Model Output Discussion - mid Autumn

[Coldie24]

The longer range MET output suggests lower pressure in Southern Europe which can only be a good thing for cold prospects over NW Europe ?

[Cambrian]

The UK and Ireland look to remain at the southern periphery of the northern blocking for the foreseeable future. 0z ECM mean anomalies day 6 and day 10 show low pressure stuck there to the southwest, a southerly running jet stream evident. 

 

Some subtle but important differences though by day 10 as the high pressure over Scandinavia extends westward and heights try to break through the Atlantic trough to cut off the Biscay low. 

From there, it gets interesting, as the low heights push east into the Mediterranean, here on the 0z GFS mean anomalies, days 6, 10 and 12.

  

The establishment of a flow from north of east is a possibility from there if the gradients steepen. Yesterday’s 12z EPS 5-day means for days 6-10 and days 11-15 show the same westward extension of the high pressure and the nudge back south of the low pressure trying to encroach from the southwest.

 

The net result, staying with the EPS charts is that the models have no great appetite for meaningfully moving low pressure up from the southwest and the impression that even if weakening fronts do manage to encroach at times from the southwest, rainfall will be below average : 7-day precipitation anomalies for days 1-7 and days 8-14 showing the stark contrast between northern and southern Europe (along a very clear demarcation that doesn’t budge one bit)…

 

…and temperatures remaining close to or just below average, days 6-10, days 11-15 means. 

 

We might see the odd incursion from the south but that is one formidable block forming to the north. If it stays there through November into December then we have a very interesting situation on our hands. 

Edited October 14, 2023 by Cambrian

[cyclonic happiness]

58 minutes ago, Tommytomtom said:

May i ask what a November warming is?  Ive googled it and nothing came up

I think they're talking about a Sudden Stratospheric Warming , it basically shoves all the cold air from the poles, southwards to our latitudes, and can lead to snowy spells, and big 'freezes'

[Battleground Snow]

3 hours ago, sheikhy said:

Horrible wet runs from gfs and ecm!!ecm esepecially rain just becomes slow moving across the uk!!!i either want the scandi high to influence our weather fully or just bugger off!!!hoping for a change on the 12zs!!

Models already teasing us in October. Imagine this was December, would be 10 posts per minute.. 

GFS 06z aligns the Scandinavian high much better to allow a cleaner feed of cold air next weekend.

Edited October 14, 2023 by Battleground Snow

[sheikhy]

1 minute ago, Battleground Snow said:

Models already teasing us in October. Imagine this was December, would be 10 posts per minute.. 

GFS 06z aligns the Scandinavian high much better to allow a cleaner feed of cold air next weekend.

My god i was just about to post the same thing my friend!back to the cold air and push west of the scandi high on 06z!!!maybe a few upgrades coming on the 12zs!!!

[minus10]

Well i was just going to post when @Cambrian beat me to it with his usual excellent informative posts..

...same theme though..day 10 z500 mean anomalies for Gfs. Ecm, Gem and Naefs 0z..

...this pattern is surely what we want to see continued  to enable Scandi/Baltic cooling and vortex disruption (if my understanding is correct)..it may mean mild weather for us but its a kind of longer term winter investment for more colder air to tap into later November/ December....

...certainly the day6 jetstream for gfes/ec 0z mean shows no sign of zonality as currently projected..

..in the meantime i think next week we are going to have to get used to a strong south easterly wind..

...good for drying ...

[Anthony Burden]

GFS once again at 144hrs onwards keen to establish the Norwegian high pressure and influence most of UK with a colder outlook.

ECM holds low pressure to the south/south west giving a milder outcome for October over UK.Getting a little intrigued by the persistence of GFS may be just may be something very interesting for cold lovers although could be another climb down by GFS we shall wait with baited breath.

[ANYWEATHER]

Amazing how a robust high predicted on the gfs 06z for next Saturday disappears just two days later...

[Captain Shortwave]

 

Well this is going to feel pretty darn raw, also that cold pool will certainly allow showers to drive in from the east. Shame we are not in a period where this could realistically deliver snow because that is a fine easterly. An interesting change from the prolonged warm period we have seen.

Longer term trends suggest that the pattern may return back to what we have been seeing recently (winds backing towards the south west), but there will be uncertainty regarding how long (if at all) we maintain that undercut through southern Europe.

