While everyone over on the Model Output discussion thread constantly seek out a Greeny High or a Scandinavian High pressure block it would be interesting to discuss how members here perceive these two Winter factors and the odds they give of delivering cold and snowy weather to the UK. FWIW here's my feelings.

 

Greenland High While these are a welcome factor for those seeking cold across the UK they are not a definitive guarantee on their own that cold weather will affect us. What they do support is a greater chance of an icy Northerly blast and for that reason those living near Northern and Western and Eastern coastal counties will welcome these as they often produce heavy convective snow showers drawn down over the open Waters to the North and NW. However, for many mainland inland locations snow is rare with gin clear cold and crisp weather with frost and ice more of an issue rather than snow. However, even to achieve these conditions synoptics elsewhere have to be favourable. For example a Northerly may well be displaced too far West over the Atlantic Ocean if pressure stays high over SE Europe keeping the UK in a milder and wetter SW regime despite Greenland High pressure so because of this it is no guarantee of cold over the UK and other complications filtering down from the NW has also known to  be a problem in the past.

 

Scandinavian High This High is often more loved by folk who live in Southern and Eastern areas as I believe it offers the best chance of severe Winter weather down here while the North and particularly the NW benefit by shelter from the prevailing east or NE winds this system delivers to the UK giving milder benign conditions there. This High pressure feature can beome very intense especially in later Winter months and early Spring and often delivers the goods in the form of sub zero conditions and snow showers close to eastern coasts most likely in February and March. Occasionally warm air drifting North from the Med can give rise to more substantial snowfall across the South and East as it engages the cold European air. Lastly but probably the best scenario of all is when Low pressure to the SW comes up against this cold block of air and gives rise to the well known but rarely experienced Channel Low scenario delivering blizzards and disruptive snowfall to Southern and SW Britain in particular. Of course where there is prolonged snow there is mild air not far away and this is how many Scandinavian High's lose their influence across the UK with the inevitable snow turning to rain event coming up from the SW we often here in this pattern..

 

Both. When both High's link across Scandinavia through Icleand to Greenland this often gives Northern Europe it's coldest and most sustained chance of little change over a long period of time. While the weather over the UK is greater influenced by the Scandinavian portion of this High the Jet Stream is pushed well South of the UK with Low pressure areas giving Iberia, Spain and the Med in general it's worse Winter weather conditions while we can be locked into cold and icy conditions with snow showers near the East Coast. The ususal type of breakdown from this scenario is dependant on which portion of the High pressure belt gives way first with the usual scenario being for mild air to cross the UK from the SW should the Scandinavian portion decline while a period of Northerly winds backing West under a toppling ridge scenario most likely occurs if the Greenland end declines. Of course this is a broad brush treatment of most likely events but as we all know the weather is far more complicated than that.

 

Conclusion  It depends on where you live as to which I feel delivers the best snow chance results for the UK with the North fairing best from a Greenland block while the South and East of England and Wales have a better chance of fairing better from snow from a Scandinavian block with it's bitter East winds and snow showers and the illustrious rare chance of that 'Channel Low' we all love down here.

---

An excellent description of those types of pressure scenarios. Well done there Martin.

 

---

I second that.

And if we keep praying hard enough to the weather Gods, they might pay attention and give us what we want.   

---

It's not a simple case of which one is best overall - every set up is different. Both GH's and SH's have spectacularly failed to deliver here (and to me, MBY is what's important )

A large SH feeding the coldest flow into the SE isn't going to do much up here. Jan 87 is a case in point. The news was full of footage of ridiculously deep snow in the SE, but we had just one brief flurry one morning. I'm assured that just 20 miles east of here (and still west of the Pennines), Manchester did OK. But then, in 2013, we did well. Four separate snowfalls from what was essentially blocking over Scandanavia - including two from fronts moving east-west.

Similarly, a GH high has seen us miss out - especially if the flow is a straight northerly.

We also need to consider how the block evolves. In 2010, I seem to recall the block moving/building southwards (you know what I mean), so it was entrenched in really cold air from the start.

