Model Output Discussion - 15th March onwards

[Nick2373]

00z the consistencies of late with the GEFS Are remarkable, this model usually struggles past five days  hats off. Anyway going forward after the brief you fall asleep and miss it warmth its back to usual business with lower than average temps and some rain.  

[Frigid]

2 minutes ago, Nick2373 said:

You would be thinking correct, i read back few weeks ago when i googled the effects of high SST's and the opinion was that this type of set would deliver more unsettled average  weather to the UK.   

A while back, someone here used ChatGPT to predict the weather for July after record high SSTs in June. Same outcome - unsettled. 

[Derecho]

Just now, Nick2373 said:

You would be thinking correct, i read back few weeks ago when i googled the effects of high SST's and the opinion was that this type of set would deliver more unsettled average  weather to the UK.   

You only have to look at an El Nino to see the effects the higher SSTs have on the eastern equatorial Pacific, the area with the greatest +ve SST anomalies often sees much above average rainfall.

But the uncertainty is where that trough will keep moving around to, looks like the weekend after next it'll still be lingering over us but there isn't a big consensus on that, the trough might get pulled west for example, though cool and unsettled is the best bet now.

[Addicks Fan 1981]

1 minute ago, Frigid said:

A while back, someone here used ChatGPT to predict the weather for July after record high SSTs in June. Same outcome - unsettled. 

Reckon the easterly trades on the dateline aren't helping at the moment, we need westerly wind bursts as summer blizzard highlighted last night else the atmosphere on the long and short of it doesn't maintain itself in the same vein.  

[Guest]

14 minutes ago, Frigid said:

A while back, someone here used ChatGPT to predict the weather for July after record high SSTs in June. Same outcome - unsettled. 

That was me. CHATGPT was very correct. 
 

Since then it’s also written my half year work appraisal for me too

Edited July 6, 2023 by Alderc

[Addicks Fan 1981]

Although we are in el niño it would seem in elaboration to my above post that what we are about to get is more akin to la niña. 

 There just seems to be conflict with how the atmosphere and upper air are behaving at the moment. 

We need a run of Westerlies over the dateline really as easterlies don't serve well shall we say and that'll transpire with the NWP output.    

[Frigid]

33 minutes ago, Alderc said:

That was me. CHATGPT was very correct. 
 

Since then it’s also written my half year work appraisal for me too

Damn I really gotta start using it then, maybe predict the Winter forecast

I do wonder, why were many LRF's and seasonals going for a warm July. Is it just the default, after recurring warm summer months? I do recall many going for HP over the country in July.. far from the truth but of course things may change. 

[danm]

1 hour ago, Quicksilver1989 said:

It's not a case of glass being empty or glass being half full it's more a case of can we make a big assumption about what the weather will be at a certain timescale with confidence.

So saying it will only be a brief breakdown would be wrong as well as writing off July as a whole. I think after this weekends little southerly it will likely remain poor through to the following weekend now. A few days ago there wasn't enough confidence to say that, only that there would be a trough somewhere in the near vicinity.

What will the weather be like on July 25th?, could be a blowtorch southerly or a chilly north-westerly. After day 10 in Summer we can only get inklings of what will happen. It might be awful but any predictions at this stage for that date would remind me of the saying 'a broken clock is right twice a day'

 

Precisely. I don't remember anyone saying that this will be a blip (as @Alderc alleges), just that it may be a blip. Clearly this is not a blip now, but equally (so far) this isn't a June 2012 situation. It could feel like that during the next 7 days, but we will see. And yes, anything beyond a week to 10 days is still highly uncertain, whatever the high res modelling and medium term anomaly charts may show. 

Looking at the models again this morning, the trend for next week is becoming more certain. Trough domination has been certain for a while, but the placement and positioning was uncertain. What looks very likely is Monday providing some settled weather in the SE, but Tuesday and Wednesday are likely to be unsettled for all as the trough swings east across the UK.

As the trough pushes east/NE, we may see it settling down again in the south on Thursday and into Friday, possibly Saturday too. Both the GFS and ECM then show another trough plunging south towards the UK at some point next weekend, but that's a way off. The GEM is similar. 

