Model Output Discussion 12z 10/05/13

[weather_it_will]

UKMO is on its own this morning at T144 with the missing deep low.

[Frosty.]

There is good model agreement for an atlantic ridge to build across the uk this weekend but the southeast only slowly improving as the trough slowly clears away into the continent, but there is also good agreement for low pressure to follow in from the northwest by early next week and for a trough to dominate our weather next week with a mixture of sunshine and heavy showers in a very cyclonic and rather cool pattern, eventually the trough fills in situ and high pressure squeezes the remains of the trough as pressure rises to the northeast and the southwest. The Gfs 00z shows a warmer and more anticyclonic spell further into FI, at least for a time.

[Guest pjl20101]

^ ^ ^ Gibby uses the wetterzentrale charts mate.

[Gibby]

Hi folks. Here is the report on the midnight output of GFS, UKMO, GEM, NAVGEM and ECM for today Wednesday May 22nd 2013.

All models show a strengthening and cooling Northerly flow between High pressure to the West and Low pressure to the East blowing down over the UK for the next 72 hours. There will be bright skies and only fleeting showers at first but by tomorrow there will be far more showers, some heavy while Friday looks an altogether inclement day with exceptionally cool weather likely with strong winds and rain at times, clearing in the NW later. The pressure pattern then releases it's grip through Saturday and Sunday with a lighter NW feed, dry weather with some sunny spells and much lighter winds making it feel considerably warmer. By Bank Holiday Monday though pressure will be falling away again from the NW with rain and wind reaching Northern and Western areas extending to more Southern areas too later though it may be that the far South and East stay dry till late in the day.

GFS then takes us through the next working week slipping down over Ireland and Wales to Southern England over the middle days of next week, filling as it goes. A showery pattern will be the most likely weather type, some of which will be heavy with hail and thunder though some places may miss them and stay dry especially near windward coasts. FI then shows slack Low pressure never far away from Southern Britain with scattered showers and a wind that settles from the NE while the NW sees drier and warmer conditions with good sunny spells in association with High pressure to the NW.

The GFS Ensembles show the short pronounced cool blip on Friday moderating as uppers become closer to average and a bit above later. However, with good support for just marginally above or average uppers no heatwave is indicated by any member at all. Instead the most likely solution looks like one of High pressure to the NW with dry conditions shown up here while the South and East is more likely to be prone to showers though certainly not a washout.

The Jet Stream continues to be unfavourable for sustained dry weather with a SE moving flow over the UK becoming weak and diffuse for a few days before a stronger surge of energy again sets up moving SE just to the West of the UK and down over Southern Europe maintaining a Low pressure belt from the NW to SE Europe.

UKMO this morning shows Low pressure sliding SE over Bank Holiday Monday and Tuesday when it is centred just off NE England with a cool NW flow and a mix of sunshine and showers following a band of rain East late Monday or early Tuesday.

GEM also shows Low pressure moving SE over the UK early next week with rain and showers at times followed by a strong rise of pressure from the Azores high settling things down with sunny spells and warm conditions developing universally over the UK by the end of the run.

NAVGEM shows the Low pressure early next week too sending it's energy down the North Sea by the end of it's run at Day 7 with a cool NW airflow over the UK with a mix of sun and showers likely later next week following a wet spell early in the week.

ECM shows a filling Low pressure slow moving over the UK next week with heavy showers and warm sunshine between for many most days next week. By Friday the Low has filled up in situ but left the UK under a still unstable and slack NW flow with the likelihood of further showers at times in places but with some good sunny spells too with temperatures close to average when taken Nationally.

In Summary it is now agreed by all models that yet another Low pressure will move SE over the UK early next week with another delay in seeing any meaningful surge of High pressure from the High out to the SW anytime soon. The Central slice of this Holiday weekend looks OK for most but rain will be moving SE across the UK on Monday in temperatures at average values at best for many. There is some differences of opinion in how the atmosphere over the UK behaves once next week's low passes with GEM developing a strong surge of Summer warmth from that Azores high while GFS keeps any meaningful ridging from this too far NW to benefit the South of the UK much, while ECM keeps a slack pressure gradient over the UK with weak Low pressure aloft maintaining the risk of some shower activity in a light NW feed and an Azores High still too far away from UK shores.

[Summer Sun]

UKMO is on its own this morning at T144 with the missing deep low.

