Model output discussion 14/04/18

[Summerstorm]

Alright here goes nothing I'm going to try my first piece of analysis of the charts. So don't judge me if I get anything wrong  I'm by no means as knowledgeable as some of the other posters on here. Anyway back on topic...

The 18z looks more settled and anticyclonic than the twelve o'clock run. Think it all hinges on whether we develop any northern blocking admitidelly in the short term the weather isn't particularly inspiring but if we don't develop the blocking then prospects look a bit better down the line. 

The impact is shown here :

The jet is split on the 12z run which means that a trough develops out to the east.

On the 18z this is very different as the jet is weaker and therefore the LP system around S Greenland is weaker, so less pressure is put on the HP system which allows it to become more dominant. 

If you compare this to the ECM at 216hrs : 

The ECM seems keen to develop strong blocking around Greenland which means that low pressure is dragged underneath,Certainly the prospects from this run look unsettled compared to the other two GFS runs. 

The GEM seems to be closer to the ECM run however the ICON 12z is closer to the GFS 18z run not developing any blocking.

The upshot is a ridge of high pressure ridging in by later next week. Which is certainly the pick of the bunch if you are looking for pleasant weather followed by the GFS with the ECM public enemy no 1 for those of a warm disposition. 

So I think it's easy to see why the forecasters are labelling the forecast as a bit messy and there seems to be a lot of uncertainty between the models. It will probably take another few days to resolve where we are headed. 

Hope this was appreciated this someone 

Edited May 9, 2018 by Summerstorm

[Weathizard]

Some things never change, GFS overdoing Atlantic energy again?

GFS/ECM comparison at day 7

[carinthian]

On ‎08‎/‎05‎/‎2018 at 09:41, carinthian said:

Nice to see many parts enjoying the high temps across Blighty yesterday. Highest temps seem to have been along an axis , say from Dorset to Yorkshire.  Our medium term charts continue to show, yes, a cold pool development early next week over parts of mainland Europe. A moderate snowfall at elevation in some Alpine regions (we have been issued a warning ). Looks southern Britain could be in the influence of a continental cyclonic flow by 144t/168t, maybe mixed with a warmer air mass from the east. Northern Britain  getting the best of any sunshine and nice temps. Certainly, interesting Spring weather this season with some extremes, especially across Britain.

C

Looks like our Portal Weather Service were spot on with its snow warning issued some days ago. They forecast moderate snowfall at elevation in our parts of the Alps for next Tuesday. This latest chart from ECM ( for next Tues ) at 850mb sort of firms up on this prediction with height temp of 0c sat right over us at aprox ( 5000 feet )  and that's cold enough to bring snow to the village especially in heavier convective precipitation at this time of year. Upper Alpine pasture grazing put on hold for a little while just yet.

C

[Lincs Observation]

Good morning all

well the bbc are quite bullish on a return to warmer climes late next week, in this forum you feel the battle between members and what they are seeing in the models is rumbling on some showing warmth some showing cool etc. To put some perspective on the month of May it is by in large a changable month historically that dividing line of late spring and early summer, so anything can happen but for what it's worth I am quite optimistic for this coming summer the trends for a more regular visit of the Azores high and  the odd plume maybe.

 

LO

[rain_shadow]

1 hour ago, Lincs Observation said:

Good morning all

well the bbc are quite bullish on a return to warmer climes late next week, in this forum you feel the battle between members and what they are seeing in the models is rumbling on some showing warmth some showing cool etc. To put some perspective on the month of May it is by in large a changable month historically that dividing line of late spring and early summer, so anything can happen but for what it's worth I am quite optimistic for this coming summer the trends for a more regular visit of the Azores high and  the odd plume maybe.

 

LO

Yes, I just hope May is not the most summery month of the year this year...dividing line between sunshine and cloudfest. It does not look too bad for next week at least.

Edited May 10, 2018 by rain_shadow

[Frosty.]

Longer term the GEFS 00z mean looks very encouraging for settled and warmer weather with high pressure taking control..fingers crossed!..it was showing this yesterday too so hopefully it's a trend.

