Model Output Discussion - Autumn arrives

[danm]

20 minutes ago, kold weather said:

So upon looking at the models the key time appears to be at 120hrs. On the 12z GFS the cutoff low gets absorbed into the broader flow caused by a small upper trough feature that moves to the south of Iceland W-E which allows the upper low to lift out.

These cutoff lows are an absolute mare to forecast because if the models get even a small amount wrong (say if the upper high is a little stronger, or the upper trough a little weaker) it can in terms of real world weather by the difference between 23c in London and 40c in London down the line.

Expect the GFS ensembles to be a bit of a mess post Wednesday as they struggle to resolve this feature. My guess is though the GFS OP will be one of the more progressive in the suite in terms of how rapidly it brings it NE. 

PS - a more progressive movement MAY allow for a hotter Tues-Wed period instead as per the 12z GFS op. Your effectively trading a smaller risk of extreme heat for a higher risk of very hot, but not quite as extreme temps.

I would happily trade in a one day extreme heat event for longer lasting heat that isn’t record breaking. 

[Singularity]

For days now, ECM & EPS have been resolutely in favour of the low that’s west of Iberia in 5 days time journeying a bit further west until Friday and then starting to lift north, which is critical to the big plume scenarios for 16th-20th.

Meanwhile GFS hasn’t been interested for the past two days and GEFS have been about evenly split on the matter.

GEM’s been on and off with it, while UKM has slowly drifted from being more like ECM to being more like GFS.

The path of this  feature must be resolved before we can take any charts for 16th onward at all seriously. Let’s see if ECM & EPS stick or twist later.

[kold weather]

3 minutes ago, danm said:

I would happily trade in a one day extreme heat event for longer lasting heat that isn’t record breaking. 

Whilst the GFS is perhaps missing the bells and whistles of some of the runs (no 20c 850hpa temps here!) I think as a run its perfectly good enough, we get abit of a reprive (but still mid 20s for the south) before another ridge comes in.

Besides, 35c is plenty hot enough on the 12z GFS for Wednesday to be fair! 

[kold weather]

4 minutes ago, Singularity said:

For days now, ECM & EPS have been resolutely in favour of the low that’s west of Iberia in 5 days time journeying a bit further west until Friday and then starting to lift north, which is critical to the big plume scenarios for 16th-20th.

Meanwhile GFS hasn’t been interested for the past two days and GEFS have been about evenly split on the matter.

GEM’s been on and off with it, while UKM has slowly drifted from being more like ECM to being more like GFS.

The path of this  feature must be resolved before we can take any charts for 16th onward at all seriously. Let’s see if ECM & EPS stick or twist later.

Something that has been noted in some of the US forums (I've also noted during hurricane model watching) is the ECM has abit of a habit of leaving upper lows that are cutoff for too long. It would perhaps give some weight that the GFS has a better handle on the situation, though even then IMO its probably 24-36hrs too fast in moving it NE.

Lookinmg at the 12z suite at least we seem to be moving away from that very rapid breakdown into a more Atlantic driven pattern though, lots of the models clocking into a new HP area developing further west and ridging back towards us again which will be a good fail safe for warm/dry conditions should the plume not make it and get driven to the east too rapidly.

[Man With Beard]

Personally I'd put more stock in the ECM than GFS when it comes to a cut-off low, I feel the GFS always wants to push it east faster than it would, but strange things have happened with the models this year so who knows.

All 12Zs so far are pretty much in the same place until Wednesday though - hot for many Sunday into Tuesday, still just as hot or even hotter in the SE on Wednesday. GFS consistently pushing a 34/35C day next Wednesday around London. But ECM this morning pushed the heat away from all by Wednesday. Will it stick or twist?

[mb018538]

If you like the warm weather, once you get above about 27/28c then it doesn’t really matter if it’s that or 32c. It’s still very warm! I know people are chasing the big fish, but if some can’t be happy with a week at 27-33c then they’ve got very high expectations! 

[MP-R]

10 minutes ago, mb018538 said:

If you like the warm weather, once you get above about 27/28c then it doesn’t really matter if it’s that or 32c. It’s still very warm! I know people are chasing the big fish, but if some can’t be happy with a week at 27-33c then they’ve got very high expectations! 

That’s ideal for me! I can deal with hotter than that but the problem is then the sleep.

[Ben Sainsbury]

At a glance, GEFS 12z looks better than 6z and 0z respectively. Less of a dip next Thurs-Friday and then more runs reach 20C at 850hPa from Saturday.

[Guest]

30 minutes ago, mb018538 said:

If you like the warm weather, once you get above about 27/28c then it doesn’t really matter if it’s that or 32c. It’s still very warm! I know people are chasing the big fish, but if some can’t be happy with a week at 27-33c then they’ve got very high expectations! 

I agree! I'm trying to keep the two separate in my head as I am more than happy with the low/mid 20s and a bit higher for usability when the sun is out. The last two days here have been gorgeous. Then I put my weather brain into gear when the models run and I go fishing for the big one  I'd like a high peak, just for the noteworthiness of it, but I appreciate not all will (and even then, I wouldn't actually enjoy the feel of it either). 

[kold weather]

Quite a few ensemble members reach 35c at some point on the GFS ensembles, probably getting towards the 50% mark now. A decent chunk of those reach 37 and a couple are still going beyond the 40c mark.

Even outside of that 50% plenty are still very hot and some sustain the 30c mark in the south for quite some time.

[Captain Shortwave]

A no to a hot Wednesday from the ECM. That is a fairly sizeable difference between the ECM and GFS regarding a shallow trough.

 

 

The ECM has this clearing Easter Scotland.

GFS has this west of Scotland at the same time;

 

The UKMO has the placement similar to the GFS, but significantly shallower. This mornings UKMO was in agreement with the ECM, so perhaps this needs a couple of runs to resolve. I would add that there are a fair number of GEFs that actually keep the warm air further north still for Wednesday (some to the Scottish Borders). 

Edited July 8, 2022 by Captain Shortwave

[Guest]

ECM t144 has the Iberian low several hundred miles further WSW compared to the GFS 12z at the same timeframe. 

Likely to prime for a plume again come Day 9/10/11.

[damianslaw]

Looking likely we will see almost a carbon copy of the third week of July last year, but this year second week. Would be good to note what temps occured last July for that week. I think we saw low 30s in the SE... but the north unlike last year does not look like seeing any appreciable warmth from this spell, reason read on...

I've been keeping an eye on the jetstream forecast and it looks a rather moderate flow generally west - east and it is this factor that I think people are overlooking, it isn't set to weaken, and is being driven on a course over Scotland, all the forcing increasingly looks like coming from it, and the cut off low feature to the SW looks a weak ineffectual player.. instead of plume and forcing from the south, it looks like the jet will force everything southwards putting pressure on heights. We could very easily end up with a typical atlantic flow beyond this very warm spell.

 

[Guest]

6 minutes ago, damianslaw said:

Looking likely we will see almost a carbon copy of the third week of July last year, but this year second week. Would be good to note what temps occured last July for that week. I think we saw low 30s in the SE... but the north unlike last year does not look like seeing any appreciable warmth from this spell, reason read on...

I've been keeping an eye on the jetstream forecast and it looks a rather moderate flow generally west - east and it is this factor that I think people are overlooking, it isn't set to weaken, and is being driven on a course over Scotland, all the forcing increasingly looks like coming from it, and the cut off low feature to the SW looks a weak ineffectual player.. instead of plume and forcing from the south, it looks like the jet will force everything southwards putting pressure on heights. We could very easily end up with a typical atlantic flow beyond this very warm spell.

