Model output discussion - summer rolls on

[Mike Poole]

GFS 18z seems to have rediscovered the heat pump.  Here T174:

 

 

[Leo97t]

Gfs starts well but becomes very westerly. I imagine this pattern is set in stone now. First 50C in Europe I've ever seen on a model map

[East_England_Stormchaser91]

41 minutes ago, Mike Poole said:

GFS 18z seems to have rediscovered the heat pump.  Here T174:

 

 

I’m not sure what GFS is on, but this run seems utterly bogus in suggesting there will only be 300-400j/kg of CAPE with a -2 LI under 33-34c with a destabilising plume/ surface shortwave @186hrs. Seems as though the models can’t seem to get with grips on the way this is going to be ironed out. My thoughts being with the upper 500hpa flow seeming to be very westerly causing uncertainty amongst the models as to how far north this prospected heat/plume will get. We need more of a kink in the upper flow before I’m going to start getting any confidence that we will see the best out of this, like last week. 

[Cheshire Freeze]

5 hours ago, Singularity said:

Yes but, with all due respect to them,  I don't give a flying fish about that as their tools are model based, and some of those models are well out of kilter with what other approaches suggest should happen based on past precedent and the notion that those strangle far west solutions are related to the models not seeing the wood for the trees, as a large but ill-fitting oak looms large in the form of the completion of the latest tropical cycle (declining MJO).

I must say, it's surprising that they find such confidence anyway, when GFS and ECM have completely opposing SLP patterns for Scandinavia. I can see that they're playing it safe by going with a middle ground - their anomaly pattern corresponds to actual ridge placement that's neither as far west as ECM or as far east as GFS - but that's not to say that the middle ground is immensely likely to come about. Perhaps they have a margin of error wide enough that either the ECM or GFS outcomes would still count as a good result?

Also for what it's worth, NOAA don't currently make use of the GSDM that I and Tamara base a lot of our thinking on, due to a lack of recent research on their part.


I won't deny that no approach is infallible, though; something like the ECM 12z is by no means being ruled out on my part.

I'm glad you added that caveat because we have seen many times (more especially in winter) that what should happen due to current teleconnections isn't always what transpires for our shores. 

An avoidance of another really hot spell will be good for numerous people who have found this summer to be a bit too much. So, if we are to see a gradual winding down of the summer from here on in then I don't think many people can grumble, given what we've experienced thus far.

[Captain Shortwave]

The hypothetic question in response would be the question of whether coldies woul be fine with a mild February after two long cold months prior to it? I suspect the answer would probably be no and I guess for records sake a very warm to hot August would challenge the very top of the summer seasons in the UK.

Back to the models (day 5/6)

UKMO

   

   

Well it isn' the extreme solution of yesterday morning but neither does the high pull away but we end up with a weaker surface high over the UK but with the heat very close to the south and in fact the south would be approaching very hot, the north considerably cooler though it would still be fine and settled.

GFS
   

   

Strange really, the Euros really have been a bit all over the place, the GFS has pretty much shown the same solution of drifting the high slowly east for several runs in a row with only slight variations. Another attempt to push the heat north into the following week as the Altantic low slowly approaches us and engages with a heat low developing close the the Bay of Biscay.

 

[Man With Beard]

Finally emerged from my internet free holiday (note to self, always check if mobile internet will work on your phone abroad before leaving ). When I left, the clusters were showing this for Thursday (then D13) 

And now at D3

Some clear changes but overall not a bad effort for the UK. So the threat of more significant heat for the UK is still there for the start of August (though toned down slightly from the D13 chart due to lack of Atlantic low "pump"). However where the heat gets to still seems debatable. Even at just D5, lots of subtle variations which would affect how far north the heat goes and how extreme the heat is. Certainly last night's ECM op (cluster 3) is neither the main cluster nor the best for getting heat further north, in fact all other clusters would appear better positioned for more extensive heat over the UK by the weekend. 

