Model Output Discussion 18z 28/07/13

[mushymanrob]

The Gfs 12z shows a lot of normal August weather with spells of sunshine but also scattered showers and occasional longer spells of rain with temperatures into the low 20's celsius across the southern half of the uk but nearer the high teens celsius for n.ireland, scotland and the far north of england.

 

... and thats sums up the outlook for the next ten -14 days perfectly frosty... thats exactly what this mornings runs are showing (so agreeing with the quoted 12z gfs), and is supported strongly by the anomaly charts.

 

some runs suggest a building azh ridge, but they have no support and are gone now, any ridging is expected to be nothing more then a temporary day or so between systems.

[Frosty.]

... and thats sums up the outlook for the next ten -14 days perfectly frosty...

 

That's the part of your post I liked mushy

[draztik]

GFS 0z all but removes the Azores high ridge at 192, in contrast to its earlier runs...

As for the ECM, its showing no ridge affect.

Edited August 7, 2013 by draztik

[Captain Shortwave]

Edited on reflection -- last night's silliness removed.

 

Have hopes now that Captain S (below) and GFS really are onto something.

Nope I jinxed it again 

At least the weekend looks nice and I guess to most that is all that matters.

 

 

Rain moving south east on Sunday but probably not too much

If there is any good from the runs this morning, the GFS ens want to keep a ridge just to the south with the jet blowing through southern Scotland

Though ECM disagrees with this and wants to push the jet south of the UK at this timeframe

The major difference between the 2 models is the handling of the low near Iceland, GFS has this low tracking a lot more slowly which given it's positioning would allow pressure to build north east through Europe which would allow a warmer flow of air over us. ECM just crashes the low through the North of Scotland.

Edited August 7, 2013 by Captain shortwave

[Summer Sun]

UKMO still hints at pressure rising from the south later with pressure low over Greenland it has every chance of doing so

 

[shedhead]

To show GFS temp predictions are not always that inaccurace, this was a post I made last Fri 2nd in response to NorthernSky saying he was off to the Highlands this week.  Unfortunately the 06 temp chart I posted is no longer available, but from memory it showed 5-7c widely across the N and 3-5c for Central Scotland, hence my ground frost call.

 

06 GFS suggests a localised ground frost for the Highlands as early as Weds....no trouble sleeping there by the look of things...

 

 

His response was...

I doubt that will happen to be honest, we all know how ambitious GFS can be with their overnight minima predictions during summer, not to mention the fact that such an occurrence would possibly be recording breaking and the set up isn't exactly conducive to tapping into the absolute coldest air available in the northern hemisphere for this time of the year.

 

So I thought it might be worth checking the o/night minima this morning to see how well GFS did in the 120hr range. OK slightly milder air got into the far north and west, but that was simply a timing issue, with the mins of 3 and 4c this morning over parts of N Eng and S Scot being bang on where GFS had them 5 days ago. 

 

Not suggesting GFS is always this accurate of course, but imo it gets critisised far more than it should for this type of thing, primarily though because it shows what many often don't want to see.

 

Edit: Given the above and even the single digit min here last night, Mushys call of an Autumnal feel does not look bad at all. 

 

Edited August 7, 2013 by shedhead

[draztik]

UKMO still hints at pressure rising from the south later with pressure low over Greenland it has every chance of doing so

 

definitely see the pressure rise, but due to the MetO not going beyond 144, we tend to look at the other models for a guide on what's ahead. Looking at the other models at that timeframe, they tend to show similar output, but at 168 the pressure is seen decreasing in all 3 models (Gem, Gfs, Ecm).

http://meteocentre.com/models/compar_models.php?map=eur〈=en&run=00&stn=PNM&&range=glb&hh=168

shed, i saw Carol Kirkwood mention those low temps in Scotland earlier, brrr!!

[DTHFCJ]

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

running through these things dont look too bad at all, more so for southern areas...

more (reds) than blues?should say (pinks) really.

I dont pretend to be an expert on these,far far from on but i take the colours to be anomalys

Edited August 7, 2013 by DTHFCJ

[UV-RAY]

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

running through these things dont look too bad at all, more so for southern areas...

more (reds) than blues?should say (pinks) really.

I dont pretend to be an expert on these,far far from on but i take the colours to be anomalys

Indeed, it's a NW/SE split as is usually the case with those further South seeing the best of warm sunshine, though to my eyes the outlook is far better than previous August's we've seen with average conditions for most.

[Northern Sky]

 

To show GFS temp predictions are not always that inaccurace, this was a post I made last Fri 2nd in response to NorthernSky saying he was off to the Highlands this week.  Unfortunately the 06 temp chart I posted is no longer available, but from memory it showed 5-7c widely across the N and 3-5c for Central Scotland, hence my ground frost call.

