Model output discussion - proper cold spell inbound?

[Chevron12345]

1 minute ago, bluearmy said:

so we either believe the models and their ens that we will see strong zonal first part next week or we don't  !

Guess we will need to until they show something different.

[bluearmy]

Just now, Chevron12345 said:

Guess we will need to until they show something different.

they seem in pretty good agreement.  that monster low at day 9 wants to push east at day 10. be a good test of what westerly flow is left by day 10 to see how much progress it makes against the developing block

[Optimus Prime]

3 minutes ago, Frosty. said:

The Ecm 12z looks cold enough nationwide at times for snow to all levels!

I think you'd be very lucky to see much at all south of the Midlands or east of the west country. Northern and western areas may stay on the marginal/right side of the line though. Certainly very typical winter weather but an improvement on recent years. 

[Daniel*]

45 minutes ago, terrier said:

So I’m seeing a lot of talk about and ssw taking place as we head into February Now I know these things can unlock the cold into Europe. But isn’t they a chance we could Still miss out on the cold. These ssw don’t guarantee cold to our shores. Not been rude or offensive to the more knowledgeable guys. Just interested and keen to learn abit more about it. 

I can’t give you a technical response but roughly 2/3 or 66.6% of SSW events lead to colder conditions here. What with this one with a clean split this bolsters the chance even more, suggesting cold air is highly likely to us and there will be blocking where this is crucial, however it will be HLB. Parallels are being made between soon to be SSW with the event from 1985, what a good winter that was - not expecting anything identical it suggests we could see synoptics such as that which like the recent supermoon, are once in a blue moon.  

[Frosty.]

7 minutes ago, Optimus Prime said:

I think you'd be very lucky to see much at all south of the Midlands or east of the west country. Northern and western areas may stay on the marginal/right side of the line though. Certainly very typical winter weather but an improvement on recent years. 

All I am saying is the 850's are cold enough at times for snow, even in the south, even south of the M4 corridor!..it looks like generally cold zonality with a few short-lived less cold / milder days here and there..the most wintry weather further n / nw.

Edited February 5, 2018 by Frosty.

[Optimus Prime]

3 minutes ago, Frosty. said:

All I am saying is the 850's are cold enough at times for snow, even in the south, even south of the M4 corridor!..it looks like generally cold zonality with a few short-lived less cold milder days here and there..the most wintry weather further n / nw.

Mmm going by 850's exclusively I'd say snow is possible for lowland areas in the NW and certainly Northern Ireland away from the coasts and Scotland. Unfortunately the air is crossing the Atlantic from a W/NW wind. Even an extreme example where RPM/PM air was noticeable cold such as 1984, 1/3 of the British Isles remained essentially snow free. 

[Bricriu]

17 minutes ago, bluearmy said:

so we either believe the models and their ens that we will see strong zonal first part next week or we don't  !

Isn't an uptick in zonal flow likely before the effects of the SSW  take effect in the Troposphere?

[chionomaniac]

Apologies if this has already been mentioned but the trop response is getting picked up

 

[karlos1983]

It is pretty difficult to get snow showers falling down south in a North Westerly flow, but I think that’s expected and accepted by its habitants, we saw this in the last spell when the uppers were pretty impressively cold. So favoured spots will do well and if you have elevation obviously that will help regardless of geographical location. 

So optimus and Karl you are both correct really. 

If you don’t live down south you can be excused of thinking -6 to -8 uppers in a northwesterly flow would deliver, but they seldom do (away from high ground) that comes from experience of past winters. 

Edited February 5, 2018 by karlos1983

[Banbury]

20 minutes ago, Frosty. said:

All I am saying is the 850's are cold enough at times for snow, even in the south, even south of the M4 corridor!..it looks like generally cold zonality with a few short-lived less cold / milder days here and there..the most wintry weather further n / nw.

Agreed it’s looking that way , a kin to the Met O update really 

[Banbury]

6 minutes ago, karlos1983 said:

It is pretty difficult to get snow showers falling down south in a North Westerly flow, but I think that’s expected and accepted by its habitants, we saw this in the last spell when the uppers were pretty impressively cold. So favoured spots will do well and if you have elevation obviously that will help regardless of geographical location. 

So optimus and Karl you are both correct really. 

