Gales and snow have been forecast for Thursday and Friday of this week.
Although the sight of snowflakes is not an unusual occurrence in the Hebridean winter, we are certainly spared the larger amounts of snow and ice that many locations of a similar latitude experience each year. Except in the severest of winters, snow never lasts long on the ground in the isles. Expect it only after a sudden rush of cold air from the north, which ushers in a temporary blanket of white upon a frozen landscape. It is then that the Hebridean landscape can be said to truly sparkle.
How does a snowflake form?
Snowflakes start their lives high in the atmosphere, where the air temperature is usually between minus -20 and -50°C. At these low temperatures, water vapour condenses in the air directly as a solid ice, usually in the form of tiny needles, prisms or stars. Gradually over time, these tiny crystals gain weight by further condensation but also by collision and adhesion with other crystals, as they gently fall down from the clouds at speeds of no more than a few tens of centimetres per second. When they finally reach the lower portions of the cloud, the air is much warmer, often near 0°C. However, instead of melting immediately (which requires an extra amount of energy), the snowflakes usually acquire a thin layer of water around their edges – this makes it easier for it to bond to other flakes – and thus, the biggest snowflakes are usually seen when air temperatures are close to, or indeed a little above, freezing (0°C).
What’s the best type of snow for snowball fights and making snowmen?
As every schoolchild knows, compressing a ball of snow between your hands helps it to stick together, thus making a better projectile. It is also easier to roll a large snowball across a field (to make a snowman) when the snow is moist and air temperatures are around freezing. This is because the act of compression (in rolling the ball) temporarily melts the surface of the snow, allowing it to stick together better. In contrast, in cold climates where snow falls at much lower temperatures than in Scotland (e.g. such as in Canada, where air temperatures of -20°C or lower are quite common), it is quite difficult to make snowballs or snowmen of any sort. Snowflake size is also much smaller in cold climates, for the reasons described above.
Local snow folklore and sayings
There are a quite a number of Scottish and Irish Gaelic folklore sayings in relation to snow. The preference of a snowfall over a hard or lengthy frost is clearly given in the following Irish sean fhacail:
“Blifar bó an tSneacht nuair a chaillfear bó an tseaca”
When translated, this literally means “The ‘snow cow” will be milked when the ‘frost cow’ dies”.
In the same frame of mind, the following saying extols the virtue of snow in providing (or seemingly providing) sustenance to the crofting family:
“Leasú seacht mblian brúcht maith sneachta”
Which means “a good fall of snow is worth seven years’ manure”, although I myself cannot think of a definite agro-meteorological benefit that could arise from a heavy snowfall!
Some of the old seanfhocail are clearly weather forecasts, such as:
“Sneacht nach dtiocfaidh faoi Shamhain, tiocfaidh sé go ramhar Lá Fhéile Bhríde”
Meaning “Snow that doesn’t come in November (Samhain) will come heavily by 1st February” (St. Brigid’s day). From a meteorological perspective, this saying has more than a ring of truth to it – lengthy spells of snow and ice early in the winter are often followed by mild and settled spells later in January and February. And since we’ve already had snow twice this winter since November (Samhain), I wonder if it bodes well for some quiet settled weather come February?
For all the latest news on Hebridean weather, visit the Hebridean Weather Blog at: http://tinyurl.com/eddy-heb-weather
November 2013 Weather Summary
From the 1st to the 20th the weather was relentlessly wet and unsettled, with frequent spells of heavy rain accompanied by strong winds. High pressure built during final ten days, however, with the result that it became much quieter and calmer, although it stayed rather dull and overcast with drizzle at times. A rare occurrence of “Nan Seachd Siantan” was observed on the 19th, when snow, hail, rain, sunshine, gales, thunder and lightning (the full seven elements of the heavens) were all reported within 24 hours.
Average daily high: 8.7°C (Highest: 13.7°C on 16th)
Average daily low: 3.4°C (Lowest: -0.8°C on 22nd)
Departure of mean temperature from normal: -0.7°C
Total precipitation: 149.4mm (5.88in; 90% of normal)
Wettest day: 27.5mm (1.08in) on 19th
Number of wetdays (>1.0mm): 22 (average is 20)
Maximum wind gust: 68mph on 14th
There were 2 nights with an air frost, 6 days with hail, 5 days with snow falling, 1 day with snow lying, and 3 days with thunder and lightning (1st, 7th and 19th).
*All observations taken in Stornoway.