The details above could still change as small changes in the placement of the trough will have an impact.

All in all, after a brief warm up between now and Saturday, next week looks cool and changeable. 

Edited July 6, 2023 by danm

[mountain shadow]

The Netweather Long Range for July is looking a major bust similar to all other longer rangers I have seen, would be good to get an update as to where things went wrong and as to whether we can expect an improvement into August.

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July

Almost all global forecast models point to a dominant high pressure over Northern Europe, but the models disagree somewhat about the location. However, analogs and some models suggest blocking high further east over Scandinavia. Meanwhile, relatively low pressure looks like persisting from Portugal to the Mediterranean basin. High pressure close to the northeast and low pressure to the southwest could cause heat plumes but with some thundery weather too, especially as the heat breaks down at times. So, we envisage a hot month of July, with temperatures above the seasonal average between +1.5 and +2°C. Highest temperature anomalies in the south, closer to average in the north. Most rainfall contributed by thunderstorms which could break out, especially across southern and central areas of Britain. Scotland could be anomalously dry though, thanks to high pressure close by.

Confidence is quite high concerning the temperatures, but lower confidence on the occurrence of rainfall, which remains the most sensitive parameter to model - especially when it is likely to be convective in nature. Rainfall around average for England and Wales, but perhaps below for Scotland.

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[mushymanrob]

2 hours ago, mb018538 said:

EPS still has troughing over the UK in a fortnight, it's just a weakening signal. There is literally zero output at the moment suggesting a move out of this unsettled rut at present. Just have to ride it out and hope for the best. Certainly being a stubborn old mule to shift now it's set in.

The EPS has been showing slacker pressure now for some time, only for it to develop further as it becomes closer.

This is just about the coldest chart you could get.. the flow at 500mb originating over the Arctic Circle and Greenland. Will this be cool, fresh, sunshine and showers or will we get a blanket of cloud? (cold air, warm SSTs)

2 minutes ago, mountain shadow said:

The Netweather Long Range for July is looking a major bust similar to all other longer rangers I have seen, would be good to get an update as to where things went wrong and as to whether we can expect an improvement into August.

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absolutely.... i saw no LRF for Summer that predicted a record breaking warm June followed by a very cool July... assuming the current predictive charts will be accurate of course.

[Derecho]

5 minutes ago, mountain shadow said:

The Netweather Long Range for July is looking a major bust similar to all other longer rangers I have seen, would be good to get an update as to where things went wrong and as to whether we can expect an improvement into August.

The long range models went for a hot July a while back.... seems like as though those synoptics appeared a month early...

[Guest]

25 minutes ago, Frigid said:

Damn I really gotta start using it then, maybe predict the Winter forecast

I do wonder, why were many LRF's and seasonals going for a warm July. Is it just the default, after recurring warm summer months? I do recall many going for HP over the country in July.. far from the truth but of course things may change. 

More from CHATGPT - interesting 

Edited July 6, 2023 by Alderc

[Bristawl Si]

1 hour ago, Quicksilver1989 said:

You only have to look at an El Nino to see the effects the higher SSTs have on the eastern equatorial Pacific, the area with the greatest +ve SST anomalies often sees much above average rainfall.

But the uncertainty is where that trough will keep moving around to, looks like the weekend after next it'll still be lingering over us but there isn't a big consensus on that, the trough might get pulled west for example, though cool and unsettled is the best bet now.

If this is the case and, if it's widely acknowledged as a big factor, why didnt various LRFs take high SSTs into account for the UK and NW Europe?

Edited July 6, 2023 by Bristle Si

[alexisj9]

2 hours ago, Addicks Fan 1981 said:

Although we are in el niño it would seem in elaboration to my above post that what we are about to get is more akin to la niña. 

 There just seems to be conflict with how the atmosphere and upper air are behaving at the moment. 

We need a run of Westerlies over the dateline really as easterlies don't serve well shall we say and that'll transpire with the NWP output.    

Well that's not due to change for a while really. It's as regular as clockwork. It's staying east and starting to propergate down.