[TSNWK]

Just now, Captain Shortwave said:

 

Well this is going to feel pretty darn raw, also that cold pool will certainly allow showers to drive in from the east. Shame we are not in a period where this could realistically deliver snow because that is a fine easterly. An interesting change from the prolonged warm period we have seen.

Longer term trends suggest that the pattern may return back to what we have been seeing recently (winds backing towards the south west), but there will be uncertainty regarding how long (if at all) we maintain that undercut through southern 

Back door mildness from Italy then balkans over Poland to us would be introducing plenty of strife on uppers if in December/January...probably no better than c couple below zero 850s at best for most in UK..

[Rain All Night]

T+168h (Sat 21st), when we still have two camps, more or less:

T+240h (Tue 24th), when in spite of the blocking present, the feel on the ground looks as though it will be "I Can't Believe It's Not Zonal" owing to the trough sitting just beneath us:

T+312h (Fri 27th), when as the heights have begun to leak away from Scandi in various directions, things look slack but otherwise fairly ordinary for us (squint to see the MSLP mean contours); note also the Azores ridge stuck way to the south:

ECM ensemble weather conditions for the south coast, to illustrate:

Edited October 14, 2023 by RainAllNight

[summer blizzard]

Euro this morning does not quite transfer the Greenland energy into Russia and so the block sinks, we are then waiting in limbo for an Atlantic trough.

GEM is a success and retrogresses to Greenland and does its best floppy easterly to floppy northerly impression. 

GFS0z was basically a wet version of the GEM. We get the heights over Greenland but the transfer is weaker meaning that we end up with a flabby low slowly moving east. 

GFS6z is much the same with a stronger Atlantic. 

 

I would tend to discount the GFS6z since the other runs keep the Atlantic weak but it does look like the Scandi High will move away quite quickly. Uncertain as yet whether or not this produces a Greenland block strong enough to keep the UK especially cool. 

 

[Frosty.]

As a coldie…hmm..being a coldie.. I do like the word oscillating..yikes .. the met office wording, not mine! … could be an interesting autumn for sure!  

[Methuselah]

10 minutes ago, Frosty. said:

As a coldie…hmm..being a coldie.. I do like the word oscillating..yikes .. the met office wording, not mine! … could be an interesting autumn for sure!  

If the charts are anything like this, I'll be a coldie in January. 

Edited October 14, 2023 by Methuselah

[northwestsnow]

Yuk.

12z ukmo painting exactly the scenario I'm concerned about.

block cant get a foothold and lows gets stuck ..

[CoventryWeather]

Can I have one of everything please? 

That is a nice block to the ne though

[northwestsnow]

18 hours ago, Don said:

Will their forecast change again?! 

Dunno - UKMET / GLOSEA solid on a block to the N/ NE for November, still 2 weeks away...

[Rain All Night]

I think some GIFs are called for this afternoon to highlight the significant differences between the outputs...

Edited October 14, 2023 by RainAllNight

[Metwatch]

Still a very tricky forecast later next week and the weekend, but confidence does seem to be growing now for a milder incursion by mid week, with good support from the ensembles of various models today.

GFS 12z coming out just now, shows a good example of the warmer temperatures actually reach the surface with high teens by Thursday and Friday, but not dry as there are deep lows all around and just to the west of the country.

The uncertanity increases substantially from Saturday, with the big question is whether the wind direction turns to an easterly or they go straight back to south westerlies. ICON is quite keen on an easterly tonight, with a deep low staying directly south of the UK. So If that easterly takes place, which is dependant on the strength / where the Scandi high moves, along with all the plethora of messy deep lows, that would lead to an undercut of colder air into the country, and potentially those colder 850s move in. UKMO doesn't want that as much. GFS and GEM seem to be sort of in the middle ground, GEM a little closer to the ICON outcome, but they then both return a westerly airflow after next weekend as heights return to Iberia - Azores / Scandi high moves further away to the east.

 

Edited October 14, 2023 by Metwatch

[Don]

9 minutes ago, northwestsnow said:

Dunno - UKMET / GLOSEA solid on a block to the N/ NE for November, still 2 weeks away...

