Model output discussion 24/01/21

[Purga]

Good Ensemble mean for ECMF backing the Op.

[Troubleatmill]

7 minutes ago, Tim Bland said:

Try midday onwards which is when most of the snow falls....

My original chart was from before it updated

[Mike Poole]

ECM mean and spread T240:

Strong signal for northern blocking there and also for low heights into Southern Europe, the scrotum-like feature shown down there on the spread chart suggests lows banging about down there.  

[Mapantz]

I'm miles behind with any model output as I've been too busy, but here's a few frames of the UKV precip-type on Saturday, for those who are interested:

  

[phil nw.]

10 minutes ago, bluearmy said:

How can midlanders moan about snowfall?

Btw, control has -13 uppers post day 11.....

If the ECM verified I won't be Nick, lol. 

Seriously though a pretty good set of runs for all coldies this evening. 

The increasing signs of stronger heights to the north in week 2 will steer the Atlantic troughs se and push the jet and cold that bit further south.

Hopefully everyone will then be able to get some snow. 

[Paul]

Just now, Noob said:

Thanks for the replay Paul, so if thats the case how come models can show complete opposites at the same time frame ? Is there some human input involved or more a case of models see outcomes differently ? 

It's all those differences in physics, way the model is run and input data. They're hugely complex beasts dealing with massive mathematical equations trying to forecast an even more complex beast which is our atmosphere, and struggling to come up with answers. Tiny changes in one place or another can make a huge difference to the outcomes we see, and the models, as good as they are will never have all that nailed. 

Things like the ensembles give a hint to how complex it all is, each perturbation within them is run with exactly the same model but slightly different starting data and even they will show wildly different outcomes for the same time.

For example - this one for 10 days away and you can take your pick between mild, cold, wet and dry with several variations in between. (Although for what it's worth, the colder outcomes look the more likely on this particular run, at this particular time).

 

[chris55]

EC day 10 on wetter. Even though day 10 is pure Fantasy Island, I am enjoying the trend, that cold pool is epic!!

[chionomaniac]

18 minutes ago, Mike Poole said:

Eyes down for the home strait then!  Some considerations:

The strat, here the NAM chart as of todays GFS 0z:

We’e now seeing at the surface the -NAM/-AO signal at the surface, and the forecast up top is a return to westerlies/+AO - and I think I remember reading somewhere that this could have an effect of sealing in the trop response...not sure about that, maybe @chionomaniac might know.   The SSW likely to be influential for 2 months since 5/1/21 anyway.  

AAM and MJO:

AAM forecast by CFS to rise, and the MJO progression will be a big part of that.  The MJO GEFS plot shows an awful lot of scatter, but that isn’t all noise, as the starting point is now in phase 7 at decent amplitude.  So we should take thoughts of a La Niña style atmosphere end to winter out of the reckoning for the time being.  

It’s timely to look at SST anomalies, given we may have an easterly within the next 10 days:

Warmer than average in the North Sea specifically, which would lend itself to convection with the kind of cold uppers which the models are suggesting are coming our way.  

Likelihood of cold February increased further on today’s output I would suggest.

 

I have often suggested that the return of upper strat westerlies ‘flush’ down the easterly component towards the trop, so yes. The reverse is true at the start of the SSW

Edited January 27, 2021 by chionomaniac

[bluearmy]

19 minutes ago, winterof79 said:

Should know better than quoting post 11 days. 

just an observation.....anecdotally a decent percentage of recent eps controls have been keen on a cold easterly  ....

see worse day 10 mean charts .....note the se euro upper ridge very secure which could hold the euro trough in place and stop it sinking away se (or it could help to bring med air around the trough into the easterly flow .....)

[Tim Bland]

2 minutes ago, chris55 said:

EC day 10 on wetter. Even though day 10 is pure Fantasy Island, I am enjoying the trend, that cold pool is epic!!

Also striking how much warm air there is around Southern Europe ! Could go straight from winter to spring if the wind switches !

[bobbydog]

20 minutes ago, Noob said:

Thanks for the replay Paul, so if thats the case how come models can show complete opposites at the same time frame ? Is there some human input involved or more a case of models see outcomes differently ? 