[stodge]

Morning all

A notch cooler in London this morning but still pleasant enough after the overnight rain. The models were offering two very different evolutions yesterday so let's see where we are today. The medium term analysis takes us to Sunday May 20th and starts as always with the ECM 00Z at T+240:

ECM not too different from yesterday. The weekend's disrupting LP fires some energy into Europe re-invigorating the trough over the continent but attempts to build HP back in are pushed south as northern blocking based over Greenland starts pushing the jet back south and the LP systems off the Atlantic start coming on a more southerly track. At T+240 the Azores HP is suppressed far to the south and the LP is moving west to east across Scotland with a second LP set to follow a similar if not slightly more southerly track. It's unsettled with rain or showers for all and quite cool especially in the north.

GEM 00Z at the same time:

Very different. The blocking over Greenland is much less influential while the Azores HP is much more influential sending a ridge NE to the south of the British Isles. The Atlantic LP is further north and positively tilted so we have a benign SW'ly flow for most with fine conditions for southern and eastern parts though more unsettled in the north west. Signs of the Atlantic trough digging south so we could see a spike of heat from Iberia for the second May Bank Holiday.

GFS 00Z OP at the same time:

A slow moving and slack evolution which ends up quite messy. As I said yesterday, you have two competing pressure patterns at work. To the west of the British Isles, we have the classic LP to the north west and HP to the south west (though the latter is very shallow on this output). To the east, heights over Scandinavia are balanced by LP over southern Europe originating from North Africa. The British Isles ends up in the col between these competing pressure systems so decent conditions particularly for the south and east but more unsettled further north and west where the Atlantic influence is most noticeable.

Further into FI pressure builds through the British Isles from the Azores to Scandinavia keeping most fine but LP remains over Europe and for the south east there would be a light NE'ly and the risk of a shower (more so for the Channel Islands).

GFS 00Z Control at T+240:

Pretty close to GEM with the Azores ridge holding off the Atlantic LP which is quite vigorous for the time of year. Further into FI HP remains mostly in charge but at the very end of FI, as the HP weakens, the European LP starts to take control with a new LP extending NW across southern Britain suggesting thundery outbreaks.

Welcome back to the GFS Parallel run and I'll be featuring this rather than the Control from now on and here's the 00Z at T+240:

More of an Atlantic influence with the trough looking to sink SE and join with the trough over Europe. Further into FI it's a see-saw between the troughs to the NW and SE and the HP to the SW and NE. The latter wins out at the very end of FI on this run.

The 00Z GEFS at T+240:

http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240

As we've seen, the "struggle" between the competing troughs and ridges continues but on this evidence the ridges are coming out on top with a majority of members looking to maintain HP close to or over the British Isles. Moving on toward the second May Bank Holiday and the signal for settled weather is very strong from the 00z. Whether the HP is in the right position or oriented to draw up the warmest air isn't clear but a majority of the members look warm to hot.

In summary, May is often a curious month with unusual synoptic patterns and sharp contrasts in temperature and weather. With the Atlantic often at its weakest, the influence of the Scandinavian HP and European trough are often felt more strongly now than at other times. Northern blocking is for the second day running a strong part of the ECM scenario while GEM is more anticyclonic and positive and GFS messy and uncertain. In truth, little change from yesterday.

Moving toward the last third of May, the possibility of unsettled conditions affecting the south east in particular from Europe remains but the signal for a dry and settled Bank Holiday has grown this morning and it may be that after the stampede for the sunshine last Monday we may see a repeat performance but it's far too early to be certain.

[Summerstorm]

I'll do a quick summary of what the ensembles are showing to see if I can find any trends and to add onto my post last night on working out where we are headed over the next couple of weeks. 

So looking at the GEFS ensembles for the six o clock run around 8 of them develop northern blocking. But only a few do to the same degree as the ECM with some weaker blocking, This means that the influence from the Azores high is stronger than the blocking.

About 40% have strongish blocking around greenland Vs 60% that have weaker or very little blocking. Looks like the odds are stacked more towards weak blocking and more HP influence although this may change from run to run. 

The midnight run has similar odds to the 6z run with around 4 or 5 members developing strong blocking. 

It would seem although the ECM has some support from the GFS ensembles it does seem to be a bit of an outlier. Although it may be supported by the ECM suite but I haven't seen them so I can't judge them. 

