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

[Man With Beard]

21 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...?

Fair point but if the air around Iceland had originated in the tropics, I suspect the resultant North Sea temperatures at 950hpa would have been 5C or so warmer than currently showing (perhaps someone knows a site where this can be tracked). I think what got us scratching our heads a few days ago was that we can find similar historic charts with a North Sea flow even from the top of Norway producing much higher temperatures - it's likely that even finer differences than a simple look at the pressure charts are responsible for the very strange upper/surface air correlation.

[Frosty.]

This plume still looks like delivering 34c 93f on saturday across the SE and widely high 20's to low 30's celsius!

[MATTWOLVES 3]

Was slightly concerned by the ECM op this morning, especially after witnessing a few days of upgrades regarding settled conditions.. However the mean and ens paint a better picture overall. Even though there is a decrease regarding pressure with the mean, the op was certainly an outlier! 

[Methuselah]

GFS 06Z suggesting a change might be about occur, come T+240+?

  

[Alexis]

1 hour ago, Man With Beard said:

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.

Brilliant explanation. Thanks.

[mushymanrob]

3 minutes ago, Ed Stone said:

GFS 06Z suggesting a change might be about occur, come T+240+?

  

indeed, that scandinavian trough is likely to cool things down across europe which might well offer some relief to those lucky/unlucky enough to be roasting atm.  its looking to me that it will be a big player in what we get for the first half of july at least,. a duel between that and the azores ridge looks like taking place just to our east... hopefully that trough will shift further east or diminish, allowing ridging to push in from the west.

[StormChaseUK]

Plume finally arrives on Saturday then ends er.. Saturday.

Outlook warmer for a time away from NE coasts,   then turning cooler from the NE

Heat still clinging onto France.

[Fourty Point Three Degrees]

ECM has ditched the idea of a 2nd plume and is now heading towards another Greeny high potential with the UK on the wrong side of the Azores/Greeny block as we saw earlier in the month. If this comes off it could determine how the rest of Summer will pan out.  Its all in lala land for now so take it with caution
 

[knocker]

1 hour ago, Man With Beard said:

Fair point but if the air around Iceland had originated in the tropics, I suspect the resultant North Sea temperatures at 950hpa would have been 5C or so warmer than currently showing (perhaps someone knows a site where this can be tracked). I think what got us scratching our heads a few days ago was that we can find similar historic charts with a North Sea flow even from the top of Norway producing much higher temperatures - it's likely that even finer differences than a simple look at the pressure charts are responsible for the very strange upper/surface air correlation.

Only this, perhaps some colder air entrained from N. Scandinavia, and thickness charts would be no use. Yes they should indicate the colder air but it would be relative and too broad scale I would imagine.

But just to add one more observation. I think too many assumptions are being made regarding the METO temp forecasts. To assume that Exeter failed to notice the CAA in the boundary layer and the reasons for it I find a tad ridiculous. Ergo there must be reasons why they semi stuck to their forecasts that we are not aware of.

Edited June 27, 2019 by knocker

[StormChaseUK]

5 minutes ago, 38.5*C said:

Azores/Greeny block as we saw earlier in the month. If this comes off it could determine how the rest of Summer will pan out. 
 

That would be an awful turn of events if the rest of the summer was like May/June  - I doubt we would be unlucky to have May - August

[Frosty.]

There's still a lot to like about the Ecm 0z ensemble mean, especially further south, less so towards day 10 but even so it's probably still a north / south split..plenty of fine and warm weather next week I would think!

[mb018538]

Not sure about that (warm) - the ridge doesn't look like it will be in a particularly favourable position for anything too warm, with cooler air spilling around the high. 

Probably around average, with a trend to more unsettled conditions as we head out of the first week of July.

[SMU]

2 hours ago, Man With Beard said:

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, 

Great post-

The initial progs ( when the GEM etc ) were churning out 35-38c maxes the cooler air & flow was only sliding SE through Scandi into the low countries & the UK always sat in SSE air- then slowly that flow carved out more SE flow before eventually being modelled ENE mixing in that chilly air...

A shame really as the all time record would have been under threat sunday should we have sustained the flow for another 24 hours -

Still I think we breach 33-34 Sat, ironically for many the heatwave will probably end up being better as the max readings have been somewhat tempered....

[Guest]

9 minutes ago, mb018538 said:

Not sure about that (warm) - the ridge doesn't look like it will be in a particularly favourable position for anything too warm, with cooler air spilling around the high. 

Probably around average, with a trend to more unsettled conditions as we head out of the first week of July.

Average at best and potentially poor again down the eastern side. Might be a bit early to start worrying but a big summer wobble potentially on the cards. Would be desperately unlucky to get locked into the Azores/Greeny ridge and associates trough twice in two months. 

[mb018538]

1 minute ago, Alderc said:

Average at best and potentially poor again down the eastern side. Might be a bit early to start worrying but a big summer wobble potentially on the cards. Would be desperately unlucky to get locked into the Azores/Greeny ridge and associates trough twice in two months. 

Ties in with NOAA 8-14 day outlook:



Sadly there are very strong polar heights and +ve Greenland heights, as well as most of the high latitudes. Could just be a matter of time before we get stuck in a rut again, let's hope not eh.

[Frosty.]

35 minutes ago, mb018538 said:

Not sure about that (warm) - the ridge doesn't look like it will be in a particularly favourable position for anything too warm, with cooler air spilling around the high. 

Probably around average, with a trend to more unsettled conditions as we head out of the first week of July.

If you were referring to my post, I only said warm as in pleasantly warm, didn't say or suggest anything about very warm..it looks decent for much of next week, especially further south..currently! 

Edited June 27, 2019 by Jon Snow

[Methuselah]

06Z ensembles:   

                             

So, not exactly great, but not too bad either...Certainly nowt to trigger any Mystic Megian summer 'doomcasts', as yet...?

[mountain shadow]

6 minutes ago, Ed Stone said:

06Z ensembles:   

                             

So, not exactly great, but not too bad either...Certainly nowt to trigger any Mystic Megian summer 'doomcasts', as yet...?

There's more to the country than London though.

[Methuselah]

2 minutes ago, mountain shadow said:

There's more to the country than London though.

Well, I did consider commenting on the ensembles for everywhere on the list, but came (after giving it a lot of thought) to the conclusion that the resulting post might be a tad 'long winded'...?

[StormChaseUK]

1 hour ago, Steve Murr said:

Great post-

The initial progs ( when the GEM etc ) were churning out 35-38c maxes the cooler air & flow was only sliding SE through Scandi into the low countries & the UK always sat in SSE air- then slowly that flow carved out more SE flow before eventually being modelled ENE mixing in that chilly air...

A shame really as the all time record would have been under threat sunday should we have sustained the flow for another 24 hours -

Still I think we breach 33-34 Sat, ironically for many the heatwave will probably end up being better as the max readings have been somewhat tempered....

Agreed excellent post.  One of the best I have read on model output discussion. A lot of people were dismissing the NE impact yesterday "it's 22C in my back garden so it can't be 8C where you are" nonesense.  Good to see an explanation at last of why it was so cold.  Met Office should explain info like that above.

Just shows how close we were to breaking records if the plume made it in.

Edited June 27, 2019 by StormChaseUK

[Derecho]

1 hour ago, 38.5*C said:

ECM has ditched the idea of a 2nd plume and is now heading towards another Greeny high potential with the UK on the wrong side of the Azores/Greeny block as we saw earlier in the month. If this comes off it could determine how the rest of Summer will pan out.  Its all in lala land for now so take it with caution
 

How does a Mid-Atlantic high in the first week of July dictate the rest of the Summer? There is no evidence that it does.

[Derecho]

17 minutes ago, StormChaseUK said:

 "it's 22C in my back garden so it can't be 8C where you are" nonesense.  

Eh?

The argument was that maxima may be underestimated where the sun comes out, your statement makes no sense.

[knocker]

52 minutes ago, StormChaseUK said:

 

Just shows how close we were to breaking records if the plume made it in.

The plume did make it in but not without air in the boundary layer being modified initially as MWB has gone to a great deal of effort to explain

Edited June 27, 2019 by knocker

[MATTWOLVES 3]

I'm a bit miffed by some of the gloom setting in again currently. All on the back of slightly less encouraging models runs overnight! This talk of a trough setting up in our vicinity is no more likely than a strong blocking high bringing us plenty of warm settled conditions, Infact I wouldn't be at all surprised to see further hot plumes making there way across us if we can get high pressure to sit favourably! Enjoy the next few days if you like the heat and are in a favourable location folks... It looks perfick!! 

[knocker]

The illuminating Camborne midday sounding

Massive inversion 958mb - 932mb 14.5C - 23.6C capping the cold advection below.

900mb temp 23.0C and 850 22.25C

SW 080/17kts

950mb wind 100.40kts and the 850 120/20 as the upper winds slacken and veer

 

 

Edited June 27, 2019 by knocker