[LetItSnow!]

You know it's bad when people are bringing out the ChatGPT model. Does that one shift as much on each run? 

[alexisj9]

1 hour ago, Alderc said:

More from CHATGPT - interesting 

Ask it including the trade winds.

1 hour ago, Bristle Si said:

If this is the case and, if it's widely acknowledged as a big factor, why didnt various LRFs take high SSTs into account for the UK and NW Europe?

They would not have known the ocean temperature in advance, that is a very short range calculation.

[Bristawl Si]

8 minutes ago, alexisj9 said:

Ask it including the trade winds.

They would not have known the ocean temperature in advance, that is a very short range calculation.

Oh right. Didnt realise that.

[Man With Beard]

Another interesting table - the ECM 00Z ensembles sea level pressure for London. The green waves indicate lower pressure passing through around 11/12th and then again around 15/16/17th.

Do I detect an uptick in pressure on the majority of runs towards the 20/21st...

[Addicks Fan 1981]

3 minutes ago, Man With Beard said:

Another interesting table - the ECM 00Z ensembles sea level pressure for London. The green waves indicate lower pressure passing through around 11/12th and then again around 15/16/17th.

Do I detect an uptick in pressure on the majority of runs towards the 20/21st...

It won't be easy to get the ridge back, but it won't be too hard to get the jetstream to it's correct position.  The better bit about our weather is at least the winds are a westerly type, next week will be interesting of how wet it gets and where the trough is exactly placed.   

[Methuselah]

1 hour ago, alexisj9 said:

Ask it including the trade winds.

They would not have known the ocean temperature in advance, that is a very short range calculation.

Are we really supposed to give credence to chatbot nonsense? I think I'll stick with the Met. Office and the models. 

[Derecho]

2 hours ago, Bristle Si said:

If this is the case and, if it's widely acknowledged as a big factor, why didnt various LRFs take high SSTs into account for the UK and NW Europe?

It's a good question, I think part of the reason why is the models were more bullish on July seeing the better synoptics rather then June and if that's the case the SST anomalies wouldn't be so high at this point.

Second there may be some background signal the models were picking up on but that hasn't materialised as expected, encouraging troughing to form in our area of high SSTs.

But that is just mere speculation on my part and the biggest factor of all is that long range forecasting for the summer months is rubbish.

[Tamara]

6 hours ago, Scott Ingham said:

The chart at T-360 however gives the first glimpse into the possible pattern change @Tamara spoke of (which i agree with)

Notice low heights draining west into the atlantic.

Doesnt take a lot to see iberian low formations a day or 3 forward from that......

Period 18-21st for the start of a pattern change is my call.

This will come further into view on sunday and thats when i expect a few better operational runs and ensemble scatter appearing.

Yes, It could well be Much tied into the following discussion and the timing of the mechanisms required to do so. This timing, much as people like @MattH fairly recently mentioned might be the case, is proving very problematic.

 Respectful genuine enquiries are welcomed, very much including when curveballs occur, and are helpful for all concerned  Curveballs always provide new learning opportunities for all with (genuine) interest A question therefore related to an incorrect assertion of the NW European trough not being as as short lived as suggested, indeed readily admitting very much expected to be short lived, is a very reasonable one.

Much of the emphasis about an Atlantic trough and downstream ridge related to the switch on the doorstep this weekend. And this has largely verified as suggested at intervals since the last third of June. This synoptic passage largely has been at the behest of short term "mini ENSO cycle" tropical>extra tropical cycling of westerly inertia to keep re-cycling June's (mostly) default pattern into July. There has been remarkable forcing from high frequency tropical convection injecting westerly wind burst inertia into the extra tropics since the Spring and the persistent anticyclonic wave breaking that has resulted. The record breaking June in the UK didn't happen for nothing after all...

