Six unusual weather phenomena to watch out for this winter

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As temperatures drop across the UK as a result of the same sudden stratospheric warming which led to 2018’s Beast from the East, Britain is witnessing some strange and spectacular weather conditions. Changes to the polar vortex over the arctic might seem like a distant concern, but according to the National Geographic this imbalance raises the odds for intense winter weather across both Europe and North America. Here are five cool phenomena that can occur in unique conditions like these.

Hard rime frost

Photo: Rosamund Kelby

Over the past weekend a large part of the UK has found itself under a blanket of freezing fog. While impenetrable mist and sub-zero temperatures perhaps make the idea of a walk sound less than inviting, those who ventured out may have reaped some incredible and rare rewards. Hard rime forms when supercooled water liquid droplets freeze onto surfaces. When paired with a light breeze, this can result in a spectacular effect by which the frost builds up on one side of an object, giving plants and trees an almost blurry quality.

Fog bows

Photo: Thomas Kelby

This is another remarkable spectacle that could rise from the mist even in poor visibility. Like rainbows, fog bows are formed when sunlight refracts from droplets of water vapour, but in this case the droplets are smaller and so fewer colours are reflected, resulting in a ghostly white arc. Though fog bows are less vibrant than their multicoloured cousins, there is something magical about encountering them on a grey winter’s day.

Hair Ice

Northern Ireland has also seen some incredible cold-weather consequences. Last week, those strolling through the forest in the counties Fermanagh and Tyrone witnessed a phenomenon known as hair ice, which is formed on rotting wood during humid winter nights when the temperature is just below zero. The phenomenon, the appearance of which has been likened to white candyfloss, occurs thanks to the presence of a particular fungus which enables the ice crystals to form unbelievably thin hairs with a diameter of about 0.01mm.

Snow rollers

Photo: Brian Bayliss

If you’re lucky enough to live somewhere rural – or at least within walking distance of the countryside, you’ve probably seen some beautiful snowscapes. If you’re particularly fortunate, you may have witnessed snow rollers, naturally occurring snowballs which form when – as the name suggests – the wind causes chunks of snow to roll and grow in size. From some angles, the balls resemble pristine white bales of hay, but it’s safe to say these would look more impressive on your Instagram feed.

Nacreous clouds

This effect is much rarer in the UK, but when it does occur the outcome is otherworldly. Nacreous clouds have an almost iridescent effect, making them appear like puddles of shining oil. They form from ice particles in the lower stratosphere in polar regions when the sun is just below the horizon, and are more likely to be seen in areas with high latitudes, meaning they are more common in regions like Canada and Scandinavia. However, they may become visible in the UK when the polar vortex is displaced, so it’s worth keeping an eye out this winter.

Aurora Borealis

Just this week, the legendary aurorora borealis have been spotted in parts of Scotland. The Northern Lights, as they are more commonly known, are a shimmering spectacle which comes about when atoms in the Earth’s high-altitude atmosphere collide with charged particles from the sun. Though this last effect is only usually visible at the top of the UK, it has historically been seen as far south as Kent and Cornwall.

Rosamund Kelby

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