Model Output Discussion 18z 28/07/13

[Frosty.]

A much warmer week ahead according to the Gfs 12z operational run, becoming very warm across southern britain as these maps show and pleasantly warm right up to the northern tip of scotland, it also looks like becoming sunnier from the south as the week goes on but with a midweek unsettled blip across the northwest corner of the uk before the summer warmth and sunshine arrives. Most of the uk having a fine spell but with isolated heavy showers popping off here and there but many areas enjoying a lot of very warm sunshine, temperatures into the 80's F for the south during the second half of the week, 28-30 celsius for the south/se and feeling increasingly sultry as we import continental air into the south of the uk but then during the weekend, this run shows bands of thundery rain swinging northeastwards across the uk and scattered thundery showers but still with warm sunny periods and temps into the low to mid 20's celsius, Bank holiday monday would be a potentially stormy day with outbreaks of heavy and thundery rain across most of the uk. I have no complaints about what this run shows for the week ahead, it's going to be a lot warmer than recent times and FI is not decided on the basis of an op run, the ens mean gives a truer picture.

[bubsy83]

What is FI?

[Methuselah]

What is FI?

Fantasy Island...The far reaches of what the models say; it is usually not worth considering... 

[ribster]

Well GFS has churned out some interesting runs today, nothing special showing any of them, except standard late August weather. Would be surprised if countryfile forecast mentions anything other than that.

[Captain Shortwave]

Well GFS has churned out some interesting runs today, nothing special showing any of them, except standard late August weather. Would be surprised if countryfile forecast mentions anything other than that.

Well the bbc/met will use a mix of NAE and UKMO data for the forecasts (standard stuff) which looks a lot drier than the GFS. 

This coming week looks decent, especially down in our area, sunny days and a pleasant south west wind, veering south east during the week. Nothing spectacular temperature wise but mid-high twenties inland by the end of the week. Not too bad. 

@Busby welcome to the model thread and as stated already FI is fantasy island, where all the interesting weather ends up, whilst we usually end up with a borefest. Lucky sods 

Edited August 18, 2013 by Captain shortwave

[Ian Brown]

Past experience tells me that the GFS is overdoing the spoiler trough, it picks up a feature and then aggressively over develops it post T96.

I think it much more likely that the feature is further SW and that pressure will build over the UK linking with the Scandi HIgh.

[Frosty.]

I think we should treat the week ahead as a Bonus warm spell at the end of a generally very good summer, the GEFS 12z mean shows the big warm up with temps soaring into the 80's F, especially for thurs/fri across the south of the BI but with a shallow trough moving in for the weekend, it also shows the PFJ shunted up into the arctic which is good to see, the shallow trough at the end of the week would mean a weekend of sunny periods and heavy thundery showers and we will still have a residual pool of very warm and humid air in situ, the shallow trough then slowly fills with the showers then becoming more isolated as weak ridging begins to extend eastwards from the atlantic anticyclone. So at least it's less bad than the op run shows in low res. It's going to turn warmer everywhere in the coming week, very warm or hot across wales, the midlands, east anglia and southern/se england with high 20's to low 30's celsius, nearer low to mid 20's c for northern england, n.ireland & scotland and the subsequent weather beyond the next 7-10 days is currently uncertain, enjoy the taste of summery weather and don't fret about the outlook would be my advice.

[Captain Shortwave]

ECM backing the UKMO

The rest of the run should be pretty tasty

Edit - Unless I've jinxed it 

Well I don't know what to say to this

ECM blows up a low to our north and blitzes the pattern

Edited August 18, 2013 by Captain shortwave

[DAVID SNOW]

I think we should treat the week ahead as a Bonus warm spell at the end of a generally very good summer, the GEFS 12z mean shows the big warm up with temps soaring into the 80's F, especially for thurs/fri across the south of the BI but with a shallow trough moving in for the weekend, it also shows the PFJ shunted up into the arctic which is good to see, the shallow trough at the end of the week would mean a weekend of sunny periods and heavy thundery showers and we will still have a residual pool of very warm and humid air in situ, the shallow trough then slowly fills with the showers then becoming more isolated as weak ridging begins to extend eastwards from the atlantic anticyclone. So at least it's less bad than the op run shows in low res. It's going to turn warmer everywhere in the coming week, very warm or hot across wales, the midlands, east anglia and southern/se england with high 20's to low 30's celsius, nearer low to mid 20's c for northern england, n.ireland & scotland and the subsequent weather beyond the next 7-10 days is currently uncertain, enjoy the taste of summery weather and don't fret about the outlook would be my advice.

