Winter 2011/12 - General Discussion

[Peter H]

Winter's over next week, according to the BBC.this morning.

[TEITS]

Winter's over next week, according to the BBC.this morning.

Even though im now in spring mode and looking for warm spells rather than cold spells its too early to write off winter just yet. My view is the first 2 weeks of March still have potential to deliver a large snow event but then the chances reduce drastically into the end of March/April. Ideally we want an E,ly with a cold pool over the continent. I disagree with some members when they say a N,ly is best at this time of year because the NW,ly during the weekend still resulted in min temps being above freezing. A good example is Liverpool were still at 5C at midnight on Saturday. The problem with a N,ly at this time of year is the combination of the longer days, stronger sun, moderating effect over the sea means temps still get above freezing. However an E,ly with upper temps of -10C would still mean max temps near freezing especially towards the SE.

[MP-R]

Easterlies may be better for lower temperatures, especially due to cloud cover keeping them suppressed during the day but northerles are generally better for more widespread snow that effects places other than the southeast. Northerlies tend to be more exciting too as although the sparkling sunshine melts the snow quicker, there are opportunities for convective showers and cloudscapes followed by very frosty nights.

[Thundery wintry showers]

The comments about the NW'ly this weekend by TEITS strike me as a little biased- comparing this weekend's half-hearted NW'ly with an easterly associated with continental cold pooling is hardly a "like for like" comparison! You can get significant snowfalls off a "Scandinavian high" type of easterly in March but it mostly relies upon Atlantic fronts colliding with the continental air (as per 12th March 2006) as the continent warms up and we struggle to get much instability over the North Sea. I do remember some snow showers in eastern areas around the 11th-16th March 2006 but they didn't amount to much, and the easterlies in March 1996 were almost relentlessly dry and cloudy.

The optimal March "lasting snow cover" setup for eastern and especially south-eastern areas is an "easterly with a northerly source" type setup delivered by eastward-ridging Greenland highs, as per the setup in late November/early December 2010. The Arctic is still pretty cold during March and the cold air head south across Scandinavia and central Europe and then across to the British Isles, maintaining more intensity towards the SE than if it comes straight down from the north. This setup was also responsible for the exceptional snowfalls in late March 1952 and mid March 1979. However if it's vigorous convection rather than lasting snow cover that takes your fancy then a northerly/north-westerly type provides more excitement.

For most western areas northerly and north-westerly are the optimal setup for both lasting snow cover and vigorous convection as easterly types (even if associated with an arctic airmass source) tend not to bring many snow showers in eastern areas across to western areas, and while frontal battleground type snowfalls are possible the fronts have to be ideally set up to produce anything lasting.

[feb1991blizzard]

I think i would rather take my chances with an early march 1995 type event than rely on convection, but to be honest, because i have lived well inland all my life, the sunshine and snow showers have never delivered massive for me regardless of the time of year, dont get me wrong, 87 and 91 were way way above anything else i have ever experienced but the initial sun and snow showers in both events, as exciting as they were, were really just the precursor to the main event which was a band of more organised snow moving from East to West and given that i dont put a lot of emphasis on sunshine hours anyway, the sun coming out would just be a hinderence with a March event with regard to maintaining a snow cover while waiting for the next shower, there is still plenty of setups that are feasable enough to deliver a big snowfall event for England and i agree that its not completely out of the question that an Easterly could deliver well into March, i would probably favour a battleground setup, a North Easterly like the end of Nov 2010 or a potent shortwave / trough tracking down the eastern side but close enough to deliver big enough in central areas like in December 1990, probably not the best examples because we are talking about March but in my opinion they are setups that could still deliver big in late season, though obviously the later in season, the more marginality creeps in.

[Thundery wintry showers]

The early March 1995 spell, bar the frontal system overnight 2nd/3rd, was as stark an example of a convective snow event as you're likely to find- a west to north-westerly flow kept firing in snow, sleet and hail showers off the Atlantic during the first eight days, giving many places accumulations during the showers but also thaws during subsequent sunny intervals. It was also quite unusual synoptically as such a cold and polar maritime dominated form of zonality has traditionally been rare in the past and has been even rarer in subsequent years.

