Model Output Discussion 12z 01/06/13

[Frosty.]

You have to remember that deep lows are not always rain makers, more like wind makers, Shallow lows can produce an awful lot of rain in generally light winds, often conducive to slow moving thunderstorms...  

That's more like it

[AWD]

As the ensembles posted by Gavin above show, it looks plausible that southern parts could see more in the way in rainfall than northern parts.

This could be because of the current HP cell we have now. The trough in the Atlantic struggles to make much progress east, so instead ejects energy underneath the block, across Southern UK and into Europe. A pattern the 500mb anomaly charts aren't a million miles away from showing at the upper level.

You don't need a deep low to produce rain. A slack pressure flow over the UK can often produce slow moving bands of rain and showers, the latter favoured for next week currently IMO.

The north has every chance of getting away with a half decent week still next week, being closer to the positive heights to the north of the UK that only slowly wane during next week.

Edited June 4, 2013 by AWD

[Frosty.]

Tonight's Ecm 12z op run is looking very peachy this weekend and pretty good well into next week with warm weather persisting, probably becoming more humid with time and a growing risk of thundery showers during the early days of next week.

[Tamara]

The ECM is my personal favourite this evening going into the start of next week. Firstly, and best of all, it looks like keeping the thundery low over France furthest away from here and secondly it holds back any troughs in the atlantic and maintains a ridge, albeit weak, over the UK. Probably quite a lot of cloud build up with this during the day but it would be stable fair weather cloud and the risk of downpours is muted

 

 

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[rmc1987]

Tonight's Ecm 12z op run is looking very peachy this weekend and pretty good well into next week with warm weather persisting, probably becoming more humid with time and a growing risk of thundery showers during the early days of next week.

BBC do not agree, they have a max of 21c for this next week for London. In fact Saturday 19c. GFS isn't quite showing mid 20s. Don't get me wrong I would love to see the mid 20s as I have seen aluded to but I can't see where that would come from based models and the forecast. Edited June 4, 2013 by rmc1987

[Frosty.]

That so called atlantic breakdown is getting further away on tonight's Ecm 12z, after a possible showery interlude in the south, high pressure to the north extends a strong ridge south, that atlantic low is well out of the picture.

[Frosty.]

BBC do not agree, they have a max of 21c for this next week for London. In fact Saturday 19c. GFS isn't quite showing mid 20s. Don't get me wrong I would love to see the mid 20s as I have seen aluded to but I can't see where that would come from based models and the forecast.

forecasts change by the hour, not concerned.

[Summer Sun]

BBC do not agree, they have a max of 21c for this next week for London. In fact Saturday 19c. GFS isn't quite showing mid 20s. Don't get me wrong I would love to see the mid 20s as I have seen aluded to but I can't see where that would come from based models and the forecast.

 

24c possible in the south on Friday so we could easily see the hottest day of the year with a 25 or 26c possible in some sheltered locations

 

Edited June 4, 2013 by Summer Sun

[Summer Sun]

Looks like the north could see a decent week next week never mind any breakdown looks like the high could well force the low south into France and down into Spain with the bulk of the UK's rain in the south

 

 

Edited June 4, 2013 by Summer Sun

[Frosty.]

The Ecm 12z ends blocked with high pressure and pleasantly warm temperatures with lots of sunshine with a strong ridge across all areas, the uppers are fine, this is much better than the latest met office update and what happened to that atlantic breakdown

Edited June 4, 2013 by Frosty039

[J10]

The current pattern reminds me of winter, when we are chasing snow charts, only to see them evaporate closer to the time, only this time looking for unsettled charts and more seriously a deep trough over the UK.

 

While there is more than bit of truth in my above statement, in that the deep trough the west now looks like staying out west for longer,  I do think that as others have said, the shower and thunderstorm risk will increase considerably next week, possibly this weekend as well, but this risk a bit lower than a few days ago.