 

 Hello frosty often read your posts, just one thing though, I cant see where you are getting "low 30's Celsius" from? The GFS shows this?

[Man With Beard]

These shortwaves are a pain to get right until T72ish, even T48. In the big picture, the charts below all show the same thing - a small trough, probably thundery, pushing through the UK next weekend introducing (eventually) fresher air behind. In our local UK picture, the small differences that each T144 chart shows make a big difference - the UKMO would suck up warmer air from the south-east with probably less of a breakdown, the GFS is probably quite wet, the ECM is somewhere between the two and GEM has a straight-forward frontal change of air mass.

 

One thing they all agree on - next weekend will not be completely settled.

 

 

 

 

[Captain Shortwave]

If it's worth any value the BOM and JMA go with an output similar to the UKMO

 

 

Just out of generic interest I might as well post the T192 charts for both to see what the UKMO could end up with beyond day 6

 

JMA is fantastic

 

So is the BOM

 

Though saying that I don't think this info is of much use. 

What will the weather be like this bank holiday weekend... answers on a postcard. I haven't got a flipping clue.

Edited August 18, 2013 by Captain shortwave

[Frosty.]

Hello frosty often read your posts, just one thing though, I cant see where you are getting "low 30's Celsius" from? The GFS shows this?

It's just potential, the gfs often undercooks max temps as it did in july during the hot spell. Edited August 18, 2013 by Frosty039

[Frosty.]

Hey the Ecm 12z is not bad at all, a very warm and fine spell followed by a humid thundery weekend and then the azores/atlantic anticyclone building in again, that's a lot better than the gfs 12z is showing, the ecm is rinse and repeat.

[Man With Beard]

Hey the Ecm 12z is not bad at all, a very warm and fine spell followed by a humid thundery weekend and then the azores/atlantic anticyclone building in again, that's a lot better than the gfs 12z is showing, the ecm is rinse and repeat.

I'm not sure I see this the same way - yes pressure builds in at T240 but the heart of the HP remains far from us, it isn't clear if it would move in or stay there - the latter option leading to a less warm NW flow.

Hope you're right though!

[Frosty.]

I'm not sure I see this the same way - yes pressure builds in at T240 but the heart of the HP remains far from us, it isn't clear if it would move in or stay there - the latter option leading to a less warm NW flow.Hope you're right though!

It would be a lot better beyond T+240 hours if this was the trend but I don't think the models have got the end of the week nailed yet, the only guarantee is it's going to become very warm and humid across the southern third of the uk by the second half of the week, confidence then drops sharply in my opinion.

[Frosty.]

ECM backing the UKMO

The rest of the run should be pretty tasty

Edit - Unless I've jinxed it 

Well I don't know what to say to this

ECM blows up a low to our north and blitzes the pattern

yes you jinxed it captain

[J10]

ECM not too bad at all tonight. Keeping the worst of the trough to the south of the UK, and then moving it east pretty quickly.

 

GFS

 

GEM

 

UKM

 

ECM

 

Comparing the 4 main runs at T+144.

GFS the worst at T+144, UKM the best and ECM closer to UKM than GFS, GEM has the whole pattern further east.

 

Has GFS overblown this feature, wouldn't be the first time.

Edited August 18, 2013 by J10

[Frosty.]

Looking at tonight's Ecm 12z op run in more detail, it's pretty good overall, the southern half of the uk warms up significantly and parts of southern/se england become hot, not only that, humidity increases as we develop a SE'ly flow which draws continental air into the uk, so it turns sunnier and progressively warmer, locally hot but midweek brings a spell of rain and stronger winds to the far northwest of the uk, then becoming settled for a few days and the weekend brings a shallow trough into the very warm and muggy airmass over the uk, this would mean a thundery weekend with some big storms and very warm and muggy with hazy sunshine, then briefly cooler early the following week but then trending warmer and more settled again as pressure rises from the southwest, I would take that, there is only 1 cool day and that's only a glancing blow across the northeast of the uk..some very summery charts here during the next 7 days.