Think of the "butterfly effect". The models are computer algorithms which try to predict the state of the atmosphere at any given time. Small changes early on can lead to big changes later. They do use more or less the same data sources but this changes as the weather itself changes. Therefore, due to the fact they run at different times, they will have the new, updated data. Also, they have differing levels of accuracy depending on which part of the world they are set up for. It also depends on the amount of money spent on the supercomputer doing the job....

The ensembles are the operational runs with slight tweaks to allow for the potential minor changes of the weather patterns, which is why they can throw up so many different scenarios at longer range.

Hope that helps 

 

Edit-  Oh... whatever @Paul.... stealing my thunder.... 

 

Edited January 27, 2021 by bobbydog

[Noob]

Thankyou makes logical sense now , more of a chance of a cold spell if a majority of ensembles showing cold . I think  moved from one bad spot Brighton to another although 2018 was niccee here but too cold for my old bones , My next questions is however , how can start data differ so much in say 6 hrs as per gfs or is that a case of too many runs and too much different data , im a mechanic by trade and too much info can lead to a head ache to get to the  final outcome ? 

 

[BLAST FROM THE PAST]

22 minutes ago, General Cluster said:

It's a stonker. But I'll nae get over-excited just yet; this time tomorrow, perhaps?

After the ‘crucial’ 00z ECM?

 

BFTP 

[winterof79]

10 minutes ago, bluearmy said:

just an observation.....anecdotally a decent percentage of recent eps controls have been keen on a cold easterly  ....

see worse day 10 mean charts .....note the se euro upper ridge very secure which could hold the euro trough in place and stop it sinking away se (or it could help to bring med air around the trough into the easterly flow .....)

Good spot. 

[stodge]

Evening all

A pleasant day in lowland East London - milder and dry but I suspect rain is on the way as we move to a much milder scenario tomorrow though that looks temporary with a brief colder snap at the weekend before a new push of milder air early next week. From there, well, plenty of confusion and a shortage of clarity on last night's model output. GEM and GFS were hinting at a change in the pattern with heights over Scandinavia but ECM wasn't interested at all.

Let's see what tonight's meanderings take us 

12Z GEM: T+120 takes us to Monday February 1st and T+240 to Saturday February 6th. By T+120 a trough covers southern Britain with a shallow area of LP over the far south east with the trough extending back into the Atlantic while a new LP starts to deepen to the south west. A weak draw of heights draws to the north means a SE'ly air flow persists over northern Britain. Milder air with positive uppers has returned to southern parts but uppers of -4 persist over Scotland. From there, the trough remain sin charge but with heights continuing to persist to the north the trough becomes elongated by T+180 extending across the British Isles and Denmark to Poland. There's a hint of upstream amplification with a new LP coming out of North America. Colder air with uppers of -8 or lower persists over the far north east of Scotland and the northern isles while cooler air with slightly negative 850s has returned to most of the rest of the British Isles.  There's more than a hint of the colder evolution from there and as you might expect, the trough disrupts south as strong heights build down from the north leaving the British Isles in a NE'ly flow by T+240. 850s of -8 or lower cover the British Isles.

 

GEM goes cold with a vengeance - let's see if it's a trend setter or out of sorts.

12Z GFS OP: at T+120 it's moving things a little quicker than GEM for which this looks more like the T+126 chart. The trough has re-aligned slightly more positive as one LP moves slowly NE towards Ireland. However, milder air has barely made it to southern and western parts with much of the north and east of the British Isles still under uppers of -4 or lower. From there, the trough fills and disrupts east across the British Isles with secondary LP crossing or lying close to the south by T+180. A NE'ly flow has set up for northern areas with strong upstream amplification though I note the shortwave development off east Greenland with some concern. Colder air is encroaching from the north by T+180 - slightly negative uppers in the south, 850s of -4 to -8 further north and uppers below -8 coming into northern Scotland. From there, stroang heights develop from mid Atlantic initially just to the north of the British Isles but by T+240 the HP is centred over Scotland with a strong ridge to the south west and a second centre over Scandinavia. The HP is propped up by a deep LP in the western Mediterranean. An E'ly air flow across southern Britain but calm conditions elsewhere by T+240 with uppers geenrally -4 to -8 over northern areas and below -8 over southern and eastern Britain.

