Model output discussion - after the beast, what next?

[Froze were the Days]

27 minutes ago, nick sussex said:

It really depends on the set up.

The last cold spell was a victim of its own success, rarely does deep cold make it so far from east to west right into the Atlantic this cold then phased with shortwave energy to the sw.  

Normally blocking patterns are harder to break down.

The current set up would need more trough disruption upstream to extend the deeper cold , at the moment the ridge is set to topple so it’s really a timing issue of how quickly it turns milder.

The GFS does try and pull the jet back into the UK , and there is some deeper cold to the ne but still too much energy in the northern arm of the jet.

The Euros are more bullish with the topple. There’s still a small chance some of that deeper cold could effect especially the east and se again if the northern arm of the jet is being overplayed .

Regardless two convective easterlies a few weeks apart is exceptional whatever happens in the medium term.

I should add in recent years we’ve been discussing the disappearance of that type of easterly, deep upper cold and convection has been nowhere to be seen.

For that reason events of recent weeks especially coming so late in the season may never be seen again for years.

My advice enjoy the next few days and savour it as a coldie! 

Were 1991, 87, end of 96/97 connected to SSW's?...seems like we need the strat warming to upset the global warming apple cart of recent years.

Edited March 15, 2018 by Froze were the Days

[IPredictASnowStorm]

For Sunday on the GFS I'm looking for that snow below us to push up further so we can get the heavier precipitation and maybe last longer

[Norrance]

13 minutes ago, snow freak said:

our weather patterns this winter, particularly with regards to the large fluctuations in temperatures on an almost daily basis seems very similar to those experienced in places like New York which frequently sees temperatures of 15c one day and then below freezing one or two days later. 

That maybe depends on where you are in the UK. We have had only two days where temps reached 10C this year. One in January and one in February and none so far in March. It has been either average or cold all year so far here.

[Derecho]

22 minutes ago, Froze were the Days said:

Were 1991, 87, end of 96/97 connected to SSW's?...seems like we need the strat warming to upset the global warming apple cart of recent years.

Funnily enough none of those were from SSW warming events. I think 97 and 91 were just random jigsaw pieces falling in the right place. Cold air build up to our east for example isn't unusual but other factors come together and make it move west.

96/97 had a very favourable SST profile. Also bear in mind 87 and 96/97 also occurred during solar minimums so perhaps that improved our chances back then.

However I think this one, like March 2013 has been sparked by the SSW events in recent weeks. I think I wrote a long post back in February about how the North Atlantic cold blob has ruined our last 5 winters by encouraging much more westerlies then usual.

I also mentioned that it would take something big to overcome it as positive and negative phases of the NAO are becoming more persistent but the SSW fits that bill well.

What is interesting is the SST picture now compared to two years ago (and the few years before that):

Today                                                         End of last March 2016
 

Why is the end of March so significant? It's something called the remergence mechanism.

At the end of March the depth of the mixing layer is at its deepest. The mixing layer is the area of the ocean that interacts with the atmosphere.

That shoals from here on but the cold /warm anomalies under the shallowing mixing layer persist. Then those anomalies are mixed to the surface again when the mixing layer deepens again later in the year.

Other factors can overwhelm this if they are really working against us. However we have low solar activity at the moment.

In summary my view is that it took a major SSW event to get us out of this rut. However now the see-saw has swung the other way we may get locked into more blocking patterns as the SSW event has left a footprint on the North Atlantic SST patterns. It could herald a sequence of colder winters at mid latitudes, whereas the arctic and Tropical warming accelerates.

Just my two cents anyway. Sorry mods if off topic.

Edited March 15, 2018 by Quicksilver1989

[Duane S.]

53 minutes ago, shawty1984 said:

If this is just a cold snap, cold enough for low level snow mid March, doesn't it put to bed the myth that once the cold and snow are here, it will be harder to shift? Something that was being said on the last cold spell too. 

