Model Output Discussion 18z 28/07/13

[Frosty.]

The GEFS 12z mean turns into a STONKER of a run and once again we have another run trending towards a warm and anticyclonic further outlook, especially for southern britain with temps into the low 20's celsius during the second half of september but under clear skies overnight, fog would form widely but followed by warm and sunny afternoons/evenings, this is exactly the type of further outlook the met office are currently going for, long may it continue.

[Gaz1985]

The GEFS 12z mean turns into a STONKER of a run and once again we have another run trending towards a warm and anticyclonic further outlook, especially for southern britain with temps into the low 20's celsius during the second half of september but under clear skies overnight, fog would form widely but followed by warm and sunny afternoons/evenings, this is exactly the type of further outlook the met office are currently going for, long may it continue.

 

Indeed long may it contimue

[johnholmes]

having another closer look at the anomaly and I think this is my best stab at what they may mean

 

Noaa

6-10 and 8-14 pretty similar to last issue

 

Along with ec-gfs outputs to me this suggests surface pressure rising off w/sw eire to settle wx down over much of uk but trough is close enough out to day 14 to e’ernmost areas on ec(6-10) and noaa(6-10 and 8-14) to ‘perhaps’ keep far e parts of uk less so. Met do not suggest this so they must have some further data, ec 32 perhaps more like their own long range mogreps suggests the trough far enough away not to have any effect in range beyond 6-8 days?? Or maybe I’m mis reading the anomaly charts

Have a look at naefs 500mb?

7 days time=T+168, see below;

http://www.meteociel.fr/modeles/naefs_cartes.php?mode=0&code=0&ech=6&map=&runpara=

 

Further out and there is really no anomaly showing on it around the uk area e/w/n/s

So maybe there will be no residual e’ern troughing effect and the main feature day 6-15 will be ridging at 500mb with a surface high close by/over w’ern areas of the uk?

 

copied into the slower thread so I can find it in the days ahead!

[Summer Sun]

Here is the latest on the models from Gibby

 

Hi everyone. Running very late tonight preparing for a busy day with my craftwork tomorrow so here's a lightning stop your of the output tonight taken from the 12 noon outputs of the regular five.

 

All models are still very confident on the course of events over the next 3-4 days but less so beyond that. The current showery conditions within which many areas are fairing far better than was expected is shown to continue over the next few days though it seems less likely that tomorrow will see as many places avoid the showers entirely. By early in the week the trough lies to the East with showers concentrated here while Western areas stay rather drier and brighter if never overly warm.

 

GFS then shows a ridge collapsing SE over the UK on Wednesday followed by a rain bearing trough also moving SE over all parts towards the end of the working week. Following that another ridge builds across England and Wales for a day or so before a mild and moist Westerly flow develops with rain and drizzle over Northern and Western hills and coasts. Then through most of FI with the exception of the odd day or two when the odd trough sneaks over the UK the weather becomes dominated by High pressure always close to the South and for a time to other areas too when war and settled conditions develop widely for a time.

 

The GFS Ensembles show a slow rise in uppers over the next few weeks towards or just above the seasonal average. There seems no reason why these warmer than average temperatures should not be reflected near the surface given that winds are often quite light and from a warm source. Rainfall amounts look quite benign over the period with almost all seeing some at one point or another but never anything dramatic.

 

The Jet Stream shows the core of flow around the UK Low at present slowly simplifying as the trough weakens and slides East next week. It then moves to a more regular West to East pattern near to Northern Scotland, perhaps turning more WNW to ESE later.

 

UKMO tonight closes it's run with a weak cold front clearing Southern England taking it's cloud and light rain away with it as a ridge builds back in from the SW for a time thereafter.

 

GEM shows a couple of occasions when weak troughs cross the UK from the NW with a little rain in places, each time replaced by a new extension of the Azores High over the UK.

 

NAVGEM refuses to let go of it's notion to maintain Low pressure close to the East Coast slipping South then West along the English Channel where it reinvigorates into a showery Low affecting the South while the North and west all this time see a lot of dry and bright if not sunny weather.

