Model output discussion - into July 2020

[Earthshine]

38 minutes ago, Mr Frost said:

Bank! Keep posting these Mark as it is always nice to dream! 

Really glad the last day of July brought that exceptionally hot day - something to discuss in the future when we look back on an otherwise very bland Summer month. (Against the 1981-2010 Anomaly)

First below average month of the year for the UK as a whole...December the next one!? 

What's even more remarkable is that if it weren't for last years record heat on the 25th July, last Friday would have been the hottest July day on record!  Almost a back-to-front July 2015.

[Singularity]

 

Keeping an eye on that tail of jet steam by the Azores islands, after that JMA 12z of yesterday which made more of it, resulting in a re-orientation of the high pressure compared to other models that set up an E'rly to ESE'rly flow rather than NE'rly.

Not actually expecting that to happen as it's only one model that's gone for it in the past 18 hours, but keeping my mind open to it. A wildcard, you might say!

[SMU]

GFS has now pretty much fallen in line with ECM just a bit further East with the wave.

Further corrections west expected.

[Singularity]

 

Much complexity can be seen when focusing on these upper-level charts.

Big questions:

How fast does the sharp trough lift out to the north? This is something GFS has generally been slower with - but not so much in this latest run.

To what extent does the shallow cut-off trough to the west of Europe influence the layout - will it orientate the ridge more toward an easterly flow for England this weekend, as opposed to north-easterly?

[clark3r]

Just looked at metoffice app it has London Heathrow Thursday 32 Friday 36 Saturday 36 Sunday 32, 2 days in a row at 36 I think is remarkable. 

[clark3r]

Latest gfs if you add on the usual 2 or 3 degrees has 36 both Friday and Saturday, in the south east, like Steve m said last night dry air from France Spain it may even go a little higher than that 

[Man With Beard]

As mentioned above, the GFS 06Z follows the EUROs for Saturday by making a lot less of the wave to the north - hot in the south again with mid 30s possible both Friday/Saturday, though still cooler and showery in the north on Saturday (I still think there's time for that to change).

However, the GFS is never keen on keeping things simple and finds a blob of rain to stick over England for Sunday - for comparison, the ECM has mostly clear skies over central areas on that day!

Edited August 3, 2020 by Man With Beard

[Singularity]

What is it with GFS and finding additional rainmakers on the periphery of hot airmasses?  In this case it actually took the shallow low I was monitoring west of Europe and started hurtling it toward southern England despite hardly any upper level westerly flow to support that.

Such a shame, as it was heading in an interesting direction before then.

[danm]

3 hours ago, CreweCold said:

I don't understand why temperatures need to be blast furnace level for people to feel satisfied. Mid 20s and settled is perfectly acceptable and useable.

My guess is a lot of us on here are weather enthusiasts and like to see records broken? Plus some actually like the furnace heat. 

[Guest]

Synoptically GFS is better however its temps in the south are skewed Sunday/Monday by the continuous cloud and rain its magically creates..... 

[CheesepuffScott]

GFS 6z for Sunday, of course erroneous precipitation over the south. What's with the models are overdoing any *potential* rain, I can remember UKV (I think) reckoned convective showers over the south for last Friday and it only had maxima of 20°C~ when it factored in the ppn that it sprung up.

[SMU]

Assuming the corrections are west & North the heat is just a snip away to the SE

I doubt we will drop below the 30s maxima Sunday

[Djdazzle]

If I was a GFS programmer, I would be banging my head against the wall saying "why do you keep doing this!"

As @Steve Murr says, a small shift would bring the south back into the hot temps.

[matt111]

8 minutes ago, CheesepuffScott said:

GFS 6z for Sunday, of course erroneous precipitation over the south. What's with the models are overdoing any *potential* rain, I can remember UKV (I think) reckoned convective showers over the south for last Friday and it only had maxima of 20°C~ when it factored in the ppn that it sprung up.

Yes the UKV showed widespread thunderstorms in the south on Thursday mornings runs but by the end of the day that had completely disappeared and of course come Friday nothing happened at all on the south. 

[Guest]

2 minutes ago, matt111 said:

Yes the UKV showed widespread thunderstorms in the south on Thursday mornings runs but by the end of the day that had completely disappeared and of course come Friday nothing happened at all on the south. 