Not at all, as has already been said, It's all about the context. The fact that we don't hold on to the colder weather for long doesn't necessarily correlate to contradicting the notion that once the cold is in it is harder to shift. Nick explained perfectly above what happened with Beast#1. Under similar conditions the block at 500mb should only really have retrogressed as far west as Greenland but the atmosphere was in full-on reverse up there 3 weeks ago and that block was in relative hyperdrive heading west!

One thing is for sure though, notions that decent easterlies and severe cold pools to tap into are a thing of the past, should be put firmly to bed after this winter is done.

[danm]

1 hour ago, shawty1984 said:

If this is just a cold snap, cold enough for low level snow mid March, doesn't it put to bed the myth that once the cold and snow are here, it will be harder to shift? Something that was being said on the last cold spell too. 

Others can correct me if I’m wrong here, but I don’t think it’s necessarily the cold air being hard to shift, more the fact that in certain scenarios a block is hard to shift - usually a blocking area of high pressure with cold air entrenched. 

As we often see in continental climates, deep cold air can often be swept away with rapid rises in temperature. However, a stubborn block can be very hard to shift. 

[bluearmy]

50 minutes ago, snow freak said:

yes I tend to agree with you on this.  those who say, get the cold in first and the snow will follow and the cold will be harder to shift doesn't necessarily ring true.  the last 'potent' cold blast from the east was supposed to be a corker but the cold really only lasted a few days and was booted out relatively quicker by milder air again.

I think that if the last spell had occurred in Dec or jan, then the trough that followed would have been a lot colder at the surface and fairly snowy 

[karyo]

Stunning ICON 12z! A small correction northwards for Saturday!

 https://www.meteociel.fr/modeles/icone_cartes.php?&ech=51&mode=0&map=0&archive=0

[Coopsy]

4 minutes ago, karyo said:

Stunning ICON 12z! A small correction northwards for Saturday!

 https://www.meteociel.fr/modeles/icone_cartes.php?&ech=51&mode=0&map=0&archive=0

What's the implications behind this? As in the small correction makes what difference?

[karyo]

Just now, c00ps said:

What's the implications behind this? As in the small correction makes what difference?

It means more areas can benefit from the easterly.

[IPredictASnowStorm]

1 minute ago, karyo said:

It means more areas can benefit from the easterly.

And that low for sunday might come abit higher and bring more snow

[frosty ground]

4 minutes ago, IPredictASnowStorm said:

And that low for sunday might come abit higher and bring more snow

With slightly milder air for the south east.... No signs of PPN thou 

[MattTarrant]

10 minutes ago, frosty ground said:

With slightly milder air for the south east.... No signs of PPN thou 

The ICON - EU as a macro scale model has really impressed me in the last month, the same can not be said about its High Res 7km charts. 

Edited March 15, 2018 by MattTarrant

[Mike Poole]

11 minutes ago, frosty ground said:

With slightly milder air for the south east.... No signs of PPN thou 

ICON-EU is not the same model as the ICON global model.

ICON T850's at (roughly) the same time:

Edited March 15, 2018 by Mike Poole

[Coopsy]

17 minutes ago, karyo said:

It means more areas can benefit from the easterly.

Thanks ?

[Pembroke Dangler]

The further north the high sets up the better Atlantic trough disruption and then perhaps a prolonging of the cold flow over the uk as long as the northern arm of the jet is weaker. 

[IPredictASnowStorm]

Seems to have moved up abit more ?

[plumehead]

With the slight corrections further north and apparent lack of ppn, what areas should be expecting to see snowfall this weekend?

[frosty ground]

peak snow for the south coast.

[Derecho]

3 minutes ago, frosty ground said:

peak snow for the south coast.

Very nice, also monday evening sees some organised showers moving south across the eastern half of the UK. Uppers around -7C still and dewpoints around 0C so it can't be too far off from falling as snow.

Not much instability to the SSW to carry on propping up the high though.

