Model Output Discussions 12z 01/06/2017

[mb018538]

Very warm in the se on that 168....need some cross model agreement before we get ahead of ourselves though!

[Frosty.]

52 minutes ago, mb018538 said:

Very warm in the se on that 168....need some cross model agreement before we get ahead of ourselves though!

This T168 from the Gfs 6z looks quite autumnal, especially further n / w / nw...pleasant enough temperature wise in the SE but cold in parts of scotland

Edited August 21, 2017 by Frosty.

[Man With Beard]

Morning all - Proof this morning that a good looking chart does not guarantee good weather - who would have thought so much cloud and drizzle/rain would come from this?
  

On to the Bank Holiday debacle. The very firm split remains this morning, except that the ECM has moved part-way towards the GFS, leaving the GEM/UKMO to campaign for a more settled outcome alone:

      

The fact the UKMO is consistently promoting such a chart is encouraging, seeing as it is often quite good when dealing with the cut-off low to the SW.

The ensembles are of little help. Both last night's and this morning's ECM ensembles are very mixed:

  

Some encouragement in that the most UKMO-like cluster has grown overnight (from cluster 5 to cluster 1), and the most horrible clusters have reduced in size and number.

Added that last night's ECM op being in a completely different cluster to this morning's ECM op, and given the general GFS/UKMO stand-off, there really isn't enough information available to call the bank holiday yet at all. Let's hope for more of a coming together on the 12Z runs.

A little sightly further ahead, and it's pretty clear that a deep trough is going to form. The question is how much of the UK it will affect by the middle of next week. The ECM ensembles leaves its options open:

  

while the GEFS looks far less settled, and does not have a cluster with heights to the east:

       

 

[phil nw.]

Yes MWB nice sum up wrt the BH weekend.

Just glancing at the latest from the big 3 for day 5 where the uncertainty really starts to show

The UKMO chart much more bullish with the Azores ridge building across and cutting off the low to the south.

Hopefully the Uk model has the right idea which would settle things down more widely across the country,at least for a couple of days or so.

However beyond that the ens upper air pattern continues to show a return to a more changeable westerly type as you suggest.

 

[Singularity]

GFS 06z then 12z for:

Friday 25th;
 

Saturday 26th;
 

Sunday 27th;
  

 

With GFS now finally picking up on that shallow surface low west of Iberia Thu-Fri, the end-of-week temps have taken a notable step upward across the south-eastern third of the UK, particularly for Sunday.

If we could combine that with a SW-NE alignment of a flat jet, that'd be great for settling things down more widely and for longer. It is of interest that both UKMO (middle) and GEM (right) keep on going for this version of events, in the face of the GFS (left) idea of having a lingering shallow low by Scotland keeping the jet aligned more NW-SE;

  

ECM was quite well aligned with UKMO and GEM on it's last 12z run, but the 00z was very similar to the GFS 12z I've just analysed so who knows what ECM will get up to this evening...! 

Both UKMO and GEM are in fact stunners for day 6:

    

It's going to hurt if it turns out they're leading us up the garden path!

 

What is it with GEM and plumes...?

It did better than the other models with the June and early July plume events but has had a fair few misses since then.

 

Edited August 21, 2017 by Singularity
Re-arranged due to width constraints

[draztik]

4 minutes ago, Singularity said:

 

It's going to hurt if it turns out they're leading us up the garden path!

 

 

Really? I mean, will it? Considering the models have led many up the path this summer... i'd consider this just another merry dance. 

GFS firm. And as we saw back around mid-July - when the GFS op, control and most of its ens suggest the same evolution update after update - it's hard to disregard it.

[knocker]

The problem with these UKMET charts is the shortage of detail but to my eye that isn't a million miles away from this morning's ecm but one doesn't know if there is any weather attached to the shallow low to the SSW that may impinge, as in the latter And this evening's gfs isn't a mile away

Edited August 21, 2017 by knocker

[mb018538]

Very warm in the se on that 168....need some cross model agreement before we get ahead of ourselves though!

[DR(S)NO]

16 minutes ago, mb018538 said:

Very warm in the se on that 168....need some cross model agreement before we get ahead of ourselves though!

Gosh mb , I had a sense of deja vu there and then realised this is the same as your post from this morning lol

Dont know if you meant that 

Anyhow, yep almost hot in the SE on the 168..... Continuing poor up here though

[knocker]

The ecm this evening is a much better run (albeit this no doubt will not be the final solution although I think we may be getting there) It drops the trough which becomes a cut off upper low SE to be NW of Coruna by 00z Saturday and develops it quite nicely As far as I can see the main advantage of this is that it forces the Azores to ridge north east which in turn delays any south east movement of the main trough.Whilst at the same time ex Gert has lost it's identity.

