16th October 2018
Established 1872. Online since 1996.

Higher than average levels of sunshine and rainfall (most of which fell at night)

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As is more often the case than not in Shetland, July saw the largely settled weather patterns of spring and early summer replaced by a more changeable and unsettled cyclonic-type, with depressions often following a track close to north-west Scotland. Across Scot­land as a whole it was a very wet month with frequent showers or longer spells of rain. Rainfall totals were 240 per cent at Lerwick and 200 per cent in Fair Isle. Provisionally, it was the third wet­test July over Scotland in 100 years of records.

Overall, it was duller than aver­age, especially in south-western areas of Scotland. One exception was the Northern Isles where – with much of the precipitation falling overnight – sunshine totals were also above average.

July began with a deep depres­sion to the west of Ireland moving slowly north towards Iceland. Mod­erate or fresh south-easterly winds brought dull conditions with patchy rain or drizzle, misty conditions and hill fog on the 1st. Fronts produced heavy overnight rain with 32.6mm recorded at Lerwick and 26mm in Fair Isle between 9pm on the 1st and 6am on the 2nd. Early mist and low cloud cleared and the remainder of the day was mainly dry with some hazy sunshine and moderate to fresh south to south-easterly winds. Apart from a little overnight rain, the 3rd saw similar con­ditions.

A secondary depression – swing­ing in towards western Scotland – tracked north to the west of Shetland during the 4th. A line of thunder­storms, accompanied by bursts of heavy rain, crossed the area during the early hours. The remainder of the day was then mainly dry and bright.

As low pressure moved away, a flat ridge crossed northern Scotland on the 6th, bringing a mainly dry day with lighter winds. These back­ed south-easterly later as a deepen­ing Icelandic low pushed fronts north-east, bringing rain to Shetland early on the 7th. The rest of the day was mostly dry and sunny with a fresh southerly wind. The next two days continued mainly dry and bright, as the slow-moving low near Iceland gradually filled. Southerly winds increased fresh to strong on the 8th, with gusts to 40mph at Fair Isle, but eased light south to south-easterly by the 9th. After a dry start, the day was rather cloudy with outbreaks of occasionally heavy rain and misty conditions.

The 10th was mainly dry and bright with sunny periods and light southerly winds. Early on the 11th, a developing wave-low on a trailing front ran north bringing heavy rain, with over 25mm recorded at Balta­sound in two hours. Between 10pm on the 10th and 10am on the 11th 26.4mm were recorded at the obser­vatory. As a “rainfall day” is the 24 hours between 10am one day and 10am the next (09-09hrs GMT), this rainfall counted as that of the 10th! After the clearance of linger­ing mist and hill fog, the day was bright and mainly dry. As the low moved away, light south-easterly winds veered south-westerly and increased strong to gale-force dur­ing the evening, with gusts to over 50mph reported at Lerwick and Fair Isle.

As the low took up a position just to the north of Shetland, the 12th was a mostly dry, sunny day with much lighter south-westerly winds. The low then slipped away towards Denmark, and high pressure in the East Greenland Sea ridged south-east towards Shetland, bringing a fine day with light north-easterly winds on the 13th. Lerwick reported the UK’s highest sunshine total for the day of 15.5 hours. Though the ridge persisted on the 14th, a fresh north-easterly wind brought cloud­ier conditions with a few showers.

The next Atlantic low moved closer on the 15th, bringing heavy rain overnight and dull, misty, damp conditions during the day. As fronts moved over the area, fresh north-easterly winds veered south-easter­ly. With a complex area of low pres­sure developing across Scotland and Faroe, the next few days were mostly cloudy with outbreaks of rain and misty conditions. The low moved away, and a weak ridge – building across northern Scotland – brought drier, brighter con­ditions.

The ridge soon declined, with the next Atlantic low – drifting in towards Ireland – driving fronts across Scotland. The 19th – starting dry and bright – clouded over, with rain accompanied by misty conditions and hill fog spreading east. As the low drifted further east over the UK on the 20th, associated fronts remained slow-moving near the Northern Isles, and Shetland remained dull and misty with out­breaks of rain and mainly light south-east to easterly winds. After a dull, misty and damp start, bright­er conditions followed for the 21st. The 22nd and 23rd were dry and sunny, as the low moved away over the North Sea and a high developed over southern Scandin­avia. Fresh north-east to northerly winds back­ed north-westerly and later light south-easterly. Fair Isle reported 14.8 hours of sunshine on the 22nd.

The Scandinavian high drifted away north on the 24th, and once again a depression in the Iceland area pushed more fronts east over Shetland, bringing cloudy con­ditions with outbreaks of rain and moderate south-easterly winds. These moved away and, in the “col” area between two highs and two lows, Shetland was cloudy with some patchy rain and little wind on the 25th. The low near Iceland drove fronts east over the area on the 26th, bringing further patchy light rain in places. Brighter, drier conditions followed outbreaks of rain on the 27th, as a shallow area of low pressure drifted east to the north of Shetland.

The low then moved into Scandinavia, and the 28th was cloudy with outbreaks of drizzle, misty conditions and light winds. The 29th was mainly dry and bright, with north to north-westerly winds freshening later as the low deepened, but eased overnight when the low moved away. On the 30th and 31st another shallow low – tracking east – passed close by Shetland, bringing a dull and damp end to the month, with misty conditions, hill fog, outbreaks of drizzle and mainly light winds.