The weather: It's all about location
by Alastair Hamilton -
Climate and climate change are, quite literally, hot topics these days; news broke recently of a temperature record of 38°C in Siberia.
In the British Isles, conversations about the weather are something of a cliché and that’s perhaps even more true in Shetland. There’s no question: we do get a lot of weather, and the contrasts from day to day, or even hour to hour, can be dramatic, so there’s usually something to talk about.
It's not just us locals who think about the weather, of course. Visitors wonder what to pack: the sensible answer – as it usually is anywhere in the British Isles – is ‘everything’. Those who are thinking of making a permanent move to the islands may wonder how they’ll adjust to a quite different climate from the one they’re used to.
The climate here is certainly different from that in, say, Surrey, and that is obviously to do with location. However, it’s not only about the difference between Leatherhead, at 51° North, and Lerwick at 60° North. Location within Shetland can, at times, make a much bigger difference than we might expect.
What’s more, one of the most obvious differences between experiences of living in Shetland and places farther south has nothing to do with the climate, but rather that difference in latitude, which produces huge differences in day length in both winter and summer. The late June sunrise above was photographed at 3.30am.
Shetland is bounded to the west by the Atlantic and to the east by the North Sea, roughly equidistant from Aberdeen in Scotland, Torshavn in Faroe and Bergen in Norway. At 60 degrees north, we’re on the same line of latitude as Seward in Alaska, Cape Farewell in Greenland and St Petersburg; and we’re a little closer to Iceland than to London.
Alaska? Greenland? Iceland? It does sound really cold, doesn’t it?
The sea’s influence
Well, it would be, but for the fact that, like the rest of north-west Britain and Ireland, our climate is modified by the North Atlantic Drift, a flow of warmer water originating in the Gulf of Mexico that eventually reaches the north of Norway and keeps the Russian port of Murmansk ice-free.
That means that, for much of the year, sea temperatures around Shetland – ranging from 7.5°C in February to 13°C in August – are higher than the 24-hour mean air temperature.
It’s still a relatively cool climate, of course, but not nearly as cold as other places at similar latitudes. With a 24-hour average of around 3°C in February, we’re roughly 9°C milder in January than St Petersburg and 6°C milder than coastal Seward.
The sea’s influence means that Shetland has fewer frosty days than places much farther south, the average being 7.6 days in February; again, in Surrey, it’s 10 days. There are memories of heavy snowfalls in the past, well into the 1990s, but in the past twenty years snow cover has usually been light and snow has seldom lain long.
On the other hand, our summer temperatures are lower than other places at the same latitude. August is our warmest month, when the average maximum temperature at the Lerwick Observatory is 14.5°C; in St Petersburg, it’s 20°C and in Surrey 22.7°C; but more about the observatory in a moment.
That warmth in the sea has another effect: away to our south-west, in the Atlantic, it creates the conditions for cyclones – areas of low pressure – which sweep up the western side of Britain and pass close to Shetland. Those depressions can be deep, especially in winter, and they produce the feature that’s most noticeable about Shetland’s weather, strong winds.
Our average windspeed throughout the year is 16.7 mph and in January, the windiest month, it’s 20.8 mph. Even in summer, the average remains above 12 mph.
Unofficially, the RAF station at Saxa Vord in Unst holds the British wind speed record; a gust of 197 mph was recorded in 1992, after which the measuring equipment blew away. However, the maximum recorded at Lerwick is 109 mph, some way short of other places around Britain, for example, 115mph at the Isle of Wight, 124 mph in South Wales and 142 mph at Fraserburgh.
As these low-pressure systems pass over, we look forward to those days when we enjoy the peace of the ridge of higher pressure that separates them, when it can be perfectly still. It may be a brief respite and we call it “a day atween wadders”.
Those days are much more common in summer, and in fact we can find ourselves enjoying a week or more of calm conditions if – at any time of year – Shetland lies under one of the large high-pressure areas that form over Scandinavia. In winter, though, as in the photograph above, they are especially welcome.
Incidentally, the Shetland dialect is rich in words about weather (wadder). A light fall of snow is a feevil; gently-falling large snowflakes are fluckra, which, said softly, seems to capture them perfectly. A snowstorm can be a moorie or a blind-moorie, depending on severity.
Out sailing, you have to be wary of flans. They’re not part of a picnic, but sudden squalls of wind. Lightning’s not that common, though we seem to see it more often in summer than we used to, when it’s hairst-blinks.
What about rainfall and sunshine? The rainfall figures are well within the normal range for western Britain. Lerwick, with 1256.8mm, is wetter than Aberystwyth (1074.7mm) or Newquay (1017.4mm). but drier than Glasgow (1318.4mm) or (especially) Ambleside in the Lake District (2005.1mm). However, there’s noticeably less sunshine at Lerwick than most other places in the UK. Our annual total is 1,109.9 hours compared with Glasgow’s 1,348.1 hours.