[snowking]

I'm not entirely sure where the notion of the 'total breakdown' has come from (though I have been a bit busy for the past couple of days so perhaps i've missed something)

As far as I can see its a largely similar story to the ensemble mean picture painted a few days back - trough anchored just to the NW of the UK next week, just close enough to promote a sufficient lowering of heights to leave the UK just the wrong side of settled, so a largely sunshine and showers type scenario, and thats very much where we look placed this evening so far (obviously with the caveat that we await the 12z ECM EPS suite).

We can see this general lowering of heights on the GEFS suite:

Today -

7 Days time:

We see a similar(ish) scenario from the ECM det.:

The rest of the ECM det. does actually show a slight rebuild of pressure once again, but given the recent volatility in operational NWP modelling, it might be best to hold fire until we have seen the ensemble mean consensus, and the strongest recommendation I could make at the moment is to stick to the ensemble means.

So the story really remains the same as it has done for some days now (and I am sure John will confirm similar from the mean height anomalies) - increasingly less settled.

In terms of the potential temperatures into next week there really is very little point speculating at present - very subtle changes in the flow, set against the background of the anomalously cool SST's at present, will make a huge difference from seeing value in the mid-high teens, to seeing temperatures soar into the mid 20's. Until we can get some sort of definitive picture on the surface flow, we are unlikely to be much the wiser.

So as has been said previously really, we are not looking anywhere near as bad as last year, just unfortunately those hoping for the almost completely dry weather of this week to continue may be left a little disappointed.

SK

Edited June 4, 2013 by snowking

[AWD]

The EC Op isn't as unexpected as might seem. Weak positive heights remain to the north of the UK allowing for conditions to remain relatively settled here into next week still, whilst the south sees an increase in showery weather and possible thunderstorm development as we go through next week.

This scenario also supported reasonably well by the GEFS Gavin posted earlier. A bit busy so apologies but can't post any charts to back this up but as Snowking says, the broad theme remains the same in that the risk of showers increases as SLP values relax next week, this currently best favoured towards the South more as energy heads into Europe. Timing is the main difference and obstacle currently IMO.

Edited June 4, 2013 by AWD

[Milhouse]

If the ECM 12z came off it woukd take us out to the middle of June with a very dry, sunny and pleasantly warm first half. UKMO, however would turn things unsettled a lot sooner. Personally i'm not getting too hung up over the models at present. I would love a continuation of the warmth and sunshine all summer long but at the moment i am loving all this dry summer weather, even though us on the east coast arent seeing quite the warmth of elsewhere.

[Gibby]

Good evening. Here is the report on the 12 noon outputs from GFS, UKMO, GEM, NAVGEM and ECM for tonight Tuesday June 4th 2013.All models continue to paint a settled and warm picture for the next 4-5 days at least as High pressure remains in control of the UK weather for the period up to the end of the weekend. The centre of High pressure will remain close to Northern Britain with a fresh Easterly breeze across the South at times with the risk of a few thundery afternoon showers across Northern and Western high ground late in the week and over the weekend.GFS then shows the risk of showers increase as we move deeper into next week with a cooler feel to things over most areas by the end of the run as winds settle more from the West through FI.The GFS Ensembles show another 4-5 days of warm uppers over the UK before things turn much closer to the June average. A few very chilly options are shown from a few members tonight with an unsettled trend developing from early next week especially in Central and Southern areas.The Jet Stream continues to lie blowing weakly well to the NW of Britain for the time being. However, it's bad news thereafter as it migrates much further South to a position well South of the UK running due West to East over the Atlantic and Northern Spain as we move into and through next week.UKMO tonight shows pressure falling from the SW as we move out of the weekend and into next week with thundery showers or longer spells of thundery rain developing for many as we move progressively through the first half of next week.GEM shows a slow deterioration in weather conditions as we move through next week with thundery rain or showers becoming quite extensive over Southern and Central areas by midweek and with pressure thereafter remaining Low or even lower by the end of the week the current fine early Summer spell would become a distant memory, at least for the southern two thirds of the nation.NAVGEM tonight shows a slower deterioration than GEM with the North holding on to dry and fine weather well into next week before all areas look like becoming unsettled later in the week.ECM finally bucks the trend shown by the other models as it's operational run tonight shows slack pressure continuing over the UK throughout the next working week as High pressure stubbornly maintains something of a ridge across the UK with largely fine conditions with sunny spells for most and just the odd scattered heavy shower in the warmth of the days. Late in the week a more sustained breakdown looks likely over the South as Low pressure finally makes a move towards SW Britain by Day 10.In Summary there is still some disagreement over the weather events of next week as the models continue to jostle with complex synoptics over and around the British isles. All models suggest an attempted breakdown at least coming from the SW but the timings vary between the models ranging from as soon as the early week from GFS & UKMO to midweek from NAVGEM and the very end of the week from ECM. The ensemble data from GFS does support an early part of the week breakdown is most likely and I would have to wait until seeing the ECM Ensemble data later before passing too much judgement on it's evolution. However, taking all this into account lets continue to enjoy the fine and warm weather of the next 5 days or so and hope this is extended over coming runs.

[ANYWEATHER]

I think, t+120 is about as far as we can go in any detail, but it looks as though the north is away for a while for any unsettled conditions, the south of the uk is imho still prone to any showery activity, I think radar watching for the south of the uk  from Friday onwards for the south of the Uk for any storms which may develop!!   Anyway mares tails here tonight [cirrus fibbirus] shows an injection of moisture at high levels...  

Edited June 4, 2013 by ANYWEATHER

[049balt]

I'm not entirely sure where the notion of the 'total breakdown' has come from (though I have been a bit busy for the past couple of days so perhaps i've missed something)

As far as I can see its a largely similar story to the ensemble mean picture painted a few days back - trough anchored just to the NW of the UK next week, just close enough to promote a sufficient lowering of heights to leave the UK just the wrong side of settled, so a largely sunshine and showers type scenario, and thats very much where we look placed this evening so far (obviously with the caveat that we await the 12z ECM EPS suite).

We can see this general lowering of heights on the GEFS suite:

Today -

7 Days time:

We see a similar(ish) scenario from the ECM det.:

The rest of the ECM det. does actually show a slight rebuild of pressure once again, but given the recent volatility in operational NWP modelling, it might be best to hold fire until we have seen the ensemble mean consensus, and the strongest recommendation I could make at the moment is to stick to the ensemble means.

So the story really remains the same as it has done for some days now (and I am sure John will confirm similar from the mean height anomalies) - increasingly less settled.

In terms of the potential temperatures into next week there really is very little point speculating at present - very subtle changes in the flow, set against the background of the anomalously cool SST's at present, will make a huge difference from seeing value in the mid-high teens, to seeing temperatures soar into the mid 20's. Until we can get some sort of definitive picture on the surface flow, we are unlikely to be much the wiser.

So as has been said previously really, we are not looking anywhere near as bad as last year, just unfortunately those hoping for the almost completely dry weather of this week to continue may be left a little disappointed.

SK

Another cracker of a post SK.

[AWD]

Worth noting that the latest 96hr and 120hr FAX charts have the front from France pushing up very close to Southern England at the weekend;

This could provide enough instability to bubble up some Cumulus or Cumulonimbus and provide Southern Coastal counties with some thunderstorms or at least, a channel "light show".

[shuggee]

The current pattern reminds me of winter, when we are chasing snow charts, only to see them evaporate closer to the time, only this time looking for unsettled charts and more seriously a deep trough over the UK.

 

While there is more than bit of truth in my above statement, in that the deep trough the west now looks like staying out west for longer,  I do think that as others have said, the shower and thunderstorm risk will increase considerably next week, possibly this weekend as well, but this risk a bit lower than a few days ago.