Over the weekend the cut off low gradually fills and the trough to the NW slowly squashes the ridge but the latter hangs on and the associated fronts do not really impact the top of Scotland until Sunday evening. They then track SE over the Monday but fragmenting all the time and the ridge then fights back on Tuesday/Weds

Edited August 21, 2017 by knocker

[Singularity]

2 hours ago, draztik said:

Really? I mean, will it? Considering the models have led many up the path this summer... i'd consider this just another merry dance. 

GFS firm. And as we saw back around mid-July - when the GFS op, control and most of its ens suggest the same evolution update after update - it's hard to disregard it.

I'd never back GFS/GEFS over a combination of UKMO and ECM hence my interest in the ECM output but given the GEM 12z I had a feeling it would edge back toward a warmer and more settled outcome - and so it has, albeit a little tenuously.

 

It manages to cut-off the low which is essentially what GFS has little interest in, but that low is a bit deeper and further north, which leaves us in a less certain state of improved weather conditions, despite the broader pattern being very similar;

 

This run goes on to keep the jet a bit flatter than the 00z which makes a lot of difference to conditions across the S. half of the UK. This sort of thing - to answer @knocker's inquiry - being where the UKMO 12z differs notably from the ECM 00z; it has a flatter jet stream passing to the N of the UK, even more so than this 12z ECM has produced. It's not that big a difference on the face of it, but fine margins look to be at play with respect to the divide between warm/very warm weather with the odds favouring not much more than some diurnal shower formation and cooler, cloudier weather with a risk of spells of rain.

   

It's not ideal by any means and we sure could do with the even flatter jet of the UKMO 12z, but (at least some) southerners may find it a satisfactory recovery in temperatures at least.

Meanwhile Central Europe appears well placed for a late summer heatwave of considerable intensity for the time of year. As I'm paying a visit to the Balearic Isles in mid-September, seeing the 25*C 850 hPa isotherm edging toward there at the end of August does make me wonder what sort of overnight temperatures I might have to face given the warming effect on an already much warmer than usual Mediterranean.

Of course with the knowledge of my time away in mind, it's probably wise to prepare for (relatively) exceptional heat to visit the UK in just under a month's time .

[Frosty.]

The Ecm 12z shows plenty of warm weather, especially across the southern half of the uk, very warm at times across the south with incursions of 564 dam which is nice to see. Definitely a more summery run with nothing autumnal about it..so once again there are better signs from some of the 12z output this evening...speaking of warmth, tomorrow will feel summery across england and wales with 23-25c widespread and 26-27c in parts of the s / se.

Edited August 21, 2017 by Frosty.

[knocker]

The EPS 850mb temp means and wind streams has the ridge hanging in there in the southern half of the UK until midweek with a quite marked temp gradient across the UK Monday and Tuesday.

This is the det.

 

Edited August 21, 2017 by knocker

[Man With Beard]

31 out of 51 ECM ensembles tonight backing the GEM/UKMO solution - a big increase on the previous two runs. Let's hope the GFS/ECM ops follow in the morning

[knocker]

Last night's anomalies are not a great deal of help in the medium term and merely indicate that the evolution for next week, and even this weekend, are is a long way from being nailed down. The models appear to struggle when you have the three current components in the mix, namely the major trough to the north west, the Azores to the south west and, the fly in the ointment, a second trough that drops south east and forms a cut off low around Iberia. How this combination interacts and who  gains ascendancy seems to cause no end of problems, As can be seen there is quite a difference between the GEFs and EPS  Best I can come up with at the moment is the percentage play is for most to remain unsettled but the south may escape with the HP nudging around.

Given all of this perhaps not worth looking further ahead but just to say there are no obvious sign of any deviation away from an upper westerly flow and little indication of a more settled regime.

Today quite a pleasant day for most except the north until the fronts have finally cleared to the NE. Tonight the cold front will encroach from the west bringing some light showery rain as it traverses the country tomorrow.

The gfs this morning really just emphasizes what I have said above, After a couple of reasonable days Thursday and Friday (N. Scotland excepted as per) our faithfull shallow low is still hanging around over Ireland but, more to the point, it's about to get an injection of life from the north west which is decidedly not good news as 24 hours later low pressure dominates and the the UK is in a strong showert westerly with more prolonged rain over Scotland.

This continues through Sunday and after a very brief respite a deep low tracks NE to be 975mb north west of Scotland by 18z Monday with the associated fronts crossing the country and gales in Scotland. The low then slowly tracks east and fills a tad leaving the UK in the strong westerly airstream. I think I'll leave it there and just keep in mind that gfs was always making more of the trough than the others but 140kt jet over the UK is just taking the mick

[mb018538]

Sadly it's all gone a bit Pete Tong again from the nice looking UKMO run yesterday...