[Mike Poole]

Cumulative snow chart from the HIRLAM out to the end of the run (Saturday lunch time):

Worth noting the footnote to these type of charts:

'Details on the map: This map does not represent the layer of snow that will be on the ground in the end. Indeed, it is a map of accumulation of snowy precipitation which does not take into account neither the cast iron, nor the difficulty of the snow to hold nor of the existing layer. In addition, the AROME / ARPEGE models give the equivalent amount of water of the fallen snow, ie the number of mm of precipitations fallen and not the true layer in snow. An average 10: 1 ratio is used here (ie 1 mm of precipitation gives 1cm of snow) but this ratio is in fact variable: higher if snow is lighter, lower if snow is heavier / moister.'

Not quite sure about the relevance of ‘cast iron’, maybe a Google translate problem!  And this text seems to be copied from the similar chart for ARPEGE referring to that model, not HIRLAM.

Edited March 15, 2018 by Mike Poole

[Methuselah]

2 minutes ago, Mike Poole said:

Cumulative snow chart from the HIRLAM out to the end of the run (Saturday lunch time):

Worth noting the footnote to these type of charts:

'Details on the map: This map does not represent the layer of snow that will be on the ground in the end. Indeed, it is a map of accumulation of snowy precipitation which does not take into account neither the cast iron, nor the difficulty of the snow to hold nor of the existing layer. In addition, the AROME / ARPEGE models give the equivalent amount of water of the fallen snow, ie the number of mm of precipitations fallen and not the true layer in snow. An average 10: 1 ratio is used here (ie 1 mm of precipitation gives 1cm of snow) but this ratio is in fact variable: higher if snow is lighter, lower if snow is heavier / moister.'

Not quite sure about the relevance of ‘cast iron’, maybe a Google translate problem!  And this seems to be copied from the similar chart for ARPEGE.

One could interpret that as saying that there'll be cast iron on the ground, come Monday...I sincerely hope there isn't!

[Interitus]

1 hour ago, Quicksilver1989 said:

Funnily enough none of those were from SSW warming events. I think 97 and 91 were just random jigsaw pieces falling in the right place. Cold air build up to our east for example isn't unusual but other factors come together and make it move west.

96/97 had a very favourable SST profile. Also bear in mind 87 and 96/97 also occurred during solar minimums so perhaps that improved our chances back then.

However I think this one, like March 2013 has been sparked by the SSW events in recent weeks.
 

1991 followed very shortly after a minor warming which was the probable cause (very close similarities to 2012)

1996/1997 followed a Canadian warming in Nov/Dec 1996 - probably related

1987 cold weather followed SSW on Jan 23th, it's just that the extreme cold occurred prior to the SSW.

2013 cold in January most likely related to SSW on the 6th. However for the March event 2 months later it is unlikely that the SSW was the direct cause.

(Better continued on strat thread?)

 

[Badgers01]

55 minutes ago, frosty ground said:

With slightly milder air for the south east.... No signs of PPN thou 

That top chart with the 850s  is a kick in the teeth for us snow starved Surrey residents - what happened to the upper cold pool with really low 500 mb temps ? 

[Guest]

THE BEAST - THE SEQUEL AND BEYOND

In this post I will briefly review the last few days, then assess the current set up and the incoming very cold wave. How cold might it get, how snowy can we expect it to be and how long long will it last? I will look further ahead and examine the broader pattern.

Last Week and This Week:

My last review was on page 5 of this thread and I shall pick up where I left off.  

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GRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!

I just spent nearly 8 hours producing this very long post for the MOD - with loads of charts and info and it was intended to be my last one of the winter. I had proof read it and I was just adding a link to the learning thread and I must have pressed the wrong button and I lost everything, including all the chart links and a saved copy of the first half of the text. All that remained was the bit above. I'm so angry and frustrated after such an effort. There's no way that I'm going to have the time or inclination to do it all again. I hate computers and modern technology and it'll take me a while to settle down again. Why??? David  

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Anyway, here's the link to my post on the learning thread that I did yesterday: