Mike Poole

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…

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.

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

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.

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).

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.

OK, so it’s a day late with the amplification, ECM T240: Same page in my book.

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…

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?

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.

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…

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

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…

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.

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.

Here we go! Pub run T222: You can see the amplification first with the trough in the Atlantic.

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

The question is how do you get to a high lat block from where we are now. I agree with this. I think what we need to ask ourselves is, given the models were showing a rampant zonal pattern indefinitely, what is the first sign on the models likely to be - if the ultimate destination is a high lat block in Scandi, the first thing we will see is a mid lat block pushing north into the UK, pushed up by WAA from the vortex. If the vortex doesn’t relent, that should continue and drive the high to our NE - where exactly we don’t know, but a Scandi high looks a reasonable aspiration from there, given a more amplified pattern is expected from teleconnections. Original post: https://community.netweather.tv/topic/99760-model-output-discussion-colder-but-how-cold-and-for-how-long/?do=findComment&comment=5015550

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.

ECM mean at T240: Pretty good support for a signal of height rises into Scandi - unfortunately the clusters don’t help, just one between T192-T240, await the extended with interest.

There’s a question mark in my mind over how this SSW will affect things going forward. I think there are two things with an SSW. In an energetic split vortex SSW, where the zonal wind doesn’t just touch 0 at 60N 10hPa but goes substantially negative and remains easterly for some time, that can downwell and affect the trop weather at our latitude over the next couple of months, maybe eked out in discrete stages. That’s not really on the table with this one, which brings me to the other thing, which is the lack of the strat vortex westerlies driving the trop pattern - it seems to me that’s largely been the case since the Canadian warming, and should continue. Which means, for me, it is up to the trop to drive the pattern it wants, unfettered from above. In which case, it is good that rising AAM and a favourable MJO phase might be driving the pattern into February in the direction of a -AO/-NAO, i.e. in a couple of weeks. But if that does happen, I wonder how much of that will be attributed directly to the effects of the SSW, and whether or not that would be correct…

ECM seems keen on some action. T240: Just appeared in last two frames.

The question is how do you get to a high lat block from where we are now. I agree with this. I think what we need to ask ourselves is, given the models were showing a rampant zonal pattern indefinitely, what is the first sign on the models likely to be - if the ultimate destination is a high lat block in Scandi, the first thing we will see is a mid lat block pushing north into the UK, pushed up by WAA from the vortex. If the vortex doesn’t relent, that should continue and drive the high to our NE - where exactly we don’t know, but a Scandi high looks a reasonable aspiration from there, given a more amplified pattern is expected from teleconnections.

Some support for the op on the ensembles, height rise through the UK looks probable, Perturbation developing the Scandi high T276: Promising…but a long way to go on this one yet.

Game on! GFS T318: There has been a signal for something on the way towards this on the EPS and clusters which definitely grew larger this morning. So very interesting to see GFS roll this out in FI this afternoon.