Model Output Discussion 22/07/12 Onwards.

[Bristawl Si]

Well the GFS has LP ending-up somewhere near Iceland, which isn't exactly unheard-of...So I can't see anything other than an improvement in our fortunes. Away from the very far NW, perhaps?

Things do seem to be improving for the medium term (thankfully the awful weather of June and upto mid-July has not made a reappearance)

and TWS's great 'call' for a mainly sunny 'high' for next 3 days, rather than a cloudy one as called by a couple of other posters, looks like coming to fruition as well.

[shedhead]

As expected the 06GFS has moved away from it's 00 evolution and is now far more in line with UKMO, indeed it's even drifted a fair bit closer to ECM. Scandi high in place, but with LP so close

frontal troughs look almost certain to move northeastwards at times, which is much more in line with the 500mb forecast chart posted by JH last nite.

GFS

ECM

UKMO

Edited August 9, 2012 by shedhead

[Glacier Point]

Looks like the punt for a warmer second week for August will be landed..

Intriguing model proposition at the moment. Our deep upper low forecast west of Ireland next week has not got the upsteam umph to make it across the UK and will be held back by the blocking ridge to our NE. Potential for rain bands and showers across the UK still there, although the details here highly uncertain.

Looking ahead, with the trough held west, something of a standoff developing, and I suspect general fizzling of the upper low allowing for a noticeable rise in pressure over mainland Europe. GEFS means starting to really go for a noticeable deep and expansive upper low covering huge area of eastern Asia which should condense any four wave pattern down to three, allowing for pressure rise in the North Atlantic to merge with upper ridge over Europe. Interesting that the last 3 updates by CPC have expressed next to zero confidence in details upstream due to conflicting tools and I suspect we're entering a volatile period of modelling across the hemisphere... should be able to give a better informed view once angular momentum budgest and MJO forecasts update tomorrow.

Edited August 9, 2012 by Glacier Point

[Snowyowl9]

Interesting runs today well the GFS 0z certainly is with the warm S-ly humid theme into next week,and thundery conditions,looking like the most thundery august since 2004.

And that starts sunday.

http://www.wetterzen...ics/brack2a.gif

But a stunning few warm/very warm days until then.

[Frosty.]

I have chosen these two charts to highlight the very best and worst of the weather we can expect in the next week or so, the ecm is by far the worse in FI compared to the gfs 06z which is a much more friendly run for the south and southeast next week whereas the ecm shows pretty much a cooler, windier and wetter spell practically nationwide at times with a cooling autumnal looking trend out to T+240 hours, the 6z does show a breakdown and some unsettled weather next week but most of it in the north and west with the southeast doing much better, everything depends on the track of the depression spreading northeast next tuesday. The next few days look very warm and fine for the majority of the BI with temps around 25c but hotter in the se at 27-28c, some overnight patchy mist/fog but soon burning off to bring lots of sunshine and just some fair weather cloud bubbling up but on sunday it looks like showers will be spreading from the southwest, some heavy and thundery, reaching the north sea coast by sun night.

Edited August 9, 2012 by Frosty039

[mushymanrob]

If this evolution continues, I think we could start to focus on the ridge to the west giving way for hight rises to our NE and E which opens up the potential for a very topsy turvy August - cooler and unsettled to start, warm and sunny to finish ?

my... looking like you called this one right!

[East_England_Stormchaser91]

Corr, look at them winds up from the mid sahara maybe into next week! Now that tells me that temps will defo reach 30+, no 2 ways about it!

[Gavin P]

Here's todays much delayed (thanks YouTube) model based video:

Next Weeks Weather Up In The Air? http://www.gavsweathervids.com/

Trough to the west/Ridge to the east = A lot of uncertainty.

[SP1986]

The 12z positions the trough a fair bit eastwards than previous runs, allowing cooler, and consequently wetter airmasses and systems in, This is not a great surprised however, it's such a frequent occurrence that most model position are pushed east when Atlantic lows are present that we probably realistically should expect this. Given we have not got meridionality or any other similar pattern at the moment, low pressure affecting the UK in close quarters or over the UK (which I think eventually will evolve to), is the only real possible outcome.

So I would expect many runs now to start pushing everything a little further east each time, afterall it's fairly normal for the elevated pressure to sit over central Europe, allowing low pressure to move over the UK, this may in time signal a lowering of the jet stream too, lattitudinally speaking.