GFS also goes cold but dry and bitter in the south.

12Z Parallel - by T+120 a lobe of trough energy extends south east across southern Britain with perhaps stronger heights to both south and north than on other models. Calm conditions over much of the British Isles with a light SE'ly over southern areas. As with the OP, milder air has just reached Cornwall and south west Ireland with colder air elsewhere and uppers below -4 in most northern and eastern areas at this time. Moving on, and in common with other models, the Atlantic trough moves east and fills across the British Isles so that by T+180 we have one LP over south-east England, a secondary LP west of Biscay and a third LP to the north west of Ireland with the trough extending north west to the west of Iceland. Heights to the north and significant upstream amplification. BY T+180 any milder air is confined to the far south east with colder air elsewhere and remaining cold over Scotland.  From there, heights continue to build to the north and by T+240 we have an HP centred to the north east of Iceland with a ridge to east Greenland. To the south, a residual trough hangs on over the southern North Sea while a new Atlantic system has aligned negatively with lobe energy heading south east towards Iberia. An ESE'ly air flow covers most of the British Isles at this time with 850s of -4 to -12 or lower for all parts though milder air is trying to push back in from the south west.

3-0 to cold but I'm not sure about the longevity of a Parallel cold spell given the Atlantic profile which looks more active than OP.

12Z ECM - the mildest option yesterday evening.  At T+120 heights from the north and south have cut the trough , part of which is heading south east into Europe with the main energy far to the west. A light NE'ly flow over southern and eastern Britain and a light SE'ly over western Ireland.  As with other models, the 850s profile is uppers below -4 for most northern and eastern areas with positive uppers reserved for Cornwall and south west Ireland. Moving on and ECM diverges again from the other models with the Atlantic trough moving to a more negative alignment in the face of heights to the north and upstream amplification. The main LP is to the south west of Ireland with a SE'ly over the British isles by T+192. Positive uppers are confined to southern counties with uppers below -8 over northern and eastern Scotland. From there, heights build rapidly to the north and by T+240 there's a large HP centred to the north and east of Iceland with a ridge to Greenland and an E'ly covering the British Isles. The temperature gradient is steep - mild air isn't far from the south coast but it's cold over northern and eastern parts.

I make that 4-0 for cold especially for northern and eastern Britain - further south, 3-1 to be charitable to mild.

Looking further ahead, the T+312 (Feb 9th) and T+384 (Feb 12th) charts for OP and Parallel respectively:

Neither OP nor Parallel keep the cold pattern in situ for long but that's GFS modelling for you (something is always happening). Neither goes spectacularly mild with the OP bringing away negative alignment and Parallel dropping part of the PV into the North Atlantic so both for the bin in my view. Control is very strange synoptically but mostly  cold. Indeed, all I get from GFS in far FI is some wild solutions which suggest the output is struggling.

If I'm being honest, the 10 HPA charts seem to be backing off more warming while leaving the PV weaker and less organised than you'd expect in February.

Conclusion: much stronger charts for cold fans tonight with all the main models getting to a similar place by T+240. Heights build to the north and apt from GFS OP stay there. The longevity and severity of any cold spell in early February to be determined but after the next milder incursion next week (which looks more half hearted with each run) the North quickly goes back cold from midweek with the south joining the party later in the week. From there, GFS puts out some wild options in FI which suggest a lot still to be resolved.

[chris55]

19 minutes ago, Tim Bland said:

Also striking how much warm air there is around Southern Europe ! Could go straight from winter to spring if the wind switches !

I know it looks really warm!

 The northern Greek islands have had a very mild winter so far (I have a family member on Skiathos.) That warmth is the result of the jetstream being so far south. This prevents the colder air forcing south west into Europe ( from the north/north east) because the southerly jet is essentially keeping them in a "barlette" type pattern.

The SSW has certainly had an effect on Europe as a whole imo.

