Dull, cool, rainy – July figures show the hard facts of miserable summer 2011

Like summer so far, this July was very changeable. Cool spells with periods of rain and showers alternated with milder settled weather. Until the 5th an anticyclone to the north maintained a ridge south across Shetland, resulting in generally fine, mild and dry conditions. As a depression moved over the UK, an unsettled south-easterly airflow followed until the 9th. As low pressure moved away east, high pressure returned across the British Isles, bringing a settled spell until the 14th. In turn this also continued east, with south-easterly winds backing north-easterly between the 15th and 19th, as a depression tracked east over northern Scotland. Low pressure then moved into southern Scandinavia and deepened, and a cool, unsettled and strong northerly airflow ensued until the 25th. July then ended less unsettled, as an anticyclone moved east over Scotland.

Across Scotland as a whole, mean temperatures were generally about 0.5°C below the 1971-2000 average. With several chilly nights, in terms of minimum temperature it was the coldest July since 1993. It was a wet month across many eastern areas, from the Borders to Inverness, with about twice the average rainfall in places. By contrast, it was a relatively dry month in Orkney, Fair Isle and the Western Isles, with between a third and half of normal rainfall. Lerwick’s rainfall was average. Sunshine amounts were well above-average in the west, but it was rather dull near the east coast. Western Scotland enjoyed one of the sunniest Julys in the series from 1929. In Shetland Fair Isle was slightly sunnier than average, yet Lerwick experienced its dullest recorded July.

July began with an anticyclone to the south-west moving in over the UK. This brought a fine, dry and sunny day with moderate north-westerly winds on the 1st. Linking with another high developing to the north-west of Shetland, the resulting ridge brought cloudier, cooler north to north-westerly winds on the 2nd. The dry conditions continued through the next couple of days, as the ridge was maintained across the area. The 3rd was bright and the 4th was sunny, as moderate northerly winds became easterly. As high pressure declined, the 5th was cloudier, with a weak front bringing patchy drizzle and mist by the end of the day.

With high pressure holding on to the north and east of Shetland, easterly winds freshened on the 6th, as a depression moved east towards Scotland. It was a cloudy, misty day with rain and drizzle accompanied by hill fog. As the low tracked east over the UK, the 7th was a mild, mainly cloudy but dry day with some hazy sunshine. Weak, showery troughs moved north to affect the Northern Isles on the 8th. Winds across Shetland backed light north-easterly by the 9th – a cloudier, misty day with a few showers and patchy sea and hill fog – as the remains of the low moved out into the North Sea. As the filling low tracked north between Shetland and Norway, the 10th was a drier, brighter day with a moderate north-westerly wind.

An anticyclone, developing near Iceland on the 11th, drifted east to be over northern Scotland by the 12th. High pressure covered the British Isles on the 13th, 14th and 15th. This brought a settled period with mainly dry, bright conditions and a good deal of sunshine, especially across Fair Isle, where in the five days nearly 45 hours of sunshine were recorded. Sometimes clear skies and light winds resulted in cool nights, with a grass frost reported by Lerwick Observatory on the 14th. As high pressure declined east, south-easterly winds freshened later, ahead of fronts pushed east by a developing depression off north-west Scotland.

As low pressure tracked east, the 16th and 17th were wet and misty, with outbreaks of sometimes heavy rain accompanied by hill fog. Moderate – occasionally fresh – south-easterly winds backed easterly. Often cloudy but clearer conditions with patchy drizzle followed on the 18th and 19th, as the depression moved out into the North Sea. Freshening winds backed north-easterly and then north to north-westerly, as an associated “wrap-around” occlusion finally cleared west from the Northern Isles. Fresh northerly winds blew on the 20th, as the filling low drifted north towards southern Scandinavia. Weakening fronts gave a dull, misty day with patchy rain and drizzle.

With a slack pressure-field covering the British Isles, the 21st was a bright, mainly dry day with sunny periods and moderate northerly winds. These continued through the 22nd – another dry and bright day – as pressure built to the west. With an anticyclone to the east of Iceland and pressure falling over southern Scandinavia, northerly winds freshened on the 23rd, becoming strong with gusts to 40-45mph by the 24th. East of Shetland strong to gale-force winds resulted in very rough to high seas also, keeping the Tall Ships in Lerwick harbour for an extra day. An occluded front, moving from the Norwegian coast towards Shetland, brought a dull and wet day. The strong northerly winds quickly eased on the 25th, as the Scandinavian low filled. The day was drier and brighter but rather misty, as the weakening occlusion remained slow-moving close to Shetland.

High pressure moved in over the Northern Isles on the 26th. The day was rather cloudy with a little patchy drizzle, the moderate northerly winds falling light. Though high pressure persisted through the 27th, light south-easterly winds brought mainly cloudy conditions with occasional light drizzle patches. High pressure declined east on the 28th and winds backed moderate to fresh north-westerly, as a weak occluded front moved in from the west. Much of the day was cloudy, with a little drizzle and some hill fog. However, as the front cleared east, the day ended mostly dry and much clearer. Light north-westerly winds, flowing around an anticyclone developing to the west, brought cloudy conditions and occasional drizzle patches on the 29th. Light winds gradually worked round into a south-easterly direction on the 30th and 31st, as the declining high migrated east across the UK and mainly cloudy conditions with an occasional drizzle patch persisted.

JULY STATISTICS RECORDED AT LERWICK OBSERVATORY

Data from the UK Met Office