The anticipation of this re-cycling continuing through the heart of the summer, and, in fact, impacting even more strongly the synoptic pattern downstream across many central and NW parts of Europe has been (and still is) predicated on a meaningful shift of low frequency tropical convection cementing a more permanent Nino-esque ocean-atmosphere feedback. The timing of this has clearly proved much more problematic across the board in respect of longer range predications with diagnostic modelling (which determines numerical modelling) pointing to this sooner rather than later, Hence quite reasonable not to have expected any trough related solution across NW Europe to be prolonged.  These particular summaries are also not UK centric & take into account macro regional synoptics, (including interests closer to home in Portugal)

At present there are complex low frequency convergence signals across the Pacific, Atlantic and African continent which are scrambling the wind-flow (jetstream) feedbacks and meaning that there is no fluid inertia across the Pacific and stubborn trade wind effects are impeding the progress, currently, of Nino feedbacks in the Pacific.

This means that split flow from upstream to downstream, introducing a more sustained sub tropical element of flow ( such sub tropical flow as was seen under the strong high frequency MJO driven forcing back in June) is not materialising as anticipated (yet). This delayed absence allows a retracted Atlantic/Azores ridge to retain stubborn strength and with a looped jet flow above and around a +NAO signature. The trough therefore sustained longer than expected. It is true in this respect that the extraordinary Maritime heat is not helping with the fuel provided for these disturbances and self perpetuating their longevity.

The lull in the high frequency signal breaking down the westerly propagation in the tropics, and in the absence of the coherent low frequency convergence appearing in the Pacific creates a decelerating forcing (-ve low level flow frictional torque on the jetstream) and setting in motion further retrograde pull on extra tropical mountain torques in the extra tropics. This now looks likely to keep extra tropical torque mechanisms suppressed over the coming 10 to 15 days based on feedback lags.

With that in mind, the interest persists in seeing when that more "formal" atmosphere/ocean coupling occurs and puts a proper halt to this retrograde motion that is retracting the Azores ridge and keeping it stronger than expected and in turn enabling the trough to sustain ahead if it.. Change likely will happen when the next CCKW (convectively coupled kelvin wave) drives both oceanic and atmospheric shift to couple El Nino sustainably and subtly alter the messy low frequency feedbacks to a more cohesive Pacific convergence zone. This development removes trade wind blocks at, and east of the dateline. These trade winds shut the door on the jet stream being able to straddle the Equatorial Pacific into the Equatorial Atlantic and so not being able to weaken the Atlantic/Azores ridging - much as often discussed in earlier summaries in late Spring and early summer when MJO driven forcing enabled sub tropical flow in a classic El Nino synoptic response

A shift in the displaced Azores heights will be equally welcome down here in reducing build up of stagnant heat. This, rather that cyclical more mobile plume like heat building from south to north (and then repeating) which has been defined as the more likely default for the summer. Based on the above analysis, it still remains the case this is likely to happen & despite errors in recent estimations. The question remains the timing - and it is sensible to wait on this for the time being. NWP is not going to read such a signal especially well - so rules about baseless extrapolations of numerical model output still hold true, even at times when Mother Nature has just thrown a curveball. 

 

 

 

 

 

[rwtwm]

42 minutes ago, Man With Beard said:

Another interesting table - the ECM 00Z ensembles sea level pressure for London. The green waves indicate lower pressure passing through around 11/12th and then again around 15/16/17th.

Do I detect an uptick in pressure on the majority of runs towards the 20/21st...

I find it easier to use the ascending/descending views when looking for these sorts of trends. And yes, there's definitely an uptick in towards the end of the 0z ens. 

Only a modest hint towards any associated warmth though. 

[Addicks Fan 1981]

Thank you very much @Tamaraand it sounds like we will have to look out for a lot of variables before we actually get somewhere. 

In the meantime we will have to endure the mediocre or sub standard summer fayre we have.  

Just checked the GEFS 6Z mean up to 384 hours ahead and the trough still has a grip albeit not as vigorous as what we will endure by the 15th of this month.  

We definitely will have to grin and bear as if it were.   

[danm]

17 minutes ago, Addicks Fan 1981 said:

 

We definitely will have to grin and bear as if it were.   

Indeed. Now is the time to grin and bear it and keep looking for the signs outlined above to translate into the models. It won't happen overnight, but hopefully the shifts will start to show up within the next week or so.