 

06 GFS suggests a localised ground frost for the Highlands as early as Weds....no trouble sleeping there by the look of things...

 

 

His response was...

I doubt that will happen to be honest, we all know how ambitious GFS can be with their overnight minima predictions during summer, not to mention the fact that such an occurrence would possibly be recording breaking and the set up isn't exactly conducive to tapping into the absolute coldest air available in the northern hemisphere for this time of the year.

 

So I thought it might be worth checking the o/night minima this morning to see how well GFS did in the 120hr range. OK slightly milder air got into the far north and west, but that was simply a timing issue, with the mins of 3 and 4c this morning over parts of N Eng and S Scot being bang on where GFS had them 5 days ago. 

 

Not suggesting GFS is always this accurate of course, but imo it gets critisised far more than it should for this type of thing, primarily though because it shows what many often don't want to see.

 

Edit: Given the above and even the single digit min here last night, Mushys call of an Autumnal feel does not look bad at all. 

 

 

I didn't actually reply to that Shedhead must have been someone else. Anyway I noticed on the bbc website that Aviemore had recorded a temp of 1c the other night! Anyway, I'm off tomorrow and have made sure to pack a couple of jumpers and a waterproof

[Frosty.]

Looking at the Ecm 00z ensemble mean, I see average august summer weather, no extremes, nothing unusually cool or warm, it's average in all respects with the best weather (as you would expect) across the southern third of the uk with longer dry and sunnier spells between any rain bearing fronts or the showers that follow and temperatures generally into the low 20's celsius, around 21-23c for wales, the midlands, east anglia and southern england, a notch higher at times in southern and southeast england with 24-25c at times. For n.ireland, n,england and scotland I see the balance tipped more towards unsettled, especially the further north you are with a fresh westerly airflow, mostly of mid/north atlantic origins so temperatures in the range of 16-19c is more realistic but with shelter, the eastern side of scotland should nudge into the low 20's celsius from time to time, it's a broadly westerly pattern with low pressure to the north and high to the south, occasionally the azores/atlantic anticyclone ridges in to the south, like it will later this week with a fine and warm weekend for the south, and the south will always be closer to high pressure so significantly better than the northern third of the uk, all in all, it's an acceptable mix of late summer weather despite the T850's being nothing to shout about, in our favour is the sea surface temperatures are at or nearing their highest point and the august sun is still very strong.. we have had a GREAT summer so no complaints from me.

Edited August 7, 2013 by Frosty039

[Bobby]

Looks like a fairly zonal setup developing as the Atlantic starts to fire up as it traditionally does at this time of year after its late Spring/early Summer lull. As is usual in these setups the best of the summery weather in the SE with the N and W more unsettled. The jetstream doesn't look too far south at the moment so likely the best weather here, although signs it will move further S later into FI, again what typically happens at this time of year. So a fairly typical mid-late August look to things at the moment. No washout likely but no heatwaves, anti-cyclonic weather in sight either.

Edited August 7, 2013 by Bobby

[Captain Shortwave]

Looks like a fairly zonal setup developing as the Atlantic starts to fire up as it traditionally does at this time of year after its late Spring/early Summer lull. As is usual in these setups the best of the summery weather in the SE with the N and W more unsettled. The jetstream doesn't look too far south at the moment so likely the best weather here, although signs it will move further S later into FI, again what typically happens at this time of year. So a fairly typical mid-late August look to things at the moment. No washout likely but no heatwaves, anti-cyclonic weather in sight either.

I am more on the fence later on when

GFS ens shows this

 

ECM shows this

 

We have a split developing at around day6/7. GFS is more keen to hold the jet somewhere across Scotland which would actually give anticyclonic conditions for the South. ECM on the other hand fires the trough through the UK bringing nationwide unsettled weather.

Developments from the middle of next week onwards are uncertain hence the next few runs will be interesting to see which model budges.

[mushymanrob]

well.... todays anomaly charts differ (so arent a reliable indicator) the gfs (on the right) chart lends its support to the gfs op run, building pressure to the south. but its on its own, with the other 'big two' sticking with the previous atlantic dominated unsettled, zonal theme.

 

the question is...is the gfs onto something? will the others catch up? ... thats major straw clutching im affraid, its most likely that the gfs anomaly will be the one out of kilter... so no real signes of anything other then average, normal, westerly weather for the heart of august.

[shedhead]

I didn't actually reply to that Shedhead must have been someone else. Anyway I noticed on the bbc website that Aviemore had recorded a temp of 1c the other night! Anyway, I'm off tomorrow and have made sure to pack a couple of jumpers and a waterproof

My apols NS, I should have checked more carefully who responded. Not sure the weather in the Highlands really matters that much anyway, it will be stunning whatever's on offer...enjoy.