 

ECM tonight looks a lot like UKMO with a few weak troughs moving SE across the UK followed by renewed High pressure ridging in from the West over the latter stages of next week and weekend. So dry and fine for much of the time with short-lived bands of light rain crossing the UK in average temperatures. Things do show signs of settling down more meaningfully late in the run as High pressure builds over the UK from the West.

 

In Summary the weather over the UK is still far from clear cut as we move through next week. High pressure remains permanently locked down in the SW, close enough to snub the life out of fronts moving SE over the UK next week but not close enough to bring us back properly into fine and sunny weather with rather benign conditions the most likely outcome for much of the time.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

[Joe8987]

Unless i'm mistaken we have had charts showing extended warm/hot spells for at least the last month and none of them have really come to fruition. 

[draztik]

Unless i'm mistaken we have had charts showing extended warm/hot spells for at least the last month and none of them have really come to fruition.

to some extent, that is true. We have seen temps reduce as we get closer to the time, but only slightly. Its to be expected, as we move further into September and the atmosphere continues to cool. I am not one to often agree with Frosty, but his assessment of a decent 3-4 week spell is not without support, esp given the gfs ens and ec32 (to some degree), give the impression of ridging throughout. There are some who question whether HP will remain dominant, citing the MJOs shift into phase 1. But, based on the long term ensembles, as they currently are, parts of England & Wales especially, could enjoy some late 'summer' weather as we move forward. (tho, as we have seen recently, the models can have their 'freakouts', and change rather quickly... lets see how next week turns out, and see the extent of the ridge, before we consider late Sept).. But as ever, we can only assess the models as they currently are. Edited September 7, 2013 by draztik

[Tamara]

re this from frosty, the end of his post

south of the uk being best placed for the most good weather in the next 2-4 weeks although the north should also join in the settled spell as time goes on.

 

I suspect this is a touch of hopecasting as nothing I can see suggests this is more than about 50% likely and even less than that % for the north. Read the Met O 6-15 and 16-30 day updates CAREFULLY, neither do they suggest that and the anomaly charts do not support the inference of 2-4 weeks settled weather, 2 weeks perhaps for some southern districts is the most one could expect looking at any model outputs from whatever source, in my estimation at any rate.

I suspect that the very large temperature differences being suggested on the GFS model at least (at 850mb) will generate quite large depressions running in the usual area to the south of Iceland by early October if not before, bring unsettled spells to the NW'ern half and even at times to the rest of the UK.

 

As well as that proviso at this time of the year all it needs is for a major hurricane to develop and recurve out into the Atlantic and any model or any forecaster is going to be wrong. Thanks to the enormous amounts of energy they release NONE of the models are much good at long time scales in picking these up let alone getting their tracks correct if they do get into the Atlantic.

 

sorry if this sounds a sour puss type post but it is an honest  opinion with a lot of experience behind it.

As ever I may be wrong and have yet more egg on my face!

If I am honest there is uneccesary splitting hairs in picking that quote Whilst it indeed might be an honest post based on a lot of very good experience, the evidence it is based on is as potentially unreliable in the current cyclical pattern as the quote picked on itself is made out to be 

 

My own view is that this cyclical pattern of the main/latter part of this summer is as entrenched as the one that led well into Spring and took so long to dislodge. And of course it did eventually..and this one will too..eventually.

 

But much as snowking posted yesterday, it is a case of when the longwave patterns in the NH starts to change the pattern. I (very humbly ) think it may take a little longer than some expect

 

The latest EPS members from the 12z suggest the same situation out close to a week and more with the same promixity of the Azores/atlantic High as seen for some very considerable time,and also as we have seen in the last 24 hrs, some tone down adjustment of the longevity of the shallow troughing weakness ahead of the atlantic ridge.

 

 

On the basis of persistent model error with the progressiveness of trying to dig the trough south for so long and over amplify the pattern, and the background pattern supportive of renewed rinse and repeat then a (cooler than we have seen) north/south split and then some renewed more general mid latitude ridging is quite feasible as the month progresses. Indeed as far as I was aware the METO see that as a possible prognosis themselves in the further outlook. I would personally rather trust the hemispheric feedback signal (until there is at least more confidence in seasonal longwave patterns) over model anomaly conundrums which have already proved to have flaws and false dawns in their attempts to progressively influence the models

 

The METO are not able to forecast hurricanes or any related tropical hurricane developments within the paramaters/time periods that are made relevant here in NWP, so such a caveat applies to any pattern at this time of year and thus without adding some kind of *disclaimer* to every forecast that is issued about such tropically originated activity, it seems to me to be quite sensible to retain it on a working assumptive back burner

Edited September 7, 2013 by Tamara Road

[No Balls Like Snow Balls]

Erm let me see...driest summer in england since 1995/96....hottest July since 2006, hottest august day since 2003, hottest september day for 7 years..warmest, driest and sunniest summer since 2006.