Also in my mind is the idea that the models often underestimate the Scandi ridge and overestimate an Atlantic ridge. If that holds true, expect the models to edge towards a UK High scenario for next week - or, at least, a slightly more of a 'topple' from any Atlantic heights in our direction. 

Edited July 31, 2018 by Man With Beard

[shaky]

16 minutes ago, Man With Beard said:

Finally emerged from my internet free holiday (note to self, always check if mobile internet will work on your phone abroad before leaving ). When I left, the clusters were showing this for Thursday (then D13) 

And now at D3

Some clear changes but overall not a bad effort for the UK. So the threat of more significant heat for the UK is still there for the start of August (though toned down slightly from the D13 chart due to lack of Atlantic low "pump"). However where the heat gets to still seems debatable. Even at just D5, lots of subtle variations which would affect how far north the heat goes and how extreme the heat is. Certainly last night's ECM op (cluster 3) is neither the main cluster nor the best for getting heat further north, in fact all other clusters would appear better positioned for more extensive heat over the UK by the weekend. 

Also in my mind is the idea that the models often underestimate the Scandi ridge and overestimate an Atlantic ridge. If that holds true, expect the models to edge towards a UK High scenario for next week - or, at least, a slightly more of a 'topple' from any Atlantic heights in our direction. 

Which ecm seems to have done this morning between 96 and 144 hours compared to last nights 12z run!!high more over the uk and not as amolified over greenland!!

[Man With Beard]

An exceptional GEFS mean chart for early next week 

Euros this morning are close but not quite following on the northern extent of heat - but clearly this kind of solution is "in the game". Mid 30Cs again a possibility on this chart. 

[SLEETY]

Autumn not far away on the latter stages of ECM either.Perhaps a final shot at some serious heat before then,but nothing long lasting it’s looking like.

[Yarmy]

Anyway, behold the GEM at T156:

 

[mushymanrob]

11 hours ago, Scorcher said:

You'd think listening to you and Mushy tonight that there was nothing noteworthy at all coming in the next few days in terms of heat. Just to be clear to anyone who is not well versed in reading charts, there is some heat coming, especially further south.

It won't be record-breaking but some of the temperatures in the south on Friday/Saturday would be the warmest of the whole year in a lot of summers!

BBC going for 32C in London on Friday, and the GFS is showing 33C- we could still end up with some places reaching the mid thirties. Now that's hot by anyone's standards. We didn't get near that in the whole of the summer of 2007. Hot in the south until Monday at least.

Funny how this amazing summer has skewed people's perceptions. 

 oh please.... if its one thing that really ticks me off is being credted with saying something i didnt!

this weekends mini heatwave has never been in doubt! niether i nor daniel has said otherwise!

but beyond that by this time next week theres precious little sign of any more heat, and IF that ridge establishes to our west, as the ever favoured ECM predicts, then there will be no fast track back to any heat - if we get any more at all.
 

11 hours ago, Singularity said:

Yes but, with all due respect to them,  I don't give a flying fish about that as their tools are model based, and some of those models are well out of kilter with what other approaches suggest should happen based on past precedent and the notion that those strangle far west solutions are related to the models not seeing the wood for the trees, as a large but ill-fitting oak looms large in the form of the completion of the latest tropical cycle (declining MJO).

I must say, it's surprising that they find such confidence anyway, when GFS and ECM have completely opposing SLP patterns for Scandinavia. I can see that they're playing it safe by going with a middle ground - their anomaly pattern corresponds to actual ridge placement that's neither as far west as ECM or as far east as GFS - but that's not to say that the middle ground is immensely likely to come about. Perhaps they have a margin of error wide enough that either the ECM or GFS outcomes would still count as a good result?

Also for what it's worth, NOAA don't currently make use of the GSDM that I and Tamara base a lot of our thinking on, due to a lack of recent research on their part.


I won't deny that no approach is infallible, though; something like the ECM 12z is by no means being ruled out on my part.

 fair comment sir.... time will tell.. and i hope you are right because i WANT more heat (beyond this weekend).
 

