Model Output Discussion - Cold spell ending - what next?

[Nick2373]

00z shows the climb up then back down to just above average over numerous days,  so not really a theme of continued mild weather ppn spikes dropping lower after the 24th. around the 29th-30th there's a massive spread in the members with the GFS And the Mean coming closer to average temps indictive of a patterrn change possilbe will there are hints of a high pressure set up but the question is will it feel spring like or cold? whatever the outcome at least there is only a few days well one day of heavy rain southwards then its pretty much what we are used to i suppose in the winter. 

[DavidS]

A switch to a more mobile and milder pattern is still there for all to see on the output this morning, but perhaps less of the exceptional mild than has been on offer for the last few days.

[Troubleatmill]

Meanwhile on our door step, Sunday in to Monday is still looking very wild , our friends over in Ireland/n Ireland could be in for a shocking time, sure if it carries on being modelled like this, the met will be out with the warnings

[AO-]

Good Morning all,

Despite some promising signals earlier and an outrageous GEM (let alone one Member of its EPS), there are no signs for anything cold in the corrected output of EC this morning. Bit disappointing though. Chances of frost, but that is all. This implies a high chance of a Euro high rather than a Scandinavian block in januari as the best possibility. The chances of southwesterlies is still the highest. Fortunately it is not very wet. 

Edited January 18 by AO-

[MJB]

26 minutes ago, Troubleatmill said:

Meanwhile on our door step, Sunday in to Monday is still looking very wild , our friends over in Ireland/n Ireland could be in for a shocking time, sure if it carries on being modelled like this, the met will be out with the warnings

Looks nasty 

[Mike Poole]

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…

[E17boy]

Morning peeps

Well the long anticipated change to mild wet and windy weather is still on the output this morning. So it’s going to be goodbyes to the cold as the Atlantic train takes over. Unfortunately we have not ended in a position to even see a transient breakdown from snow to rain which is a shame. I think the  theme for the next 2 weeks will be Atlantic driven albeit there will be high pressure in the forecast as well giving  some dry weather. We have still got February to go there is me hoping outside drivers will eventually rescue this winter not forgetting the growing concerns as we go through these next few weeks that time will slowly start to tick down. 

[bluearmy]

4 minutes ago, Mike Poole said:

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…

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

[Mike Poole]

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:

[AO-]

10 minutes ago, Mike Poole said:

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…

The members that come up with a Scandiblock, lack cold at first, as reflected in the EPS I just posted. Nevertheless interesting to follow the evolution.

[winterof79]

Trend? #Teits

Edited January 18 by winterof79

[Anthony Burden]

Morning all,GEM shows how quickly a Scandinavian high pressure can show itself now that a pressure rise looks favourable around the last week of January along with all the uncertainty involved with the polar vortex could get a sudden return to very cold scenario.

[tight isobar]

Gfs n gem offering up similar Synoptics- into the latter stages! There is certainly a scope for formats of heights into the Scandinavian plots.. and with momentum gaining, it’s more than a feasible evolution.. as per we’ll watch and see this possibly developing scenario. And watch  ens supporters for the switch!…

Edited January 18 by tight isobar

[jules216]

There was a lot of wibe around the seasonal forecasts of "back loaded winter" perhaps they meant 20-28.02.2024 period. As currently there is a big overwhelming signal of very mild Europe in next 3 weeks. Currently the best and only really coolish and snowy period date here in central Europe is 25.11-10.12. Which is as front loaded as it gets. The clusters 240-364 on EPS are showing what would be almost a record breaking warmth being summer time. This winter is a very good match of a blend of last 2. Few december promises and almost snowless January,followed by a week of cold in February and then the really cold pattern sets in spring time. This is almost happening every single year since 2017. This trend shouldnt be ignored. As I ve seen very little re-analysis after the wibe ends ",what has gone wrong". My oponion is that its a blend of factors. 1. Haddley Cell expansion - high pressure from north Africa as legacy of hot summers - pushing north creating a wall that prevents cold air to push too much south, and SST once they cool enough its spring when cold synooptics kick in, Late March - April. 

