Model output discussion 10/02/21

[Scorcher]

2 hours ago, Don said:

I know but nowt exciting and does not look great today for those of us hoping for a late cold snap.  The chances of that seem to be quickly fading now.

The chances have been very slim for quite a few days now. Even last week I was posting about this- the evolution was never going to support a prolonged cold spell. All logic and rationality seems to desert people in here during winter.

Many were still convinced that the cold air was going to make a swift return but the evidence suggested otherwise. This appeared to be nothing but fantasy to me.

Edited February 19, 2021 by Paul

[Scorcher]

21 minutes ago, Griff said:

See my reply a couple of hours ago... Cold and snow is the dream, cold with sunny days will certainly do. 

The setups being shown would only be cold by night unless you get lingering fog. I suspect many places would still make double figures now by day in the setup the ECM is showing for next weekend. The strengthening sun makes a big difference in late February.

[Griff]

2 minutes ago, Scorcher said:

The setups being shown would only be cold by night unless you get lingering fog. I suspect many places would still make double figures now by day in the setup the ECM is showing for next weekend. The strengthening sun makes a big difference in late February.

It won't be July though, so realistically let's go with periodically warm in the sun (let's not curse it before it even has a chance to happen ) 

[Frosty.]

I like the ECM 12z operational, the Atlantic gradually hits the buffers as it becomes more anticyclonic / blocked...(the form horse!! )...certainly ends on a higH note! ...no pun intended!  

 

 

[Mike Poole]

ECM clusters.  The T192-T240 showed only 1 cluster so that doesn’t tell us anything.  Move on to the timeframe into march T264-T360 and we have this:

All red borders, bar frame 2 of the 3rd one, first of all.  So Scandi block of the four scenarios.  The first one looks the best bet for a block that could develop an easterly, second is UK high, third could be promising with a bit of a shift north.  

Still in the game for a cold first half of March in my opinion.  Nothing guaranteed of course, it is a reasonable chance...

[MATTWOLVES 3]

1 hour ago, Scorcher said:

The chances have been very slim for quite a few days now. Even last week I was posting about this- the evolution was never going to support a prolonged cold spell. All logic and rationality seems to desert people in here during winter.

Many were still convinced that the cold air was going to make a swift return but the evidence suggested otherwise. This appeared to be nothing but fantasy to me.

Sorry mate but your wrong there.The winter has an whole as delivered far better than the last few,it could have been better,especially regarding the fact we had so much Northern blocking! Its not a case of irrational thinking at all! This is why Exeter kept bringing up the idea of colder into March,they was obviously seeing something...perhaps a downwelling of the 3rd and final warming! Now they decide to remove the idea perhaps partly due to a bad EC46 run! The final warming gave us a chance to receive another decent cold shot,and that's what myself and others have been basing a potential late Feb/early March cold spell on...nowt to do with irrational thinking....there are other experts in the field who have also spoken about blocking towards the NW later this month as well,so I assume we must all be irrational! Exeter have changed there mind so much this Winter that I'm now having serious doubts to the credibility of those long range forecasts! Perhaps they should write them up every week like the beeb instead of daily,and I wouldn't be surprised to see them change it again inside the next several days,and back to a cold risk again...all its going to take is for Heights that are forecast to develop close to us next week to inch that bit further North. And it all honesty it wouldn't come as any surprise if they did,and there prognosis changed again.

And worth pointing out last nights 18Z runs showed the way for cold,this morning the idea was dropped like a stone...and now again we have the 12z para hinting again at thus outcome!! That to me shows the models could be sniffing out a pattern change,and also struggling somewhat with the evolution of those Heights later this month..first we have Heights towards scandy at day 9 or so,fast forward a few more days and those Heights move NW bringing that risk of significant cold...will be very interesting to see where the 18z takes this!! If onboard we are still in the game.

Edited February 19, 2021 by Paul

[Don]

1 hour ago, Griff said:

See my reply a couple of hours ago... Cold and snow is the dream, cold with sunny days will certainly do. 

Sunny days and chilly nights are ok and yes could be worse, but still unexciting.

[stodge]

Evening all

12Z GFS OP last night was a bit of an outlier it seems - ho hum. It might yet indicate a direction of travel - it might not.