That said, in July 2017, Shetland had more sunshine than Cornwall, with 192.9 hours compared to 153.5 hours; and that wasn’t the first time – it had happened on seven previous occasions. Recent Shetland summers have seen long spells of dry, clear weather.
Is west best?
But climate and weather in Shetland aren’t just about latitude or those passing depressions. Within the islands, the weather we have, and the microclimate, are heavily influenced by the lie of the land and local shelter. We also need to keep in mind that those climate records come from the Lerwick Observatory, which stands on a hill outside the town, at an altitude of 85m (278 feet) above sea level.
The observatory - one of only three staffed specialist observatories in Britain - provides a wide range of data, not only to do with weather. It’s run jointly by the Meteorological Office and the British Geological Survey, and weather data has been recorded here since 1919.
But it’s also a seismographic recording station, measuring earthquakes all over the world, and is one of only two stations in the UK – the other is in Cornwall – recording ozone levels. The observatory also monitors data from around 150 unmanned sites around Britain. Staff moved into a new, £1.2m building in early 2014.
The location of the observatory means that, broadly speaking, the weather it records is likely to be marginally cooler and a little windier than that experienced in most settlements in the islands, bearing in mind that most houses are below the 30m contour and enjoy rather more shelter than the observatory.
It’s also because the eastern side of the islands – which includes Lerwick – tends to have more low cloud and fog than the west. Sea fog is fairly common, particularly in the summer months; it forms when warm, moist air moves over the colder sea, causing the moisture to condense into the droplets that make up the fog.
We quite often see fog a few days after the onset of warm weather in the south of the UK or mainland Europe; sometimes, it’s accompanied by strong winds.
That difference between east and west is often quite marked and it stems from the ridge of hills that runs roughly north-south down the Shetland mainland. Propelled by the breeze, the foggy air warms up as it descends on the leeward side of the hills; it’s possible to watch the fog simply disappear as it rolls down the slope. Each year, there are many days, in summer especially, when this phenomenon (known to meteorologists as the Foehn effect) results in clear blue skies to the west of the hills while the east side of the islands – including the observatory – is blanketed in fog.
This has led to the saying that, weather-wise, “west is best”. The effect is reversed when fog comes in from the Atlantic, though that is very much rarer. There are no official weather stations in the west of Shetland but past amateur estimates have suggested that Hamnavoe in Burra – not far from where I live - receives between 10% and 15% more sunshine than Lerwick and that seems very plausible. There are days, too, when Lerwick is clear of fog because it’s dispersed by the hill on the nearby island of Bressay.
The temperature difference between east and west in these conditions can be significant; we wouldn’t be surprised to find a difference of five degrees, or even more. Earlier in June, when the temperature was around 18° in the east, people were reporting shade temperatures of 24°C or even 26° in the west. The Foehn effect isn’t the only cause of these differences. When air is moving slowly over a few miles of moorland warmed by the sun, its temperature can rise considerably.
Shelter is a major influence on local climates. The growth of trees and shrubs demonstrates just how much difference a lower wind speed can make. The plantations around Kergord, in relatively sheltered Weisdale, are an example, but we see the same benefit on a smaller scale in long-established planting in Lerwick and Scalloway, where protection comes from both topography and buildings.
Creating windbreaks around any garden, even those in the most exposed locations, dramatically improves growing conditions.
So, in the end, is Shetland’s climate an asset or a liability? Of course, if you’re with Sir Ranulph Fiennes, you’ll take the view that there’s no such thing as bad weather, only inappropriate clothing, which isn’t a bad maxim anywhere in the UK.
There are swings and roundabouts. Temperatures are almost always lower in summer than places farther south, and if you yearn for the mercury to soar into the high twenties or thirties, Shetland won’t hit the mark. On the other hand, it’s not unknown for Shetland to be the mildest place in the UK on winter days.
Prolonged spells of strong wind can be wearisome, but then again, we can witness those dramatic storms. Even in Lerwick’s relatively sheltered harbour, things can become quite lively, as the photo above suggests. And those ‘days atween wadders’ can be stunning.
Few of us in the west and north of the British Isles would want any more rain, but there are many wetter places than Shetland. Most of us would also like a bit more sun, especially in winter, but that’s limited by latitude as much as by climate.
Summer – with those unfinished sunsets and the twilight we call the ‘simmer dim’ – is very special. And compensation on those winter nights can come in the form of the Northern Lights.
And, as we’ve seen, that general picture disguises variations within Shetland. In more ways than one, it’s all about location.
Posted in: Exploring Shetland