[TEITS]

35 minutes ago, Mike Poole said:

 

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…

Brilliant post as you have summed this up perfectly.

On a different topic I note some are being a little OTT with regards to next weeks mild weather. Just using the GFS only one day does my location reach a max temp of 13C. The other days for next week is around 8/9C. So just above average and nothing exceptional. What is noticeable next week is just how wet and windy it shall be although thankfully the low pressure on Wednesday should be the last one for a considerable time.

In summary after the wild weather this sunday and early next week the next destination is fairly clear to me. However the route it takes and how long the journey will be is up for debate. If members thought the recent chase was stressful they ain't seen anything yet.

[AO-]

13 minutes ago, jules216 said:

There was a lot of wibe around the seasonal forecasts of "back loaded winter" perhaps they meant 20-28.02.2024 period. As currently there is a big overwhelming signal of very mild Europe in next 3 weeks. Currently the best and only really coolish and snowy period date here in central Europe is 25.11-10.12. Which is as front loaded as it gets. The clusters 240-364 on EPS are showing what would be almost a record breaking warmth being summer time. This winter is a very good match of a blend of last 2. Few december promises and almost snowless January,followed by a week of cold in February and then the really cold pattern sets in spring time. This is almost happening every single year since 2017. This trend shouldnt be ignored. As I ve seen very little re-analysis after the wibe ends ",what has gone wrong". My oponion is that its a blend of factors. 1. Haddley Cell expansion - high pressure from north Africa as legacy of hot summers - pushing north creating a wall that prevents cold air to push too much south, and SST once they cool enough its spring when cold synooptics kick in, Late March - April. 

The pattern evolving atm is quite atypical for this winter. That is one reason why I expect this pattern to be broken down sooner with the help of background drivers. It is of course wishful thinking, but a mild interlude of one week in Scandinavia is a lot considering the history of this winter. That doesn't mean we get winter by the way.

Edited January 18 by AO-

[Gary L]

15 minutes ago, jules216 said:

There was a lot of wibe around the seasonal forecasts of "back loaded winter" perhaps they meant 20-28.02.2024 period. As currently there is a big overwhelming signal of very mild Europe in next 3 weeks. Currently the best and only really coolish and snowy period date here in central Europe is 25.11-10.12. Which is as front loaded as it gets. The clusters 240-364 on EPS are showing what would be almost a record breaking warmth being summer time. This winter is a very good match of a blend of last 2. Few december promises and almost snowless January,followed by a week of cold in February and then the really cold pattern sets in spring time. This is almost happening every single year since 2017. This trend shouldnt be ignored. As I ve seen very little re-analysis after the wibe ends ",what has gone wrong". My oponion is that its a blend of factors. 1. Haddley Cell expansion - high pressure from north Africa as legacy of hot summers - pushing north creating a wall that prevents cold air to push too much south, and SST once they cool enough its spring when cold synooptics kick in, Late March - April. 

I'm not an expert in background signals but it seems there's far too much emphasis placed on them. I'm assuming they tip the balances by a few % in the direction of some scenarios (e.g. HLB). 

[Met4Cast]

I know some are downbeat about this current colder period due to the lack of snowfall (in southern areas, anyway) but the teleconnections advertised this period very well. 

This current cold spell isn't over yet but already it seems a return to blocked/colder conditions is the broad direction of travel into February. The mechanism and drivers for this to occur are already in motion. 

The MJO looks to progress through the Maritimes into the western Pacific, with this frictional torque has risen with +MT following on behind. MT always follows FT. Westerly momentum is transferred from the earths rotation into the atmosphere and the response is AAM tendency goes up, driving total AAM upwards. Indeed, AAM tendency has recently turned positive once again in response to the MJO progression eastwards.

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.