 

On this occasion UKMO looks to be on the money when looking at the ensemble runs of GFS and ECM they are closer to UKMO pressure wise

 

Edited May 22, 2013 by Gavin.

[Frosty.]

As Gibby mentioned above, the Gem 00z brings a strong rise in pressure with the Azores anticyclone ridging northeastwards across the uk with a much warmer and sunnier outlook for all areas, a really summery looking end to the gem, the high would probably migrate towards scandinavia and help to create a large blocking high, it's a classic summer set up and I would love it to be right,

[Tamara]

As long as this entrenched trough disruption pattern continues, much as it has for many months now, then the chances of the Azores High ridging in to settle things down will continue to be thwarted. In the winter time an amplified pattern is exactly what many (not all ) look for to get the ideal synoptics. At this time of year though it simply brings cool temperatures, spells of rain and heavy showery downpours and just brief spells of drier weather between the low pressure systems. And few of us of whatever persuasion welcome that, especially against the background of recent summers.

 

It could be that we might have to be grateful in the circumstances that one such window occurs in the middle part of the Bank Holiday weekend and that although it is not going to be especially warm, at least some dry conditions will allow outdoor activities to be held without being interrupted in any way. However before then, there are two distinctly unpleasant days to come more especially for eastern and south eastern areas, and the latter part of the Bank Holiday sees the next area of general rainfall arriving in the North West.

 

Next week is impossible to give close detail, but it looks possible that an almost carbon copy repeat of the sequence we saw over a week ago might happen where a low sank south down the length of the UK and led to the conditions we have seen this week. On the basis of the predominant amplified pattern, then realitistically , the GEM as welcoming as it looks this morning, appears like it could be another false dawn much as the GEFS ensembles have promised recently but not proved accurate.

 

At some stage, the pattern will evolve into something different (whatever that 'different' might be) but we are getting used to seeing the jet stream where it is a lot these days for sure and until that changes then as I see it, our late spring/summer weather is unlikely to improve very much at all.

[Cheshire Freeze]

As long as this entrenched trough disruption pattern continues, much as it has for many months now, then the chances of the Azores High ridging in to settle things down will continue to be thwarted. In the winter time an amplified pattern is exactly what many (not all ) look for to get the ideal synoptics. At this time of year though it simply brings cool temperatures, spells of rain and heavy showery downpours and just brief spells of drier weather between the low pressure systems. And few of us of whatever persuasion welcome that, especially against the background of recent summers.

 

It could be that we might have to be grateful in the circumstances that one such window occurs in the middle part of the Bank Holiday weekend and that although it is not going to be especially warm, at least some dry conditions will allow outdoor activities to be held without being interrupted in any way. However before then, there are two distinctly unpleasant days to come more especially for eastern and south eastern areas, and the latter part of the Bank Holiday sees the next area of general rainfall arriving in the North West.

 

Next week is impossible to give close detail, but it looks possible that an almost carbon copy repeat of the sequence we saw over a week ago might happen where a low sank south down the length of the UK and led to the conditions we have seen this week. On the basis of the predominant amplified pattern, then realitistically , the GEM as welcoming as it looks this morning, appears like it could be another false dawn much as the GEFS ensembles have promised recently but not proved accurate.

 

At some stage, the pattern will evolve into something different (whatever that 'different' might be) but we are getting used to seeing the jet stream where it is a lot these days for sure and until that changes then as I see it, our late spring/summer weather is unlikely to improve very much at all.

 

I think the most striking thing in recent times is for the Jetstream to try to amplify/head south whatever the synoptic pattern. This means given the chance it does just that. 

[nitro_deluxe]

Whilst the weather may have been in a 'rut' the past few weeks, a few fine warmer days seem to be overruled by a week or more of cool drabness.. However the distinct lack of any more extreme weather may be a god send to some. No floods but no drought conditions either.

To some weather watchers perhaps monotonous - to a lot of every day folk reliant on the weather, perhaps a breather?

Longer term, hmmm difficult to say - mid to upper 20s would be nice, throw in a few storms to keep moisture (adrenalin levels) up and comfy humidity levels during say darkness. Perhaps bottom line remains, for us in the UK anyway? expectations may be set at the wrong level, I.e., far too high

What we all want isn't always going to be what we will actually get.Hard as it is sometimes to accept..