[shedhead]

well.... todays anomaly charts differ (so arent a reliable indicator) the gfs (on the right) chart lends its support to the gfs op run, building pressure to the south. but its on its own, with the other 'big two' sticking with the previous atlantic dominated unsettled, zonal theme.

 

the question is...is the gfs onto something? will the others catch up? ... thats major straw clutching im affraid, its most likely that the gfs anomaly will be the one out of kilter... so no real signes of anything other then average, normal, westerly weather for the heart of august.

610day.03.giftest8.gif

Indeed Mushy, some warmth at times for all, but also further Autumnal feeling mornings there in the mix.  The weather seems about 3-5 weeks advanced imo, it's got a feel of early to mid Sept about it, both now and looking forward.

Edited August 7, 2013 by shedhead

[mushymanrob]

Indeed Mushy, some warmth at times for all, but also further Autumnal feeling mornings there in the mix.  The weather seems about 3-5 weeks advanced imo, it's got a feel of early to mid Sept about it, both now and looking forward.

 

indeed, the grass is wet, theres dew about, its soft green and toadstools are out, it does smack of early september early in the morning.

 

this might be more in evidence after the atlantic kicks in by the weekend. some breezy days look likely and when the winds from the northwest it wont feel very summer like.

 

still, there might be a decent settled spell in september as a consolation prize, nice weather is always welcome even if its not in summer.

[Methuselah]

Shame no-one can reliably forecast the weather, for more than 10 days ahead, then... 

[summer blizzard]

Unusual to see a polar vortex stirring. -10C upper temps widespread so soon.

[Tim Bland]

Unusual to see a polar vortex stirring. -10C upper temps widespread so soon.

 

Possibly a precurser to an early / cold winter? Other side of the coin though is build up of arctic ice which is linked with milder winters

[Frosty.]

The Gfs 06z shows a lot of high pressure across the south & east at times throughout the run but with some unsettled weather too, however, the further south and east you are, especially the southeast, it looks like those areas would have a lot of fine and warm weather during the next few weeks with a few cooler and more unsettled blips but the further northwest you are, it looks progressively more and more like the balance is tipped in favour of more unsettled than settled and also the most average temperatures, occasionally just below average but a few warmer intervals too, but definately best towards the south/se, sometimes very warm with temperatures nudging into the low 80's F but generally low to mid 20's celsius, for n.ireland, cumbria & scotland, max temps in the mid to high teens celsius but also a few occasions where it reaches the low 70's F. High pressure features more in the low res beyond T+192 hours so the mid to late august period might turn out pretty good for at least the southern half of the uk, If I lived in southern or southeast england I would be more than happy with this particular run, it's generally dry and warm for long periods of time whereas the northwest of the uk is wet and cool in comparison, you can tell which days are wetter by the dip in temperatures on certain days, overall it's very acceptable late summer weather away from the northwest corner of the uk.

[Tamara]

I don't see anything autumnal at all. It looks like a typical latter summer pattern to me and whilst relatively cooler certainly than July, temperatures look fairly average for the first half of August and I think that the figures that Karl (Frosty) gave this morning are reasonable enough

 

I would be cautious about any suggestions of the jetstream coming far enough south and sinking the trough south right into the UK as suggested in about 8 days time or so on the ECM. Also the GFS might be being overly optimistic about its Azores ridging on the other hand - at least up to now. The 12z GFS is currently rolling out at the time of typing.

 

We have been here with this before - and the split in conditions across the UK continues to seem most likely at present. If take a look at the latest NAEFS for ten days ahead, then this scenario is well supported

 

It would be a good half way house between the GFS and ECM atm. And the middle way is often proved to be closest to reality. At least for now - pending output to come over the next day or so which might be more conclusive one way or the other.

 

But we are not seeing any progressive autumnal signal at all - just a westerly pattern which is much closer to what one might expect in a traditional latter British summer

 

Edit: Well the GFS and UKMO out to day 6 look in good agreement for the Azores High to be close enough to the south and south west to ensure some fair weather there, and thus the summary as above looks reasonable right into the greater period of uncertainty and put question marks over any trough solution for the greater part of the UK after this time

 

UKMO

 

 

GFS

 

 

Pretty good agreement between the two models at that time period

Edited August 7, 2013 by Tamara Road

[Frosty.]

Unusual to see a polar vortex stirring. -10C upper temps widespread so soon.

problem solved..

[Summer Sun]

UKMO has continued hints of high pressure pushing in early next week from the south

 

 

GFS agrees with this

 

Edited August 7, 2013 by Summer Sun

[draztik]

GFS and MetO do show agreement. However, the GEM 12z does not fully agree, and sees the pressure rise as being a brief flash in the pan. Like last night, all eyes on the ECM.