If you don’t live down south you can be excused of thinking -6 to -8 uppers in a northwesterly flow would deliver, but they seldom do (away from high ground) that comes from experience of past winters. 

Straight through the Cheshire gap usually gets snow to Oxon

[Troubleatmill]

2 minutes ago, karlos1983 said:

It is pretty difficult to get snow showers falling down south in a North Westerly flow, but I think that’s expected by its habitants, we saw this in the last spell when the uppers were pretty impressively cold. So favoured spots will do well and if you have elevation obviously that will help regardless of geographical location. 

So optimus and Karl you are both correct really. 

If you don’t live down south you can be excused of thinking -6 to -8 uppers in a northwesterly flow would deliver, but they seldom do (away from high ground) that comes from experience of past winters. 

Yep totally agree, we have seen this kind of flow before & not too long ago either (in the last fortnight). If you did well then you will probably do well again, if not then think we are waiting for some HLB to deliver, 200 or 300m will be the snowline id of thought

[Frosty.]

My take on the Ecm 12z is that most days on this run look cold enough for snow, even further south and there are only 2 or 3 days that don't so on balance there is potentially plenty of wintry weather on the way during the next 10 days in terms of cold zonality with hail, sleet and snow showers, frosty and icy nights, even some wintry frontal activity at times and still the potential for something much more wintry during the second half of Feb as has been discussed.

Edited February 5, 2018 by Frosty.

[Mucka]

The output has gone in completely the opposite direction to what I expected today, certainly no sign of the cold pushing back West.

Can it be so wrong across the board?

That seems very unlikely but I am having issues digesting the output at the moment, pass me a Rene.

If we do get a sudden turn around and signs of useful blocking by mid month it will be a huge fail by the models.

[ALL ABOARD]

4 minutes ago, Mucka said:

The output has gone in completely the opposite direction to what I expected today, certainly no sign of the cold pushing back West.

Can it be so wrong across the board?

That seems very unlikely but I am having issues digesting the output at the moment, pass me a Rene.

If we do get a sudden turn around and signs of useful blocking by mid month it will be a huge fail by the models.

I agree with you mucka and the way im reading the Met update over the last three days is that any atlantic influence will be met with a cold block already in situ over the UK. 

Given that the models have continued to trend to a more mobile outlook, im suprised the text hasnt really changed given that its been almost three days of new information. 

Interesting times ahead ? 

[chionomaniac]

The first signs of the SSW trop disturbances are there on the latest ECM 12Z by day 10 #arctichigh

That to me is the starting point.

[That ECM]

7 minutes ago, chionomaniac said:

The first signs of the SSW trop disturbances are there on the latest ECM 12Z by day 10 #arctichigh

That to me is the starting point.

Interesting, not showing on gfs. Something to watch out for on future runs. Due to that high and therefore moving PV towards us hence causing more of a nw flow for a period? TIA if an easterly is to happen, how in your opinion do you think this will happen?

Edited February 5, 2018 by That ECM

[karlos1983]

22 minutes ago, Banbury said:

Straight through the Cheshire gap usually gets snow to Oxon

It does help when you don’t have those welsh mountains breaking up the showers. So if cold uppers do end up sufficiently low for snow, the Brecon Beacons usually suck them up and punch them to bits before  they get to the south west. Your streamer just hops on the M40 and shuffles on down 

ECM mean the PV looking weaker with each passing frame, maybe the jaw dropper charts aren’t to far away!

[stodge]

16 minutes ago, Mucka said:

The output has gone in completely the opposite direction to what I expected today, certainly no sign of the cold pushing back West.

Can it be so wrong across the board?

That seems very unlikely but I am having issues digesting the output at the moment, pass me a Rene.

If we do get a sudden turn around and signs of useful blocking by mid month it will be a huge fail by the models.

I don't follow this at all. No one was expecting the cold air to come back west as early as mid month.

The PV is under attack and a split vortex is still on course for the 9th-10th after which the two vortices will themselves be subject to strong warmings.

It's a hugely significant event but its immediate tropospheric response isn't yet clear. We are going to have to endure a final Atlantic onslaught next week and all the models tonight have a very deep LP around or to the south of Iceland at T+240.

From there, of course, there are any number of possibilities and as I've said from the start, the SSW doesn't guarantee cold or snow - all it does is buy us a seat at the table not a winning hand. 