[Purga]

Wow - there could be some snow tomorrow in the SE & E Anglia !

 

Amazing stuff ...

[Summer Sun]

Wow - there could be some snow tomorrow in the SE & E Anglia !

 

Amazing stuff ...

 

Or maybe not look at the snow risk its nill away from Scotland

 

 

Only chance further south is on the highest ground like the chilterns but even then thats only a slight chance

Edited May 22, 2013 by Gavin.

[Frosty.]

An increasingly good Gfs 06z (eventually) this morning with the Azores anticyclone beginning to extend it's warming ridge influence across the uk throughout a large chunk of FI, a northwest-southeast split evolves but eventually all parts of the uk become fine and warm as the culprit low finally drifts away northwards towards iceland and stays there with high pressure then covering the uk in warm and sunny weather. In the meantime an unsettled and very cool spell for the next few days before a weak atlantic ridge pushes east across the uk during this coming weekend with saturday looking the driest and sunniest day with respectable temperatures returning, by sunday it looks like pressure will be falling with showers breaking out in inland areas but with sunny periods it would feel pleasantly warm, into next week a trough sinks southeast across the uk with a mixture of sunshine and heavy showers and longer periods of rain and temperatures around average but cooler in any persistent rain but towards the end of next week the complex trough structure begins to fill and clear off with high pressure beginning to fill the void, later in FI looks summery, very similar to the Gem 00z in FI.

Edited May 22, 2013 by Frosty039

[Weather Boy]

An increasingly good Gfs 06z (eventually) this morning with the Azores anticyclone beginning to extend it's warming ridge influence across the uk throughout a large chunk of FI, a northwest-southeast split evolves but eventually all parts of the uk become fine and warm as the culprit low finally drifts away northwards towards iceland and stays there with high pressure then covering the uk in warm and sunny weather. In the meantime an unsettled and very cool spell for the next few days before a weak atlantic ridge pushes east across the uk during this coming weekend with saturday looking the driest and sunniest day with respectable temperatures returning, by sunday it looks like pressure will be falling with showers breaking out in inland areas but with sunny periods it would feel pleasantly warm, into next week a trough sinks southeast across the uk with a mixture of sunshine and heavy showers and longer periods of rain and temperatures around average but cooler in any persistent rain but towards the end of next week the complex trough structure begins to fill and clear off with high pressure beginning to fill the void, later in FI looks summery, very similar to the Gem 00z in FI.

 

All absolutely correct Frosty.  However, we have seen this before on the GFS, whilst the ECM kept saying 'no'.  We can see from looking out of the window this week which one was right and unfortunately it wasn't the outcome that most of us would have preferred. 

 

Yet again the ECM is far from convinced with the latest run being LP dominated until right at the end of the run when we get this:

 

That's hardly a chart for dusting down the BBQ although it is more neutral than us being in a hearty trough.  Certainly nothing like the GFS.

 

Now the question I want to ask is this: do we say that because the GFS got it wrong for this week that therefore we should ignore what it is saying for next and go with the ECM's pessimism?  Or do we form the view that, combined with the other background signals that have been indicating a better pattern for the turn of the month, that the GFS may well be on to something and expect the GFS to come up trumps this time?

 

I'm not sure that there is a scientific response to that question (although if there is, I'd like to hear it) which is why weather forecasting is still at least a little bit of an art as against pure science.

[Frosty.]

All absolutely correct Frosty.  However, we have seen this before on the GFS, whilst the ECM kept saying 'no'.  We can see from looking out of the window this week which one was right and unfortunately it wasn't the outcome that most of us would have preferred. 

 

Yet again the ECM is far from convinced with the latest run being LP dominated until right at the end of the run when we get this:

 

That's hardly a chart for dusting down the BBQ although it is more neutral than us being in a hearty trough.  Certainly nothing like the GFS.

 

Now the question I want to ask is this: do we say that because the GFS got it wrong for this week that therefore we should ignore what it is saying for next and go with the ECM's pessimism?  Or do we form the view that, combined with the other background signals that have been indicating a better pattern for the turn of the month, that the GFS may well be on to something and expect the GFS to come up trumps this time?

 

I'm not sure that there is a scientific response to that question (although if there is, I'd like to hear it) which is why weather forecasting is still at least a little bit of an art as against pure science.