I would agree that a snow event relying entirely on convection is hit and miss, but it is rare for a predominantly "convective" snow event not to give at least some trough activity promoting more organised snowfalls if an unstable airflow persists for upwards of about three days. The late November/early December 2010 was characterised mostly by sunshine and snow showers off the North Sea without a single Atlantic system coming close to the British Isles, but from time to time troughs gave more organised snowfall.

[feb1991blizzard]

The early March 1995 spell, bar the frontal system overnight 2nd/3rd, was as stark an example of a convective snow event as you're likely to find- a west to north-westerly flow kept firing in snow, sleet and hail showers off the Atlantic during the first eight days, giving many places accumulations during the showers but also thaws during subsequent sunny intervals. It was also quite unusual synoptically as such a cold and polar maritime dominated form of zonality has traditionally been rare in the past and has been even rarer in subsequent years.

I would agree that a snow event relying entirely on convection is hit and miss, but it is rare for a predominantly "convective" snow event not to give at least some trough activity promoting more organised snowfalls if an unstable airflow persists for upwards of about three days. The late November/early December 2010 was characterised mostly by sunshine and snow showers off the North Sea without a single Atlantic system coming close to the British Isles, but from time to time troughs gave more organised snowfall.

Sorry, i was referring to that event, if i remember rightly it was on a Thursday night / Friday morning and produced a good 5 inch fall for the West Midlands, wheras any of the convective falls of that 2 week spell failed to produce lying snow of any significance, and again the 30th Nov 2010 event here which produced 6 inches was a much more organised band of snow, it started in late evening, absolutely belted it down for 3 hours and then stopped and was clear skies again until the morning, yet all the other showers put together during that long cold spell could only muster 2 inches between them all, i appreciate that i am being a little IMBYish but i always seem to have done better out of fronts / troughs than with the showers variety.

[TEITS]

Fair points about a N,ly.

Must admit when it comes to photographing some stunning cloudscapes then a cold convective N,ly is ideal. I do enjoy the months of March, April with regards to showers especially when we have an arctic airmass. I may appear like I only like snow but to be honest I find interest in all the months of the year with the exception of probably Sep, October.

[J10]

I have seen lying snow from Northerlies in Mid April 1999. It snowed overnight and gave above 2 inches of snow by morning, admittedly it thawed very quickly the next morning/afternoon.

Football fans will remember this as the night Ryan Giggs scored that goal in the FA cup Semi final v Arsenal.

[onemanmows]

Across most parts of the country, the snowiest winters of the 90s were 1990/91, 1993/94 and 1995/96, and 1996/97 was notable for an extended spell of snow cover from 30 December to around 10 January in some central and eastern parts of England. But with just localised exceptions, none of them were as snowy as 2009/10. Maybe the 1990s winters appealed by comparison with those of 2000-08 but the winters of 2009-11 rather put the snowier winters of the 1990s into perspective.

From a Pennine skiing perspective I'd put winters into four broad groups:

The Hard Winters - mid to late 70's to mid to late 80's. Most winters good snow cover for long periods, high volume falls.

Still Cold where's me snow - late 80's to mid to late 90's. Plenty of cold but high volume snow fall the exception not the norm.

Blairite - late 90's to late 00's (2001 and 2005 both delivered a four of five week block of skiable snow but 2001 was Foot and Mouth so the hills were closed) Hardly any high volume snow fall. Prolonged hill snow or ice the exception rather than the norm.

New Cold - 08/09 winter onwards

This winter so far has felt more like a lean early 90's than 'modern' winters of the 00s - the right conditions where there but it just never quite came through. Hopefully early spring with deliver some snow although I'm expecting cover to last days rather than weeks. I tend to get a feel for winter by looking at the wider environment never been convinced it would be extremely snowy but had hoped it would be snowier than it has been - what really nailed it as a poorer winter was a skein of about 70 geese heading north above Perth in the first week of Januray. That didnt really give me cold and snowy feelings.

[Isolated Frost]

Heights anomalously low to the north- but tilted nw-se allowing polar maritime outbreaks... look at that strong subtropical ridge though- the Azores high very much stronger than ever.

SLP -ve anomaly to the north-east, allowing colder air into the northern half of the UK- rather than low SLP to the north-west, which would have been less beneficiary.

