Weather extremes of 2006- 27th Feb-7th March severe cold spell

Cold spell and record Aberdeen snowfall, 27th Feb – 7th March 2006

For much of the last week of February a ridge of high pressure extending southeast from Greenland to Iceland drew a persistent cold north easterly flow across much of the UK and Ireland. The source of air having travelled across the North Sea left the boundary layer very moist and consequently the skies were mostly cloudy (especially on north and east coasts) throughout the period with occasional wintry showers. This prevented the temperatures from falling sharply away overnight but also attaining reasonable temperatures by day (across the south of England maximum temperatures were approximately 1°C below average during February). There were fortunately some long spells of sunshine in favoured spots and across much of England away from the east coast on the 25^th but it was still cold in the wind. A major pattern change was underway at this time across northwest Europe, which was to bring record snowfall to Aberdeen and an extended period of unseasonably low temperatures everywhere.

An extremely highly amplified jet developed and subsequently a deep longwave trough was also then developing across Scandinavia aiding to advect a very deep cold air mass of Arctic origin south into parts of north and east Europe (with top of the boundary layer temperatures approaching –20/–25°C)! The UK still under the influence of the ridge from Greenland/Iceland remained fairly benign (but cold) throughout the final days of February as the coldest and most unstable air was pulled away to the east. However, on the 27^th the trough axis altered and moved slightly west placing the UK in a direct feed of very cold northerly winds originating from within the Arctic Circle. The change of air mass was heralded by a spell of rain, sleet and snow (mostly snow over high ground such as the Pennines) sweeping south through the day; behind which there were frequent snow showers across northeast Scotland and across the extreme coastal areas of northeastern and eastern England. It became clear and crisp inland though with the showers unable to penetrate far inland but became colder because of the strengthening northerly wind.

Reanalysis panels from Wetterzentrale for 12Z on 28^th February 2006

http://www.wetterzentrale.de/archive/ra2/2006/Rrea2006022812.gif

Conditions in the mountains of Scotland deteriorated very quickly on the 27^th as the onset of Arctic air took place. An RAF helicopter that was called out to rescue a climber, who had broken their ankle, was caught out in the conditions on the Cairngorms, which incorporated winds of up to 60mph and heavy snowfall. After the winchman noticed the rotor blades icing up, the helicopter was forced to make an emergency landing, and was stranded on the Cairngorms for several days. The spokesman for RAF Lossiemouth described the weather conditions at the time of the rescue as “utterly horrendous”.

Falls were mainly slight at first at lower levels but there were initially some heavy falls at low levels overnight on the 28^th and into the 1^st March across the extreme coastal part of east England and across Norfolk. Strong winds from due north drove bands of heavy snow showers inland from the North Sea. Coltishall in Norfolk reported 6cm on the ground by 23Z. However, these showers decayed rather rapidly as they moved inland leaving much of central and southern England clear and frosty.

The exception to this was during the afternoon of the following few days throughout the cold spell when solar heating was sufficient enough to kick off convection inland. Some of these snow showers were potent and created temporary hazardous conditions as snow accumulated rapidly from these snow showers. The strong March sun was able to melt the snow at lower levels in the south when an adequate break in the snow showers occurred; this happily preventing further disruption from occurring.

The first few days of March brought increasingly frequent heavy snow showers to the north of Scotland with the Northern Isles, northeast Scotland, Wales, Northern Ireland and extreme coastal part of eastern England also badly affected by the snow. Winds were predominantly from the north across Scotland and Northern Ireland but tended to back west-northwesterly across England and Wales as a weak ridge developed southwest of Ireland – this actually acted to push snow showers further inland at times across northwest England through the Cheshire gap and right through to the south coast across Wiltshire and Dorset from the Bristol Channel. Several polar lows formed but only one affected Aberdeen late on the 2^nd and into the 3^rd bringing the first snow f the spell to the central belt of

Scotland

. Another polar low degenerated into a trough and brought heavy snow to Northern Ireland early on the 3^rd and went on to bring a decent covering of snow to much of the north of England that afternoon and evening.

The snow in Aberdeen (some 26cm by the morning of the 3^rd) broke records to become the deepest snow in March since records began in 1957 when 25cm was recorded. Some of the greatest snow depths recorded over the period are outlined in Table 1 below.