I don't think we should ever ignore the gfs, it has 4 runs a day so it increases it's chances of hitting or being close to the target at least once or twice a day, it's a shame the ecm stops at T+240 as it would be interesting to see how the gfs and ecm would compare further into FI but considering how the met office are now indicating a marked improvement in June, the gfs keeps showing azores high pressure building in FI and is therefore on the right track IMO.

Edited May 22, 2013 by Frosty039

[snowking]

RE: Risk of snow tomorrow

 

Looks to be the potential for up to 10cms above 200m in Scotland, with the risk of a few cms across the highest ground elsewhere (Pennines in particular)

 

Other high ground likely to see snow falling - Wales, NE England, perhaps Chilterns, Cotswolds and Downs too, though accumulation unlikely in these areas other than temporary deposits

 

To lower ground the chance of a wintry mix within the showers with supportive dew point profiles, but the atmosphere generally from around 900mb downwards is less supportive - you will be relying on downdrafts if you wish to see anything wintry here.

 

The next risk then comes as this rather active occlusion:

 

 

Heads in from the North-East. Mostly rain, but sleet/snow likely across the higher parts of the Pennines, perhaps the North York moors too - perhaps a few flakes to lower levels overnight during any heavier bursts.

 

SK

[Panayiotis]

Or maybe not look at the snow risk its nill away from Scotland

 

 

Only chance further south is on the highest ground like the chilterns but even then thats only a slight chance

NAE vs GFS ? I know which one I would choose!

[Summer Sun]

Once again this afternoon GFS appears to be over cooking the low early next week when compared to UKMO

 

 

[AWD]

Compared to the UKMO 12z of last night, the last two UKMO runs have definetly trended towards the GFS 12z of last night however, with another trough now likely to influence our weather next week and to make things worse, the GFS still has weak trough conditions in FI instead of it's recent high pressure scenarios.

[Frosty.]

A very unsettled Gfs 12z op run but at least the majority of the upcoming Bank holiday weekend looks fine and pleasantly warm with sunny spells and only a few showers scattered around, however, it looks like turning more unsettled from the west during monday as low pressure takes control, then next week is very unsettled with sunny periods but heavy showers with hail and thunder and occasionally merging into longer spells of rain, temperatures around average and feeling pleasant in the sunny spells but feeling cool when the showers and persistent rain occur, unlike the 6z where FI became anticyclonic, this run remains with a large complex trough which is very reluctant to go anywhere and just remains glued to the uk although eventually showing signs of filling in situ, the gfs swing-ometer from settled to unsettled continues.

[mushymanrob]

... and right on cue, here we go yet again.

[Frosty.]

Once again this afternoon GFS appears to be over cooking the low early next week when compared to UKMO

 

 

The thing is though Gavin, whether it's a shallow trough or a deep low, it looks like next week will be unsettled and showery but it's not a write off because in this type of pattern there would be good sunny spells between the downpours and temps look close to average, beyond next week it could just as easily become settled as remain disturbed, and this weekend looks reasonably good for most of the uk.

Edited May 22, 2013 by Frosty039

[Steve C]

I don't really understand the gloom and despondency. My brother's birthday is early in June and it often (I'd say mostly) coincides with weather you wouldn't describe as summery.

 

I'm just hoping for a couple of usable days over the bank holiday, which the charts imply. There's plenty of time for summery weather later. I'll only become worried about the Summer, if there's nothing settled in the next six weeks or so.

[Summer Sun]

Looks like the GFS Op is going to be an outlier for early June with the ensemble run building pressure strongly across the northern half first before moving south for a time towards the end the high heads back north re-establishing northern blocking again

 

Ensemble's on the left Op's on the right

 

 

 

Edited May 22, 2013 by Gavin.

[Skeggy Winter Storm]

... and right on cue, here we go yet again.

yes mushy dont look great atm even Tromso in norway had a very nice 24c we must be unluckiest country ever hope some nicer charts show there hands soon and send the trough packin

[Frosty.]

Looks like the GFS Op is going to be an outlier for early June with the ensemble run building pressure strongly across the northern half first before moving south for a time towards the end the high heads back north re-establishing northern blocking again

 

Ensemble's on the left Op's on the right

 

 

 

Interestingly, the GEFS 12z mean looks exactly as the met office are describing for early to mid June with northern and western britain doing unusually well compared to the south and east, as it's usually the other way around.