Weakened NH energy with a more calm profile- however the subtle stronger Azores high ridging into the UK doesn't help. Notable -ve anomaly in SE Europe and +ve anomaly in NW Russia.

SLP especially high near the SW- letting little cold air in as the +ve SLP anomaly spreads into the UK. Magnificent NW Russia +ve SLP anomaly- however January didn't have the retrogression required- however, an exceptional change from December's -ve anomalies to the north.

I expect February will come out similar to January, with a bit more retrogression of the +ve anomalies around Russia- with a similar NH pattern.

December was very active and jet tilt allowed it to be very wintry in the north and west generally.

January had the problem of not enough of a retrograde motion from the +ve blocking height anomalies around Russia, and a still strong Azores high ridging too far north.

Subtropical ridge development has been unfavourable, and despite a strong strat warming, height anomalies have not been in the sweet-spot, however central and eastern England have endured a very cold first half of February.

I am sure March will indeed provide the best synoptics for wintry weather as I see another large warming at 30hPa and another bite at the cherry in terms of +ve height anomalies to the north of us. Generally, a winter where we were so near and yet so far.

Here is a snapshot of the 2 week spell from January 24th to February 7th. These are the air temperature anomalies for Europe.

Frigid. So close...

February so far- massive -ve anomalies in S Europe heights, and the Azores high +ve anomalies engage with the Russian high +ve anomalies, leaving SE England with the best cold chances.

SLP anomalies very similar, note the link-up and low SLP over the canadian arctic. All that was missing was -ve anomalies to the SW of us- undercut and display... anyhow it's over and done with now, here's hoping Spring can deliver the wintry goods, the strat thread will be most interesting in that regards.

Edited February 20, 2012 by Isolated Frost

[feb1991blizzard]

The other sickener this winter has been that a few weeks ago while that really bitter cold was covering the continent, even a South Easterly (as long as it had reasonable pressure gradient) would have still done us proud and brought big snowfalls.

[Snowy Easterly]

i really hope GMT is not scrapped otherwise February will feel even more like a spring month sometimes, it is too early for this stupid warmth

[Thundery wintry showers]

Sorry, i was referring to that event, if i remember rightly it was on a Thursday night / Friday morning and produced a good 5 inch fall for the West Midlands, wheras any of the convective falls of that 2 week spell failed to produce lying snow of any significance, and again the 30th Nov 2010 event here which produced 6 inches was a much more organised band of snow, it started in late evening, absolutely belted it down for 3 hours and then stopped and was clear skies again until the morning, yet all the other showers put together during that long cold spell could only muster 2 inches between them all, i appreciate that i am being a little IMBYish but i always seem to have done better out of fronts / troughs than with the showers variety.

This is a very well-reasoned post and I think what you say does hold true away from areas exposed to the north and east. Showers are always hit and miss, meaning that some areas get a fair amount from them while other nearby areas don't get much, and during November to February they tend not to deliver large precipitation totals in inland areas. Organised snowfall on the other hand tends to penetrate further inland and deliver larger totals over a larger area.

In the recent past my main bone of contention has been with the people who infer from this that an unstable showery airstream is no good and that we need a strong Atlantic frontal influence and marginality to generate proper snowfalls (late November 2010 with the GFS's mega-low that never was being a stark example). The problem with this argument is that it fails to recognise that unstable showery airstreams quite often bring belts of more organised snowfall, and that most people won't be happy with 36 hours of heavy blowing snow if the end product on the ground is an inch of slush and ice. As with most areas of meteorology the objective assessment of what is "best" overall for snow lovers depends on the specifics of the situation. Late November 2010 was one side of the coin, while on the other, it is clear that snow lovers were better off with the frontal battleground of 12th March 2006 than if we'd had a straightforward easterly spell from the 11th-16th March as the easterlies either side of that event just gave eastern areas a scattering of light snow showers.

[feb1991blizzard]

This is a very well-reasoned post and I think what you say does hold true away from areas exposed to the north and east. Showers are always hit and miss, meaning that some areas get a fair amount from them while other nearby areas don't get much, and during November to February they tend not to deliver large precipitation totals in inland areas. Organised snowfall on the other hand tends to penetrate further inland and deliver larger totals over a larger area.