Well that's not entirely true, on Friday very weak convective activity spread into the central south, just enough to get a few drops out, temps fell very quickly places like Bournemouth and was only 22c by the middle of the afternoon as the cloud completely supressed (this wasn't cold front related), Southampton just up the road was at nearly 30C at the same time. We don't big storms to ruin the day just some heavy cloud cover..... 

[Man With Beard]

ECM clusters this morning.

First T96 - this shows the "straight line" southerly on the 500mb lines (well almost!), the classic sign of a plume). I think this was first picked up by the clusters 7 days ago - so a good prediction in this case:

Now the slightly messy bit next Saturday. This is where 500mb charts might not be so useful because the "wave" feature is so small, but the following charts for T132 and T156 do show to some extent how the weather could be affected by small margins:

  

So I think the key is to look where the lines bend back west after the first little wave approaching Scotland encroaches. Particularly useful is to follow the 582 line. By T132, clusters 1,2,3 and 5 all seem as if they will introduce some westerly air to northern areas; cluster 4 may only do that for the far north, and cluster 6 hasn't allowed any westerly influence in yet.  By T156, in clusters 1 and 4, the 582 line bends back south - this would stop the less warm air reaching southern areas and allow continental air to return quickly. Clusters 2, 3 and 5 aren't far off doing the same thing, but perhaps less clear-cut if we will return straight into continental influence Cluster 6 never really changes the direction of the flow at all and might keep it hot in the south-east throughout (those seeking a new UK record would be pinning their hopes on this very small cluster trumping the others - unlikely though!). 

If one ignores the intensity of heat question, though, what we most likely see is a very quick return to settled and warm/very warm conditions for all parts of the UK by T156.

By T192, only one cluster, but a good positive anomaly over the UK, and lines straight from the south again - so continuing settled and probably increasingly warm/hot again as we approach the middle of next week.

Even by T264 (into the following weekend), yet again we see riging anomalies just to the north/east of the UK, signs of a weak trough to the SW and yet more of those 500mb lines straight from Iberia - which could mean yet another plume injection at this stage! 

I think the overall picture, on most days between D3 and D11, is either very warm, hot or very hot. Give or take a couple of "off days", it's a great set-up for a heatwave!

 

[Djdazzle]

Quite a few different options on the GEFS for next Sunday.

[kold weather]

45 minutes ago, Singularity said:

What is it with GFS and finding additional rainmakers on the periphery of hot airmasses?  In this case it actually took the shallow low I was monitoring west of Europe and started hurtling it toward southern England despite hardly any upper level westerly flow to support that.

Such a shame, as it was heading in an interesting direction before then.

Could well end up being a convective feedback issue, its certainly a problem with the GFS in the past in more tropical type airmasses and being a little overzealous with the instability actually present. It looks like it creates a decent thermal low which again maybe quite questionable to what extent that actually happens.

Friday IMO probably is another 34-36C type day, of course IF we keep the flow going on Saturday and the uppers hold long enough, we will be in a position on Saturday in the SE to get somewhere close to the 37-38c we saw last week and also August 10th 2003. 

Regardless of what happens, I'd suspect the usual upgrading in temperatures to occur as we move closer to the time, and the current forecasts maxes of 31-32c to slowly shift upwards as the week rolls on. 

I'd be surprised if somewhere doesn't at least get to 35c given the time of year, flow over a now more reasonable temperature channel and also heat over Europe.

[Mr Frost]

28 minutes ago, Alderc said:

Well that's not entirely true, on Friday very weak convective activity spread into the central south, just enough to get a few drops out, temps fell very quickly places like Bournemouth and was only 22c by the middle of the afternoon as the cloud completely supressed (this wasn't cold front related), Southampton just up the road was at nearly 30C at the same time. We don't big storms to ruin the day just some heavy cloud cover..... 

When it comes to models/charts forecasting thunderstorms in advance for the UK...it is always best to just look out the window/radar on the actual day. They are absolutely useless nine times out of ten! 

Friday was a close call for the SE - thunderstorms just off the coast. (Thanks to @staplehurst from Convective weather)

July was a pretty poor month in general.

There is a recurring theme this Summer of SE England hogging all the warmth/heat...only for the storms to break out everywhere else! SW Scotland and NW England (June) for example which is quite bizarre.

