Model output discussion - summer rolls on

[Methuselah]

2 minutes ago, Frosty. said:

I don't understand why there are doom and gloom comments, the GEFS 6z mean shows a north / south split next week, higher pressure and best weather further south but still a chance of some rain but the coolest and most changeable conditions further north and then there are strong signs that high pressure will become more dominant for most / all of the uk beyond next week with predominantly warm and settled weather.

Indeed Karl...It's hardly as if Day 10 Summer's over 'solutions' are famed for their reliability, is it? 

[len]

7 hours ago, Man With Beard said:

But look at how this Mid-Atlantic ridge is expected to develop. Compare D9, D11 and D13. Watch how the oranges /reds work their way, on the majority of clusters, from left to right. This suggests to me a good chance of a ridge passing through the UK at a higher latitude than in the past 10 days, eventually turning the flow more southerly. 

Thanks for posting these regularly MWB.

They look really interesting. Trouble is, (my Icelandic being shakey n'all) I haven't a clue what they mean MWB?

I've been hoping someone else would ask.....but obviously they all read Icelandic.

Any chance of a rundown please?

Len

[Frosty.]

The ukmo 12z looks more changeable and cooler the further north you are but pretty decent across southern uk with some nice azores ridging and warm temperatures, very warm at times for the s / se.

[Polar Maritime]

The GFS shows some pretty cool uppers pushing South into Wk2.

 

 

[Mike Poole]

The push of high pressure over the UK, which I mused about last night seems still to be on the cards although obviously it's late into the runs so could change.

GEM at T240:

GFS takes until T264:

but looking at the rest of the run, it doesn't seem to push the high east of the UK to draw up significant heat.  Still more runs needed.

[Frosty.]

Another good GEFS mean longer term..the 12z indicates increasing support for high pressure building in across the uk..As for next week, from what I can see it's a typical n / s split..best of the fine and warm weather across southern uk, generally cooler and more changeable further north but then towards the end of august and into early september the signs are encouraging for another warm anticyclonic spell..glass half full!

Edited August 16, 2018 by Frosty.

[Mike Poole]

Interesting end to the ECM 12z, yesterday had the high pushing into the UK at the end of the run. This time pushing through, here T240:

Interesting feature to the south as well.

[Singularity]

GEFS holding pretty steady today (and seeming very sure of itself!), EPS still all over the place in terms of ensemble spread.

The bias adjusted versions shown above are both a couple of days quicker with the mean MJO cycle initiation time compared to the anadjusted. 

It will be interesting to see how much effect, if anything significant, adjustments to a quicker initiation have on the pattern, if they take place. Sometimes the bias adjustment gets it wrong, though with the Nino base state in place, they currently make sense to me.

 

The 12z operational runs might well be at the sooner end of the scale, as they've allowed more in the way of ridging to reach across Europe, resulting in an extra day (or two in the far south) of warmer than average conditions compared to the preceding runs.

There's now some considerable mid-Atlantic amplification being modelled next Thursday or Friday, in response to a major clash of airmasses over NE Canada giving rise to a very large and deep trough that amplifies the downstream pattern just when the ridge would otherwise head east to the UK. I'm unsure whether forcing from the tropics will entirely dictate whether this major storm actually comes about or not; chaotic variability might be enough to make or break it.

Even with it coming about, the amplified ridge topples after 1-2 days and we see some ridging toward Scandinavia being explored, so I'm wondering if this could be the final hurdle to get past before we arrive at the return to a Nino-like pattern that has been sought after by heat/thunder enthusiasts ever since the last spell of supportive weather drew to a close on 7th August.

 

If we can get there by next weekend, there will be one week left for the month to redeem itself, or at least make itself seem less of a shortfall on what could feasibly have been (had there not been such a strong CCKW so-timed as to prolong the 'Nino lull').

In many ways, knowing what could have been can be one of the worst things about being a meteorologist, as the most exciting or satisfying outcomes have a habit of not coming about. Much of late Feb through early August was a welcome respite from that! Let's not forget just how much 2018 has given us (well, most of us, depending on your tastes!) .

[ICE COLD]

Nice to see the pretty blue colours back on the ECM . Wonder if the PV will ramp up early this year ?? 

[Frosty.]

13 minutes ago, ICE COLD said:

Nice to see the pretty blue colours back on the ECM . Wonder if the PV will ramp up early this year ?? 

As a coldie, I like to see the expanding cold pool across the high arctic from the end of summer and especially  through autumn but at the same time i'm not ready yet to let go of summery potential in mid august and the ecm 12z shows some nice azores ridging and warm fine weather across southern uk, indeed potentially very warm for a time depending on sunshine amounts, there is a cool unsettled blip from the north later next week before high pressure ridges in from the west and temperatures start to rise once again.☺

 

[cheese]

1 hour ago, ICE COLD said:

Nice to see the pretty blue colours back on the ECM . Wonder if the PV will ramp up early this year ?? 

If it can hold off until it is actually useful, i.e November onward, then fine by me. 

[Man With Beard]

4 hours ago, len said:

Thanks for posting these regularly MWB.

They look really interesting. Trouble is, (my Icelandic being shakey n'all) I haven't a clue what they mean MWB?

I've been hoping someone else would ask.....but obviously they all read Icelandic.

Any chance of a rundown please?

Len

I'll try! 

A bit of it is my guesswork. 

The charts show the ECM ensembles - 51 of them - gathered into clusters (which are groups of ensembles with a similar pattern). 

The colours show the variance within the particular cluster from the expected 500mb values for the time of year (more red = higher values, more blue = lower values). So red means more chance of a ridge, but care is needed as if you'd normally expect a deep trough in a location at the time of year on the chart, you'd need very high anomalies (deep red) to get an actual ridge. 

The lines i think are just one example run from the cluster, showing pressure lines at 500mb level. 

Biggest cluster is top left. 

[damianslaw]

Quite a bit of consistency between ECM and GFS today, both showing a continuation of the rather changeable conditions in a broadly westerly airflow, average temperatures overall, and quite humid at times - warmer for a time in the SE, before we see the azores high amplify thanks to frontal trough activity moving out of NE Canada and edging SE over the UK just before the bank holiday weekend, a couple of cool showery days and chilly nights, with the ridge quickly nosing NE behind the trough and heights building to the NE as well - so a possible fine warm dry end to August could be on the cards. 

Keep an eye on developments over NE Seaboard though, some cold uppers appear to be developing relatively early this year over Greenland and could drive some deep cyclogenesis - another feature as predicted for Thursday/Friday could easily crash the promise of a fine end to August.. by late August there is far greater forcing from the polar jet than earlier in the summer season, its far more difficult to sustain ridge development than from March - July.

[Mike Poole]

5 hours ago, len said:

Thanks for posting these regularly MWB.

They look really interesting. Trouble is, (my Icelandic being shakey n'all) I haven't a clue what they mean MWB?

I've been hoping someone else would ask.....but obviously they all read Icelandic.

Any chance of a rundown please?

Len

To add to MWB response ^, I've put most of this through Google translate a while back and have come to the following conclusions, anyone please correct me if I've got details wrong. 

A cluster is a group of runs that meteorologists think are similar for forecasts several days out.

Example chart:

The colours show geopotential height anomaly at 500mbar (Z500) against 1981-2010 data, a question remains in my mind whether this changes with seasons?, contours show actual Z500 values for one run for each cluster (of runs that are deemed by the guys at ECMWF to be similar).

Top left is the time of the run, and the time of the forecast.

Top right, the flokkunigluggy thing is the time frames that this particular cluster is valid, before or after there may be more or fewer clusters, depending on what the models are saying.

Then the 6 cluster diagrams, in order of decreasing likelihood, these break the 51 ECM ensembles into groups that behave the same way as uncertainty increases as forecast time increases. The numbers above each chart state the number of runs in each cluster, and the percentage, and then the Fulltr. This means 'delegate' so this is the number of the ensemble run which best reflects the cluster as a whole, so it's not an average, it's one run that best fits the defined cluster in the interpretation of ECMWF. 

Finally, the bottom bit depicts four synoptic patterns relevant to Iceland, and fortunately for us also!,  and gives their likelihood from climatology, colour coded as follows:

Blue - Positive North Atlantic Oscillation (NAO)

Green - Negative NAO

Red - (Scandi) Blocking

Purple - (Atlantic) Ridge

These colours also border the cluster plots above, basically saying (because the plots themselves cover such a small area of the globe) what the wider picture for each cluster is. 

Hope that helps!

 

Edited August 16, 2018 by Mike Poole

[len]

23 minutes ago, Mike Poole said:

To add to MWB response ^, I've put most of this through Google translate a while back and have come to the following conclusions, anyone please correct me if I've got details wrong. 

A cluster is a group of runs that meteorologists think are similar for forecasts several days out.

Example chart:

The colours show geopotential height anomaly at 500mbar (Z500) against 1981-2010 data, a question remains in my mind whether this changes with seasons?, contours show actual Z500 values for one run for each cluster (of runs that are deemed by the guys at ECMWF to be similar).

Top left is the time of the run, and the time of the forecast.

Top right, the flokkunigluggy thing is the time frames that this particular cluster is valid, before or after there may be more or fewer clusters, depending on what the models are saying.

Then the 6 cluster diagrams, in order of decreasing likelihood, these break the 51 ECM ensembles into groups that behave the same way as uncertainty increases as forecast time increases. The numbers above each chart state the number of runs in each cluster, and the percentage, and then the Fulltr. This means 'delegate' so this is the number of the ensemble run which best reflects the cluster as a whole, so it's not an average, it's one run that best fits the defined cluster in the interpretation of ECMWF. 

Finally, the bottom bit depicts four synoptic patterns relevant to Iceland, and fortunately for us also!,  and gives their likelihood from climatology, colour coded as follows:

Blue - Positive North Atlantic Oscillation (NAO)

Green - Negative NAO

Red - (Scandi) Blocking

Purple - (Atlantic) Ridge

These colours also border the cluster plots above, basically saying (because the plots themselves cover such a small area of the globe) what the wider picture for each cluster is. 

