A Sky worth subscribing to

The much heralded 'digital switchover' has taken place in our part of the world. Our trusty old terrestrial analogue television signals are no more. I suppose it will be a little piece of history by the time the switchover programme completes in 2012; another milestone in the digital communications revolution. Despite all the advance publicity and my desk-sharing with a colleague working on a project to support those less able to manage the change, I still managed to forget about it when the time came. I had a grumpy five minutes on returning from holiday to discover nothing was where I had left it on my television.

Now I am thoroughly re-tuned and unsurprised to discover that in spite of having the best part of a hundred channels to select from, I still have difficulty finding much I can be fussed to watch. Lucky, then, that there is no shortage of alternatives to the (not so) little black rectangle in the corner of the room. Top of my list just now has to be weather watching; probably not what News Corp and the other stakeholders in BSkyB had in mind when trying to entice me to subscribe to Sky, but a whole lot more entertaining.

Spot the glider!

Although it may be deserving of many epithets, nobody could accuse this summer's Scottish weather of being dull. After the fierce, tree-culling gales of May, in Edinburgh this last week we experienced violent thunderstorms and flash floods accompanied by strange mammatus clouds. These clouds, so named because they have the appearance of breast-like mounds projecting below the main cloud base, are quite rare in Britain. They will be more familiar to my readers in the US where their appearance is often an early warning sign of tornadoes. They signify unusually turbulent currents within the thunderheads above, and steep temperature gradients

Storm moving across Fife

On a calmer note, our prolonged daylight hours after sundown have this week been showing an even rarer feature, one of the best displays of noctilucent clouds for many years. Noctilucent clouds are made of tiny ice crystals at great altitude, far exceeding that of any other clouds. On summer nights, when the Earth's surface is in shadow but the sun sinks not far below the horizon, high layers of the atmosphere (the mesosphere) are still illuminated in the northern sky giving the clouds, where present, a ghostly, diaphanous glow.

Some of these effects have been quite localised. They require being in the right place at the right time and with a camera to hand. I haven't managed either of these particularly well and sadly have no pictures of these phenomena of my own. However, there is a wonderful shot of the noctilucent clouds over Portobello beach on the website Talk Porty. I was out of town when the Edinburgh storms came although a week earlier I did witness something similar in Dundee; no mammatus clouds but midnight skies in the middle of the afternoon and the city bombarded with hailstones the size of hazelnuts. This picture of RRS Discovery was taken on my mobile phone shortly after the storm passed, about 4pm on a midsummer day!

Unstable airflows have been moving across northern Britain for months now. They may not make for ideal summer weather but the visual effects have been dramatic. As our great painters of clouds, John Constable and JMW Turner, knew well, there isn't a single colour on the palette that can't be found in the sky in the right conditions. It makes for great viewing day and night. It is a Sky worth subscribing to, except of course we don't need to.