Model Output Discussion - Spring Has Sprung

[Pembroke Dangler]

Lovely 6Z run from day 9 onwards but we are relying on a shortwave being ejected east from the parent low in the Atlantic to trigger the height rise to our west at 210 which is plausible but lots that could go wrong with this evolution much like this weeks low which headed north and splits. 

[Penrith Snow]

 syed2878 Yes it was GFS that first spotted the collapse in this weekends cold spell.

when GFS first forecasted that todays low north for earlier this week everyone said it must be wrong, it wasn't.

If every ECM 10 day chart this winter had verified it would have rivalled 1963! Instead we are looking at a winter to rival 1998.

Appalling.

Andy

[Lukesluckybunch]

Control goes similar direction to the op run..but not nearly as good!

[Met4Cast]

The GEFS 00z run has backed away from the idea of an SSW, looking very different from the previous runs.

61% of members still suggest a reversal but this is down from 80%+ yesterday. 

[jmp223]

Given up the chase this winter.  One notable week of cold at the start of December, but the lack of an amplified MJO when we needed it most really let us down, as well as the much predicted and hoped for (including by me), SSW around New Year. This winter has been an unmitigated disaster for coldies. Had great synoptics in play on a couple of occasions, but there was always one element that stalled or failed causing a domino effect which allowed for a mild incursion.  I wish you all good health, and will hopefully be back here toward the end of Autumn, albeit with tempered expectations and much less Bullish when it comes to Cold.

[Met4Cast]

2 minutes ago, jmp223 said:

Given up the chase this winter.  One notable week of cold at the start of December, but the lack of an amplified MJO when we needed it most really let us down, as well as the much predicted and hoped for (including by me), SSW around New Year. This winter has been an unmitigated disaster for coldies. Had great synoptics in play on a couple of occasions, but there was always one element that stalled or failed causing a domino effect which allowed for a mild incursion.  I wish you all good health, and will hopefully be back here toward the end of Autumn, albeit with tempered expectations and much less Bullish when it comes to Cold.

It has been like pulling teeth, hasn't it? 

Particularly given for the majority of this winter we've had a weak stratospheric vortex and it hasn't been driving the patterns, the troposphere has very much been in charge. We were in a very favourable position in terms of teleconnections in mid January for a continuation of cold/blocked patterns but then we saw a SSW (not a major one) reflect back, reshuffling the pattern away from something favourable and instead we ended up very mild and stormy. 

A fascinating winter from a stratosphere & teleconnective point of view at least, if not from a cold/snow point of view.

[festivalking]

 jmp223 See you  in a couple of weeks 

[Downburst]

 Penrith Snow I don't think a sample of two countries show the UK is leading in warming over anywhere else. Perhaps you mean in the last 12 months or so over Finland?

[bluearmy]

I’ve been watching gfs ops playing later week 2 with the strat pattern and we begin to see some consistency now 

if we take current modelling on gefs, eps and the ec and gfs op at face value, there will be an ssw just beyond mid month 

this will be caused by an Asian ridge moving across the Alaska and then pushing into the pole and stretching the spv over our side of the pole 

this at 10hpa. As we go down through the strat, the vortex is more stretched and infact has begun to split 

a couple days later we have a n russian master and Icelandic daughter split 

At 50hpa this split is more evident with the daughter almost making it to Newfoundland. 

so by day 10 we have a scenario where the split in the atmosphere is more defined lower down with clarity in the trop ref a split 

 

so you could argue that the stretching of the spv is fairly instantaneous through all levels of the strat but it seems lower down the split is clearer 

the concern I have had over the past couple days is illustrated later in this run 

A day later and at 10hpa, the split is no longer evident with the Icelandic daughter absorbed back into the Asian master as a trough extension across the Atlantic sector 

 

meanwhile, lower down in the mid strat, things look pretty good at the same timescale as far as split sustainability is concerned 

 

But this is where it gets ‘ugly’ (and has often done so for the past few runs ). Initially the mid strat split tries to widen further but quickly begins to return east to join back up with the master segment which is itself drifting west into n Scandinavia and extending further west.  So we end up with 10hpa , 30hpa and 50 hpa like this at day 16

 

this is mirrored as we head down through the strat 

so to begin with, we have the whole strat moving very much in tandem as it splits but high up, that split is brief and like an elastic band, it begins to pull the vortex segments further down back together over the next few days. 

this is an explanation as to why we are likely to see the Atlantic jet firing up as we go through the latter part of week 2.  It may not be so different to what we saw in January where a decent looking trop profile was blasted away quite quickly. 

we would need a wedge or weak ridge to deflect the jet onto a southern trajectory such that we stay on the cold side when it arrives nw europe.
 

it’s not a done deal by any means but I think this is where the modelling is getting the strengthening atlanttic profile from. it may not be a bad thing if we get our ducks in a row when it happens. The gfs 06z op looks like it re amplifies behind the system heading east. 
 

just thought it interesting to see how the waves seem to head down/up/ down through the atmosphere 

 

 

[BarnetBlizzard]

 bluearmy Possible the Atlantic jet could fire up and head below the UK into Europe and trap High pressure above us resulting in an Easterly? Or am I living in fantasy land 

[bluearmy]

 BarnetBlizzard it’s possible 

But so were many things over the past few months that didn’t happen ! 