Well into the mild and benign spell down here in lowland East London but will we move seamlessly into spring or has winter one last surprise for us? Let's see if tonight's output has any clues in the medium and longer term.

Charts for T+144 (Thursday 25th) and T+240 (March 1st) from GEM, ECM, GFS OP and GFS Parallel:

T+144 :

T+240:

The T+144 charts look remarkably similar - heights over central and south eastern Europe with a new HP building NE from the Azores.  A shallow LP to the north of Scotland and a deeper mid-Atlantic trough well to the west but heights building across the British Isles and notably in the south. From there to the start of March (T+240) and the build of heights continues - GEM and GFS OP keep the core of heights to the south or south west - OP keeps a bit more energy in the northern arm of the jet but GEM offers a hint of heights to the north east. ECM has a strong build of heights up over Scandinavia supported by a shallow trough over the Ukraine and new heights building from the west but it's Parallel which is best for cold fans with a substantial core of heights over or just to the west of Scandinavia and an E'ly moving across southern Britain. 

Why does this work? Well, between the pre-existing heights over Europe and the new heights building over the Azores a shallow LP develops and as the HP from the Azores tries to push north this extends east into Iberia and across the Mediterranean basin supporting heights further north over the British Isles and Scandinavia. It's an example of how what is little more than a shortwave pays dividends.

Moving further into the new month, charts at T+312 (March 4th) and T+384 (March 7th) from GFS OP, Parallel, Control and of course CFS:

T+312:

T+384:

OP doesn't really get there though like the CFS it has a large HP right over the top of the British Isles by T+312. Control is a bit messy though not without hope but Parallel is tonight's gem. It's a belter for cold fans with uppers below -12 over southern and central England in a chill ENE'ly and the retrogression pattern holds with the HP holding firm south east of Greenland keeping the air flow between north and east. We keep seeing these colder evolutions so the signal is there id not well defined at this time.

Beyond next week, the signal is strongly for heights to build toward and over the British Isles but whether these will migrate to Scandinavia remains to be seen. It's by no means certain but it's no lost cause at this time and it could be, as has happened many times before, we get a final spell of winter in early March before the true arrival of spring. Let's hope.

[Scorcher]

21 minutes ago, MATTWOLVES said:

Sorry mate but your wrong there.The winter has an whole as delivered far better than the last few,it could have been better,especially regarding the fact we had so much Northern blocking! Its not a case of irrational thinking at all! This is why Exeter kept bringing up the idea of colder into March,they was obviously seeing something...perhaps a downwelling of the 3rd and final warming! Now they decide to remove the idea perhaps partly due to a bad EC46 run! The final warming gave us a chance to receive another decent cold shot,and that's what myself and others have been basing a potential late Feb/early March cold spell on...nowt to do with irrational thinking....there are other experts in the field who have also spoken about blocking towards the NW later this month as well,so I assume we must all be irrational! Exeter have changed there mind so much this Winter that I'm now having serious doubts to the credibility of those long range forecasts! Perhaps they should write them up every week like the beeb instead of daily,and I wouldn't be surprised to see them change it again inside the next several days,and back to a cold risk again...all its going to take is for Heights that are forecast to develop close to us next week to inch that bit further North. And it all honesty it wouldn't come as any surprise if they did,and there prognosis changed again.

And worth pointing out last nights 18Z runs showed the way for cold,this morning the idea was dropped like a stone...and now again we have the 12z para hinting again at thus outcome!! That to me shows the models could be sniffing out a pattern change,and also struggling somewhat with the evolution of those Heights later this month..first we have Heights towards scandy at day 9 or so,fast forward a few more days and those Heights move NW bringing that risk of significant cold...will be very interesting to see where the 18z takes this!! If onboard we are still in the game.

I don't see how what you've said here has proved me wrong at all. I'm not talking about the past. I'm talking about what the models are showing. It doesn't matter what has happened before now- I was commenting purely on the patterns the models were showing.

Yes the winter has been reasonable for cold weather fans but that is irrelevant here.

Reading this thread last week you would think it was only a matter of time before we returned to sub-zero temps looking at what people were posting. There was nothing to suggest that in the model output, regardless of whether it has 'delivered' up to now or not.

Have you not asked yourself why Exeter keep changing their minds? It's because more than about a week ahead, there is always a great deal of speculation when predicting the weather. Regardless of your level of expertise or access to data.