I thought GLOSEA was the same as the UKMET, i.e. their own model?

Edited October 14, 2023 by Don

[Rain All Night]

3 hours ago, RainAllNight said:

I think some GIFs are called for this afternoon to highlight the significant differences between the outputs...

And the other two:

The Scandi block does not seem to look as strong any more as it had looked on some outputs a few days ago.

The weather from mid-week onwards does not look pleasant for anybody.

Edit to add ECM 12z ensemble meteogram for my location: Yeah, I wasn't kidding about that last statement. Rain arriving as early as Tuesday here now, and worsening thereafter.

There seem to be a minority of ensemble members still clinging on to the idea of further cold next weekend.

Edited October 14, 2023 by RainAllNight

[Kirkcaldy Weather]

Right I thought its a great idea making a post on exactly what ingredients are best plus discuss general requirements for snow  

My personal snow checklist is the following 

• Dam of AT LEAST 528. Values below this are also perfect
• THE MOST CRUCIAL ASPECT -- YOU NEED A DEWPOINT AT OR BELOW 0C. A dewpoint higher than 0C will be sleet you often notice rain starting to mix with wintry precip from about 1.5 > 2C dewpoint but when it drops to and under zero degrees its pure snowfall given you have other fitting parameters but DP really is king.
• 850hpa temps you start to notice the turning of rain to wintry precip from -5 generally but perfect ingredient being 850hpa at -8 with the snow changing its structure ie wet to dry with the lower you go at 850hpa 

Looking closely at this pattern I've identified the key timing which will be crucial if it is indeed snowfall your expecting.

Very akin to how Jan into February 09 played out

Another fine instance of the separating energy with the Rossby Wave Breaking

Here's what you'd look for in this setup its the energy along the southern isobars of the Scandi High. 

Ideal scenario would have a similar upper level cold pool generate but this is dependant on how much energy goes west into said cold pool vs how much moves east into the cyclone upstream

 

We've got a blend of the 2009 setup with 2018 and 2010 really, 2009 never really retrogressed to a strong Greenie high and that elongation from Scandi through Iceland over Greenie is exactly as played out in 2010 and 2018

Obviously taking what month it is occurring in gives better logic its just common sense your easier getting lower dewpoints and 850hpa values in December - say March and April than October.

Another big point will occur with the pivot shortly before the retrogressive state, this is a trait that models have struggled to comprehend even going back 13>14years and I recall with 2018 it was modelled farther south across Europe for plenty of days before the pivot was understood and the majority of times when this occurs if you track along the isobars its natural path more often comes to UK.

Elongating high in 2010

Setup we will be bringing in soon 

Looks like the pivot begins later Thurs with the WELL below average 850 temps slide in anywhere from 10 > 20C below average

Start of the week into Thurs as previously discussed. Initial cyclone northern Spain pairing to UK ridge and initial upstream cyclogenisis from Scandinavia south. Next part of the Rossby Wave begins to break sending energy and new cyclone southeast to Portugal + Spain

Thursday teatime we have the upstream cyclone deepen and increased pressure through Scandinavia particularly North. Pivot gets underway then its the question how does the energy separation develop, GEM sends a good chunk of energy westward a la 2009 which ends up being sufficient for a new cyclone crossing the UK again like 2009

Goodness some ridiculously sexy scenarios evolving at pace 

 

 

At this speed it gives the vibes this is setting the scene for Winter 23 / 24 to be 

 

 

 

[Rain All Night]

Here are all 103 ECM, GFS and GEM 12z ensemble members at day 10 (Tue 24th October). It looks to me as though the heights that remain beyond next weekend are not likely to be enough to bring us weather that is very far removed from the ordinary.

I'll throw in the ECM, GFS, GEM and JMA 12z deterministic charts for the same day as well.

If anyone has found my last few posts to be depressing, particularly when contrasted with @Kirkcaldy Weather's optimistic post above, then this morning's EC46 (which bear in mind is an 0z run, so is 12 hours out of date compared to the other outputs shown above) did show raised heights to the north persisting for the foreseeable future; however, many of the T+240h charts shown above - as well as our experiences of July and August this year - illustrate that you can have raised heights to the north whilst also still having Atlantic low pressure systems reaching the UK... oops, did I just end up making the post even more depressing than it already was?