Looking at the sea level pressure on the ensembles in a graph shows the uncertainty, however the control run keeps the pressure above 1015hpa into later next week after a more unsettled spell throughout the weekend and early next week. Through the mid term it doesn't look too bad with not many precipitation spikes. Long term the prospects look promising with most of the members agreeing on height rises towards the end of the month as has been suggested throughout the week.

 

Edited May 10, 2018 by Summerstorm

[Man With Beard]

Clusters certainly making more of Northern blocking today

[stodge]

The 6Z Control has a very strong signal for blocking in low-res. Indeed, the evolution would, if occurring in early January, have this forum in meltdown:

A fine example of a retrogressing HP but of course no likelihood of verification. The GEFS, as James suggests and I alluded to earlier, is signalling strong HP for the second May Bank Holiday weekend but the majority of the Members show the HP centred to the north or north east of the British Isles so an E'ly or even NE'ly flow so it's hard to see any temperature records being broken this time and it may be eastern coasts will struggle with sea fog and haar but for most and especially the further west and northwest you are, it looks fine and settled.

Let's see how this plays over the next week or so.

 

[BlueHedgehog074]

14 hours ago, Summerstorm said:

Alright here goes nothing I'm going to try my first piece of analysis of the charts. So don't judge me if I get anything wrong  I'm by no means as knowledgeable as some of the other posters on here. Anyway back on topic...

The 18z looks more settled and anticyclonic than the twelve o'clock run. Think it all hinges on whether we develop any northern blocking admitidelly in the short term the weather isn't particularly inspiring but if we don't develop the blocking then prospects look a bit better down the line. 

The impact is shown here :

The jet is split on the 12z run which means that a trough develops out to the east.

On the 18z this is very different as the jet is weaker and therefore the LP system around S Greenland is weaker, so less pressure is put on the HP system which allows it to become more dominant. 

If you compare this to the ECM at 216hrs : 

The ECM seems keen to develop strong blocking around Greenland which means that low pressure is dragged underneath,Certainly the prospects from this run look unsettled compared to the other two GFS runs. 

The GEM seems to be closer to the ECM run however the ICON 12z is closer to the GFS 18z run not developing any blocking.

The upshot is a ridge of high pressure ridging in by later next week. Which is certainly the pick of the bunch if you are looking for pleasant weather followed by the GFS with the ECM public enemy no 1 for those of a warm disposition. 

So I think it's easy to see why the forecasters are labelling the forecast as a bit messy and there seems to be a lot of uncertainty between the models. It will probably take another few days to resolve where we are headed. 

Hope this was appreciated this someone 

Having a quick look at the models and would have to say that it does all look a bit messy at the moment. Some kind of blocking High Pressure to the North does look a possibility within the next few days or so, and the weather probably being pretty mixed overall. Though chances of some drier, warmer periods, especially between Lows and where ridging from the Azores and/or from any blocking to the North/North-East tries to influence the U.K.  

[Summer Sun]

12z UKMO has high pressure building into early next week t144 moving north of Scotland t168 later will show us where it might go

Edited May 10, 2018 by Summer Sun

[Mike Poole]

As others have said the outlook looks very messy for the next week or so, but for the models that go out longer than that, an improving outlook for the UK seems evident from the 12s.   One thing that has interested me in the recent model viewing compared to winter is that with the current slow evolution, lack of strong jet, the UKMO model doesn't have much to offer in terms of guidance as it only goes to T144 on all but one site, the timescale of interest is later than that at the moment.

ICON at T180:

GEM looks interesting at t240, would like to see where that would go after:

Potential plume?

GFS at same time, weekend after next looking really good here:

And still OK at the end of the run:

Overall impression, considerable improvement towards the end of next week than previous runs.  All good.

Edited May 10, 2018 by Mike Poole

[Mike Poole]

For the last couple of days, the output has had the UK stranded for some days in a col, a no mans land between the Azores high and Scandi high, but I think the 12z GEFS mean is suggesting the Azores high is winning, leading to a link up, this's not inconsistent with the 12z op runs.  GEFS mean at T192 and T252

 

Edit: and this at T348, remember this is a mean chart, a massive signal for a summery end to May:

Edited May 10, 2018 by Mike Poole

[Frosty.]