So no records broken then, just the hottest / driest etc in recent times. A record is for instance the hottest / coldest day ever recorded. its a bit misleading to be honest.

[Man With Beard]

Disagree that non of the warm/hot spells came off - we had 3 weeks virtually unbroken good weather on the south coast before Friday - exceeded 25C on 7 occasions in that time, pretty warm for late Aug/Sept.

Back to the models, I would agree though that no excessively warm weather looks likely - westerlies/nwesterlies the most likely outcome based on current trends, once the trough clears east?

Edited September 7, 2013 by rjbw

[Frosty.]

Disagree that non of the warm/hot spells came off - we had 3 weeks virtually unbroken good weather on the south coast before Friday - exceeded 25C on 7 occasions in that time, pretty warm for late Aug/Sept.Back to the models, I would agree though that no excessively warm weather looks likely - westerlies/nwesterlies the most likely outcome based on current trends, once the trough clears east?

I think we could get winds sourced from a southwesterly tropical maritime direction when the azores/atlantic anticyclone builds in during mid to late september. Edited September 7, 2013 by Frosty.

[Frosty.]

The Gfs 00z operational run brings a good deal of fine and pleasantly warm weather to the southern half of the uk thanks to the azores/atlantic anticyclone extending a ridge across the south but the north of the uk is more exposed to a more atlantic pattern with more in the way of unsettled weather at times. I got the sense when flicking through the charts that the azores/atlantic anticyclone is itching to have the opportunity to take control and waiting for things to quieten down in the iceland region where a sequence of vigorous depressions are pushing east, there is a lot of ebb and flow as the high tries to gain the upper hand and occasionally it does, at least across england & wales with some warm days with light winds and overnight fog but with occasional unsettled days but most of the rain on the gfs 00z along with the stronger winds is mostly restricted to the northern third of the uk.

[mushymanrob]

. Now the moddels i hope they start showing autumnal weather soon.

 

take a look at them, it is autumn, what they are showing is typical early autumnal weather...

 

Some areas have actually had their best summer since 1995 too.

 

"some areas" being the operative two words... summer 2013 wont go down overall in history as a truely great summer because it wasnt nationwide.

 

cant see anything much other then pretty normal early autumnal weather on offer. some runs suggest warmer/drier, other runs dont, but the anomaly charts and mjo dont offer any real hint of anything settled, warm, or sunny.

[bluearmy]

the current theme is for the azores ridge to continue to affect the uk whilst shallow troughs work their way around and interrupt the broadly 'settled' conditions (on a sliding scale N to S). The depth of the troughing continues to be the difficulty for the nwp. the propensity for a mid month deep depression north of scotland is still there and so is the more extensive build of heights thereafter.

Edited September 8, 2013 by bluearmy

[Frosty.]

The Ecm 00z operational run shows a nice ridge of high pressure pushing into the uk by midweek and displacing the filling shallow trough with a few days of fine and increasingly pleasantly warm weather with temperatures recovering into the low 20's celsius across the southern half of the uk, the ridge holds across more southern areas but it turns more unsettled across the north of the uk for a time before another ridge pushes northeast. The best of the weather is across england and wales with warm sunny spells and light winds but with chilly nights and dense patches of fog forming, this is also true of tonight where thick fog and even a touch of ground frost is likely to develop after the scattered sharp showers die out this evening. Looking further ahead, the ecm 00z shows an unsettled interlude but atlantic high pressure is always waiting in the wings to push across.

Edited September 8, 2013 by Frosty.

[Summer Sun]

UKMO continues to show the Azores controlling our weather by next weekend

 

 

ECM in FI shows a deep low crossing the north but this is not the first time its shown something similar to this only for it to shift it further north away from the UK closer to the time

 

 

Once the low clears high pressure rebuilds once again

 

[Frosty.]

