Model Output Discussion 18z 28/07/13

[Frosty.]

Tonight's GEFS 12z mean is another cracker, very easy on the eye with anticyclonic conditions taking total control after tomorrow's storms and torrential downpours, that could be the last rain some of us see until early to mid september if the latest mean is anything to go by, it looks increasingly benign, firstly we have the classic pincer movement as the scandi high and azores high join forces to bring a lovely warm and sunny bank holiday monday and then continuing fine and warm with long sunny spells & light winds with temperatures comfortably into the low to mid 20's celsius for the rest of next week and even into the following week but overnight under clear skies, temperatures could possibly dip down to high single digits celsius, especially in rural areas, a bit warmer in towns & cities, only the far north of the uk has a risk of being a bit more changeable but the PFJ continues to stay way north of the uk along with those pesky lows, hope that continues for a good while longer.

Edited August 23, 2013 by Frosty039

[Summer Sun]

Whilst low pressure systems line up to hit Greenland and Iceland the UK is under high keeping things dry, quiet and settled

 

 

High pressure stays with us through next weekend according to tonights ECM giving us a nice settled start to September

 

 

 

Edited August 23, 2013 by Summer Sun

[Summer Sun]

ECM ends with high pressure dominant over the UK looks rather warm as well with +15 uppers close to the south

 

 

A summery start to Autumn looks on the cards this evening

 

Edited August 23, 2013 by Summer Sun

[Cloud 10]

Some very cold air showing up on the ECM 12z around the Greenland area for the time of year,with 850 temps. well below normal.

 

Might just warm the cockles of some coldie's hearts. 

 

 

 

 

Meanwhile over the UK it looks like good agreement for the Azores high to pay us another visit,so the weather settling down generally as we go into the early part of next week giving some pleasant conditions for many areas.

 

 

 

 

[Bristawl Si]

Extended Summer into September then - luverly!

[Frosty.]

Well, tonight's Ecm 12z might just be the best run since the July heatwave, there is no holding back with this run, it doesn't pull any punches, it really goes for it with the azores/atlantic anticyclone building in next week and then intensifying over the top of the uk, that T+240 hours thickness chart is absolutely sensational with the 564 dam line extending a long way north, this run takes it to the maximum and outstrips even what the gefs mean is showing, it brings a classic end of summer/early autumn HEATWAVE..   it's an absolute BEAUTY.....BANK  

 

you can almost feel the heat rising off some of these charts, they are incredible  

[draztik]

Ecm op does not have ensemble support this evening.



op vr the ensemble mean

 

Edited August 23, 2013 by Paul

[Summer Sun]

Ecm op does not have ensemble support this evening.

op vr the ensemble mean

 

 

Not all that cold though

 

[DAVID SNOW]

Not all that cold though

 

 

 

Not cold,just average.

[Captain Shortwave]

Ecm op does not have ensemble support this evening.

op vr the ensemble mean

 

As would likely be the case at day 9, given the output I see two possible solutions after day 8

One is the ECM solution, just using the day 10 chart for show

 

GFS is a little slower with this but the result is the same, the jet remains flatter to our east allowing heights to build overhead.

The other solution is shown by the GEM, again the day 10 chart

 

Note the trough digging to our east holding the high further west, more akin to the ECM mean you posted.

This is inline with the phase 1 projection from the MJO, but is this and the ensembles doing this too quickly?

At around day 7 we get a renewed push of warm air from the Azores which is a response to a trough exiting the Eastern seaboard

 

 

Slightly different but both show something similar in the evolution. How things develop from day 6-8 will determine whether the high stays west or drifts further east. Of course of note that other factors could change the output like the jet moving north or south which will have an effect too.

[BlueHedgehog074]

Personally would say that GFS 12Z perhaps looks a little bit 'ropey' tonight in that it shows the tendency for the Azores High Pressure system to occasionally stay out a little to our West/South-West (although still nearish enough to the UK to prevent too much in the way of precipitation). The High Pressure cell doesn't really ridge in directly over us until much later in FI - though, as you would expect, this will likely to keep changing and changing until the models are sure where exactly the High Pressure cell will head. The heart of the High Pressure system might not even end up over the UK at all (although clearly I could be wrong). Also, that deep Low Pressure system the GFS shows tracking to the North of Iceland may need watching as it seems to be putting a bit of forcing on the High trying to ridge over us:

 

(example from the GFS @ 162 hours. Bit of a duel occurring between the High Pressure to the South and the Low Pressure to the North)

It will probably be nothing more than a passing Low scraping the North of the UK with a risk of rain affecting some Northern areas, although if this Low does end up making more of an impact in future runs, then it's possible even areas further South could become affected by this Low. However, I think there is probably more chance that it will become less of a nuisance in future runs, or at least not get any worse than it is now, since:

 

1). GFS has the habit of over-doing Lows.

 

2). The Jet Stream generally strays to the North of the UK throughout the GFS run (image example at 162 hours).

 

As such, this shouldn't restrict any ridging of High Pressure from the South-West too much, just as longs as the GFS continues to model the Jet Stream to flow to the North of us.

 

I would personally say the 12Z ECMWF is the most encouraging model of the main three tonight with High Pressure from the South-West making the most impact over the UK. Even that deepish Low to the North of Iceland seems to be less of a menace on that run for late next week. The 12Z ECMWF also seems generally more High Pressure dominated than the old, dusty, previous 00Z ECMWF run, where the heart of the High Pressure system stayed more towards the South-West of the UK.

 

(comparison between the two runs at 192 hours. 00Z run to the left. 12Z run to the right)

Edit: Fixed the problem where only one chart was showing.

 

While there is that possibility the ECMWF could be starting to pick up a trend to something more High Pressure dominated, and perhaps more warmer too, we could do with the GFS following more in the ECMWF's footsteps if you're wanting to see prolonged, warm, UK-wide settled weather. As it is, the GFS still looks settled on the whole (but with the risk of some rain spilling down from the North-West on Tuesday according to its precipitation charts with further occasional risks of wet weather for the North/far North). However, I think we do still need to be cautious that the GFS won't restrict the ridging the High Pressure makes from the South-West any further as you could just end up finding that the High Pressure may just stay about just to our West or South-West and never quite make it properly over the UK.

 

It does look like, at least, next week should be generally settled and not too cool either, although with some mysterious to still be unraveled, such as how far North-East can the High Pressure really get. Ideally, if you're wanting another very warm/hot, settled spell, then getting that High Pressure cell to go just about far enough East/North-East so that we can become affected by South-Easterly (or possibly Easterly) winds is probably what we would want.

 

So while a settled spell is looking likely, things could still go wrong... Beware of some of the models seemingly 'to good to be true' outlooks. The models could just trick ya! ;-)

Edited August 23, 2013 by DiagonalRedLine

[Cloud 10]

Some very cold air showing up on the ECM 12z around the Greenland area for the time of year,with 850 temps. well below normal.

 

Might just warm the cockles of some coldie's hearts. 

 

ECH0-168.GIF  ECH100-168.GIF

 

 

Meanwhile over the UK it looks like good agreement for the Azores high to pay us another visit,so the weather settling down generally as we go into the early part of next week giving some pleasant conditions for many areas.

 

Make that the middle part of next week after those three cold fronts on the latest

fax chart have cleared. 

 

[BlueHedgehog074]

That's sure a lot of fronts (he hee). I suppose if those ECMWF charts you posted continue to show some very cold uppers that we might be greeted with an early snowfall. ;-)

 

Already, there's some noticeable improvements on the GFS 18Z run for later next week with the High Pressure somewhat further North and going straight through the UK, rather than sort of getting stuck to the Southern part of the UK, or getting knocked to the West/South-West of us. It's true, though, that the High Pressure cell did make it over the top of us eventually on the previous GFS run, but it did seem to take its time.

 

The Low that tracks over the North of Iceland is less of an issue, as well, even though it still looks fairly deep.

 

Could be a sign that it's following the 12Z ECMWF's outlook. It does also add a little more confidence about the solution we may head in, although I would have to admit since the ECMWF's Mean 500hpa Pressure Ensemble charts have the main area of the High stuck to our South-West, this is certainly not a definite yet:

 

(example at 224 hours)

 

Nevertheless, I do think more GFS runs will obviously be needed to see what really happens.

 

Edited August 23, 2013 by DiagonalRedLine

[William of Walworth]

I'm impressed by your analysis, DiagonalRed!

[BlueHedgehog074]

I'm impressed by your analysis, DiagonalRed!

Thanks! (although I think I probably rushed the last part a little in that I probably would have been better saying: 'more runs from various models (not just the GFS) will be needed to see where we continue to trend in regards to the likely High Pressure outlook next week').

[Frosty.]

The latest fax charts show the link up of the scandi & azores anticyclone which perfectly coincides with Bank Holiday Monday and will ensure a fine and warm day with lots of sunshine and light winds with temperatures into the low to mid 20's celsius range, tuesday also looks fine and sunny for most of the southern half of the uk but scotland turning cloudier as weakening cold fronts push southeast into the higher pressure and continue to weaken in the process, these fragmenting fronts eventually push down across the rest of the uk but will probably be no more than a band of cloud that becomes more broken and allows sunny spells to come through, by midweek, the azores/atlantic anticyclone begins to build strongly into the uk with long sunny spells and although briefly fresher/atlantic air will push in behind the fronts, it will then warm up again from midweek with an increasingly summery spell through the second half of next week..a very nice end to summer 2013 is expected.

 

In summary, heavy showers and storms across the eastern half of england today, becoming brighter and drier further west, sunday looks warm and generally fine with sunny spells and light winds with temps as high as 25c 77f for the south & east, low 20's c further north and west, monday looks sunny and warm and the further outlook is very summery.

 

Apologies for the charts being out of sequence but they would not load any other way

Edited August 24, 2013 by Frosty039

[mushymanrob]

remember last february?... the ecm kept on predicting snowmageddon charts that didnt materialise (in the timeframe predicted) but eventually it was proven right, that a prolonged deep cold spell was on the cards and was likely to happen and did happen.

 

im wondering whether the models have actually correctly picked up on a 'hot' spell, and that its the timing of one they got wrong.. this weeks heatwave/warm spell was picked up first by the gfs, out at +t300, slowly the ops came around to agree, only for it to go pear shaped nearer the time. but the models are still suggesting pressure rise from the azh becoming displaced into next week... only this time its a clear, clean hp cell without any pesky shortwave/cut off low embedded in it.

 

so @ t240 good agreement from both the ecm and gfs

 

 

and the gfs goes on into fi with a VERY plausable evolution, one which could produce some cracking warm sunny weather

 

 

and if im correct the anomaly charts show strong agreement (and have done for 3 days now), although im not so sure how far east they expect the displaced azh to get, to my eyes it appears to remain just to our west.

 

 

 

but i think there appears to be strong support for a gradually improving picture, with an evolution towards a decent lengthy spell of settled, dry, sunny and warm/very warm weather from wednesday onwards...

Edited August 24, 2013 by mushymanrob

[johnholmes]

but i think there appears to be strong support for a gradually improving picture, with an evolution towards a decent lengthy spell of settled, dry, sunny and warm/very warm weather from wednesday onwards...

 

I'd go along with the dry, settled bit mushy, how long well out = to day 15 from last evening at least, as to sunny, that will depend on just where the surface high settles. As to how far east any upper ridge gets then that is not clear from the anomaly charts so far. Like you post they are suggesting at the moment not beyond the UK.

The positioning so far of the upper ridge does suggest that largely dry and relatively calm weather may well affect much of the UK. Length again is not yet clear.

As the nights lengthen this may mean under clear skies some mist/fog forming at prone inland spots.

[mushymanrob]

but i think there appears to be strong support for a gradually improving picture, with an evolution towards a decent lengthy spell of settled, dry, sunny and warm/very warm weather from wednesday onwards...

 

I'd go along with the dry, settled bit mushy, how long well out = to day 15 from last evening at least, as to sunny, that will depend on just where the surface high settles. As to how far east any upper ridge gets then that is not clear from the anomaly charts so far. Like you post they are suggesting at the moment not beyond the UK.

The positioning so far of the upper ridge does suggest that largely dry and relatively calm weather may well affect much of the UK. Length again is not yet clear.

As the nights lengthen this may mean under clear skies some mist/fog forming at prone inland spots.

 

yeah, i guess sunshine amounts are in doubt IF the surface high parks its backside to our west... we often get cloud circulating around the northern flank , but i guess the southeast would fare well!

 

oh god not more heavy dews...i hate dew, its wetter then rain (for grasscutting purposes).

[bluearmy]

week 2 naefs spreads allow for trough incursions, moreso further north. however, the high anomoly stays west so as we've seen on many occasion this summer, an unwelcome trough coming in allowing for a cut off feature to head se is always an option unless we get the mean anomoly further east.  there are shades of early july in the way that there is no sign of pressure being able to rise to our ne over the next two weeks, once this current ridge subsides. that period didnt turn out too bad !

[Frosty.]

The 500 mb anomaly charts must have improved then John, I seem to remember you saying a few days ago that the anomaly charts didn't support the link up of the azores/scandi anticyclones, but clearly, the ens mean charts did and have been proved correct. I think the ensemble mean from both ecm and gefs have been very consistent in this respect.

Edited August 24, 2013 by Frosty039

[Cloud 10]

Bank holiday Monday looking very pleasant with some sunshine and light winds.

 

 

 

The next bank holiday looks to be shaping up nicely as well. 

 

Meteociel - Modèle Numérique américain CFS

 

[Summer Sun]

GUS ensembles keep the summer warmth going into September

 

 

[johnholmes]

The 500 mb anomaly charts must have improved then John, I seem to remember you saying a few days ago that the anomaly charts didn't support the link up of the azores/scandi anticyclones, but clearly, the ens mean charts did and have been proved correct. I think the ensemble mean from both ecm and gefs have been very consistent in this respect.

 

I am not sure how you can say the ensemble mean has been proved correct when it has not got to the relevant date yet?

As to where the actual upper ridge will end up by early September it would, looking at the major wavelength pattern around the northern hemisphere, to be unlikely to be centred much if any east of the UK.

It matters little really but in the large scale. I suspect any surface ridge will be shown on charts by the end of the month with a position somewhere from WSW of the UK and at times just ENE of the country. Light winds and decent temperatures for many away from dawn and its possible mist/fog patches under clear inland skies IF that is the case. Too far away to have any real detail on that.

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[Captain Shortwave]

Bank holiday Monday looking very pleasant with some sunshine and light winds.

 

fax60s.gif

 

 

The next bank holiday looks to be shaping up nicely as well. 

 

Meteociel - Modèle Numérique américain CFS

Only 2970 hours for the toppler to be watered down to naff all 

Sunday and Monday look good for many, temperatures reaching the mid-twenties in the south, not bad at all

@Rob, I agree, the original signal from the GFS appears to have been wholly justified, just happens we got a blip over the bank holiday.

Edited August 24, 2013 by Captain shortwave