Mike Poole

January 20

The GFS 6z in FI gives a pointer as to what we might be looking for if the retrogression idea comes off, from T192:

850 temperatures at T384:

January 20

ECM clusters T192-T240:

All show a ridge through the UK to Scandi, but this is much stronger on cluster 2 (20 members) than cluster 1, which has a more westerly influence.

T264+:

The Scandi high option seems to no longer be on the table this morning, with a UK high being the destination in cluster 2, whereas the more mobile cluster 1 eventually puts up an Atlantic ridge. This is the retrogressive option - and this seems to fit with the signal from the seasonals, and also the ECM 46 - which, as @blizzard81 noted earlier, was a stronger signal for heights to the NW yesterday than recent runs.

I’m still not wildly optimistic that a cold spell is on the way in February, but all the evidence seems now to suggest that if it does materialise, it will be from height rises somewhere to the NW.

Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5019542

January 20

ECM clusters T192-T240:

All show a ridge through the UK to Scandi, but this is much stronger on cluster 2 (20 members) than cluster 1, which has a more westerly influence.

T264+:

The Scandi high option seems to no longer be on the table this morning, with a UK high being the destination in cluster 2, whereas the more mobile cluster 1 eventually puts up an Atlantic ridge. This is the retrogressive option - and this seems to fit with the signal from the seasonals, and also the ECM 46 - which, as @blizzard81 noted earlier, was a stronger signal for heights to the NW yesterday than recent runs.

I’m still not wildly optimistic that a cold spell is on the way in February, but all the evidence seems now to suggest that if it does materialise, it will be from height rises somewhere to the NW.

January 19

ECM clusters T192-T240:

Cluster 2 (14 members) has a proper go at a Scandi high. Cluster 4 has a strong high but ends up to the east of the UK. Cluster 1 (contains the op) has a less strong build of heights, and cluster 3 weaker still, remains +NAO regime.

T264+:

Clear retrogression signal shown on cluster 1 - even makes the Atlantic ridge regime (purple border) at the end - this has been hinted at previously, but this looks a stronger signal. Cluster 2 has a high in the vicinity of the UK, to the east. Cluster 3 has a strong then weakening Scandi high (some members surely in the previous cluster 2). So still plenty in the mix there, from which something colder could develop…

January 19

1 minute ago, bluearmy said:

Neither are particularly exciting

7 has too many euro heights showing and we know with the same anomoly that the euro heights will be more prominent

6 does at least have some low euro heights which we could manoeuvre around a bit

either way we need to get through these phases

Joe b was commenting yesterday that he thought we’d miss out 7 and come back in 8

8, now that does look good.

But there’s a minefield to cross before we are in 8 at any decent amplitude!

January 19

3 minutes ago, feb1991blizzard said:

What is 6-7 late jan-early feb composite like for us? suspect it needs to be more 7-8(ish).

February composites for 6 and 7 El Niño, amplitude >1.

6 looks rubbish, I’m sure someone was ramping it slightly on here the other day, can’t remember who. 7 looks good but that’s where the question mark over amplitude on the model output is at the moment.

January 19

I think we may get a heads up on this one from the MJO analysis, because looking at today’s:

Ignoring what the model is predicting, we are right now going into phase 5 at high amplitude. If that amplitude is maintained, where the models have it decreasing, as we go through phase 5, then I’d be a little more confident it wasn’t going to collapse on us the moment it reaches the ‘good’ phases.

Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5019183

January 19

I think we may get a heads up on this one from the MJO analysis, because looking at today’s:

Ignoring what the model is predicting, we are right now going into phase 5 at high amplitude. If that amplitude is maintained, where the models have it decreasing, as we go through phase 5, then I’d be a little more confident it wasn’t going to collapse on us the moment it reaches the ‘good’ phases.

January 19

7 minutes ago, mulzy said:

Indeed Nick. The EPS look pretty benign to me (at last it dries up after next week's rain and gales). No significant cold - here is the 2m anomaly from last night's EPS - nothing cold here. We may be looking at weeks 3 and 4 to save winter but my expectations are much lower after being burnt on the chase that has delivered a handful of frosts only.