 

Was thinking the same thing J1.  A block to our north - when will the Atlantic break through to re-introduce those Sw'lys?!  It appears that like in winter when the forum is keen to hold onto the high to perpetuate cold temps, the models keep pushing back 'breakthrough day'.

[Tamara]

At this time of year a weak pressure pattern easily transfers itself into convective downpours due to intense surface heating and available moisture, and sharp contrast to colder upper air temperatures. During the winter the same pattern however leads to benign quiet conditions. So the low pressure trough/high pressure anticyclone signal is much more blurred in the summer than it is in winter.

 

On that basis, whilst a mobile westerly pattern with the atlantic breaking through leads to spells of more organised rain and then brighter showery weather it tends to be a lower impact type of weather to the aforementioned type.

 

In that sense the model pattern in summer can have even more subtle implications for conditions on the ground than might appear on face value model output at other times of year. In terms of the present model suggestions then after the anticyclonic pattern (probably) fades from next week then much depends on which model solution is correct. The ECM model shows a weak ridge, but in terms of the suggestions made just now it still means a stable North Sea influence much like we saw at the start of this settled spell from Saturday with upper temperatures not too low to spark showers. However the UKMO and GFS currently have a different suggestion which implies the thundery low closer and thereafter a showery more cyclonic pattern being established even though the lower pressure pattern is quite shallow. For the reasons given.

Edited June 4, 2013 by Tamara Road

[Geordiesnow]

Was thinking the same thing J1.  A block to our north - when will the Atlantic break through to re-introduce those Sw'lys?!  It appears that like in winter when the forum is keen to hold onto the high to perpetuate cold temps, the models keep pushing back 'breakthrough day'.

 

But a high to our North in summer also means lower heights to our South like in winter so low pressure and weather fronts wont be too far away, just like it is in winter. 

 

The ECM is decent enough on face value but it would not need much movement to have a cooler NE'ly or the Atlantic trough to start undercutting and affecting parts of the UK with cool wet weather. 

 

Would rather see lower heights across Greenland but the reality is, this is not going to happen so lets hope we have something like the ECM where high pressure can remain close by to keep the weather warm and settled especially the further West you are. 

[mike Meehan]

I would prefer heights over the Alpine area to get a nice south/south easterly flow  

[NorthernRab]

But a high to our North in summer also means lower heights to our South like in winter so low pressure and weather fronts wont be too far away, just like it is in winter. 

 

The ECM is decent enough on face value but it would not need much movement to have a cooler NE'ly or the Atlantic trough to start undercutting and affecting parts of the UK with cool wet weather. 

 

Would rather see lower heights across Greenland but the reality is, this is not going to happen so lets hope we have something like the ECM where high pressure can remain close by to keep the weather warm and settled especially the further West you are. 

 

True, but such synoptics won't necessarily lead to UK wide unsettled conditions, much of Scotland can possibly benefit from such a set-up, as the models are showing for early next week.

[Geordiesnow]

True, but such synoptics won't necessarily lead to UK wide unsettled conditions, much of Scotland can possibly benefit from such a set-up, as the models are showing for early next week.

 

Indeed, NW and SW Scotland can tend to be drier in these type of set ups but if people want a summer which is warmer and drier then having high pressure to our North with a developing Greenland high is not really the way to go. The GFS 18Z shows what could go wrong and not even positive Frosty and Gavin can argue that the 18Z in the medium term has hints of summer 2012 to it. 

 

Although its still in the medium term it does look more likely there will be a breakdown to this fine settled weather, all signs does point to it whether we like it or not. That said, as per usual with the weather little changes can alter the picture so more runs are needed. 

[Jimmy0127]

I can't see anything, including tonight's ECM (pictured), to suggest that continental air will survive beyond 7 days from now. GFS for the first time in days is correcting the low eastwards. Breaks my heart.

A spell like this ten years ago, we'd have seen high twenties, surely? As opposed to twenty.

 

 

 

Edited June 4, 2013 by Jimmy0127