 

Not sure the jet is far south enough to bring an Atlantic influence to many away from the northwest? My interpretation is for the vague NW/SE split to continue for the foreseeable with very little in the way of meaningful precipitation for the south especially. I think the door remains open for a plume for the same areas, though I am still doubtful of its longevity and intensity despite some very intense runs in the suites  

Edited July 8, 2022 by Steel City Skies

[kold weather]

3 minutes ago, damianslaw said:

Looking likely we will see almost a carbon copy of the third week of July last year, but this year second week. Would be good to note what temps occured last July for that week. I think we saw low 30s in the SE... but the north unlike last year does not look like seeing any appreciable warmth from this spell, reason read on...

 

That spell really wasn't that noticeable down here at all, I think maxes in London were only around 28c peak, and for most of the time 26-27c. Whilst nice enough it was one of those rare cases that the further north you were the better, as you say quite the opposite to this week coming up. That spell was more noteworthy for its high min temps anyways down here.

 

 

 

[MattStoke]

Oof. Here it comes.

[Guest]

ECM day 9 is H.O.T  edit: @MattStoke beat me to it, the scamp.

Edited July 8, 2022 by Steel City Skies

[JayAlmeida]

ECM 12z wanting a noticeable cooldown Wed, Thu.

Before doing the plume FI limbo thing again. Wonder if it'll stay in FI forever?? 

Edited July 8, 2022 by JayAlmeida

[Mike Poole]

Direct hit for the plume at day 9 on this afternoon’s ECM, T216:

It is the width of the cone of hot air that strikes me with all the model runs showing this surge of heat north, regardless of whether it hits directly on any individual run.  My recollection of plumes at this time of year, the region of +20C uppers is usually much narrower, if it reaches the UK at all.

Edited July 8, 2022 by Mike Poole

[Captain Shortwave]

Week 2 on the ECM is on a similar trajectory to this morning’s GEM. The heat just drifts northwards despite the rather ordinary looking pattern.

 

You wouldn’t think that the 20c isotherm would be across the far south of the UK here. But it is….

Edited July 8, 2022 by Captain Shortwave

[MattStoke]

Just now, JayAlmeida said:

ECM 12z wanting a noticeable cooldown Wed, Thu.

Before doing the plume FI limbo thing again. Wonder if it'll stay in FI forever??

It’s been showing on the ECM ensembles for the 17th/18th for several days now despite people claiming it’s being pushed back.

[Guest]

2 minutes ago, JayAlmeida said:

ECM 12z wanting a noticeable cooldown Wed, Thu.

Before doing the plume FI limbo thing again. Wonder if it'll stay in FI forever??

Well no, it hasn't really stuck at all. It's moved from Day 10/11 to Day 9/10 in the last 24 hours so it is moving forward. Allowing for the variance in output from the GFS and ECM during the past few days (and beyond for the longer range GFS), it has consistently looked around the 17/18th  

I really need to up my typing speed vs you, Matt!  

Edited July 8, 2022 by Steel City Skies

[Guest]

No idea what to make of the ECM t240 this evening 

[danm]

20 minutes ago, kold weather said:

That spell really wasn't that noticeable down here at all, I think maxes in London were only around 28c peak, and for most of the time 26-27c. Whilst nice enough it was one of those rare cases that the further north you were the better, as you say quite the opposite to this week coming up. That spell was more noteworthy for its high min temps anyways down here.

 

 

 

It was actually a lot better than that last year in London during that week in July. Four consecutive days above 30°c, with a peak of 32.2°c and a few days either side when temperatures were in the mid to high 20’s:

[JayAlmeida]

6 minutes ago, Steel City Skies said:

Well no, it hasn't really stuck at all. It's moved from Day 10/11 to Day 9/10 in the last 24 hours so it is moving forward. Allowing for the variance in output from the GFS and ECM during the past few days (and beyond for the longer range GFS), it has consistently looked around the 17/18th  

I really need to up my typing speed vs you, Matt!  

If it's still there on Mondays charts for the 17/18th then we are in business.

Still just a bit too far out at the moment.

Edited July 8, 2022 by JayAlmeida