Indeed, my worry is that while some expected amplification will happen as predicted, it (as often) won’t be sufficient to deliver a proper UK cold spell, the MJO declining into the COD (as it is prone to do when it gets anywhere near the helpful phases in my experience) looks a big risk.

Then we end up with one of the EPS clusters that has high pressure in the vicinity of the UK, not farther north. Although in that instance, a retrogression scenario is possible. I would like to see a much stronger signal back on the ECM 46 for February, it being watered down recently is concerning. But at least the raging zonal spell will be short lived, and then we are back in the game…

January 19

ECM clusters this morning, T192-T240:

Firming up now on the extension of heights north into Scandi. Both clusters show this. The first cluster is actually showing a good position for the centre of the high 500hPa heights by T240, getting there on surface pressure contours (27 members)..

T264+:

Cluster 1 holds the Scandi block in a good position, cluster 2 collapses back to +NAO, clusters 3 and 4 risk ending up with a UK high. This might retrogress on cluster 3 beyond the timeframe.

January 18

All hell’s broken loose on the extended clusters, T264+:

It’s like the model’s got wind of something .

Even on clusters 4 and 5, which continue the +NAO regime, there are blocking attempts, but they don’t take hold.

Clusters 1 and 6 build a Scandi high, I imagine the different members will mean different outcomes for the UK here, but the general pattern is what is important this far out.

Clusters 2 and 3 show retrogression towards Greenland.

Original post: https://community.netweather.tv/topic/99793-model-output-discussion-cold-spell-ending-what-next/?do=findComment&comment=5018480

January 18

All hell’s broken loose on the extended clusters, T264+:

It’s like the model’s got wind of something .

Even on clusters 4 and 5, which continue the +NAO regime, there are blocking attempts, but they don’t take hold.

Clusters 1 and 6 build a Scandi high, I imagine the different members will mean different outcomes for the UK here, but the general pattern is what is important this far out.

Clusters 2 and 3 show retrogression towards Greenland.

January 18

Big changes on the ECM clusters tonight - you may not be surprised by this if you’ve followed the earlier output this evening.

T120-T168:

The changes beginning to show at T168 with a trough in the Atlantic and ridge through the UK towards Scandi, in all clusters, most pronounced on clusters 1 and 3.

T192-T240:

The signal gets magnified on cluster 1 in this timeframe building the Scandi high (33 members). More muted on cluster 2.

We await the extended clusters (not out yet).

January 18

24 minutes ago, Stuie said:

How does that work with a positive NAO Mike?

It is part of the process that will (hopefully) turn it negative - but not in 10 days time, nailed on positive until then as the GEFS based output you show indicates.

January 18

OK, so it’s a day late with the amplification, ECM T240:

Same page in my book.

January 18

3 minutes ago, Cold Winter Night said:

It's right around the time renewed amplification was expected. We have the AAM increase supporting this, contrary to FI Scandi High output in past years. Now let's hope the stratosphere will behave well for once.

Yes, if it wasn’t for the fact that we’re expecting this from the GSDM analyses and background signals, we wouldn’t give the odd run showing it at day 10 the time of day…but as it is…

January 18

Just now, Cold Winter Night said:

GFS Op, like GEM, now has a Scandi High in place at Day 10 and it is beginning to advect cold Westward.
Good to see this signal repeated.

Yes, GEM very much on the same page at T240:

Good to see these sorts of charts in the 10 day range. Can we reel this one in?

January 18

13 minutes ago, sebastiaan1973 said:

How reliable is EC46 with MJO?

Additional note. Amy Butler suggests the Greenland anticyclone was reinforced by the minor warming.

But what makes the stratosphere’s current behavior unexpected and somewhat rare is that the polar vortex seems to be more disrupted at the lower levels, closer to the stratosphere-troposphere boundary. For more than a week, high pressure has been sitting in the troposphere over Greenland . It’s possible that the recent minor stratosphere warming reinforced this Greenland high pressure, which then drove a wedge into the stretched-out polar vortex in the lowest part of the stratosphere, splitting it into two lobes.

The polar vortex is acting up | NOAA Climate.gov

WWW.CLIMATE.GOV

The latest forecast says a major disruption of the polar vortex is on its way, but the stratosphere has been acting up for a while. Our bloggers explain what it might mean...