[BarnetBlizzard]

 bluearmy I'll presume this GEFS member has got it right then  

[Met4Cast]

As good as the GFS det was in the extended it doesn't have much support at all.

[Purga]

Well, there still seems to be some potential lead in the coldies' pencils yet acc. to ENS - prone as they are to flip of course!

GFS 06z                                                                 ECM 00z

 Met4Cast  Ah so you're the half empty man

[Rain All Night]

On 08/02/2024 at 12:44, Rain All Night said:

0z/6z deterministic runs, Thu 8th to Thu 15th (day 7)

It's the battle of the bulge with those southerly surface contours over the UK at day 7. I want to see them curving to the west to indicate resilience against the Atlantic influence, but only ECM and maybe GEM are really obliging with this.

0z/6z ensemble means, Thu 8th to Fri 23rd (day 15)

The ensembles still suggest that height rises will prevail against the Atlantic mid-month, but the signal for these heights to go on to become a significant presence to our northeast or northwest has weakened. From about 20th Feb onwards, the mean heights recede, and we begin to see frames showing the mean surface pressure contours tracing from the Atlantic to the British Isles once more.

0z/6z deterministic runs, Fri 9th to Fri 16th (day 7)

I missed yesterday afternoon's runs, so I'm disappointed to come back and see these this morning, in particular the appearance of that potentially huge low off the coast of Newfoundland late next week. It seems there is an inclination for systems to be running from southwest to northeast, and there is no sign of the Scandi high that had been appearing on many recent ensemble runs. Unless that huge low pushes up some kind of ridge (see ECM and ICON), this doesn't look like a good spell of weather coming up - I had been expecting dry, if not cold.

0z/6z ensemble means, Fri 9th to Sat 24th (day 15)

Most of these (with GEM being the notable exception) at least want to lift the Atlantic away for a few days from about the 17th Feb, but that's a little disappointing given the significant height rises that were being shown just a day ago. There are still some ensemble members that want to offer height rises to the west or northwest later on, but the Scandi high is gone.

[Lukesluckybunch]

1 hour ago, Met4Cast said:

good as the GFS det was in the extended it doesn't have much support at all.

 

Very true..although not a total outlier! Hopefully it was a sign of things to come..on the 12z

[Bricriu]

 Met4Cast 61 per cent is still high. It could be just inter run variance. In any case if it doesn't happen it might be just as well if we see a repeat of what happened with the last ssw, albeit for different  reasons this time. I mean the last thing we want is an emerging cold spell through late February to be upended  by a ssw.

[bluearmy]

 

 Bricriuwas back up to 74% after the 06z run 

if it’ keeps swinging back and forth in the 60-75% area then would begin to wonder a little 

it should gain traction with around a week to go 

[TEITS]

 Met4Cast You mentioned the lack of -10c ensemble members earlier but so far today we have seen 3 operational model runs produce upper temps at or below -10C. ECM, JMA, 06Z GFS.

My point is when you have such scatter in the ensembles I look for some kind of consistency in the operationals. If the ECM and other models continue to show some promising charts then the number of ensembles at -10C will increase.

 

[Froze were the Days]

 BLAST FROM THE PAST That's put that to bed then...another failure.

[Don]

2 hours ago, bluearmy said:

it’s not a done deal by any means but I think this is where the modelling is getting the strengthening atlanttic profile from.

Oh I think it most probably is going by how winter and the strat have panned out so far!

[minus10]

Well looking at the anomalies it seems there is still a reasonable signal for those height rises to the north west later in the month..

Gefs6z/eps 0z

...basic pattern similar on a broad scale with a split vortex?..more of a trough over scandi down to Europe on the Eps..

...this height rise also shown on yesterdays cpc anoms..

..what does this mean for the airmass  temp  though..looking at 850 temp anoms for gefs/eps for the same time..

...seems that eps is more bullish with both the heat extending up into Siberia, heat over Greenland and Canada and also colder for the uk in general..

..looking at the surface...2m temp anoms..

...generally more heat around on the eps but also colder for most of the uk...interesting...as we know good broadscale synoptics often dont lead to colder air at 850 or indeed the surface but certainly on the anoms this colder signal for the uk is one we need to see gain traction..although overall it seems fairly tenuous when you consider the amount of heat also being shown..

...one last point...the last 4 gefs runs..

...ops aside...first sight they dont look that good however look closely and you can see the mean ever so slowly decreasing..back towards long term average and a bit below...also couple of ens hitting -14 850s in the latest...so if we are looking for trends then maybe this is a positive sign...fully understand that the situation is not good at present for cold with the many let downs...just trying to find evidence of more positive trends that could still deliver...

 

[Lukesluckybunch]

Icon giving it a good go at height rises in the preferred places!a real good effort..not a million miles away from that real cold stuff!

Edited February 9 by Lukesluckybunch
Adding

[frosty ground]

if only there was some cold air to the north 

[CoventryWeather]

Pretty dire modelling at the moment, nothing dry on the horizon, warm or spring-like. Continuation of a wet theme seems like the way forward. 

Hoping the SSW doesn't happen, I just want warmth now. The amount of hype for this winter and nothing to show shows how awful UK winters are now.

Give me a good spring and summer now, not a delayed winter or extended autumn.