic titled “It’s a fine day. Isn’t it?”.
High pressure brings dry weather. PARTIALLY TRUE. Usually high pressure (also known as an anti-cyclone) brings mostly dry weather because the high pressure limits how big clouds can grow to produce rain. But in the right conditions high pressure can bring showers/drizzle – especially in winter when calm overnight conditions form fog and low cloud – which can create a microclimate using the ‘mild’ sea waters around NZ to produce localised drizzly cloud. Auckland is well known for this weather – it’s called “Anti-cyclonic gloom”. Also, when the weather is humid (when a high is exiting NZ and a northerly flow is developing) thunderstorms can develop and sometimes form repeatedly for days in a row in the same region (like South Waikato in summer). This can lead to flooding. Finally, highs can also park themselves in a way where they create an “atmospheric river” – basically a moisture-rich flow of air in the atmosphere on *edge* of the high. The high pressure zone can encourage the flow to curve around into one place causing flooding, in the same way a hill can make water go around it and flood certain places nearby.
Fog is just cloud on the ground. TRUE. Fog is simply water vapour that has condensed – just like any other cloud, except it’s on the ground. When you think about it, clouds higher up can also cover the tops of mountains and hills – where if you were on the summit it would be foggy.
Lightning hits the ground from the sky. PARTIALLY TRUE. Actually, not all lightning hits the ground – some goes from cloud to cloud – but the lightning that does hit the ground does also come out of the ground. Cloud-to-ground (CG) lightning comes from the sky down, but the part you actually see comes from the ground up! A typical cloud-to-ground flash lowers a path of negative electricity (that we cannot see) towards the ground in a series of spurts. Objects on the ground generally have a positive charge under a typical thunderstorm. NOAA (The US version of MetService) has a great write up about the different types of lightning which you can read here.
Hurricanes, Typhoons and Cyclones are all the same thing. MOSTLY TRUE. They all Tropical Storms. But there are a few slight differences. *Hurricanes form in the Atlantic (almost entirely North Atlantic) and also the Pacific Ocean north of the equator and east of the International Date Line (or put simply, Hurricanes form around the Americas). Hurricanes spin anti-clockwise. *Typhoons also spin anti-clockwise and they form west of the International Date Line in the western Pacific and form all year around (and yes, a hurricane that forms in the eastern Pacific and crosses westwards over the International Date Line then becomes a ‘typhoon”). Typhoons are the most powerful tropical storms on earth. *Cyclones form in the South Pacific and Indian Ocean and they spin clockwise. Tropical Cyclones in the South Pacific aren’t usually as powerful as Hurricanes or Typhoons but on rare occasions can be.
Every region in NZ can receive snow. TRUE…but only just. In 2011 snow flakes not only fell in some parts of Auckland but they settled in some areas for a time too. Further north, the ranges in Northland on the boundary of the Far North, had snow. The Kaimai and Coromandel ranges get snow on the summits most years – we just don’t always see it because of the thick bush cover. However snow in Auckland and Northland is incredibly rare – perhaps only once or twice a lifetime will it be seen and with climate change it may even become a thing of the past this far north of Antarctica – as northern NZ is in the zone where possible snow chances fade out.
Lightning never strikes twice in the same place. MYTH. Lightning frequently hits the same place many times. Ask the top of Sky Tower for starters!
No populated parts of NZ stay below 0 degrees across the day. MYTH! While it’s true most main centres warm up above 0C for all 365 days a year, there are few places that can break this rule. Parts of Alexandra in Central Otago can have daytime highs below 0 and freezing fog too. Twizel and Queenstown are close contenders, as are Waiouru and Ohakune in the North Island’s Central Plateau. But for the most part, NZ warms up above freezing temperatures in the middle of the day even in the depths of winter. So where are the cold spots? We spoke to NZ frost expert James Morrison who confirmed parts of NZ have had sub-zero daytime highs. “-5.0c at Lake Coleridge June 1972, -0.8c Waiouru July 1976, -0.4c Waiouru July 2011, -0.5c Chateau Ruapehu July 2018”. James goes on to add “Ranfurly’s lowest max was -21.1c”. Wait, hold on, did you just say the *HIGH* was -21.1? “Yes, it was in July 1903 found from old records rediscovered just a few years ago. In fact, Ranfurly also had highs of -15 and -20 that month. They also had 18 consecutive days where the temperature didn’t rise above freezing!” Incredible – those are facts even we didn’t know about! (thanks James for the additional info!).
We look forward to tackling more NZ Weather MythBusters in the future – and thanks to all of you for asking us many questions over the years!
— By head forecaster Philip Duncan, WeatherWatch.co.nz