We had the high building in over the top of the cut off low, leading to some nice, warm settled weather. Today that's gone off the menu completely, and we have:



Much more low pressure dominance, and the Jetstream picking up once again:



We may just about scrape an acceptable bank holiday weekend, but looking dicey again after that. Plus by then we will be pretty much into September!

[Frosty.]

I don't know if it's my imagination but the 00z in the last few days seem to be showing the worst outlook and then the 12z looks generally better..let's see if it continues again today!

[knocker]

The ecm predictably varies quite considerable from the gfs Saturday onwards but it has shifted to a much more unsettled outlook from the previous run.

By 00z Saturday it also still has the old low in it's death throes just west of the Hebrides with the cut off low NW of Iberia. But from here although England and Wales remain fine on saturday, Scotland and NI are still pretty wet as the low finally loses identity  The difference now from the previous run is the energy/trough tracking in from the NW doesn't allow  any significant ridging from the Azores and thus Sunday becomes a showery for most with perhaps just the far south escaping. Monday in a showery westerly before the next system tracks rapidly north east to be over Stornoway by 00z Tuesday with heavy rain and gales in Scotland and N, Ireland.

Oh and Sidney says hi on this bright and sunny morning to all those concerned about his welfare

Edited August 22, 2017 by knocker

[summer blizzard]

I must say that this summer has taught me a lot about the power of westerly and easterly wind bursts over the Pacific and their downstream effect for the UK. In that context it's clear to see why modelling for ~10 days out is screwing the UK. 

[karyo]

Interesting to see that the models are giving a new lease of life to the remnants of tropical storm Harvey as it crosses the Yucatan peninsula and makes his way to the gold of Mexico. There it regains tropical storm status (at least) and heads for Texas. This could be also having an effect on the north Atlantic pattern.

[DR(S)NO]

1 hour ago, summer blizzard said:

I must say that this summer has taught me a lot about the power of westerly and easterly wind bursts over the Pacific and their downstream effect for the UK. In that context it's clear to see why modelling for ~10 days out is screwing the UK. 

I'm sorry, I'm not knowledgeable enough to understand these charts.... But I'm guessing that these may go someway to explaining why this Summer seems to have promised plenty in 10 days time but delivered very little 

[Man With Beard]

ECM ensembles back to being all over the place for the bank holiday. GEFS 00Z adamant on a return to less settled.

[Man With Beard]

It does seem as if it's game, set and match for the more optimistic charts presented by the GEM and UKMO for the bank holiday weekend, at least for northern areas (yet again). Still a possibility of a very good weekend across the south though - if the fronts stay away (as many models forecast) and the sun gets out, perhaps 24-27C a possibility in this area. But given the way things have conspired in recent weeks, I guess we'd all be pretty surprised if a spanner doesn't get thrown in the works once again to prevent this.

Now a very subjective opinion based on how things are working out - I just wonder if we're going to miss out on our usual September high-pressure spell this time round. I just don't feel that the Atlantic is in the mood to stop throwing lows at us. But just an opinion.

 

Edited August 22, 2017 by Captain Shortwave
To move discussion on

[Frosty.]

The Gfs 12z shows a warm largely fine spell for friday and the whole bank holiday weekend across the south / south-east with temperatures into the low to mid 20's celsius..pretty good for those areas.

Edited August 22, 2017 by Captain Shortwave
To move discussion on

[damianslaw]

44 minutes ago, mb018538 said:

Your input is always valued knocker!

Its the same on here as any other weather forum though....when things are mundane and really un-inspiring, you tend to see a downward trend in the level of posts. Maybe everyone has had enough of this July and August Groundhog Day! 

Traditionally this is a very quiet time in this thread, its still the summer holidays for those south of the border, and the prospects of lengthy sustained warm period for weeks ahead, diminishes i.e. hopes for summer goodness quickly ebbs away as we begin to think about the autumn. 

Back to the models, I said reliable timeframe is very short at the moment, probably 96 hrs tops, so the weather for the bank holiday still can't be called on with any certainty. The models today though have flipped away from more promising fayre compared to yesterday, with the atlantic westerlies gaining momentum and influence on any ridge development, which appears very fleeting if it appears at all, and most likely will only get a foothold on southern parts, with the north yet again destined to endure more westerly misery, Scotland really has had a very westerly summer, with barely a break. 

Looking further ahead, tropical storm activity looks more potent this year compared to the last 4 seasons, which could make for a rather different September compared to the last four, with perhaps less in the way of settled high pressure spells, more cyclonic stutturing frontal features.. and any shot from the NW will be quite chilly.