Difficult to know yet how reliable the 46 dayer is with anything since it is a new approach with 100 low resolution runs since last year. But as @Met4Cast posted above, other models are showing the same MJO trend.

It has been a very unusual winter in the stratosphere, starting with that Canadian warming (the first for 30 odd years). But that left the strat vortex weak, and allowed the trop to lead the dance since. What effect the latest warming will have into February is not clear, but provided the strat vortex doesn’t end up in the wrong place, it may at least allow the upcoming trop drivers for amplification to unfold unfettered.

January 18

8 minutes ago, Met4Cast said:

As the MJO continues into phase 6 (and possibly 7, this is more uncertain) we see a configuration favourable for high latitude blocking. It seems probable we'll see a period of mild (perhaps exceptionally so) weather as high pressure builds northwards through the UK but there is an increased likelihood of Scandinavian blocking & thus, colder easterly winds 6th - 15th February as a broad timeframe.

The starting pistol, to borrow a phrase from Tamara has been fired. NWP modelling isn't quite in range of this period yet however we're already seeing signs of pressure rising to the NE via a route through the UK, I suspect these runs are a little progressive in terms of timing but do advertise the broader direction of travel.

Eyes down.. the next chase is about to begin.

Good post, the question mark for me is the highlighted bit. The ECM 46 dayer is consistently modelling the MJO to nosedive into the COD the moment it gets to phase 7. Should this happen, my concern is that any high latitude blocking available will get watered down from current expectations and it doesn’t take much of that for the UK to register a miss!

The same model has indeed watered down the signal for high latitude blocking, which probably supersedes the seasonal model updates of 1st Jan which were much more bullish, because a lot had happened since 1st Jan including in the strat, of course. I think the modelling still needs to move quite a bit to support the idea of a cold February, we will see…

January 18

4 minutes ago, bluearmy said:

Cluster 1 looks like it could be retrogressive with the euro heights ???

Does actually, need to see the next few frames really, here it is at T360:

January 18

ECM clusters this morning, there is only one in the T192-T240 timeframe, so that’s not much help, so for a pattern change we look to the extended T264+:

Cluster 3 is the most interesting one we’ve seen yet as that looks like it might develop a proper Scandi high (14 members). Custer 1 has a go and flattens, so does cluster 2 to be honest.

This latest chase is still in the starting blocks really. The idea is there in the modelling, and, on balance the signal for a Scandi high is maybe a little stronger this morning. Background drivers notwithstanding, there is an awful lot that can go wrong with such an evolution, and only one way it can go right - in terms of ideal positioning of the high to bring in cold air from the east. But in a sense, it is what we are expecting to see as a possibility on the models, and it is there within the possibilities - many more runs needed…

January 17

ECM clusters tonight T192-T240:

Almost a 50/50 split between cluster 1 that builds heights towards Scandi, and cluster 2 which does not.

T264+:

Cluster 1 remains +NAO, while cluster 2 is the Scandi block regime - but I would imagine this representative member hides a rather motley crew of options as far as they affect the UK.

The carrot remains dangled, but no more than that at this stage.

January 17

2 minutes ago, Gowon said:

There's potential there you just need to know where to look - you're too focused on those Iberian heights.

Just now, Kasim Awan said:

No I'm not too focused. They're there and they're very influential. This time I'm not backing down from my ascertions which are scientifically and evidentially supported. A cold easterly wind is not possible with a 580hpa high over Iberia, no arguing that.

From the runs I’ve seen, the Iberian heights pumped up by the zonal spell are part and parcel of any evolution to a Scandi high, by means of building those heights first through the UK and then into Scandi with a deep Atlantic trough providing the WAA for such an evolution.

January 16

Here we go! Pub run T222:

You can see the amplification first with the trough in the Atlantic.

January 16

ECM clusters T264+:

Cluster 2 shows the heights into Scandi evolution, 17 members, some leap still to turn that into a full Scandi high, but it’s a strong signal in that direction. Cluster 1 heading the same way with a slower evolution. Cluster 3 remains westerly.

Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5015700

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