The GEFS 00z mean turns into an absolute peach of a run during the second half of september with increasingly anticyclonic weather for most of the uk with long sunny periods and light winds with temperatures into the low 20's celsius, perhaps nearer mid 20's c across more southern areas but under clear skies, thick patches of fog are likely with minimum temps into the low to mid single digits celsius. In the meantime, the week ahead shows a gradual improvement which is generally sustained across the far south with a lot of fine and pleasant weather but with overnight fog, eventually becoming progressively more unsettled across the north of the uk for a while before the azores/atlantic anticyclone builds in across the uk, in the longer term, things are looking very good for those of us who like fine and warm weather with the PFJ forced to retreat well to the northwest/north later, there has been no downgrade in the mean, the trend towards a warm and fine further outlook is very much intact.

[Summer Sun]

Here is the latest from Gibby on this sunny Sunday morning

 

Good morning. Here is the report on the midnight outputs for the UK from the outputs of GFS, UKMO, GEM, NAVGEM and ECM for today Sunday September 8th 2013.

 

The General Situation. The UK lies in a slack Westerly flow with Low pressure over Northwest Britain. Through today and tomorrow this transfers East and weakens as a trough swings East over England and Wales with showers, heavy and thundery in places. Through the early days of the week the weather will become largely dry in the West bt with a few more showers in the East as Low pressure lurks over the low Countries for a time. It will be quite cool especially by night and under the showers. By midweek a ridge covers the UK before a weak cold front crosses SE later with some occasional light rain for a time before the end of the week looks like the weather will become dry again with the ridge from the SW re-establishing itself again, especially across the South.

 

The Fax Charts show a complex and showery Low pressure area simplifying over the next 24 hours or so as the whole system pushes bodily South and East to take most of the showers away with it. Things are shown to take longer to dry up in the extreme east before a ridge topples over the UK midweek and in turn followed by a series of weak fronts over the latter half of the working week turning things more cloudy with some drizzly rain for a time in cloudy and quite chilly feeling West to NW winds.

 

GFS then shows a spell of rather cloudy West to NW winds over the UK lasting several days with the North most at risk of occasional rain as weak troughs pass by. the South would maintain a lot of cloud with only limited brightness but little if any rain in temperatures close to average. This pattern persists for a time before High pressure to the South slides East and leads to a more definitive trough to move West to East over the UK later with some showery rain for all before High pressure builds back close to the West once more to end the run with any remaining showers limited to the extreme East under a cool Northerly breeze while elsewhere becomes dry and fine but cool especially at night.

 

The GFS Ensembles show a good consensus of agreement over the next 5 days or so before the spread between members becomes quite large. The general message though is that the greatest risk of rain is reserved for the north with the South seeing very little and just occasionally. The operational was a warm outlier in the South yet again with temperatures overall trending close to average for mid September.

 

The Jet Stream shows the flow troughed down over the UK at present which weakens steadily over the coming days as the Jet flow re-establishes itself flowing West to East over or to the North of Scotland in response to the Azores High ridging NE to Britain.

 

UKMO today shows the Azores High elongated towards the UK early next weekend with a mostly dry week ahead interrupted by a brief cold front giving a little rain over the UK for a time before fine and dry conditions look like returning again in time for next weekend.

 

GEM today shows a West to NW flow too with a cold front clearing SE early next weekend. Thereafter the North would see the main share of further rain from further injections of Atlantic low pressure which does extend further South at times but on the whole the South and SW would continue to see the best chance of staying largely dry and at times bright.

 

NAVGEM finally joins the suite too finally giving up the idea of the Low hanging around to the South this week in preference of a cold front moving SE at the start of the weekend then setting up a fresh NW flow with a lot of cloud but only a little rain this chiefly in the North.

 

ECM is quite similar but does show a more vigorous Westerly flow developing later next weekend as a deep Low moves East to the North. So after a benign weak with just a little rain on a cold front towards the weekend the weather will turn windier and wetter in the North for a time before fine weather returns yet again behind another  weakening cold front moving SE giving just a little rain to the South ahead of another ridge from the Azores High. 