[Met4Cast]

2 minutes ago, Gary L said:

I'm not an expert in background signals but it seems there's far too much emphasis placed on them. I'm assuming they tip the balances by a few % in the direction of some scenarios (e.g. HLB). 

Comments like this confuse me and I think it's down to a lack of understanding of "background signals" that trigger it. The teleconnections are what drive our weather and create the weather patterns that we see, NWP modelling is based entirely upon these signals. Understanding teleconnections allows you to view NWP modelling in a much broader context. "Too much emphasis" absolutely cannot be placed on the things that literally drive our weather. If anything, not enough emphasis is placed upon them. 

I think where people get caught up is that they expected certain drivers to produce specific weather conditions outside their front door & unfortunately, that's not how it works. You can use these drivers to get a flavour of the broader, global scale weather patterns but the micro scale, i.e outside your front door is so local & isolated compared to the northern hemisphere that x + y does not necessarily = a snow day. 

This current cold period & blocking spell we're in the middle of was well advertised weeks in advance. The MJO cycling through phase 1/2 and slowly through 3 helped to generate a Rossby wave packet within the Pacific which led to wavebreaking in the Atlantic & the Greenland high that has brought about the current cold weather. This, in conjunction with a high total AAM state (increased westerly momentum within the atmosphere) led to a perturbed and amplified jet stream capable of generating the HLB we've seen. 

A strong +EAMT (East Asian Mountain Torque) event created the Pacific jet extension which developed a downstream trough, causing a jet streak which then created a downstream trough, follow this all the way into the Atlantic with each "wave" amplifying the next. We've got a Greenland high, we've got cold weather across the UK, broadscale pattern? Check. The next step is the micro, i.e small-scale weather systems that may or may not bring about snowfall in specific areas, that's something background/teleconnective signals can never help you predict. 

Ironically, the "downfall" to this cold pattern & the reason for next weeks milder & stormy weather isn't because of a sudden change in background tropospheric forcing but down to the recent SSW. The SSW has helped to displace the Canadian vortex eastwards towards Siberia which has flattened the pattern.  A case of bad timing, again, something teleconnections can never help you predict. 

[Mike Poole]

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…

[Met4Cast]

2 minutes ago, Mike Poole said:

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…

Other modelling appears to be suggesting a similar thing in phase 6 too.

Theres certainly consistency between the modelling there! Fortunately, phase 6 in the context of El Nino does still broadly favour Scandi heights. Throw in the tendency for a south shifted jet stream and we could see some decent undercutting, but details details! 

Not *too* concerned about the MJO forecasts at that range.

Edited January 18 by Met4Cast

[johncam]

1 minute ago, Met4Cast said:

Comments like this confuse me and I think it's down to a lack of understanding of "background signals" that trigger it. The teleconnections are what drive our weather and create the weather patterns that we see, NWP modelling is based entirely upon these signals. Understanding teleconnections allows you to view NWP modelling in a much broader context. "Too much emphasis" absolutely cannot be placed on the things that literally drive our weather. If anything, not enough emphasis is placed upon them. 

I think where people get caught up is that they expected certain drivers to produce specific weather conditions outside their front door & unfortunately, that's not how it works. You can use these drivers to get a flavour of the broader, global scale weather patterns but the micro scale, i.e outside your front door is so local & isolated compared to the northern hemisphere that x + y does not necessarily = a snow day. 

This current cold period & blocking spell we're in the middle of was well advertised weeks in advance. The MJO cycling through phase 1/2 and slowly through 3 helped to generate a Rossby wave packet within the Pacific which led to wavebreaking in the Atlantic & the Greenland high that has brought about the current cold weather. This, in conjunction with a high total AAM state (increased westerly momentum within the atmosphere) led to a perturbed and amplified jet stream capable of generating the HLB we've seen. 

