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Isolated Frost

Scandinavian highs... do they deliver for the north-east?

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I was thinking, with indications of a pattern change and high-latitude blocking (with the signal for a Scandinavia/nordic high becoming more prominent before d15), whether they are the holy grail in Scotland and the NE of England, as well as the south-east.

I'm pretty young, and wasn't here for the Scandi highs of 1991, and those prior to that- but in recent years, the dominant cold spell 'starter' is the Greenland high, with troughing towards Scandinavia, allowing north to north-easterly flows to dominate.

archivesnh-2010-1-1-0-0.png

archivesnh-2010-11-26-12-0.png

The December 17 - January 12 2009-2010 period gave me 34cm of lying snow at one point, with record low temperatures of -11c.

The November 24 - December 7 2010 spell gave me 42cm of lying snow at one point, with new record low temperatures of -12c.

The dominance of low pressure towards Scandinavia and Central Europe, with the upper high towards Greenland, ridging south and east towards Iceland and Svalbard, generally gave an unstable arctic continental flow, with heavy snow from the NE.

However, the Scandinavian high of February 2012.

archivesnh-2012-2-2-0-0.png

Gave me a grand total of 1cm of lying snow (though it was extremely cold), whilst those further south-east (more prone to the continental flow, and closer to the upper air cold pool), received over 10cm, and even 15cm.

I also recall this:

archivesnh-2010-12-1-0-0.png

In which it was very cold here, but there was no snow, whilst the south-east (in particular London) was receiving a fair amount of snow.

So, I was wondering, does the Scandinavian high deliver for the NE and Scotland? Maybe the instances I have experienced were not 'true' Scandi highs (I mean, the spells shown below show the surface heights peak in the Kola Peninsula and Norway respectively).

Are there any major instances of Scandinavian highs delivering similar snow totals or any major snow totals for those further north?

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I think Scandinavian highs can deliver significant snowfalls to E Scotland and NE England, but generally only in association with a specific setup. The high must ridge across to the north of Scotland pulling in a cold easterly or north-easterly airflow, and bring in very cold arctic continental air, with the instability over the North Sea providing frequent and heavy snow showers. The two most famous examples occurred in February 1991 and January 1987. In both cases disturbances in the easterly flow caused snow showers to be replaced by more general areas of snowfall at times.

http://www.wetterzen...00119910208.gif

http://www.wetterzen...00119870111.gif

We've had relatively slack easterly flows delivered by a Scandinavian high which brought big snowfalls to many eastern coastal areas but relatively limited falls in inland areas, on 20-22 November 1993 and 27-29 December 2005:

http://www.wetterzen...00119931122.gif

http://www.wetterzen...00120051228.gif

Snow stuck around for 8 days at Durham and for 7 days at Aberdeen Airport and Leuchars from the November 1993 cold spell. I recall reading reports of some 15-20cm of lying snow in some spots near the east coast as well.

On occasion though, if a really cold airmass accumulates over the Balkans, a south-easterly can bring a fair amount of snow- I remember that mid-February 1994 turned rather snowy at Tyneside:

http://www.wetterzentrale.de/pics/archive/ra/1994/Rrea00119940215.gif

I think the main issue with the Scandinavian high is that it often gives us a combination of surface cold off the continent and relatively mild air at 850hPa (often above -5C) and this translates to generally dry cloudy weather. In the SE, the short track over the North Sea means that temperatures hover around freezing and any precipitation falls as snow, but in the NE the longer sea track often pulls the surface air temperature up to 3-5C and showery activity near the east coast tends to be rain, sleet and graupel.

The Scandinavian high is sometimes associated with "battleground" frontal snowfalls, for which you don't necessarily need particularly cold 850hPa temperatures- sometimes values just below 0C suffice. However these snowfalls tend to mainly affect central, western and/or southern parts of the UK, and as the frontal systems head into NE England and E Scotland they tend to weaken and the surface winds with a long track over the North Sea often raise the temperature above freezing and give a rain/sleet mix rather than snow.

Edited by Thundery wintry showers
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Hmm, interesting topic, the late November/early December 2010 spell was the most impressive spell of snowfall I can remember, with around 18 inches of snow lying by the Friday. The Wednesday delivered here too if I recall correctly, as it led to the closure of the Forth Road Bridge in the early hours, although it did become lighter through the day and into Thursday as the flow got weaker.

I think the answer is that it depends on a number of factors, and that generally, providing the heights are low and also with the usual upper air temperature caveats, Scandi highs can deliver for the northeast of England and central and southeast Scotland. Northeast of about Angus, though, it's relatively rare for any convective easterly to deliver because there's a longer sea fetch with higher heights (being closer to the high) and also because the upper cold pool is usually strongest further south. You really need disturbances in the flow to deliver for more than about 20-25 miles inland, but if there some kind of marginal frontal setup then being further west is usually a big advantage.

A few examples from my memory now.

22nd/23rd February 2005 gave 8cm of snow here from overnight convection showers.

archives-2005-2-23-0-0.png

However, this period was very marginal for snowfall and it melted through the day. There was another snowfall on the 1st of March of around 5 inches but that was from a separate disturbance from the northeast with heights not really over Scandinavia.

26th/27th December 2005. Convective showers gave 4cm of snowfall by midday on the 27th, although there was no snow from it in central Edinburgh. In hindsight we did well to get lying snow as uppers were well above -8C, which tends to be the point at which things get very marginal and sleety.

archives-2005-12-27-0-0.png

February 2nd 2009. 7cm of snow accumulated from the early hours through to the afternoon, when a disturbance moved northwards from the south, turning the flow southeasterly and bringing a period of drizzly rain which could so easily have been snow. A really disappointing event here after it promised so much.

archives-2009-2-2-12-0.png

A very surprising snowfall was this one from the January 2005, which gave 2cm, but only seemed to affect a small strip of northeast Fife and southeast Angus:

archives-2009-1-5-0-0.png

A lot of good snowfalls in that list, and that wasn't including any from 2009/10 or 2010/11, so they do frequently deliver to my location at least.

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