In the recent past my main bone of contention has been with the people who infer from this that an unstable showery airstream is no good and that we need a strong Atlantic frontal influence and marginality to generate proper snowfalls (late November 2010 with the GFS's mega-low that never was being a stark example). The problem with this argument is that it fails to recognise that unstable showery airstreams quite often bring belts of more organised snowfall, and that most people won't be happy with 36 hours of heavy blowing snow if the end product on the ground is an inch of slush and ice. As with most areas of meteorology the objective assessment of what is "best" overall for snow lovers depends on the specifics of the situation. Late November 2010 was one side of the coin, while on the other, it is clear that snow lovers were better off with the frontal battleground of 12th March 2006 than if we'd had a straightforward easterly spell from the 11th-16th March as the easterlies either side of that event just gave eastern areas a scattering of light snow showers.

Good point, there are no right and wrong answers as to what synoptics are the best, even if its assumed that everyone's number one priority, like mine, is depth of snow, in the late November 2010 spell which i mentioned earlier, Buxton, which some parts of saddleworth are of the same altitude, had the same 6 inch fall but also had a number of convective falls as well during the spell, had over a foot of lying snow in total, and that may well be on the conservative side, and baring in mind thats only 20 miles South of here and still with the shelter of mountains to the east, then thats a big difference, i suppose the point im making is, its personal experience that sometimes gives one perspective, and im sure, looking at the charts that Saddleworth would have had decent falls from feb 5-6th 1991 before any organised band made it across on the afternoon or evening of the 7th and im sure there are many other examples of this so i would never turn my nose up at any synoptics that are cold enough to threaten widespread snow, rather wait and see then make a judgement afterwards.

[Peter H]

i really hope GMT is not scrapped otherwise February will feel even more like a spring month sometimes, it is too early for this stupid warmth

I really think you'll be out of luck unfortunately.

Temperatures of plus 12 today. Up to 14 tomorrow (somewhere over the UK will reach 17 over the next day or so, I would imagine. So much for the cold February that everyone was predicting.

Winter is over for this year I'm afraid.

[Weather-history]

.

Winter is over for this year I'm afraid.

Not necessarily, we could have a fairly wintry December at the end of this year.....

[sebastiaan1973]

First 20 days De Bilt -2,2c. 10th place since 1900.

http://mscha.org/knmi/winter.cgi?station=260&month=2

[johnholmes]

Not necessarily, we could have a fairly wintry December at the end of this year.....

very true

[Peter H]

Not necessarily, we could have a fairly wintry December at the end of this year.....

Indeed.

Very pleasant here today. There were days last summer that weren't as good.

Edited February 21, 2012 by Peter H

[AutumnMists]

Winter is over for this year I'm afraid.

Were you saying that about Summer in August?

[Peter H]

Were you saying that about Summer in August?

Well, I've even given up looking at the weather on TV religiously, so it must be over.

[Alex95]

Northerlies are generally better than easterlies by this time of year as if the uppers aren't cold enough the easterly would deliver cold, dry weather rather than snow. Obviously there are exceptions though. Convective NE'lies often deliver the most troughing, I had 4 prolonged snow events from the Nov/Dec 2010 event an they were all as a result of convective snow showers from the North Sea. I know some places to the west of the Pennines saw 10-15cm despite NE'ly winds which is quite unusual. Easter 2008 started as a NE'ly, but then a trough brought 6 hours or so of heavy snow from the NNW, affecting W Scotland, Cumbria, Yorkshire and then finally E and SE, and probably parts of the Midlands too.

Some inland areas which regularly miss out from convective northerlies tend to do better in Spring as the sun is strong enough to keep some of the convection going over land, so the showers tend to die out less as they move S'wards.

[bluearmy]

First 20 days De Bilt -2,2c. 10th place since 1900.

http://mscha.org/knm...ion=260&month=2

shurely shum mishtake (quote peter h)

[Cloud 10]

First 20 days De Bilt -2,2c. 10th place since 1900.

http://mscha.org/knm...ion=260&month=2

shurely shum mishtake  (quote peter h)

Can't help being "reeled in" by the number 1 on that list.

http://modeles.meteo...956-2-2-0-2.png

http://modeles.meteo...56-2-14-0-0.png