Worst summer in living memory and rare clouds

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Clear skies have been all too rare this summer, but during a brief parting of the clouds last Wednesday there was a rare sight.

It gave us a glimpses of the rare and extremely beautiful noctilucent cloud, which could be seen from across the Isles.

What are noctilucent clouds?

Meaning ‘night-shining’, noctilucent clouds are the highest known clouds, forming brief and very tenuous layers at an altitude of 80km in an upper part of the Earth’s atmosphere known as the mesosphere.

Here, they remain brightly lit by the Sun during the northern hemisphere summer (because they are so high), and thus, if the conditions are right, they may occasionally be spotted from across the Hebrides during the period from late May through to mid-July.

Time lapse animations of these clouds show shimmering ‘electric blue’ colours, alternating with ash-white waves.

When combined with the faint background hue of an aurora (as was the case last Wednesday night), the resulting sight can be awe-inspiring.

For many decades, the cause of such clouds was unknown, as the water vapour needed for their formation cannot ascend to such a great height from the surface of the Earth.

Indeed, before the start of the 20th century, there are no reported observations of such clouds from anywhere in the world.

Recently, however, NASA have confirmed that the water (ice) in these clouds owes its origin to meteors entering the Earth’s atmosphere from space - hence, these clouds are very much “out of this world”!

Weather Summary

for Summer 2015

It has been worst start to summer in living memory, if not in the complete instrumental record for the Isles, which began in the late 19th century.

In Stornoway, months of May and June (combined) saw a record amount of rainfall (nearly 250mm or 10 inches), together with a record deficit of sunshine.

It was also the coldest start to summer in more than 35 years.

And although it turned a little bit milder at the start of July, rainfall depths for July already exceeded the monthly average by the 11th, with the persistent cloud and rain showing no sign of abating (at the time of writing).

All-in-all, it may possibly turn out to be the worst summer since 1816, the infamous ‘Year without a Summer’ – when snow fell in June and widespread famine afflicted much of Europe and Scotland.

Highest temperature: 21.1C (1st July – the day of spectacular thunderstorms).

Lowest temperature: -0.2C (14th June) – lowest in June since 1886.

Average temperature (May + June): +9.1C (coldest since 1979)

Deviation of temperature from average (May + June): -1.2C

Total sunshine (May + June): 200.5hrs (only 55% of normal, dullest since records began in 1929)

Total rainfall (May + June): 241.9mm (9.52in), or 190% of normal (nearly double the average and wettest since at least 1877).

For more weather information, don’t forget to follow Eddie on Twitter at https://twitter.com/eddy_weather (on Facebook: http://on.fb.me/1SxdpYR) or read his Hebridean Weather Blog at: http://bit.ly/1qGLyJm

Photograph courtesy of Rachel Bibby at www.58northphotography.com