Edited February 19, 2021 by Scorcher

[Jordan S]

Evening

Another low pressure system developing to the southwest of us tonight bringing very strong winds back to some western areas of England, Wales tomorrow morning with 50-60mph likely along parts of the coast and on hills with possibly 40-50mph in some more sheltered inland locations in the west then becoming stormy once again for the Western isles tomorrow evening with gusts of 55-65mph very likely with a chance of upto 70-75mph for a short time locally.

More rain will move north through mainly the west of England and into Wales on Sunday with rainfall intensity fluctuating so outbreaks of rain which will move east during Monday but fragments,weakens later in the day.

Gfs..

Gem..

A similar pattern to today and tomorrow for tuesday morning with another low pressure system moving in close by, heavy rain moving into northern Ireland then Scotland with possible hill snow at first for Scotland, the weather front oriented at first southwest to northeast instead of south to north such as today's.

Gfs..

Gem..

Gfs..

A further 50-75mm likely in a few places this band of rain slowly moving southeast during wednesday and effecting Wales and northern England before weakening.

Higher pressure building with it becoming drier still likely later next week mainly for England and Wales, it will also probably still be a little colder generally particularly at night with a frost possible locally.

Quite likely that more rain will move into northern Ireland and Scotland by next Saturday, most likely remaining mainly dry further south with any rain likely at the moment to be mostly light and patchy during next weekend.

Although a lower chance that high pressure will be further north covering most parts bringing more widespread frosts with mostly dry weather for all.

Ecmwf..

Here's the Gfs and Gem upper air temperature overview for most of next week. 

Edited February 19, 2021 by jordan smith

[legritter]

Hi gang  ,still time for cold and snow to turn up ,feast your eyes on tonights ecm 240hrs ,move that north and BOOOM ,and tonight gang i have sausage baps galore plus some STELLAS, GFS is starting up ,you never know ,ps brown sauce tonight is Daddies.  

[Mike Poole]

41 minutes ago, legritter said:

Hi gang  ,still time for cold and snow to turn up ,feast your eyes on tonights ecm 240hrs ,move that north and BOOOM ,and tonight gang i have sausage baps galore plus some STELLAS, GFS is starting up ,you never know ,ps brown sauce tonight is Daddies.  

Just got a bread roll and sausages out the freezer for tomorrow morning, thanks to that post!  

It wouldn’t surprise me if one of the pub run brothers throws out a decent cold run again tonight.  This isn’t resolved yet.  Whatever the anomaly charts say!  The signal from the strat is still there, NAM plot, yes it is weaker than the last one, as would be expected, but at the surface it could deliver.  However it’s a plot showing -AO NH wide at the surface, no guarantee at all about how that translates to the UK, here be dragons!

 

Edited February 19, 2021 by Mike Poole

[Tamara]

At the moment, the numerical models are reading diagnostic signals well

Global relative atmospheric angular momentum continues to operate deleteriously to the La Nina base state.

 

However, as suggested was the signal to end last weeks cold spell, extratropical forcing lost the ammunition from the tropics to sustain the upstream forcing to hold that higher latitude blocking in situ as extra polar jet energy forces a more mid latitude downstream ridge and Atlantic fronts are able to make ingress. Meanwhile further south towards 'home to be' some quite delightful Spring-like weather is being enjoyed, and as a very pleasant flavour of the much warmer months to come.

The switch in upstream forcing, as predicted in a previous post, has come about through steeply falling angular momentum tendency as rapidly weakened tropical forcing within the Pacific cuts off the poleward propagating eddies migrating into the extra tropics. This, at the same time as some stability/re-organisation returns within the polar field.

 The Global Wind Oscillation is responding accordingly and, based on two/three day consolidated lag data, is completing an orbit across the El Nina attractor phases on destination towards 'transitional La Nina' Phase 8 -  signifying rapid scrubbing of +AAM anomalies from the atmospheric circulation

 

Putting all this together, and in the face of no real signal for further renewed tropical forcing in the foreseeable future, then a mid latitude pattern has strong medium to longer range support. There should be some pleasant early Spring sunshine likely at times, in between rain-bands - the latter more particularly earlier within the 10 day period.