Edited January 27, 2021 by chris55

[swebby]

43 minutes ago, bobbydog said:

To be fair, its not the models that fail to deliver, charts we don't like may be the ones that verify. More often than not, its the weather that fails to deliver.

Its all here in this book-

To be even fairer, it's the UK weather that fails to deliver.

The charts could say snow in the UK at day 8-10, and inevitably the weather delivers snow 8-10 days later - but it's in Athens or Lisbon or Rome........

[MATTWOLVES 3]

Great coverage in here by you lot gang..not much I can add,we have uncertainty come the weekend.. snow is a possibility.. The ECM finally seems to have come on board with its progression to colder conditions..Now if this comes off im pretty sure the GEM commands a little more respect,being the first model to show a colder scenario..We could still be seeing the affects of the January 5th warming event. So during the next few days yet further warming is expected...a reversal would be nice...and for me it only serves to bring us a more prolonged chance of wintry conditions. Can I just say before I go....is it just me thinking this!! We have some great posters on here and I've learned a fair bit from following it all.But some with the best of knowledge do not like to be challenged over there forecasts or ideas. Its a forum and there is nothing wrong with being challenged on something you post. My nan always used to tell me Knowledge is power...but unfortunately it nearly always tends to come with a big ego! 

I can't believe we havnt had a boom on this evenings output.

Edited January 27, 2021 by MATTWOLVES

[sebastiaan1973]

Just like this morning there is a cluster of easterly winds. Beautiful Control.

[Mike Poole]

14 minutes ago, Tim Bland said:

Also striking how much warm air there is around Southern Europe ! Could go straight from winter to spring if the wind switches !

Long way ahead, but if February goes cold as I think it will, and probably early March, we could see a sudden flip to warm like happened in mid-April 2018 only a bit earlier in the year, and we know what happened after that, just saying for those interested in summer heat.  

[sebastiaan1973]

Control is very impressive with a monster Arctic High.

[stodge]

3 minutes ago, sebastiaan1973 said:

Just like this morning there is a cluster of easterly winds. Beautiful Control.

Yes, ECM Control achieves a nirvana for cold fans with the HP starting in the North so we get a nice E'ly but the HP then moves SW to the west of the British isles so the airflow moves slowly from east through north east to north over a week. To be fair, after the -14 uppers at T+288 it gets almost mild (-11 by T+360) for south eastern parts.

[Man With Beard]

Looked at the ECM ensembles, tbh they do not resemble a beast from the east at the moment - not a lot of deep cold runs.

Of more interest to me is right in our face: Saturday and Sunday. Potential for two large snow events for England and Wales - but neither guaranteed yet. In general though, S Wales looks primed for at least one of the two events to score, and possibly in a major way (maybe even red warning quality) - otherwise, drawing a line from Anglesey to Kent represents a potential area for snow action. But anywhere England/Wales is still in with a chance of a good covering by Monday. Could be another radar checking weekend for precipitation and marginality.

[sebastiaan1973]

2 minutes ago, Man Without Beard said:

Looked at the ECM ensembles, tbh they do not resemble a beast from the east at the moment - not a lot of deep cold runs.

Of more interest to me is right in our face: Saturday and Sunday. Potential for two large snow events for England and Wales - but neither guaranteed yet. In general though, S Wales looks primed for at least one of the two events to score, and possibly in a major way (maybe even red warning quality) - otherwise, drawing a line from Anglesey to Kent represents a potential area for snow action. But anywhere England/Wales is still in with a chance of a good covering by Monday. Could be another radar checking weekend for precipitation and marginality.

I see a lot of northern blocking. What a beast is member 10.

Model charts for Europe (Mean Sea Level Pressure) | ECMWF IFS HRES (10 days)

METEOLOGIX.COM

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ECMWF IFS HRES (10 days) - Current forecast valid for 02/07/2021, 01:00am of parameter "Mean Sea Level Pressure", model chart for map "Europe"

 

[Tim Bland]

Exactly MWB ! May as well concentrate on the next few days for now. Tomorrow it’s the chance for the far north and Scotland and then attention turns to the south at the weekend. Chance for everyone to see proper snow at some point in the next 4 days.