Model Output Discussions 12z 03/05/2016

[knocker]

Today

A weakening front will travel SE across the UK.

The GFS this morning

A wet/showery weekend, including Monday and by 1800z that day there is a depression 970mb lying between Iceland and Scotland leaving the UK in a westerly airstream. This low tracks away NE and as it does so a quite amplified upper air pattern evolves with a trough to the west of the UK and HP to the east. Ideal then for a shallow unstable low pressure feature to form to the SW/S and some WAA before tracking N bringing much convective activity to the UK. The problem is the pattern is so mobile the trough moves east with more fronts tracking across the UK from the west

[mb018538]

It would appear that a portion of the middle of next week (Tues/Weds/Thurs, though how much is open to much debate) could turn warm to hot, with some convection tied in too as knocker says. Lots of tropical activity really stirring things up at the moment!

[Man With Beard]

Oh not you too!

[sparky1972]

morning all, will be keeping a keen eye on peoples views regarding model output and i will be hoping to read that the weekend of 9/10/11 sept will be dry, off to Goodwood Revival. 

[MP-R]

8 hours ago, Man With Beard said:

Keep in mind that some intense heat is forecast for Iberia early next week (40-44C), considering it is now September. Should a plume be encouraged, it could well contain some major hot weather.

Oh absolutely. The ECM especially was alluding to some 15-20C 850 temps being scooped up by the incoming Atlantic low.

[knocker]

Given the continuing difference between the GFS and ecm I think much caution should be engaged before getting too carried away with the ecm briefly giving temps in the high 20s for the SE.

At weds 00z the ecm splits the trough () and has a cut off upper low to the SW with HP in western Europe extending over the UK. It then proceeds to track the cut off low east whilst at the same time developing it into an extended negatively tilted trough just to the west of the UK and with the HP now centred to the east the stage is set for S/SE airs and some very brief WAA before the front continues it's journey east and normal service is resumed.  And all of this is a long way away

 

Edited August 31, 2016 by knocker

[Captain Shortwave]

Day 6 charts

      

 

A the models seem to be a lot closer together in terms of the general idea during the mid-range this morning with low pressure moving ENE between Scotland and Iceland with a sharpening trough in the Atlantic allowing heights to strengthen over Europe, the trend for a more dominant high pressure cell over the Europe and the UK seems to has diminished somewhat though as many posts have alluded to there is some unseasonable warmth over Iberia and there is a route to push it north towards the UK again as that trough sharpens to our west. Still major questions on how this would pan out but if we can get to this position by the start of next week, well 30C would not be out of the question if that hot air can be advected our way again. Still the ECM and GFS differ from this point onwards with the GFS more progressive with bringing westerlies back in whilst it is the turn of the ECM to develop widespread dry and very warm conditions.

Day 8

   

Overall the general theme continues as it has for some time, the south looks mostly dry and warm, the north more changeable but far from a complete washout.

In the longer term, the GEFs still suggest that heights to our east/north east will become dominant as we approach the second third of the month.

      

An impressive and persistent anomaly that would deliver drier than average and above (possibly well above) average temperatures as the ridge is pretty much perfectly placed to maximise warmth during this time of the year. Of course this signal could wane, especially as the modelling of the tropical systems in the Atlantic evolve in the coming days. 

Edited August 31, 2016 by Captain Shortwave

[Summer Sun]

ECM shows temperatures sometimes well above average next week high 20's more than possible for some

[mb018538]

I see the ECM has the 20c isotherm over the UK for a time....in the second week of September!!

Anybody know offhand if that would be the latest time the T850 20c line has crossed the UK? Interested to know

[Man With Beard]

35 minutes ago, mb018538 said:

I see the ECM has the 20c isotherm over the UK for a time....in the second week of September!!

Anybody know offhand if that would be the latest time the T850 20c line has crossed the UK? Interested to know

It happened in 1906

resulting in 35.6C - in Yorkshire!!!!

About 50% of the GEFS ensembles back the ECM's idea of a stalled trough in the Atlantic for the end of next week - which, like last week, would promote a temporary suck of heat from the south.

The thing that makes this really interesting is the anomalous heat over Iberia that's coming up. This would be on the very hot end of the scale for Spain/Portugal even at the very height of summer.

What I'm saying is, if the pattern works in the way the ECM suggests this morning, there is a lot of wood on the fire...

[Singularity]

There I was thinking ECM was losing the plot as it diverged so much from all the other output yesterday... and now here we are with the notion of trough disruption on the base of the major Atlantic trough early next week gaining ground and leading to some eyebrow-raising plume scenarios.

I should have guessed that the theme of the second half of the summer - as outlined by Tamara's excellent Sunday update - would show itself yet again.

We've had three major plume chances these past two months. The first delivered strongly but the other two have fallen short. This is a good reflection on how easy it is for the small scale features not to play ball - but also how they certainly do sometimes, and with impressive results.

That projected heat over Iberia is astounding. Heated air close to the surface is perhaps more significant in late summer and early autumn, as this is the time when the seas are warmest and hence will mitigate the heat of such layers of air least. I fear this would equate to  an oppressively warm night or two for England in particular, with this being a greater component of the heat than the daytime highs (we're losing over 20 minutes of sun-up every week now).

So that's an interpretation of what might, if a lot falls into place, be coming our way in a whole 6-9 days time... place your bets

[knocker]

The EPS is suggesting a rather flatter fairly mobile pattern with the trough to the west slowly tracking east with the UK in a SW airstream. It would portend some warm pleasant conditions for the south as the HP briefly nudges north but the hot air would be constrained south of Central France.

So very pleasant for two or three days but no cigar

[Singularity]

1 hour ago, knocker said:

The EPS is suggesting a rather flatter fairly mobile pattern with the trough to the west slowly tracking east with the UK in a SW airstream. It would portend some warm pleasant conditions for the south as the HP briefly nudges north but the hot air would be constrained south of Central France.

So very pleasant for two or three days but no cigar

Perhaps you are right - but when one allows for variation in the timing of events among the individual ensemble runs, the southward extent of the cool anomalies in the Atlantic, and northward extent across Europe and into the UK, seems noteworthy to me at least. I believe that at this point in time it translates to a glancing plume event for the SE - and happening on a short enough timescale that a multi-day mean will hide the true magnitude. So one or two increasingly warm days, then a single hot day for the SE corner.

A lot of room for further adjustments, of course.

[knocker]

 

1 hour ago, Singularity said:

Perhaps you are right - but when one allows for variation in the timing of events among the individual ensemble runs, the southward extent of the cool anomalies in the Atlantic, and northward extent across Europe and into the UK, seems noteworthy to me at least. I believe that at this point in time it translates to a glancing plume event for the SE - and happening on a short enough timescale that a multi-day mean will hide the true magnitude. So one or two increasingly warm days, then a single hot day for the SE corner.

A lot of room for further adjustments, of course.

I accept that a multi-day mean could hide the truth of a sort time scale event but I did also consult the 12 hour 850mb mean charts and at this stage there would have to be a quite significant increase in amplification and/or less eastward pattern mobility for a significant plume event. In any case given the time scale and lack of agreement between the models this is a tad academic at the moment.

Edited August 31, 2016 by knocker

[Singularity]

29 minutes ago, knocker said:

 

I accept that a multi-day mean could hide the truth of a sort time scale event but I did also consult the 12 hour 850mb mean charts and at this stage there would have to be a quite significant increase in amplification and/or less eastward pattern mobility for a significant plume event. In any case given the time scale and lack of agreement between the models this is a tad academic at the moment.

I did not know there were 12 hour means out there... Impressive. Can't argue with that - clearly the det run is a particularly extreme outcome relative to its ensembles. Even so I'm surprised not to hear of more in the way of a plume signal from the ensembles. Perhaps many do not see the cut-off low formation?

Indeed, this is all a bit of fun speculation. The lighter side of meteorology

[knocker]

The GFS is getting there Mind it;s worth a look at the 6 and 12 for this time

Edited August 31, 2016 by knocker

[Nouska]

4 hours ago, Singularity said:

I did not know there were 12 hour means out there... Impressive. Can't argue with that - clearly the det run is a particularly extreme outcome relative to its ensembles. Even so I'm surprised not to hear of more in the way of a plume signal from the ensembles. Perhaps many do not see the cut-off low formation?

Indeed, this is all a bit of fun speculation. The lighter side of meteorology

The IMO site has 6 hourly means for the 15 days covered by the ensembles. It only covers part of the British isles for 850 temps but from what I see of the 00Z run, the peak of the plume is at +138 hours.

It's all looking pretty good out to the end of the run and based on this I've put in a high CET guess next door.

[Captain Shortwave]

Some impressive ridging even by day 6 from the GFS and GEM

   

I am surprised to see both of these models revert back to this after ditching this solution this morning. In fact both deliver a lot of fine and very weather out to day 10 and beyond.

The UKMO looks flatter though it would still be fine and very warm for England and Wales, wind and some rain for Scotland and N.Ireland mind you.

The GEFs are tending to follow the operational to some degree at the moment so I am not sure how good a guidance they are at the moment. There are large changes there even in the mid-range where you would expect more stability than the operational. We await the ECM suite with interest.

Edited August 31, 2016 by Captain Shortwave

[Summer Sun]

Warm perhaps very warm at times and settled pretty much sums up tonight's GEM

[Scorcher]

The GFS 12Z looks fantastic for next week- is Gaston going to help the jet to go way north of the UK? If so it would be great for the long suffering areas in the north and west with a potential warm easterly developing with an area of high pressure over the whole UK.

[Summer Sun]

ECM looks warm and settled next week once the weekend's rain is out the way it looks like a nice start to Autumn

 

[knocker]

Sure is a roller coaster ride with the det. outputs these days with some significant differences with the last two ecm runs for next week. Mainly appertaining to the trough to the west. In fact the anomaly at T156 just about shows an Omega block. But all for the good because now the GFS and ecm are more or less on the same page with HP being the order of the day from Tuesday onwards  Of course this is a million miles away from being nailed down but definitely a step in the right direction and better than a transient plume scenario as it could, repeat could, bring some more sustainable fine weather to most.

[phil nw.]

Day 5 and UK model looking more unsettled further north with the Atlantic low closer to Scotland and the Azores high flatter compared to the others.

The ECM/GFS op runs more in line with latest ens outputs so we wonder if the UK model will eventually show it's solution to be the correct one.

Recent height anomalies have built +ve hts across the UK towards Scandinavia next week for some time now so with the UK model pushing lower pressure across to our north just casts that little bit of uncertainty on how settled next week will prove to be.  

 

[phil nw.]

The first half of September looking quite reasonable for many according to the gefs.

A couple of graphs showing the expected 2m temperatures and rainfall-one for C.England and the other C.Scotland.

Low rainfall totals for the 2 week period with some warm days showing especially further south.Day to day variations of course but based on those and the height anomaly charts it's looking like a decent start to Autumn.  

[damianslaw]

As we enter early September once again dry settled quiet weather surfaces, becoming a regular feature it seems.. the weekend looks quite unsettled though, however, ECM now showing a similar output to GFS, i.e. high pressure ridging in from the south and pivoting itself towards scandi, all thanks to how ex tropical storm systems are forecast to interact with the jetstream, the effect warm air advection being pumped up through east atlantic promoting the ridge and the jet to stretch far away to the NW. 

Going off today's models next week is looking very good indeed if you like warm dry sunny weather. Think I'll take a break from model watching for a bit given the quiet times ahead - I find September the most trying month of the year in this respect and whilst it is often very mellow pleasant, it is the 'dullest' time of year for model watching, I always relish October when it comes..