22nd February 2018
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March weather ‘warmer’ and sunnier than average

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During the first half of the month pressure was generally high over the British Isles. As its focus moved from west of – to a position over – the UK, an initial cold northerly airflow across the Northern Isles soon became a milder west or south-westerly, bringing an end to the snow cover that seemed to have lain across Shetland for much of the winter. With fronts trailing around the northern flank of the high from time to time, we did not see as many of the anti-cyclonic benefits enjoyed by the rest of the UK.

The third week was more unsettled, as Atlantic depressions tracked north-east past – or east over – the north of Scotland. The Northern Isles escaped relatively unscathed, as the weather over much of mainland Britain ended on a very stormy note with significant snowfalls, especially across Nor­thern Ireland, northern England and parts of Scotland, where heavy snow, gales and blizzards brought very severe conditions. A snow depth of 38cm was reported in Lough Fea.

Across Scotland as a whole – despite the cold start – mean temp­eratures were close to the 1971-2000 normal. It was a relatively dry month in most parts, though some coastal areas in south-east Scotland were wetter than usual. Sunshine totals were close to – or somewhat above – average.

With a depression over southern Scandinavia, the month began with cool northerly winds with a mixture of sunny or clear spells and wintry showers on the 1st.

Winds eased and showers died out during the 2nd, as a ridge ex­tended south across Iceland and a small high pressure cell developed over the UK. This brought a fine dry day on the 3rd, with Fair Isle recording 9.9 hours sunshine.

After a very cold and frosty start, freshening south-westerly winds on the 4th brought thickening cloud and patchy rain, sleet and some hill snow later in the day, as the high slipped south and weak fronts moved in off the Atlantic.

Draped around the northern edge of the high, one of these brought outbreaks of rain and milder north-westerly winds on the 5th, which resulted in an accelerating rate of thawing of the deep snow still covering Shetland. As high pressure moved back over the UK, this was eventually pushed away, and the 6th was drier and brighter, with mild westerly winds finally bringing an end to the snow cover.

Between the 7th and the 10th, with high pressure centred over the British Isles, Shetland remained mainly dry with variable cloud amounts, as mild westerly winds slowly backed south-westerly.

The high again moved south on the 11th, allowing frontal systems to swing down from the north-west bringing some early rain, which cleared to brighter conditions with scattered showers later, as fresh south-westerly winds eased and veered northerly behind the front.

As high pressure drifted out into the Atlantic, winds turned westerly on the 12th, with outbreaks of rain turning showery by the 13th, as low pressure moved south over the Baltic and winds veered to a cooler north-westerly direction.

The 14th was a colder day with a fresh north-westerly wind. Though many places were dry, there were one or two light snow flurries. A shallow low, slipping south-east from Iceland, brought some rain and sleet early on the 15th, followed by brighter and drier conditions as Atlantic high pressure – migrating east over southern Britain – pushed a ridge north over Scotland.

A couple of mainly dry and bright days followed with mild south-westerly winds freshening, as the ridge slowly declined ahead of fronts moving in off the Atlantic, bringing some rain later on the 17th. This cleared overnight to leave the 18th mild and dry with a freshening southerly wind, as a developing low moved north to the west of Scotland.

Overnight rain cleared to showers during the morning of the 19th, and strong southerly winds veered west-south-westerly and increased gale or severe gale-force for a time, as the low continued north past Shetland. Gusts to 72mph were recorded in Fair Isle. Easing winds veered north-westerly and showers died out on the 20th as the filling low moved away and pressure built across Scotland.

A ridge brought a reasonably fine day on the 21st, but patchy rain reached Fair Isle during the evening. This became heavier as it extended to the rest of Shetland overnight. The 22nd was cloudy with some patchy rain, as fronts were pushed east by a small low west of Scotland.

The 23rd was dry and bright with light winds as another ridge built across the area. This declined on the 24th and, after a mostly dry day, rain and strengthening south-easterly winds spread from the west during the evening as further fronts moved east.

These cleared overnight and, with pressure high to the east and low over the Atlantic, the 25th was dry and bright. Southerly winds backed north-easterly later in the day. Rain, spreading north over­night, persisted on and off for much of the 26th. It was also misty with hill fog. Fresh north-easterly winds eased as a small low centre moved north over mainland Scotland.

The next two days saw a mixture of brighter spells, showers or longer periods of rain, as the low became slow-moving near Shetland. Winds became cyclonic variable in both direction and speed on the 27th but, as the low turned and headed into the North Sea, colder north-easterly winds strengthened, reaching gale-force across Shetland during the morning of the 28th.

The 29th was drier and brighter with scattered wintry showers and fresh north-easterly winds, the 30th mostly dry and bright but with a strong and cold north-east to northerly wind.

Early on the 31st, as the low turned yet again and headed back over central UK – a position from which it had left five days earlier – north-north-easterly winds increas­ed to gale-force in the north. However, conditions did improve later in the day as winds moderated, and the mixture of heavy rain, sleet or wet snow turned to rain showers, as temperatures slowly rose.

Dave Wheeler

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