[Captain Shortwave]

yes you jinxed it captain

Sorry 

Hopefully the ECM ens will be better

[East_England_Stormchaser91]

Looking at tonight's Ecm 12z op run in more detail, it's pretty good overall, the southern half of the uk warms up significantly and parts of southern/se england become hot, not only that, humidity increases as we develop a SE'ly flow which draws continental air into the uk, so it turns sunnier and progressively warmer, locally hot but midweek brings a spell of rain and stronger winds to the far northwest of the uk, then becoming settled for a few days and the weekend brings a shallow trough into the very warm and muggy airmass over the uk, this would mean a thundery weekend with some big storms and very warm and muggy with hazy sunshine, then briefly cooler early the following week but then trending warmer and more settled again as pressure rises from the southwest, I would take that, there is only 1 cool day and that's only a glancing blow across the northeast of the uk..some very summery charts here during the next 7 days.

Once again frosty, outstanding detailed forecast! Looking very forward to this now. My favourite weather of all (humid and very thundery) looks set to take place this weekend. Would be fantastic to have a last real good shot at getting some cracking pics in . Sorry if its more convective thread talk, but with these outputs, I just can't help it!

[forecaster]

The EC rainfall field doesn't paint a pretty picture over the south of the UK on the weekend. It looks plausible that it's more broadscale rain associated with an occlusion rather than purely convective sunshine-and-showers type weather. I do find it hard to see positives in that, so hopefully it would change on later runs! The 850hPa temperatures max out at 12/13C (from Saturday) on that run which is not very inspiring if you don't have a dry boundary layer.

[BlueHedgehog074]

Even though it is still a week away, it is looking more and more probable that the chance of this happening next weekend (no rain) is looking less likely:

 

 

It is possible that the GFS, at least, has probably done that usual sneaky trick of 'over-deepening Low Pressure systems' to try and catch us out, and that the 12Z ECMWF's and 12Z UKMO's less deeper versions of the Low Pressure system (which sits over the Southern part of the UK for the weekend) is the more likely scenario. Just in case, though, more runs from a variety of models would be needed to see who really is the winner with next weekends outlook. But I would agree that the GFS will probably be the model to dump its possible over-powered Low Pressure system idea.

 

Who knows, there could even still be enough time for the models to bring more of a High Pressure influence for next weekend, by perhaps backing the trough/low pressure system further South-West allowing the High Pressure from the North-East to have more of a role for the UK:

 

(UKMO used as an example)

^^ Black arrow on that model showing one solution that could happen if the Low Pressure system ended up being modeled further South-West. Or we could even see scenarios such as models slowing the progression the Low makes towards the UK/Southern part of the UK (which could increase possible thundery chances further if more warm air gets vacuumed up from the South-East).

 

Whatever happens, the North or far North will probably end up being the least unsettled for next weekend (unless the UKMO's and ECMWF's idea of placing the Low over the the Southern part of the UK (edit: at least for next Saturday anyway) is incorrect. Also, as mentioned earlier, there's still enough room for some changes to still occur, which will affect how unsettled it could end up for the bank holiday).

Edited August 18, 2013 by DiagonalRedLine

[Captain Shortwave]

Whilst the GFS op was similar to it's previous outputs, the control run is similar to the UKMO

 

A fair number of ensemble members go for something similar as well.

Hopefully tomorrow mornings runs will shed some light on the weather for next weekend.

[East_England_Stormchaser91]

Hmm, if you are looking for prolonged warmth, then this morning's run is not too good I'm afraid. It has to be said. Infact, towards the end of the month it could even get quite cool. Of course things will chop and change. 

[fine wine]

Gfs looking a little better than last night with a hot Saturday. On this run the short wave fades and drops south pretty quickly although there isn't a massive pressure build afterwards. Still, an improvement certainly.