Hope that helps!

 

Thanks to both you & MWB.

Much clearer. I get it about 80% now! Hope it helps others.

[Mike Poole]

Pub run maybe about to go off on one, push this on faster we'll see, T120:

Edited August 16, 2018 by Mike Poole

[Mike Poole]

Interesting chart at T240 on the GFS 18z

Return of summer for the south! . It has that low to the south as per ECM but not in quite the same place.  Interesting times once again.

Then this at T276:

Then it loses the plot, if it ever had it.  But that hot late August early September is definitely on the cards, for me it's never been off them! 

Edited August 16, 2018 by Mike Poole

[johnholmes]

Little sign on the 2 available 500 mb anomaly charts I use of any marked change in pattern. No GFS for 2 days now but ECMWF abd NOAA 6-10 show a similar pattern, consistently over the past 2-3 days of a flow just N of W, a day or two of settled weather for sure at times but no prolonged ridging in the next two weeks would be my suggestion based on their outputs. Better the further S and E one lives. Warmth there at times, even a bit humid depending on just where any surface high cell develops temporarily but no prolonged dry and heat.

Both show troughing into Europe

links below

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[carinthian]

That's one heck of a frontal wave at 72t forecast time stretching from the deepest Tropics to the Arctic Circle. Try forecasting where the rain will be from that set up.  Staying hot over continental Europe this weekend and possibly SE England tapping into some of that heat for a while. Obviously the main frontal activity looks to be further North and West across the British Isles, but where precisely will this mainly occur ( ie ) Will the rain affect Trent Bridge for the start of the next test match or not? Based on the raw output to produce that chart, I would say difficult to forecast right now.

C

Edited August 17, 2018 by carinthian

[Man With Beard]

@Mike Poole brilliant analysis of the clusters charts - just to add, the anomalies are according to climatic norms for the particular month.

Back to the output : well interesting to see how the models, for once, have pushed back the introduction of cooler air - a few days ago we were thinking Tuesday next week, but now Thursday may be the day for the southern half, UKMO for example

Make no mistake, if cloud levels allow, it could be hot next week. The east coast looking particularly good. 

Onto the clusters, a really good test coming up, because for several runs now it has been promoting a height rise to the east around the end of the bank holiday - last night's chart for 27th below:

Strong trough Atlantic VS strong ridge to the east = a fair chance of a southerly draw, at least temporarily. 

This is still 11 days out though so we'll be interesting to see how close it gets. 

 

Edited August 17, 2018 by Man With Beard

[mb018538]

Most of those look quite transient again, for something significant we really need to see those darker reds appearing like earlier in summer:

 

NOAA 6-10 and 8-14 day anomalies seem to be pulling the centre of the high more towards the south of Greenland and the states rather than our way!

http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

[Frosty.]

Longer term the GEFS 00z mean looks great, it indicates high pressure becoming the dominant feature and pleasantly warm surface conditions, especially across england and wales.☺

[Interitus]

15 hours ago, Polar Maritime said:

The GFS shows some pretty cool uppers pushing South into Wk2.

 

 

The interesting thing is that this appears to be associated with a Rossby wave packet which ended the UK heat wave last week. The chart below shows after initial amplification over the north Atlantic (start of arrow, top right of diagram), the wave packet crossed Eurasia sending a surge of warmth northwards into the Arctic (Tiksi reached 24.9°C, normal August max 11.1°C) and a northerly flow is contributing to a wet few days for northern Japan (> 3 inches rain in last 24 hours) and the coolest temperatures since early June for some places. In the coming days it's set to lead to a warm up for Alaska and western Canada but then cooling and some early frosts and possibly some snow in it's wake, for more central Canada and towards Hudson Bay. Finally it reinvigorates over the Atlantic and reaches the UK again around the end of next week.

(chart courtesy Steven Cavallo http://arctic.som.ou.edu/scavallo/real_time_plots.html)

 

[danm]

The NW’erly has been watered down on this mornings runs. All in all the week ahead looks fine and warm for many, always that bit more unsettled further north. 

We do get a NW airflow of sorts by Friday but then both the GFS and ECM show the high building back in, to southern parts at least, by the weekend. 

So no heatwave (although it could temporarily get into the high 20s midweek in the south) but plenty of fine, settled weather with low to mid 20’s for many. Can hardly complain with that. 

Edited August 17, 2018 by danm

[Singularity]

 

This latest GFS run on the right-hand side has added a little low running across Wed-Thu (no thanks, had enough of those lately!) hence the quicker arrival of cooler air from the northwest, but I'm watching with interest the way that the trough near Iceland keeps trending west - it's not going to take much more for it to be caught up with by the deep NE Canada trough, potentially becoming an extension of it with a flatter shape that allows ridging to hold on more across S UK Thu-Fri before building back across more during the weekend.

Something to keep an eye on, at least. The 06z shows the flatter high even without the full merger of the two troughs.

Even with this, though, it looks difficult to avoid another fresh, blustery sort of Friday for the N half of the UK such as is being experienced today. I remain hopeful that the final week of the month will be kinder to those who reside there.