The rather huge downside to this is, if the low pressure system does end up sitting with the western half over the UK, and with a rigid high pressure over Europe then providing the low has a short fetch of returning polar maritime air, we could actually be looking at a serious amount of rainfall in western, and northwestern areas (coupled with below average temperatures).. this is the not so good outcome of such a pattern. We definitely need the low to be kept out west of to track towards northern Norway, otherwise the outlook may not be so wonderful away from the far southeast.

[mushymanrob]

The 12z positions the trough a fair bit eastwards than previous runs, allowing cooler, and consequently wetter airmasses and systems in, This is not a great surprised however, it's such a frequent occurrence that most model position are pushed east when Atlantic lows are present that we probably realistically should expect this. Given we have not got meridionality or any other similar pattern at the moment, low pressure affecting the UK in close quarters or over the UK (which I think eventually will evolve to), is the only real possible outcome.

So I would expect many runs now to start pushing everything a little further east each time, afterall it's fairly normal for the elevated pressure to sit over central Europe, allowing low pressure to move over the UK, this may in time signal a lowering of the jet stream too, lattitudinally speaking.

The rather huge downside to this is, if the low pressure system does end up sitting with the western half over the UK, and with a rigid high pressure over Europe then providing the low has a short fetch of returning polar maritime air, we could actually be looking at a serious amount of rainfall in western, and northwestern areas (coupled with below average temperatures).. this is the not so good outcome of such a pattern. We definitely need the low to be kept out west of to track towards northern Norway, otherwise the outlook may not be so wonderful away from the far southeast.

yeah, its disappointing if you are hoping for something similar to the current weather, the gfs insists on the atlantic winning . pity.

[SP1986]

Well we'll have to wait for the UKMO and ECM, but the GFS is a very good trend setter in most cases, and it's been toying with this idea for a few days on and off, so it must have some 'mettle' to it. However if it is to become the new trend, I wouldn't expect the ensembles to pick up on it yet, as a whole.

[mushymanrob]

Well we'll have to wait for the UKMO and ECM, but the GFS is a very good trend setter in most cases, and it's been toying with this idea for a few days on and off, so it must have some 'mettle' to it. However if it is to become the new trend, I wouldn't expect the ensembles to pick up on it yet, as a whole.

well the mjo is taking a dive into neutral, after passing phases 7, 8, 1, if it had got to 2 we might have had some hope.

[Frosty.]

A disappointing Gfs 12z for those looking for a sustained spell of high pressure, the gfs shows an angry looking low to the west of the BI towards midweek and next week in general looks unsettled with heavy rain scattered across the uk on nearly every day next week. The current anticyclonic spell looks like fragmenting by sunday with bands of showers spreading northeast, some heavy with thunder but with a lot of dry and bright weather too. Early next week indicates a band of persistent rain spreading north and east across all areas followed by a mixture of sunshine and showers with some longer spells of rain. The gfs further into FI shows atlantic high pressure building with a trough dropping southeast into the uk and higher pressure to the south and east of great britain.

[SP1986]

The GFS ensembles and UKMO show a return to wet and relatively cool conditions mostly, but not exclusively for western parts of Britain. This is hard to argue against as the GFS and UKMO outlooks (plus the GFS ensemble mean) are exactly the same.. so it looks very likely it will actually occur, unfortunately, carrying on the familiar GFS evolution, post warm spells.

[Summer Sun]

Hot end to ECM

Edited August 9, 2012 by Summer Sun

[shedhead]

The GFS ensembles and UKMO show a return to wet and relatively cool conditions mostly, but not exclusively for western parts of Britain. This is hard to argue against as the GFS and UKMO outlooks (plus the GFS ensemble mean) are exactly the same.. so it looks very likely it will actually occur, unfortunately, carrying on the familiar GFS evolution, post warm spells.

Agreed, a 2 or 3 day blip a Summer does not make. Must confess to being a little surprised quite how far GFS has drifted towards ECM during it's last two runs, but as you say it's now becoming very hard to argue against a return to largely usettled conditions across central and western areas in particular, tho no doubt some will continue to do so...

On the plus side, with winds predominating from a southerly quater temps at least should be near or above the seasonal average, meaning it should feel very pleasant in any sunshine and not exactly unpleasant under a full cover of cloud,

Edited August 9, 2012 by shedhead

[jessandjon]

any chance of thunderstorms in plymouth area over the weekend???

[tinybill]

Corr, look at them winds up from the mid sahara maybe into next week! Now that tells me that temps will defo reach 30+, no 2 ways about it!

well looking at the charts deep in to fantasy world don't take bets any time after August 12 our summer coming to an end

[WheresTheSnow]

GFS + ECM not looking good tonight then. What I said before was wrong.