10 hours ago, mb018538 said:

Well those NOAA charts didn’t show a westerly centred high a couple of days ago - so if you ask me they weren’t completely accurate again. They had above average heights (which was quite obvious anyway) but the high was more UK centred. Net result is going to be temps probably 5-10c below where they may have been otherwise.

NO SUITE showed an amplified atlantic ridge, the 6-10 day chart DID when it entered that timeframe. the 8-14 day chart didnt, but no model suite is infalible. no one has ever said that they are completely accurate, if they were, no one would use anything else!

[johnholmes]

Well I read the somewhat negative remarks here and there about the use of anomaly charts but I remain convinced that, as they are mean charts, they provide a more reliable view of how the upper air will pan out in the 6-14 day time frame, on average, note that phrase. Beyond that time scale I have never really ventured.

Currently the NOAA 6-10 and 8-14 along with the ECMWF-GFS set of latest charts are at variance with some of the conclusions some folks are drawing from the charts they use. As mushy suggests above time will tell. Like any set of charts from whatever source the anomaly charts need to be used with care. If they are and after a fair amount of experience in how to interpret them they give results of 70%+ accuracy in the time scales they show. Remember they are predictions of the atmosphere at 500 mb NOT the surface.  have shown that time and time again over the years that I have used them. My weather file has umpteen pages of posts copied into Net Wx over the years showing both the 'good' and 'bad' guidance they gave in winter and summer.

Still each to their own and I do try not to get involved in the my method is best or better than yours which breaks out in here from time to time. We are all weather enthusiasts, so best we just enjoy the weather whatever our preference.

Back to the 500 mb anomaly charts (none posted today as they are on the same page as the last set I posted) but as I suggested above they are at variance with other outputs and UK Met forecasts for the 6-15 day period. 

[Interitus]

11 hours ago, Summerstorm said:

At the moment we want low AAM as the La Nina state is still hanging on and this promotes the strengthening of Sub Tropical HP belts such as the AH which is why the early summer was so dominated by constant HP due to the lack of energy in the Jet Stream which i think i'm right in saying.

On the contrary, the June mean 250mb vector wind suggests that the North Atlantic jet may possibly have been stronger than average, but displaced and following a different trajectory from normal, i.e. aimed to the north of, rather than at the UK.

Long term mean (1981-2010)

2018 June jet

 

[Met4Cast]

1 hour ago, SLEETY said:

Autumn not far away on the latter stages of ECM either.Perhaps a final shot at some serious heat before then,but nothing long lasting it’s looking like.

Pretty sure someone said that exact same thing yesterday before someone jumped on them about it 

There’s some impressive Northern blocking going on towards the end of the ECM this morning. “if only it were winter” springs to mind.

Edited July 31, 2018 by Daniel Smith

[Frosty.]

Quite an autumnal looking finish to the Ecm 00z with a Northerly setting in..very cool across the far north.

[Methuselah]

11 minutes ago, Frosty. said:

Quite an autumnal looking finish to the Ecm 00z with a Northerly setting in..very cool across the far north.

Indeed...We could be on the run-up to a roller coaster Autumn?

[Scorcher]

1 hour ago, mushymanrob said:

 oh please.... if its one thing that really ticks me off is being credted with saying something i didnt!

this weekends mini heatwave has never been in doubt! niether i nor daniel has said otherwise!

but beyond that by this time next week theres precious little sign of any more heat, and IF that ridge establishes to our west, as the ever favoured ECM predicts, then there will be no fast track back to any heat - if we get any more at all.
 

I haven't accused you of saying anything in particular- where did I say anything about what you actually said? It was the tone and subject matter of your post that I thought could be misleading- it's about emphasis! I was aiming the comments more at Daniel in any case as I agree that you have discussed this weekend's heat in previous posts. I nearly always agree with you but I'm entitled to disagree from time to time.

[stodge]

Morning all :)

Not sure about wading into this bad-tempered bear-pit today but I'm past caring.

Some of the more outlandish 850HPA charts when this coming weekend was in low-res haven't materialised and we're back to the dilemma we've always had with two competing scenarios.

In Scenario A the HP builds across the country then breaks from its parent Azores cell and meanders east into the North Sea or Scandinavia. This allows a S'ly or SE'ly feed of hot air to come from the Continent but pressure falls to the west and we get a thundery breakdown as the trough crosses the country easy to west before HP builds in again from the SW and the process re-starts.

This is the traditional "three fine days and a storm" scenario with a period of building heat reaching a crescendo before storms and fresher air cause a re-set.

In Scenario B the HP stays out to the west and never encroaches or the ridge builds across the UK but never breaks from the parent cell. This keeps us dry, warm or very warm but doesn't allow for the encroachment of hot air as the feed is from a N'ly or E'ly quarter across the south. This is our "fine summer spell" weather - lovely for the holidaymakers with onshore breezes but no exceptional heat or storms.

There were and remain charts showing renewed northern blocking and retrogression and this would ruin August as we'd get the trough dropping into Scandinavia and a cool N'ly setting up down the North Sea. However, theses are far from certain but the truth is that old modern wives tale I've just made up:

"if the core of the High be in the west neither heat nor storms will we get"

"if the core of the High doth move east there'll be too much heat for man and beast" (I know, needs some work).

Both GFS and GEM play to Scenario A but Scenario B has its supporters too keeping the heat well to the south.

"

[Derecho]

51C is being forecast for central Portugal on Saturday, this would smash the all time European heat record of 48.3C set in Sevilla in August 2003... madness and with all these heat records going its yet another sign of climate change intensifying our heatwaves.

Will the UK get caught up in this intensely hot airmass? Difficult to say. The high pressure over the UK this weekend needs to move east to tap into this hot air. Plenty of GFS 00z ensemble members are showing this to be fair, just look at P1! This uncertainty seems to have been going on for an age now.
 

As it stands the prospect of intense heat hitting us is very uncertain but should it come into fruition the UK temperature record will probably go too. Still need to wait 2-3 days before things become clearer for us.

In the meantime temperatures warming up to the late 20s/early 30s for many central and southern areas later this week following the cooler blip.

[Singularity]

13 hours ago, Summerstorm said:

At the moment we want low AAM as the La Nina state is still hanging on and this promotes the strengthening of Sub Tropical HP belts such as the AH which is why the early summer was so dominated by constant HP due to the lack of energy in the Jet Stream which i think i'm right in saying. Conversely high AAM would promote the opposite promoting blocking in higher latitudes hence the increase in blocking over Scandinavia in the last few weeks fortunately we've mainly managed to stay on the warm side of the jet mostly due to high amplitude from the MJO but this week it has dropped (MJO) and this shows the effect this can have on our weather and is why posters like Singularity have been commenting on saying they are worried about if the AAM doesn't drop then HP may be situated further east over Scandinavia or we may have higher latitude based blocking leading to a more Northerly component to winds as shown by the ECM this evening and this is what Tamara is saying in her post i think hopefully this seems a little more simplified. 

Hi James,

Thanks for weighing in on this - your assessment is largely correct, apart from the section I've quoted - what you describe there is true for May-June, but as the summer progresses and heat budgets increase, there is an increasingly strong shift away from those outcomes toward ones that see low AAM still strengthening the subtropical high, but encouraging it to locate well west of the UK, leaving us open to areas of LP moving in from the west or northwest. Conversely, high AAM goes from promoting ridges amplifying in the mid-Atlantic toward Greenland (with troughs dropping down across the UK) to supporting ridges amplifying through S UK and on to Scandinavia with broad troughs out west of Europe. So friend becomes foe, and foe becomes friend.

 

Currently, I have a sense that the models are being confused a bit by the intense heat plume bringing about some instability across Scandinavia at a time when pressure should be on the rise. I believe there is room for a low to move through that area, but not for one to become stuck there and serve as the seed for a broad trough to develop like ECM shows this morning. 

The best fit to the teleconnections of the deterministic model runs this morning is the GEM 00z:

 

Broad Atlantic trough west of Europe - tick.

Low moving through Scandinavia rather than stalling out there - tick.

I'm not convinced that the low will travel that far east in the first place, though; further deceleration of the upper westerlies could mean it moves more N than NE as it leaves Iberia, such that we then look more south than west for the rebuild of ridging across the UK.

[Rob K]

43 minutes ago, Quicksilver1989 said:

51C is being forecast for central Portugal on Saturday, this would smash the all time European heat record of 48.3C set in Sevilla in August 2003...

06Z GFS takes it up to 52C!

[Leo97t]

42 minutes ago, Singularity said:

Hi James,

Thanks for weighing in on this - your assessment is largely correct, apart from the section I've quoted - what you describe there is true for May-June, but as the summer progresses and heat budgets increase, there is an increasingly strong shift away from those outcomes toward ones that see low AAM still strengthening the subtropical high, but encouraging it to locate well west of the UK, leaving us open to areas of LP moving in from the west or northwest. Conversely, high AAM goes from promoting ridges amplifying in the mid-Atlantic toward Greenland (with troughs dropping down across the UK) to supporting ridges amplifying through S UK and on to Scandinavia with broad troughs out west of Europe. So friend becomes foe, and foe becomes friend.

 

Currently, I have a sense that the models are being confused a bit by the intense heat plume bringing about some instability across Scandinavia at a time when pressure should be on the rise. I believe there is room for a low to move through that area, but not for one to become stuck there and serve as the seed for a broad trough to develop like ECM shows this morning. 

The best fit to the teleconnections of the deterministic model runs this morning is the GEM 00z:

 

Broad Atlantic trough west of Europe - tick.

Low moving through Scandinavia rather than stalling out there - tick.

I'm not convinced that the low will travel that far east in the first place, though; further deceleration of the upper westerlies could mean it moves more N than NE as it leaves Iberia, such that we then look more south than west for the rebuild of ridging across the UK.

I think some people are being very pessimistic. As the GEM showed this morning continued hot weather is definitely still on the cards. Models have been acting up this summer predicting breakdowns which never came to be. However obviously breakdown remains an option. I guess we just need more runs

[Methuselah]

2 minutes ago, Rob K said:

06Z GFS takes it up to 52C!

And, as we all 'know', the GFS always under-cooks afternoon maxima!

[Djdazzle]

You couldn't make it up - GFS 6z building a Scandi High at the same time the ECM is building the Scandi Low.

Even at T180, I can't ever remember such a divergent synoptic setup between two major models.

[Man With Beard]

Latest ECM clusters: T168, T192, T240, T300, T360

        

For T168/T192, we're generally seeing ridging slightly to the SE which suggests the UK being on the hotter side of things. But how low pressure might form to the S/SW will create bigger weather variances. It is not inconceivable at all that an incoming low will time its approach to the UK in such a way (e.g. cluster 2/4) to suck up the record-breaking heat over Iberia, and produce record-breaking heat over the UK by this time next week (A scenario absolutely not to be ruled out yet!!). Alternatively, if a low pushes through the pattern more seamlessly (like cluster 3), then the hottest weather will be kept south of the channel and possible thundery excitement for us. In a nutshell, difficult to call and a few variations possible, but unlikely to escape without more 90F days in the process. T192 sees the chance of a weak passing trough, but could be a fairly insignificant feature.

Further out, uncertainty grows further. The main clusters (1/2) look very warm and settled out to D10, and several clusters still warm/settled out to D12 (how this wouldn't equate a prolonged spell of hot weather I do not know). However, not all clusters are settled, and the unsettled ones grow in number by D15. 

I would sum it up like this. D3-D7 is hot especially in the south. Potential for something warm rather than hot between D8-D12 (another plume being a small but genuine possibility) but remaining mostly settled aside perhaps a day (maybe D8). Then D12-D15 the jet may start to move south, and Atlantic systems begin to approach the UK with more gusto.