Model output discussion - first hot, thundery plume of the summer

[NApplewhite]

1 minute ago, NApplewhite said:

Average pressure in July and High pressure throughout August. Sadly the orientation of the High is to the NW so id expect average temperatures due to the NW origin of the air.

End of July is looking very wet anywhere north and west of London and the South East.

[knocker]

Oh to be on the east coast this morning

[mountain shadow]

That is one dreadful ECM op run which is really pushing a zonal start to July. Out of kilter with the ensembles I hope.

[northwestsnow]

Another excellent set of 00z runs with high pressure generally in control- only fly in the ointment being EC det - which has reverted back to yesterdays 00z run.

Mean out shortly- hopefully an outlier.

Ha MS we posted pretty much the same thing at the same time!

Edited June 27, 2019 by northwestsnow

[northwestsnow]

Mean is better but i suspect there will be a bit of a split with some members following the op-

My gut feeling is high pressure in our locale may begin to come under pressure from the Atlantic by the 2nd week in July,we'll see.

[knocker]

No great argument from the EPS mean anomaly this morning

[northwestsnow]

1 minute ago, knocker said:

No great argument from the EPS mean anomaly this morning

If that was a winter chart i would be hoping for some Atlantic retrogression and a NE-ly courtesy of a scandy trough..

Shirly that won't be on the menu in July?

[knocker]

15 minutes ago, northwestsnow said:

If that was a winter chart i would be hoping for some Atlantic retrogression and a NE-ly courtesy of a scandy trough..

Shirly that won't be on the menu in July?

Well the GEFs had a practice run next week dropping the TPV over Scandinavia

 

Edited June 27, 2019 by knocker

[Guest]

2 minutes ago, knocker said:

Well the GEFs had a practice run next dropping the TPV over Scandinavia

 

Has to be said the signs are there in the models in the 6-10days range for a significant pattern change. Fingers crossed we aren’t staring down the barrel of a southerly tracking jet or trough through true high summer.  

[Jonathan Rhodri Roberts]

10 hours ago, Mapantz said:

Whereas the UKV has temperatures of 28°C and 29°C in the Southwest on Friday. 

Unusually strong to gale force gusts of wind with that heat though for here in southwestern UK so that'll really take the edge of the temperature I'd have thought 

[Polar Maritime]

Gale force winds along S/W Coast's & Wales this evening.

[nick sussex]

A rather disappointing ECM op but I wouldn’t give up hope .

A northward correction in the jet track would improve things and it only really goes downhill by day 8 so certainly not at the stage you can put your money on it .

Meanwhile the vile heat continues here , although it could be worse , further east in France temps are already in the 33 c range! 

The level of heat is astonishing for this early in the season , I shudder to think what the temps might be hitting if this was mid end of July .

[Man With Beard]

Now we are within the period of interest re: upper air/surface air, we can see some charts showing how, between 850hpa and 1000hpa,  a layer of cold air has worked its way into the North Sea and been directed towards the UK.

The EURO4 charts below show 850hpa and 950hpa temperatures for today and tomorrow, and I've chosen midday to avoid additional night time cooling. 

  

  

You can see just how cold the air is at the 950hpa level - just 7C - which is actually much colder than the North Sea itself at the surface. This air must have originated north of Iceland as that's the only place where the sea is that cold at present, and, with low cloud and no land contact, it's had nothing to warm it. It is only now hitting the warm upper air (if you look at wind charts for 850hpa and 950hpa levels, you can see that they are coming from different directions). 

The result is this unusual situation where the air is much colder lower down in the atmosphere. Perhaps the only recent comparison I can think of is March 1st 2018 when we achieved the all-time record low March temperature - very cold uppers were in place in the morning, but on the south coast, uppers actually got above freezing by midnight. Yet the temperature stayed below freezing, and a few areas got freezing rain. The warmer uppers had not had time to affect the surface cold on arrival.

And so it is at the moment. You can see how the upper air is only quite slowly warming up the 950hpa air between Thursday and Friday - I guess because uppers are not yet that high over the North Sea, and because there's far less heating over sea than land. You can also see how pockets of the cooler 950hpa air have worked inland into places like Yorkshire, driven by a fair breeze - and also how Scotland is heating itself up due to being under almost stagnant winds.

In addition, you can see just how close the hotter surface air is to the south coast especially by Friday (perhaps why the Met Office persist with ideas that 30C or more may be breached on that day), though on these charts that air is just off shore.

But, at last, by Friday night, you can see the impact of the change in wind direction. Now with winds more southerly than northerly, the colder 950hpa temperatures are blown away, and we start to see a more normal relationship between 850hpa and 950hpa returning, with it being warmer closer to the ground (though not completely restored yet)

  

I guess if the breakdown could have stalled one more day, we might have eventually seen what we'd normally expect from a plume in terms of uppers/surface temperatures, and perhaps those high 30Cs.

This to me explains why we are not seeing the usual returns on a plume - bear in mind, plumes usually involve winds coming from France at all levels. This plume only has winds from France at an upper level until later on Friday (earlier for the SW).

So hats off to the models really, especially the ECM, which has been on to this since Friday. If we could have freely seen the 950hpa temperature/wind pattern at that time, it would have made a lot more sense (please let us know if anyone knows such a place!!). What I'm slightly confused about is that some professionals must have had access to this data, but didn't think to check - surely anyone making a forecast for a living must give extra weight to the ECM, and the disparity it was showing would have made them think to look at the layers between 850hpa and 1000hpa. I saw a quote from a professional forecaster going for really high temperatures based upon 850/1000 thicknesses alone. Such an analysis, alas, was evidently not enough for the scenario this week.

[johnholmes]

Thank you for the very good post on what seems to have happened. I suspect that UK Met may have an internal review on why they were not very quick to spot what the model(s) were showing.

[danm]

3 minutes ago, johnholmes said:

Thank you for the very good post on what seems to have happened. I suspect that UK Met may have an internal review on why they were not very quick to spot what the model(s) were showing.

Hi John, what is odd is that the Met Office app (presumably using raw UKMO data) has been showing temperatures for this week in the low to mid 20s at best, which was correct, yet some of their video forecasts at the same time were showing high 20s/low 30s for parts of the south, completely at odds with their app and website. Naturally that’s due to human input in the video forecast, but it is strange how bullish they were for higher temperatures when even their own raw output was suggesting otherwise, and most other model output seemed to reject the higher temperatures too. 

Funnily enough it’s the BBC who have been consistent this whole week. Their temperature forecasts have been bang on (video and app/website). 

Edited June 27, 2019 by danm

[Derecho]

29 minutes ago, Man With Beard said:

This to me explains why we are not seeing the usual returns on a plume - bear in mind, plumes usually involve winds coming from France at all levels. This plume only has winds from France at an upper level until later on Friday (earlier for the SW).

Yes some earlier forecasts from the Meto were too high but I do think it will be a halfway house and the GFS went way too low, here are the predicted temperatures at 14h today from Sundays 18z and the current temperatures at 10am.

  

Clearly too low in parts of the South. Chivenor for example is already at 21C and parts of the NW are also at 21C, so for a few days in advance the GFS 2m temperatures definitely appear to be cold biased. However I don't expect anything above 30C today.

[knocker]

32 minutes ago, Man With Beard said:

 

(if you look at wind charts for 850hpa and 950hpa levels, you can see that they are coming from different directions). 

 

I

I'm not quite following this bit MWB apart fro the different position of the ridge

 

[joggs]

2 hours ago, knocker said:

The above is interesting

Why?

[mb018538]

Slightly concerning that polar heights just won’t drop off at all, and after a recovery to neutral towards July.....there is a trend there again towards a negative AO as we head into July. The met update today states it if we fall into the wrong spot of the block we could see an early June re-run. I thought we may have turned a corner but we could be heading back to square one by mid July. Ensembles trending wetter and average pressure falling too after the first week of July.

[knocker]

2 minutes ago, joggs said:

Why?

Because the post referred too bears no resemblance to this.

[Man With Beard]

14 minutes ago, knocker said:

I'm not quite following this bit MWB apart fro the different position of the ridge

 

ok slight lack of clarity on my part - the difference is noticeable in the areas where the very warm air gets in at an upper level (SW today, more widely tomorrow):

  

   

Edited June 27, 2019 by Man With Beard

[knocker]

10 minutes ago, Man With Beard said:

ok slight lack of clarity on my part - the difference is noticeable in the areas where the very warm air gets in at an upper level (SW today, more widely tomorrow):

  

  

And hopefully the Camborne midday sounding will show the 'colder' air undercutting the warm air aloft. Go and stand in corner immediately for using that word knocker

[Methuselah]

45 minutes ago, johnholmes said:

Thank you for the very good post on what seems to have happened. I suspect that UK Met may have an internal review on why they were not very quick to spot what the model(s) were showing.

Given that, for several days now, it's been clear from the charts that the surface isobars lead, via the North Sea, back to the Iceland area, some forecasts (for surface conditions) have clearly been more than a tad 'optimistic.

Is it possible that the perceived need for more and more science can sometimes overwhelm what far simpler observations are actually indicatting...?

Edited June 27, 2019 by Ed Stone

[shaky]

Fantastic gfs 06z for next warm!!sunny warm light winds!!looks better than the 00z with high more stronger at 168 hours!!

[Derecho]

28 minutes ago, Ed Stone said:

Given that, for several days now, it's been clear from the charts that the surface isobars lead, via the North Sea, back to the Iceland area, some forecasts (for surface conditions) have clearly been more than a tad 'optimistic.

Is it possible that the perceived need for more and more science can sometimes overwhelm what far simpler observations are actually indicatting...?

Could well be the case, I think ECM was the first to pick up on this cooler North Sea flow. I highlighted it last Friday but only in terms of cutting off the high upper air temperatures. They are still heading our way of course but I didn't realise how stubborn the cool surface air would be to remove.

So ironically that little low feature the ECM picked up on was enough to peg temperatures back across the whole of the UK. The double whammy is that when it did actually cross the UK it hardly produced any thunderstorms at all.

Before then a lot of forecasts were going for the early-mid 30s during the weekdays this week but that was because the plume from France pushed Northwards without any cooler North Sea air being able to undercut it.

Meteorology eh?

Edited June 27, 2019 by Quicksilver1989