I've seen SH's build giving us an easterly but, due to the orientation of the high, the air has been coming from central Europe. I remember one such set up in 2004 or 2005 and there was much excitement - but (IIRC) Retron pointed out that the flow could be traced back to the Balkans, and wasn't particularly cold. I don't think any lowland areas got more than a slushy covering.

For me, the most potent mix of cold air and PPN seems to come from a Greenland High with a deep low in the North Sea, bringing a really unstable NW'ly flow. What is also usually great, but much rarer, is a block to the NE, with very active Atlantic fronts moving in from the West or Southwest and grinding to a halt over the UK - preferably over me!

---

The question is, will this be as far as we get as in  just discussing them instead of reaping the rewards of seeing either/all.

This is the best set up for me

http://www.wetterzentrale.de/archive/2010/brack/bracka20101218.gif

---

 

It was indeed a beaut!

 

---

Totally IMBY but it's a strong Scandy high every time. The classic S England winter events have almost all been delivered by a Scandy high - 1978, 1987, 1991 to name three. As you say the Nirvana here is a Scandy high and Channel Low, which have the potential to deliver blizzard-like conditions given the right track.
The three Channel lows in succession in Feb 1978 is my all-time favourite weather event. The weak, cold sunlight fading behind a deepening pall of altostratus, lowering to a smooth, purple-tinged canopy as the deepening depression approaches and the sun sets and the freezing easterly wind picks-up. Then the first icy snow crystals hitting the road and swirling around in the increasing gale, as the evening turns to night and the snow thickens into drifts. An incredible scene to follow in the morning with 6-8ft drifts, with sculptured curving overhangs.
A very rare event, and each year I wonder if it will ever be repeated.

---

For me there's no contest  a big fat Greeny High every time , Scandy highs are bobbins here with a ratio of 1/20 delivering something. The last one gave us  a few days of freezing rain, now a Greeny high is nirvana for these parts.

Either will do for me as long as its not a dry Greenland high induced northerly. From a synoptic point of view I find Greenland highs more interesting in the variety of ways that manifests on our weather.
But Scandi highs probably edge it for me with the heavy convective snow showers coming up against the Pennines. 1991 was the holy grail but 1995 , 2009 ( with only a few hours of showers, red warning fiasco aside) and 2010 and probably lots of others if I looked back in my records.

Being brutally honest though, Scandi highs can be irritating in the mass hysteria they generate as if they are the only away to get a decent cold spell. Also incredibly frustrating if the models sink the good stuff way south and it ends up only delivering the goods to a tiny proportion of the population, in the far SE whilst we ponder what could have been. Likewise if there was some synoptic setup that only brought snow to the people of West Yorkshire it would likely frustrate most others.

---

fantastic description Neil....this is what us South Coasters hope for every year.... And end up being disappointed most years!  but I remember those 3 years very well indeed!

This is what made the winter of 78/79 special everyone got a dumping of snow during this winter  due to varying blocking patterns. Is another winter like that too much to ask.

Any is fine for my area as I am near the spine of the country. We can do well in both set ups.

---

Not had a decent Scandi High in the heart of winter for years. The problem with Scandi highs is that if there is no cold pool to the east that is then advected westwards, they are bobbins. An example is the January 2010 easterly. It looked promising and exciting after most the country was snow covered with the potential of an easterly on top but it was pathethic, infact it even started a slow thaw!

I remember the winter of 2002-03, the first time I posted on TWO during the winter season, there was an easterly during December 2002. It delivered little.

http://www.youtube.com/watch?v=wzGrEJ0V5t8

The winter of 1995-96 had a number of Scandi highs which delivered either as an easterly or fronts coming up against them and then stalling.

---

 

I would think late Jan 1996 would be one example of a Sandi high delivering for both the eastern and western parts of England. There were insane amounts of snow in Lancashire in early Feb 1996 as a front coming in from the west stalled against the block. I remember crossing the pennies in mid Feb a few weeks after the thaw and there were still massive drifts. Actually one thing 1995/96 had over 2009/10 and 2010/11 was snow drifts, 1995/96 brought the biggest snow drifts I have ever seen. 

For my home area of the UK (North Yorks Moors area) anything works well! The only time we miss out is with a NW wind. The best is usually a strong easterly or north easterly via a scandi with almost lake effect snow from the North Sea, heavy snow can pile in the the North Yorkshire coast in this set up. The other is a really unstable northerly.

 

Couldn't agree more.

Spot on

---

 

This delivered close to a foot down here. More than 12 hours of heavy snow. 2010 was a good year :)

 http://www.wetterzentrale.de/archive/2010/brack/bracka20100106.gif

 

I wasn't even a year old in Feb 1978 so I have no idea what it was like...

---

I'd love to know why the front in Feb 1996 delivered loads of snow in Manchester, whereas in the winter of 2012/2013 we kept missing out?

Great topic btw Martin.

I don't mind either setup but the Greenland High seup of Dec 2009/Jan 2010 is the most impressive I've ever experienced.

---

It's no surprise, I'm sure, but I have a distinct preference for a ridge or high over Scandinavia - it seems to be the best way to get a foot of snow here. That said, the last time we had a foot was the winter of 1995/6, scary to think that's almost twenty years ago.

The best Scandinavian Highs in my experience are the ones that form to the north of the jet, bringing a plunge of polar continental air with them. For whatever reason these are really rare, with the more common option being the Azores High ridging northwards and then transferring to Scandinavia, something which takes far longer to bring deep cold air to our shores. The reason being you have to wait for the newly-in-place high to pull cold air down to its east, then shunt the cold pool westwards towards us - all the time hoping that no Mediterranean air gets mixed in. When a high forms to the north of the jet the latter stage is already under way, as by the time the high ridges our way the cold pool is already in place.

That's the reason why people have bemoaned the lack of a cold pool in some recent highs over Scandinavia, as it's just a displaced Azores High rather than a cell forming from the Siberian High. As you need the pattern to last for several days in the case of a displaced Azores High there's a much greater chance of it going wrong before the deep cold air actually gets here.

The widespread snow events are rarely defined by one or the other anyway; there'll be a mixture as the blocking high wobbles around to the NW, north and NE. Assuming you can get an active enough jet to the south the pattern can rinse and repeat multiple times.

---

Wasn't this the same setup as December 2010, it delivered around 14" in Medway?

---

Best snow event here outside the best winters of the last 30 years was down to a Greenland high.

---

No, December 2010 started from the warm Azores High:

http://www.wetterzentrale.de/archive/ra/2010/Rrea00120101116.gif

Heights were then reinforced by warm advection near Greenland:

http://www.wetterzentrale.de/archive/ra/2010/Rrea00120101119.gif

The displaced Azores High ridged far enough north to pull down some really cold air:

http://www.wetterzentrale.de/archive/ra/2010/Rrea00120101121.gif

And that cold air started moving southwards:

http://www.wetterzentrale.de/archive/ra/2010/Rrea00120101125.gif

The jet kinked over us and the rest is history:

http://www.wetterzentrale.de/archive/ra/2010/Rrea00120101128.gif

Compare that to the textbook example of 1987, with the Siberian High ridging westwards:

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870101.gif

The Azores High ridges NE'wards as the Siberian ridge continues moving westwards:

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870104.gif

Further warm advection occurs. Note the cell from the Siberian High is now NE of Svalbard:

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870107.gif

The warm advection moves ever NE'wards, linking with the heights from the Siberian cell:

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870110.gif

And a couple of days later:

http://www.wetterzentrale.de/archive/ra/1987/Rrea00119870112.gif

If that cell wasn't there to link up with the advection from the Azores High, 1987's cold wouldn't have been anywhere near as noteable. Getting warm advection is often the key to unleashing a really cold flow, but if it can connect with an upper high that's to the north of the jet... that's when the really cold stuff happens.

The Azores High, rather than the Siberian High, has been the driver of recent events and 2010 is no exception.

2010 incidentally delivered "only" 7 inches of snow here, a total beaten in 1985, 1986, 1987, 1991, 1993, 1995 etc. The coldest day had a high of -0.4C which was the first ice day in years - but it paled compared with the high of -8C in 1987, frequent highs of -2C in 1986 and highs of -3C or -2C in 1995/6 and 1996/7.

---

">http://www.youtube.com/watch?v=UYEUTHKP_F8