I'm NOT going to say a SSW will lead inevitably to colder conditions over the British Isles - it COULD but I'm not saying it WILL.

There is a lag as we all know - ten days from 9th-10th takes us to 19th-20th and the very edge now of GFS FI - look at the GEFS of T+372 off the 12z and you'll see plenty of interest.

We may finish up with benign boring dross or we may not - it's going to be an interesting few days of model watching.

[Duane S.]

25 minutes ago, Mucka said:

The output has gone in completely the opposite direction to what I expected today, certainly no sign of the cold pushing back West.

Can it be so wrong across the board?

That seems very unlikely but I am having issues digesting the output at the moment, pass me a Rene.

If we do get a sudden turn around and signs of useful blocking by mid month it will be a huge fail by the models.

My take, assuming the effects of the SSW propogates down as swiftly as largely expected, it could be a very abrupt change indeed. Literally at any suite in the next few days.

Much more abrupt a change than we are used to seeing.

When you consider what the models have to contend with (the SSW and Pacific forcing), this is very much outside the norm. And let's be honest... they struggle at the best of times!

Mid month onwards will be the POI

Edited February 5, 2018 by s4lancia

[snowblind]

1 hour ago, SteveB said:

It's so long ago we had a blizzard down South, most on this forum were probably not born.

I know I was only 4-5yrs old, and I'm nearly 43.

Last time we had, what I'd call, a proper blizzard down here was January 1982.

[Allseasons-Si]

Mmmm!!!

where did that come from,ppn developing along this trough.

snow flurries here now

 

just shows what can pop up at close range

[Singularity]

It is worthy of some note that the trough across the UK makes no eastward progress at all between day 6 and 10, having only managed a few hundred miles between days 5 and 6.

Shame we see such a massive storm system sweeping into it though, as opposed to a weaker feature that could even become a runner into the base of the old trough.

Given the AAM/MJO background and reducing zonal winds, I'd not be at all surprised to see that alternative scenario at least get explored a bit within the next two days.

 

I did have a quick glance at the GEFS for any solutions akin to that, but they're struck trying to reinstate the Scandinavian high via ridging from the Azores so the flow is totally different; SW-NE versus NW-SE. This may be to do with the MJO taking its time moving along while at high amplitude in phase 7. These reinforcements from the Azores would be helpful if the Scandi High wasn't getting shoved aside a bit beforehand; we'd shut out the Atlantic influence and await the HLB extending increasingly toward Iceland and perhaps even Greenland later on, as the SSW made itself known. Such an outcome looks a long shot now though as it would require substantial adjustments to the weekend pattern away from what all of the deterministic model runs are depicting. 

With the current AAM/GWO background, troughs digging south and disrupting against blocking highs makes more sense as the means of initiating a lengthy cold spell. We saw the models adjust for this with respect to Thu-Fri this week, but unfortunately having initially looked promising, the trough disruption has trended away from something sufficient to deliver the goods going into the weekend. The SSW was poorly timed relative to that attempt; a few days later and we might have snatched something before the zonal flow underwent temporary strengthening.

With every new trough that comes along next week, there should be a better chance of it undergoing the level of stalling and disrupting that we need to move to the next stage. At this time the likely trend is much clearer than the likely pace of change.

[tight isobar]

9 minutes ago, Allseasons-si said:

Mmmm!!!

where did that come from,ppn developing along this trough.

snow flurries here now

 

just shows what can pop up at close range

Forming on sat-..

Almost becoming an organised band(snow showers)..one of note to keep eyeing!!

Edited February 5, 2018 by tight isobar

[Chesil View]

12 minutes ago, s4lancia said:

My take, assuming the effects of the SSW propogates down as swiftly as largely expected, it could be a very abrupt change indeed. Literally at any suite in the next few days.

Much more abrupt a change than we are used to seeing.

When you consider what the models have to contend with (the SSW and Pacific forcing), this is very much outside the norm. And let's be honest... they struggle at the best of times!

Mid month onwards will be the POI

 I would concur with this S4L. The change in the modelling is likely to be very abrupt. Your earlier point about a piece of the vortex dropping to our south under a block is very valid and something I had also been musing over..............78 redux? for the 40th anniversay.