 

In Summary it looks like another period when the Azores High is going to continue to rule the roost as regards the weather over the UK with any attempts to bring more unsettled weather down from the NW rather weak and reserved mostly for the North. With winds from the West or NW for much of the time and given it is now September temperatures are unlikely to be much if any above average but with no cold air to tap into conditions would be workable for many though cloud amounts look likely to be large at times. So after today's and tomorrows potential sharp showers things turn benign for the foreseeable future with little interesting synoptics to talk about currently.

 

http://www.norton-radstockweather.co.uk/Model-Analysis%282859336%29.htm

Edited September 8, 2013 by Summer Sun

[William of Walworth]

 

 

cant see anything much other then pretty normal early autumnal weather on offer. some runs suggest warmer/drier, other runs dont, but the anomaly charts and mjo dont offer any real hint of anything settled, warm, or sunny.

Current operational output contradicts this at least to some extent though (see examples from Frosty and Summer Sun above). Are you saying that the anomaly charts etc are contradicting the idea of ongoing HP influence altogether? I'd be interested to see what you think of Tamara's analysis further up, she reckons HP will remain  a significant player as the month goes on, Of course there's likely to be interruptions to this at points, especially in the North, but I'm seeing a fair bit of benign weather on the cards for many. No heatwave of anything, but some perfectly pleasant September weather a reasonable hope at least, surely.

Edited September 8, 2013 by William of Walworth

[Summer Sun]

Average to slightly above temperatures and little in the way of rain sums up things for the foreseeable future this morning

 

[Frosty.]

Current operational output contradicts this at least to some extent though (see examples from Frosty and Summer Sun above). Are you saying that the anomaly charts etc are contradicting the idea of ongoing HP influence altogether? I'd be interested to see what you think of Tamara's analysis further up, she reckons HP will remain  a significant player as the month goes on, Of course there's likely to be interruptions to this at points, especially in the North, but I'm seeing a fair bit of benign weather on the cards for many. No heatwave of anything, but some perfectly pleasant September weather a reasonable hope at least, surely.

Spot on William, perfect summary there.

[Frosty.]

The GEFS 00z control run turns into a stunner, it's the closest we could get to a mid/late september heatwave with temperatures widely of 25 celsius plus, some parts of the south would reach the high 20's celsius or even 30 celsius, yes it's that good, the anticyclone position enables very warm/hot air to drift up from southern europe, since temps in the uk can breach 80F in october, this run would bring a glorious spell of summery weather as autumn deepens. In the shorter range, a gradual warming trend and settling down after a showery start, then more unsettled across the north but high pressure holding across the south, the azores/atlantic ridging has to roll with the punches for a time as deep lows track east from iceland but the pay off is worth it, even if this run is an extreme version of what actually develops, the latest GEFS mean is showing a warm, benign and sunny further outlook as it is.

[No Balls Like Snow Balls]

Even though HP seems it's gonna be the major driving force down South for next week, it doesn't mean however that we will be basking in wall to wall sunshine and warm temps. It looks like there will be large amounts of cloud around, and the below precip charts illustrate that even the South is not immune from rain.

 

 

 

 

With the latest 5 day Met Office forecast showing max daytime temps of 15c, 17c, 17c, 16c and 18c for various locations it wouldn't feel particulary warm once the sun disappears behind any cloud even if it manages to appear at all.

 

 

 

 

 

 

[draztik]

what is this i see! Tho, as its at t360... Usual caveats apply! But at least this is interesting, as opposed to the benign weather on offer over the next 10 days or so

[ANYWEATHER]

A cool, changeable week coming up for just about all ,with the uk sandwiched between high pressure to the west and low pressure to the east. So feeling very much like the Autumn season that is now upon us. Certainly not a wash out week, but rather a lot of cloud feeding from the Atlantic and indeed from the North sea for Eastern parts on Tuesday. 

[Frosty.]

Taking a snapshot at T+144 hours, all the models show the azores/atlantic anticyclone building a ridge eastwards across the uk, the ecm & ukmo 00z look to be rather more advanced in this development but the others are not far behind, anyway it's the trend which is most important at this range, I think there is plenty to be encouraged about looking ahead to the second half of the month, it could be a very nice spell on the way once the azores/atlantic high gets it's chance to build in strongly.