Of Swallows and Saharan Dust ... (in December?)

A Case of Seasonal Wires Crossed?

Swallow

I read a warning this morning about potentially toxic dust from the Sahara that may cross our paths tomorrow here in parts of the UK. A number of newspapers were running the story, but we failed to find any mention of the anticipated scenario on the weather forecast.

I was just beginning to think that I must have got the wrong end of the stick when I finally tracked down (a version of) the report on the Met Office News Blog here.

It seems that, desert dust apart, we are in for some unusually mild weather for the time of year in the next few days. And to add to my seasonal confusion, guess who turned up at RSPB Minsmere today ... a Swallow!

I remain unsure about the weather for tomorrow (Thursday 17 December) in the UK; but just to be on the safe side, you might care to take a look at the following, particularly if you have a health condition that could be affected by unusual dust ...

• Metro
• The Guardian
• The Mirror

Frostflowers: Fractal, Feathered or Fern-like?

This is the time of year for Jack Frost and his ice patterns!

The swirls in the photo above graced the roof of my car some days ago and made me wonder how they came to form in the way that they do.

I am, alas, no scientist, but it seems that small environmental changes, for example in air temperature, air movement, in the number of water molecules or in the quantity of dust particles, cause an ice pattern to grow, perhaps by developing long frond-like arms, thereby deviating from its original flower-like design.

But what causes these formations in the first place? Well, in the case of windows, it seems that frost patterns emerge when a pane of glass is exposed to sub-zero temperatures on the outside and moist air on the inside. Water vapour in the atmosphere condenses and becomes frost on the internal surface of the glass. These days with central heating, we rarely see frost patterns inside our homes, but I recall the high sash windows of my teenage years and the chilly patterns that delighted us on winter mornings.  

• The Story of Snow: what we sometimes miss
• Fern pattern
• Frost photos