Edited August 9, 2012 by WheresTheSnow

[Polar Maritime]

well looking at the charts deep in to fantasy world don't take bets any time after August 12 our summer coming to an end

Yes GFS is showing very cool temperatures, with winds from the N/E out into FI.

[OldMetMan]

It seems to be the "3 fine days and then a thunderstorm" situation we're in at the moment.

The current HP strengthening over and to the E of the UK at the moment is a little more developed than was shown by the models earlier in the week, but the theme of keeping it transitory remains, with some consistency, across the models today. Thereafter, a new significant LP development looks likely to our W sweeping the remnants of the current LP to our SW, NE across us, accompanied by what I think is a strong possibility of thunderstorms.

Over N America, there are some shifts in the 500mb flow that are interesting. The persistent upper high is retrogressing to the W and there is now a stronger, more southerly positioned and growing amplitude upper low over Canada, extending down the US east coast. Downstream it seems to be setting itself up for a Rex block, but not one in our favour, with the upper high well north of us and the upper low close by. At the surface, with hot air on the near continent, there is considerable potential for thundery downpours with any frontal or trough activity.

I've mentioned from time to time the influence of the tropical Atlantic on the patterns here and interestingly the GFS, a long way ahead admittedly, is showing a low, clearly of tropical origin that is forecast to become quite a vigorous extra-tropical LP heading our way. There is currently much potential tropical storm activity developing and it looks as if the upper flow over the Caribbean is changing and likely to turn any storms poleward rather than due W as has just happened with hurricane Ernesto, which, at this stage at least, would only enhance the LP dominated weather here..

So, all things considered and given the consistency across the models, unsettled seems to be the key word. The quite intense HP forecast to extend from Scandinavia across to Greenland I find intriguing for this time of year - not that it helps us any! I stick by my opinion that late August and September will see things settling down - ex-tropical storms notwithstanding!

Edited August 9, 2012 by OldMetMan

[WheresTheSnow]

Ive only just started reading the models but my interpretation of the 18z is that, the weather will become more unsettled next week with that low pressure moving in, maybe the East & SE having the best of conditions, maybe? One thing I can see for sure is that in FI high pressure builds over the UK, of which the 12z didnt show! Sorry if thats completly wrong, still trying to understand how to read the charts!

[johnholmes]

Don't knock yourself, everyone has to learn so keep making posts with your view on what the charts are showing. Just don't fall into the habit some have of 'cherry picking' for your favourite weather!

By the way I only glanced at the 18z but your summary seems okay to me.

Have a look in the Guides section, there is one in there somewhere about how to use GFS to do your own forecast and lots of other guidance on various weather issues.

oh and ask if you are not sure, most folk are happy to try and help and I'm always happy to chat via pm if you prefer it that way.

not sure what happened their probably jh finger trouble!

my rough notes on ECMWF-GFS 500mb outputs this morning.

Ec-gfs

Both quite similar this morning with +ve and –ve areas and orientation/position of ridge/trough

They do suggest to me an unsettled outlook with almost a nw-se split, some warm interludes for the se look possible less so for the nw which will be breezy at times I suspect as lows track from sw-ne north of Scotland

and the link

http://www.meteo.psu...0z/hgtcomp.html

The consistency does give credence to the overall prediction of an unsettled mix of weather into the 3rd week of August, possibly longer but certainly no wash out for southern areas and not totally bad for the NW, some drier brighter slots likely between weather systems.

that is a bit simplistic but the overall pattern is being set if you look at the link.

both of them and noaa are being pretty consistent with the idea of the trough - ridge set up and also how the pattern is being predicted well upwind(states area)

Edited August 10, 2012 by johnholmes

[shedhead]

Hard to argue with any of the above from JH, so little point in reiterating it. Forecast wise it's far from a write off next week, but all areas do look likely to see some rain or showers at times, lightest and most scattered for the SE, heaviest and most frequent across the NW.

Looking at the longer term, confidence in my own prediction of a pattern chance for the last week of the month remains low; in fact I now think it will be September before we see an improvement that offfers the prospect of more than 2 or 3 fine days back to back.

The latest 500mb anom chart for the start of the final week of Aug continues to look very familiar...

Edited August 10, 2012 by shedhead

[TonyH]

Well since the latter part of July we have been getting decent warm to hot interludes such as this, and contrary to some prevalent posters this spell is a sunny one.

The so called pattern change to me therefore was in mid July. Plenty of dry or mostly dry days since then, all in all much more of a typical average summer pattern since the cool rains that prevailed to mid july.

More of this next week too with rain or showers at times, but decent dry sunny spells and warm between times.