A strong +EAMT (East Asian Mountain Torque) event created the Pacific jet extension which developed a downstream trough, causing a jet streak which then created a downstream trough, follow this all the way into the Atlantic with each "wave" amplifying the next. We've got a Greenland high, we've got cold weather across the UK, broadscale pattern? Check. The next step is the micro, i.e small-scale weather systems that may or may not bring about snowfall in specific areas, that's something background/teleconnective signals can never help you predict. 

Ironically, the "downfall" to this cold pattern & the reason for next weeks milder & stormy weather isn't because of a sudden change in background tropospheric forcing but down to the recent SSW. The SSW has helped to displace the Canadian vortex eastwards towards Siberia which has flattened the pattern.  A case of bad timing, again, something teleconnections can never help you predict. 

So according to your last paragraph then teleconnections can't always forecast the weather if the SSW overrides it? Or am I not reading this correctly?

[sebastiaan1973]

3 minutes ago, Mike Poole said:

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…

How reliable is EC46 with MJO? 

 

5 minutes ago, Met4Cast said:

Comments like this confuse me and I think it's down to a lack of understanding of "background signals" that trigger it. The teleconnections are what drive our weather and create the weather patterns that we see, NWP modelling is based entirely upon these signals. Understanding teleconnections allows you to view NWP modelling in a much broader context. "Too much emphasis" absolutely cannot be placed on the things that literally drive our weather. If anything, not enough emphasis is placed upon them. 

I think where people get caught up is that they expected certain drivers to produce specific weather conditions outside their front door & unfortunately, that's not how it works. You can use these drivers to get a flavour of the broader, global scale weather patterns but the micro scale, i.e outside your front door is so local & isolated compared to the northern hemisphere that x + y does not necessarily = a snow day. 

This current cold period & blocking spell we're in the middle of was well advertised weeks in advance. The MJO cycling through phase 1/2 and slowly through 3 helped to generate a Rossby wave packet within the Pacific which led to wavebreaking in the Atlantic & the Greenland high that has brought about the current cold weather. This, in conjunction with a high total AAM state (increased westerly momentum within the atmosphere) led to a perturbed and amplified jet stream capable of generating the HLB we've seen. 

A strong +EAMT (East Asian Mountain Torque) event created the Pacific jet extension which developed a downstream trough, causing a jet streak which then created a downstream trough, follow this all the way into the Atlantic with each "wave" amplifying the next. We've got a Greenland high, we've got cold weather across the UK, broadscale pattern? Check. The next step is the micro, i.e small-scale weather systems that may or may not bring about snowfall in specific areas, that's something background/teleconnective signals can never help you predict. 

Ironically, the "downfall" to this cold pattern & the reason for next weeks milder & stormy weather isn't because of a sudden change in background tropospheric forcing but down to the recent SSW. The SSW has helped to displace the Canadian vortex eastwards towards Siberia which has flattened the pattern.  A case of bad timing, again, something teleconnections can never help you predict. 

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

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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...

 

[Met4Cast]

2 minutes ago, johncam said:

So according to your last paragraph then teleconnections can't always forecast the weather if the SSW overrides it? Or am I not reading this correctly?

The state of the stratosphere needs to be taken into account. An unstable profile (such as we have now) often favours higher latitude blocking. If the strat had been in a strong position we'd likely have seen the current blocking fail. 

SSW's cannot be predicted with any real accuracy at longer ranges so it's always a wildcard. Unfortunately on this occasion instead of amplifying the blocking signal, it's flattened it with a displacement event. You win some, you lose some..

[StretfordEnd1996]

These temperatures next week will feel balmy 

 

But as HP has more of an influence, it may not be a full week of mild-fest temperatures than it may initially seem - cooler at night in less than a weeks time 



Sat 27th dawn - frosty morning potentially



 

That's thanks to this build of HP over the country



So Sun-Thurs, very mild and wet no doubt. Back end of next week it settles down and with that comes more average temperatures. 

It goes to show how HP can often present uppers with contrasting ground temps - at least for a time .. this example (into FI now admittedly) 



Same chart ground temps 


Where does the HP go from here, one may ask.

Who knows.