winter

Dreaming of a white Christmas? theWeather Club Mon, 18/12/2017 - 10:56

As we head closer to 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. 

Winter is coming

The maps above show the UK winter (Dec, Jan, Feb) averages for 1981-2010. The analyses are based on 1 km grid-point data sets which are derived from station data (Source: Met Office)

As we approach the winter season and temperatures start to dip, we take a look at winter weather in the UK – what affects it, seasonal extremes, what an ‘average’ winter looks like and link to some ‘wintry’ articles of interest.

How does hoar frost form? theWeather Club Wed, 30/11/2016 - 10:11

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.  

What causes these beautiful frost patterns?

Clear nights and plunging temperatures can deposit a thick frost by daybreak. For frost to form, the temperature of the surface must be below 0°C. But what causes these pretty, leaf-like patterns? The patterns are the result of very tiny imperfections on the glass, such as scratches, specks of dust and salt, or the residue from washer fluid. These variations in the surface affect the way that the ice crystals form and branch out, forming the beautiful patterns captured in this image, taken in North Yorkshire on an smartphone by Paula Davies.