Hope-casts/avid expectations of renewed ridging to the north and east in the extended period, *should be* set objectively/tempered c/o the lack of tropical forcing and adopting a sanguine approach to long range numerical modelling signalling of a further post SSW downwelling wave twitch - of which the GEFS most particularly can tend to exhibit over enthusiasm.

That doesn't mean such modelling is certain to be inevitably wholly wrong - further cold weather of course cannot be discounted, as perhaps manifested by back door cold air advection on the southern flank of mid latitude ridging (for example) - but while Met Office updates tend to be overly reactive to numerical modelling vicissitudes in respect of  interpreting diagnostic signals, there is some sense to their current expectations that any such possibilities would very highly likely be moderated in comparison to those of early to mid February.  At the very least.

Stronger isolation and longer days one obvious factor - though its known that deep cold air origins can overcome such mitigation for a time yet. With that in mind, the other reason, is because the longer time goes on, then any residual lag (if there is any) from the winter-time weakened stratospheric/tropospheric state fades out. This most especially hastened/mitigated in effects due to the tropics and extra tropics  becoming more hostile than previously towards supporting the mountain torque mechanisms that induce momentum transport of rossby wave packets to assist destabilising the polar profile once again. Such destabilisation clearly has to be proportionately stronger to support sustained cold air advection far enough away from an arctic source, the further time heads into the early new season

There are those who would indeed like that to be the case, and it is not unrealistic that sunshine by day and some frosts by night within calm centres of anticyclonic conditions might be the ultimate outcome, for the UK latitude anyway..

Edited February 20, 2021 by Blessed Weather
Unnecessary comments removed

[tight isobar]

Reading an-awful lot around various agencies-/and indeed in here of a leap into spring.. with a continued uping of tropical maritime like float!!!.. .. @false dawns are fuitile with eventual heartbreak!!..the drivers are in spring sequence.. yet the evolutionary.. is raising an eyebrow!.   Mass scale gwo.. and indeed locale geographicals.. are at battle... some elevators also.. as-screenshot@euro melterts @height sources.. that are already hinting out in la-la to re-intro.. a winter bite... ebbing into March..will be brave watching.. on both fence sides... but the honesty -and possibilities.. say winter wants a final crack @the whip!!!.. an-incursion of 1 last notable punch .. can only be ruled out via the very naive...   plots to note .. as highlights.. @possible roads to evolutionary points...     ciao-fa-now

[Mike Poole]

A lot more amplified on the pub run T180 compared with the 12z T186:

[Mike Poole]

GFS // T174 compared with 12z T180:

Better WAA, this could be a stonker. Remember there is a strat element in this in terms of a probably final downwelling of easterly winds, the // has much higher resolution vertically. 

[Griff]

// is having fun

[Mike Poole]

GFS pub run // T198, looking interesting:

[MATTWOLVES 3]

I've got a feeling the para is getting the urge to build these Heights further North...or is it me being a little overly enthusiastic

[Griff]

1 minute ago, MATTWOLVES said:

I've got a feeling the para is getting the urge to build these Heights further North...or is it me being a little overly enthusiastic

Fairly consistent with the 12z. Plenty of time for favourable corrections

Satisfactory. 

[MATTWOLVES 3]

7 minutes ago, Griff said:

Fairly consistent with the 12z. Plenty of time for favourable corrections

Satisfactory. 

Can I start to get a little excited now....I've got bugger all else to do on a Friday evening these days

@Griff @Mike Poole i think its coming...been a while since I said that

Edited February 19, 2021 by MATTWOLVES

[ribster]

6 minutes ago, MATTWOLVES said:

I've got a feeling the para is getting the urge to build these Heights further North...or is it me being a little overly enthusiastic

Quite irrational

[Tim Bland]

GFSp 12z Vs 18z.  Fairly good consistency for 11 days out...

[Griff]

My interest today extends beyond the fun of a couple of gfs parallel runs... 

Curious that (pick your favourite model) is suggesting amplification and heights around the UK. 

Now I'm not the entertainments officer and not responsible for anyone's excitement levels (), but there are reasons for interest. No promises, but not suggestive of westerlies and wet

[Mike Poole]

GFS // T276, high a little too close to us here, but at that timescale a lot can change:

Important thing is another run that develops the easterly.