Edited October 14, 2023 by RainAllNight

[WYorksWeather]

Some have already had a look above but I'm going to do what is now becoming my usual post on the GFS vs ECM comparisons.

To T+72, broad agreement now on an area of low pressure sitting just to the west of Spain/Portugal.

 

Both GFS and ECM blow this up into a major low and send it blasting our way by T+120. Have to say that looks quite nasty on the wind speed charts - as an indication, UKV has widespread gusts into the 60+ mph range, some isolated spots reaching 90mph. Too early for details yet though I think. It's also quite mild though under the SE flow - ECM at 19C on raw output which will likely get to 21C in reality.

 

At T+168, both GFS and ECM still look quite miserable. The easterly never gets going properly, more of a south-easterly, so we're stuck with lows floating over us, and temperatures probably about average with not much of a diurnal range, maybe slightly above average with the mild nights.

 

It remains messy right out to T+240 - more low pressure on both GFS and ECM. ECM perhaps slightly better for the SE corner but GFS is pretty wet and windy for everyone. An ex-tropical storm is sitting in the bottom left of the ECM chart, which we should probably look out for in a few more days when we may have a better idea of what it might do.

 

Heading out of the ECMs range and looking at the GFS extended, it probably goes into silly season with this ridiculous low at T+384 (one to add to the list of GFS being drunk). A 950mb low generated from an ex-tropical storm impacting Greenland, with close to hurricane-force winds (note that this is a mean wind chart, not gusts!). I don't think we're going to see this happen somehow...

 

Overall, I'd say it's just generally quite a messy outlook. Lots of low pressure, probably not as cold after the next few days as we were perhaps expecting, but equally no signal for anything combining mild and settled weather. Probably disappointing for everyone. If like me you'd still value a few more settled and mild days at this time of year, you're probably out of luck for the moment. But for early cold fans, probably not much joy after the next two or three days either.

Both charts are fairly representative of the ensembles as well. Never really straying too far from the mean.

 

Edited October 14, 2023 by WYorksWeather

[LRD]

11 minutes ago, WYorksWeather said:

Some have already had a look above but I'm going to do what is now becoming my usual post on the GFS vs ECM comparisons.

To T+72, broad agreement now on an area of low pressure sitting just to the west of Spain/Portugal.

 

Both GFS and ECM blow this up into a major low and send it blasting our way by T+120. Have to say that looks quite nasty on the wind speed charts - as an indication, UKV has widespread gusts into the 60+ mph range, some isolated spots reaching 90mph. Too early for details yet though I think. It's also quite mild though under the SE flow - ECM at 19C on raw output which will likely get to 21C in reality.

 

At T+168, both GFS and ECM still look quite miserable. The easterly never gets going properly, more of a south-easterly, so we're stuck with lows floating over us, and temperatures probably about average with not much of a diurnal range, maybe slightly above average with the mild nights.

 

It remains messy right out to T+240 - more low pressure on both GFS and ECM. ECM perhaps slightly better for the SE corner but GFS is pretty wet and windy for everyone. An ex-tropical storm is sitting in the bottom left of the ECM chart, which we should probably look out for in a few more days when we may have a better idea of what it might do.

 

Heading out of the ECMs range and looking at the GFS extended, it probably goes into silly season with this ridiculous low at T+384 (one to add to the list of GFS being drunk). A 950mb low generated from an ex-tropical storm impacting Greenland, with close to hurricane-force winds (note that this is a mean wind chart, not gusts!). I don't think we're going to see this happen somehow...

 

Overall, I'd say it's just generally quite a messy outlook. Lots of low pressure, probably not as cold after the next few days as we were perhaps expecting, but equally no signal for anything combining mild and settled weather. Probably disappointing for everyone. If like me you'd still value a few more settled and mild days at this time of year, you're probably out of luck for the moment. But for early cold fans, probably not much joy after the next two or three days either.

Both charts are fairly representative of the ensembles as well. Never really straying too far from the mean.

 

Yep. Good summary. Wet, rather than especially cold, looks the likely outcome for the rest of this month. That's fine. The cold stuff can wait another 6 weeks. Although a foggy Halloween and frosty bonfire night might be nice

Edited October 14, 2023 by LRD