Mysterious lightning

Sprites are more than just mythical creatures — they are an electrical phenomenon that occurs high above active thunderstorms at altitudes above 50km (30 miles).

Sprites are rarely observed, however when they do appear they are a large but faint, reddish-orange flash that is nearly impossible to witness with the naked eye. The phenomenon is best viewed at night and also from a distance of at least 150km away. Despite it being a challenge, sprites are best captured on camera using highly-sensitive equipment, and although difficult, it is not impossible as this image shows.  

How does hoar frost form?

Under clear, cold nights in winter, a hoar frost can form.

A hoar frost forms in a similar process to that of dew; the difference being that ice crystals are deposited, as opposed to water, because the temperature of the surface is below freezing.

Hoar frosts most commonly attach themselves to the branches of trees, leaves and grasses, but can also be seen on objects such as gates and flowerpots. Sometimes the deposits can be so thick that it may even look like a dusting of snow has fallen, creating a typical winter wonderland day.  

Dreaming of a white Christmas

Now it’s December, one of the questions we are often asked as meteorologists is “Will it be a white Christmas?” The first thing to clarify, is what exactly is being asked – do you want to know if anywhere in the UK will see a single snow flake or are you envisaging streets and roofs with a dusting of the white stuff when you wake up on 25 December.