Edited August 3, 2020 by Mr Frost

[Zak M]

MetO showing 37c on their graphics on Friday.

These will also most likely upgrade nearer the time. 

 

Edited August 3, 2020 by Zak M

[Tamara]

I admit especially to tuning out of individual operational outputs, but more especially the GFS which provides too much of a distraction with its intra day vicissitudes and inconsistencies when trying to look at trends day on day. To put it another way, I would conserve energy and not spend much time at all poring over intra day details - especially with so much erratic continuity each and every 6 to 12 hours. Most especially several days away.

From my own viewpoint things are shaping up still for an excellent spell of summer weather. The earlier attempts by GFS operationals and a minority of its ensembles to wedge a trough between the Scandinavian high pressure and the Azores ridge to the west is redolent of the default regime we have moved away from (for a time anyway) and is typical GFS bias in these type of situations to want to overplay Atlantic ridging. This has the effect of lowering pressure too much downstream c/o excessive retrogressive pull which over weakens the "bridging" between the two anticyclones.

In some respects, and this was alluded to in a post of mine last week, we are are likely to see the opposite trend of the bulk of the summer so far, for a little while, whereby NWP (more especially GFS) might be over progressive with negative momentum bias and will be coerced into re-adjusting upwards increase of pressure on strength of downstream ridging rather than the opposite trend of the summer to date to overdo Azores ridging eastwards and then incrementally retract it afterwards..

There is bound to be something of a rinse/repeat element to the upcoming very warm/hot spell but the transitioning ridge from the Azores to take over from an existing downstream ridge (to then become the renewed downstream ridge) is a classic evolution of some of the more extended very warm spells in summers at this latitude.

With that in mind, I think the weekend sequence is rather a distraction to the fact that prospects look very warm, in general, for a rather longer time instead of extremely hot for a shorter period of time.  There is a reasonable chance that the relatively cooler North Atlantic air encroaching into the northern half of the UK at the weekend will "warm out" heading into next week as the renewed anticyclone absorbs the heat advection from the continent.

The first half of August is increasingly looking very promising. Uncertainty grows thereafter in terms of possible return to default - as the superimposition of the eastward progression of the high frequency MJO forcing on the pattern completes its orbit. This MJO wave is presently cutting off the upstream Pacific amplification process that has been the spoiler for NW European downstream pattern this summer. Once it fades and its influence is removed, then the low frequency walker cell across Africa and the Indian Ocean resumes charge of proceedings.

When that happens, easterly inertia will be added back to the atmospheric circulation from the tropics into the extra tropics as torque tendency switches negative which in turn will promote falling angular momentum - and cue re-amplification upstream.  This signal, in basic synoptic terms, for this part of the Northern Hemisphere would likely be indications of the main upper heights shifting decisively westwards and a trough migrating around the perimeter with pressure falling more generally across NW Europe and Scandinavia.

However, as stated yesterday, that is subject to further clarity at this distance and can wait for another time. Its time to enjoy summer proper for many

 

 

[MattStoke]

15 minutes ago, Zak M said:

MetO showing 37c on their graphics on Friday.

These will also most likely upgrade nearer the time. 

 

Saturday looks potentially even hotter on the computer model suite to me.

[mb018538]

2 minutes ago, MattStoke said:

Saturday looks potentially even hotter on the computer model suite to me.

Maybe they’ve taken note from last Friday, and expect the airmass to be super-heated as it as a week ago. 37c a week after 38c is mental.

[Djdazzle]

19 minutes ago, mb018538 said:

Maybe they’ve taken note from last Friday, and expect the airmass to be super-heated as it as a week ago. 37c a week after 38c is mental.

Maybe this time they will be too high with the prediction? I remember they went for a 37C day in 2018 which ended up several degrees lower.

I wouldn't rule it out by any means, even though the uppers are slightly lower than last week.

I think that Saturday also has the potential to be very hot. Sunday could also be hot if less is made of that pesky wave!

[SLEETY]

Looks like the models are underplaying the temps.Met office going for 37c fri now,which is higher than yesterday’s forecast high.

Maybe 38c be reached again and perhaps highest temp record be broken,let’s hope this winter we are looking at records being broken the other way,as if..