TABLE 1. Deepest snow cover recorded during the cold spell 27^th Feb – 7^th March

Station	Date	Snow depth (cm)
Glenlivet, Banffshire	3.03.2006	29
Aberdeen Dyce Airport	3.03.2006	26*
Wick, Caithness	6.03.2006	25
Kirkwall, Orkney	5 & 6.03.2006	16
Aviemore	3.03.2006	13

* Deepest snow in March since records began at Aberdeen airport in 1957.

Lerwick is likely to have recorded far more but with drifts in excess of several feet reported, the observations were coded “measurement impossible due to severe drifting” until the 8^th when 12cm was reported after the thaw began to set in across the far northeast.

Where skies cleared over the snowfields some very low temperatures were attained, the coldest in March since 2001 but even more remarkably the lowest minima of the winter and nationally since January 2003 (see Table 2, below).

TABLE 2. Lowest minima recorded during the cold spell 27^th Feb – 7^th March

Station	Date	Minima (°C)
Altnaharra, Sutherland	2.03.2006	–16.4**
Kinbrace, Sutherland	2.03.2006	–14.7
Loch Glascarnoch, Wester Ross	2.03.2006	–14.1
Braemar, Aberdeenshire	2.03.2006	–12.7
Capel Curig, Snowdonia	3.03.2006	–12.4
Hawarden, Flintshire	3.03.2006	–12.4
Tulloch Bridge, Lochaber	2.03.2006	–12.2

** The lowest temperature recorded in the UK since 8^th January 2003 when Aviemore recorded –18.6 °C.

All schools in Shetland were closed for 4 days following the blizzards that swept across the island on the 28^th and then became unrelenting through the following 3 days. The duration of the event was one of the longest for some time and the strength of the northerly wind drifted snow up to 5 feet deep in places making the accurate measurement of the snow depth at the island station in Lerwick almost impossible.

Apart from Shetland, the heavy snow worst affected Aberdeenshire, with over 300 schools closed from the 28^thuntil the 6^th March. Many of the routes within the region were closed due to drifting snow and those that weren’t affected were still extremely hazardous. The A90 was closed after a lorry jack-knifed on the 1^st and became impassable over time as the falling snow outpaced efforts to grit and clear the road. Several minor incidents where cars lost control and slid off the main road resulted in long delays on the routes around Aberdeen causing travel times to treble. On the rails, four trains became stuck in drifting snow in the Laurencekirk area, south of Aberdeen forcing the closure of the main Aberdeen to Dundee line.

At times the snow showers banded together and were accompanied by lightning; so called “thundersnow” with extremely heavy squalls of snow hit Aberdeen, and put the city’s station Northsound Radio off air for 15 minutes after its transmitter mast was struck by lightning.

Air travel was also badly affected by the snow with airports at Campbeltown, Islay, Inverness, Kirkwall, Stornoway and Tiree all closed as heavy snow showers continued to fall unabated. Flights from Aberdeen Dyce were severely disrupted by the snow throughout the period with frequent clearance of ice and accumulating snow on the runways required, unfortunately the de-icing equipment failed, further delaying flights from the airport.

Ice had also formed in the River Dee, postponing the annual boat race between Aberdeen University and Robert Gordon University on the 4^th. Other sporting events cancelled on the weekend of the 4^th included several Scottish football league fixtures, as snow lay deep across the lower division pitches. All second and third division matches were postponed due to frozen or snow covered pitches and in the first division the matches at Brechin and Stranraer were called off too. Further south several football matches in England were also postponed due to frozen pitches.

A heated debate between Aberdeen FC and the SPL occurred regarding the weekend away match at Celtic. Aberdeen FC requested that the match be postponed in order to prevent unnecessary risk to travelling supporters in the atrocious driving conditions around Aberdeen. The request was declined however, and Celtic went on to beat Aberdeen 3-0!

This northerly spell across Scotland was notable for its duration as well as its intensity, which led to several days of heavy snow showers across the northeast and an accumulation (with very little thawing) of up to a foot and more in places. Further south there was little or no snow but the harsh frosts and suppressed daytime temperatures made the spell the coldest first 10 days of March since 1987 with a 2.8°C negative anomaly. Philip Eden also cites the first 7 days as the coldest since 1971!

David Jameson (C) April 2006