I agree mike, the GEFS 00z mean in particular also showed  high pressure eventually winning and you're right about the 12z mean later next week which shows the azores high ridging in..hopefully this trend will continue to firm up and following the changeable period with shallow slow moving troughs and ridges... high pressure will begin to dominate through late May into June!

Edited May 10, 2018 by Frosty.

[Mike Poole]

22 minutes ago, Frosty. said:

I agree mike, the GEFS 00z mean also showed the azores high eventually winning and you're right about the 12z mean later next week which shows the azores high ridging in..hopefully this trend will continue to firm up and following the changeable period with shallow slow moving troughs and ridges... high pressure will begin to dominate through late May into June!

Yes, GEFS is certainly saying so, here's the end of the run, both the mean and spread:

The uncertainty on this run set being so low over the UK at T384 is very interesting, of course the whole set could be biased, but I think we've seen a big shift today in the model output as a whole towards fine weather taking hold from about a week Saturday. 

Edited May 10, 2018 by Mike Poole

[Frosty.]

If anything, the GEFS 12z mean looks even better than earlier today..a very nice end to spring if this is anywhere near right..a very happy ending!

 

Edited May 10, 2018 by Frosty.

[Derecho]

Mixed outlook over the next week with some cool westerly air at times. Not too much rain apart from Sunday which could see a fair bit of rain the the east if the 12z GFS is to be believed.

Next thing I have my eye on is this potential northerly next week. The low could be quite deep. It may not all be too bad as the northerly could encourage pressure to build in its wake. Some high pressure could ridge in before the low moves SE across us but we shall see.

Could be some cool temperatures later on next week.

[I remember Atlantic 252]

Let's hope the northerly fails then! EC looks decent as it misses us, why chart small? mike's always are, but Quicksilver's above isn't?

Edited May 10, 2018 by I remember Atlantic 252

[johnholmes]

1 hour ago, Mike Poole said:

Yes, GEFS is certainly saying so, here's the end of the run, both the mean and spread:

The uncertainty on this run set being so low over the UK at T384 is very interesting, of course the whole set could be biased, but I think we've seen a big shift today in the model output as a whole towards fine weather taking hold from about a week Saturday. 

Are you seriously beleiving a chart at the end of the run?

Surely the experience of us all is that 240h is as far as any reasonable hope of it being close is about all we can expect. That only if all the upper air anomaly charts supports the synoptic output be that ECMWF, GFS or any other. If there is little agreement then it is best to wait.

Just my view.

 

[Mike Poole]

ECM 12z following the earlier runs, here clearly showing the arrival of the honourable member from the Azores at T144:

But then it blows up a big low in the Atlantic, leaving the high pressure struggling to build again. T240:

Don't think I buy this run, a 970 low looks out of place given the slack slow moving weather of late.  Will be interested to see if the ECM ensembles follow the GEFS.

[Mike Poole]

19 minutes ago, johnholmes said:

Are you seriously beleiving a chart at the end of the run?

Surely the experience of us all is that 240h is as far as any reasonable hope of it being close is about all we can expect. That only if all the upper air anomaly charts supports the synoptic output be that ECMWF, GFS or any other. If there is little agreement then it is best to wait.

Just my view.

 

No, not really, but it isn't one run, I was commenting on the very low uncertainty on the ensemble of 21 runs, which does look to me unusually small vis-a-vis the UK, and I did note the possible bias of the whole lot.  Usually the GEFS ensembles at this range are an averaged mess, the fact that they are not on this run I thought as indicative of a signal, that's all. A suggestion, no more, I was saying what the GEFS showed, and then suggesting what I think the 12z suite showed as a whole.  

Edited May 10, 2018 by Mike Poole

[Summer Sun]

1 hour ago, I remember Atlantic 252 said:

Let's hope the northerly fails then! EC looks decent as it misses us, why chart small? mike's always are, but Quicksilver's above isn't?

 

It's an error since the forum update last week if you just post the link images show but are not clickable if you save them to PC/Phone and upload they become clickable

[I remember Atlantic 252]

They're clickable, just need a magnifying glass to see them properly

[Mike Poole]

Well I've got to raise an eyebrow at this from the ICON 18z which has the Azores Scandi highs connect as early as this Sunday! T72:

Here at T111, could the good times be coming quicker? It's certainly the trend across model output today: