Model Output Discussion - 15th March onwards

[danm]

10 minutes ago, mushymanrob said:

Im talking about the anomalies. In particular the NOAA.. i use them daily and not very often do they embarrass me. 

People often dismiss them, but offer no actual proof, ie one of their predictive charts in comparison with reality. 

They often spot emerging trends well before others, usually between 8 and 12 days. 

 

Im sorry to have this repetitive, cyclical argument but will always respond to charges that are inaccurate.

I don’t think it’s a case of the anomalies being wrong, it’s that those charts show broad scale patterns, whereas what we’re debating are relatively small synoptic changes that could have significant impacts on what we experience at the surface, whilst still sitting within the envelope of what the anomalies show. 

I don’t think many people think that we could suddenly see a large anticyclone start to be modelled for next week, just that the positioning of the trough is still very uncertain. Even small changes can have pretty significant impacts. 

[Derecho]

Mixed results looking at recent predictions, this weekend for example...

6-10 day outlook leading up to this period

Model output

 

It has got the positioning of the trough wrong (close range output ended up with it to our SW instead) and underestimated the blocking to our north-east. Broadly it's good but as I said earlier, small details make a huge difference and charts like this won't be able to pick these significant differences up. Now for the weekend we have a plume of sorts.

Edited July 3, 2023 by Quicksilver1989

[mushymanrob]

10 minutes ago, Quicksilver1989 said:

Mixed results looking at recent predictions, this weekend for example...

6-10 day outlook leading up to this period

Model output

 

It has got the positioning of the trough wrong (close range output ended up with it to our SW instead) and underestimated the blocking to our north-east. Broadly it's good but as I said earlier, small details make a huge difference and charts like this won't be able to pick these significant differences up. Now for the weekend we have a plume of sorts.

Well lets see what this weekends chart verifies at first before any decisions are made! 

 

[Derecho]

5 minutes ago, mushymanrob said:

Well lets see what this weekends chart verifies at first before any decisions are made! 

 

Indeed, I think the charts often do very well when it comes to where areas of high pressure will sit (you can see that from the charts above), though low pressure positioning is often much harder to nail down when slack SLP gradients are involved or the key area of low pressure is small scale.

Edited July 3, 2023 by Quicksilver1989

[Addicks Fan 1981]

5 minutes ago, mushymanrob said:

Well lets see what this weekends chart verifies at first before any decisions are made! 

 

Reckon they'll be some twists and turns in the forthcoming output in the next set of runs.  The best case scenario will be if the trough retrogresses.  

[MP-R]

2 hours ago, MattStoke said:

One year ago today, a computer model through out something ridiculous.

The rest, as they say, is history.

Ahhh those were the days. What a cracking summer it was!

[Nick2373]

18z shows still below average temps then a brief warm around the 07th,08th bringing humid conditions then a cool down to below average, with this there should be some thunderstorms intense at time in areas some rain pushing in from the west 10th,11th mix this in with thunder storms and the could get even more lively. Then cooler conditions out until the 15th, then hints of something perhaps warmer than of late.  

[mushymanrob]

7 hours ago, Quicksilver1989 said:

Mixed results looking at recent predictions, this weekend for example...

6-10 day outlook leading up to this period

 

Actually i will address this now im not on NLC watch!

The NOAA charts are the 5 day mean 500mb/hpa charts, so not the same as surface. You cannot define a daily detail off a 5 day mean. That chart you posted does allow a 24/36 hour plume, but it also tells us that its transitory and low pressure to our Northwest will dominate the 5 day timeframe. When used in conjunction with the 8-14 day chart you can determine the most likely evolution at 500mb. And i now use the EPS which usually supports/confirms the NOAA version.
These dont give you surface definition, but do give you the range of what surface conditions are likely to be. They can "flip flop" but thats very rare. They are most likely for the timeframe they cover to be far wrong. They did predict this current cool unsettled spell, in fact werent you putting a "not so bad" spin on it only last week?
I find that their biggest area of inaccuracy, is the timing of the pattern they predict... the chart you use is centred on the 7th, when a more exact match might be a day or two later.
But these charts, and the EPS, the latest ECM daily anomalies AND the time longitude charts all predict troughing, albeit shallowish, to dominate through the mid Month period at least.
 

[ANYWEATHER]

The green snot is still with us this time next week albeit relaxes a little in a few days time

[MattStoke]

Air fairly warm and pressure relatively high across the far south through next week on the ECM. Probably not bad conditions there. More unsettled and cooler further north, though.

[Derecho]

19 minutes ago, mushymanrob said:

The NOAA charts are the 5 day mean 500mb/hpa charts, so not the same as surface. 

They did predict this current cool unsettled spell, in fact werent you putting a "not so bad" spin on it only last week?
 

Though that is the whole point I'm making, yes it does well to pick up on the broad 500mb pattern but the small differences in the overall pattern make a big difference to what we see at the surface.

You could have a scenario where almost all the high pressure cells are in the right place... but still have a trough over or to the west of the UK, both would bring very different weather at the surface.... which is ultimately what is key here.

Predicting the centre of low pressure in summer is difficult as we don't have large scale features such as an Icelandic low like we do in winter. I'd only read as far as saying a trough will be around or near the UK based on those charts.... and it could be to the north-west, south-west, north-east or directly over us.

I wouldn't therefore write off the first 3 weeks of July or say it's terrible by any means.

Besides yesterday and today, it looks pretty reasonable this week and not worthy of the 2012 comparisons made by a few members this time last week.

Thank god we don't get summer months like August 1986 anymore, I'd worry for the sanity of some if we did.

[Addicks Fan 1981]

1 hour ago, Nick2373 said:

18z shows still below average temps then a brief warm around the 07th,08th bringing humid conditions then a cool down to below average, with this there should be some thunderstorms intense at time in areas some rain pushing in from the west 10th,11th mix this in with thunder storms and the could get even more lively. Then cooler conditions out until the 15th, then hints of something perhaps warmer than of late.  

Think we are pretty much in a westerly regime here with the azores high being weak and suppressed.  It could be worse though, but I think the weak el niño we are in as things stand is suppressing the azores high.   

[LetItSnow!]

25 minutes ago, Quicksilver1989 said:

Though that is the whole point I'm making, yes it does well to pick up on the broad 500mb pattern but the small differences in the overall pattern make a big difference to what we see at the surface.

You could have a scenario where almost all the high pressure cells are in the right place... but still have a trough over or to the west of the UK, both would bring very different weather at the surface.... which is ultimately what is key here.

Predicting the centre of low pressure in summer is difficult as we don't have large scale features such as an Icelandic low like we do in winter. I'd only read as far as saying a trough will be around or near the UK based on those charts.... and it could be to the north-west, south-west, north-east or directly over us.

I wouldn't therefore write off the first 3 weeks of July or say it's terrible by any means.

Besides yesterday and today, it looks pretty reasonable this week and not worthy of the 2012 comparisons made by a few members this time last week.

Thank god we don't get summer months like August 1986 anymore, I'd worry for the sanity of some if we did.

I do believe summer months like August 1986 could make an appearance again one day in our lifetimes. I would find it interesting to witness actually. 

[Derecho]

2 minutes ago, LetItSnow! said:

I do believe summer months like August 1986 could make an appearance again one day in our lifetimes. I would find it interesting to witness actually. 

I think there's the chance we can get a few very cool days however across a month it's too easy these days to tap into a source of heat. I think it's easier in the likes of December to get notable cold because blocks can persist for weeks but in summer month you'd be relying everything to stay in the right place for weeks.

Not impossible but very difficult. August 2014 was the worst August in recent times and that was still over a degree warmer then August 1986.

[mountain shadow]

Looking dreadful still for the next two weeks for the North and West in particular. 

Little sign of the UK trough shifting.

[Addicks Fan 1981]

17 minutes ago, Quicksilver1989 said:

I think there's the chance we can get a few very cool days however across a month it's too easy these days to tap into a source of heat. I think it's easier in the likes of December to get notable cold because blocks can persist for weeks but in summer month you'd be relying everything to stay in the right place for weeks.

Not impossible but very difficult. August 2014 was the worst August in recent times and that was still over a degree warmer then August 1986.

Agree with what you've said there, by the way I checked the mike ventrice website yesterday and checked the hovmollers plot. 

It would seem by the 17th that a weak westerly wind burst will be merging through. 

We have got to hope that it's a game changer though as this weather seems very inclement for the time of year.    

Edited July 4, 2023 by Addicks Fan 1981

[ANYWEATHER]

Ecm has low pressure anchored to the Uk next week as well…️

30 minutes ago, LetItSnow! said:

I do believe summer months like August 1986 could make an appearance again one day in our lifetimes. I would find it interesting to witness actually. 

Yes, it’s only a matter of time before the phantom ex Hurricane Charlie makes an appearance again…

[Guest]

ECM is really poor this morning through the entire run, I was going to say I did think there was maybe some light at the end of the troughy tunnel with both the GEM and GFS Ops run indicating the trough would start to lift out towards day 10 however both their respective ensembles suites present a really, really poor mean with the vast majority of ensembles keeping the trough firmly anchored to the Uk. Looks like we are properly stuck in a rut. 

GEM

GFS

[terrier]

The ecm and its ensembles are awful this morning. Looks like we are proper stuck in a rut with this pattern. Glad I’ve cancelled my stay cation last week of July. Hopefully august will bring us something better. Because July is shaping up to be a nightmare of a month if it’s sun and warmth you’re after. Should have know better than to book a week on the east coast in this country

[Addicks Fan 1981]

Have checked the ECM ensembles myself up to day 10 and it doesn't actually look too bad, worse if you are up north.  Nothing spectacular though and could be better, but we are in a weak el niño regime with our weather currently so likely to have some disruption of some degree.  

[mb018538]

UKV shows 30c being reached on Friday & Saturday

[Downpour]

Regarding the anomaly modelling, what I would say is that the interpretation of the anomalies often fails to live up to reality. Too often, members see a blue ring near the UK, then write off that week. Yet as others have said, the exact position of the trough will make a huge difference to the weather on our small island. 

This week's much vaunted 2012-esque rainfest has verified to an unmemorable two-day wonder. And the coming weekend could be warm from many. Anomalies have their place of course, but by their nature are very broad brush – and therefore can flatter to deceive on our small island. 

[Addicks Fan 1981]

That's what I read on the latest ENSO bulletin that the tropical atmosphere is consistent with weak el niño.  It seems to be coupling with easterly trades hence why we are having trough activity.  Its going to be a big battleground to getting the azores high in properly.   

[Bats32]

1 hour ago, mountain shadow said:

Looking dreadful still for the next two weeks for the North and West in particular. 

Little sign of the UK trough shifting.

It's been pretty much solid rain for 2weeks or so, can't see that shifting anytime soon up here.

[Mike Poole]

ECM clusters, T120-T168:

All suggesting a warm up over the weekend, the key is how close the low gets to the UK and how quickly, cluster 4 looks the most progressive here.

T192-T240:

I still don’t think this period is sorted.  There is a lot of uncertainty here, hence the 6 clusters, the trough could have gone through, cluster 1, be hanging around in some cases rather benignly, or still hanging out west.  

I find the new daily run of the regimes plot from the ECM 46 interesting.  Here’s the last 6:

The longer term signal hasn’t changed much, with blocking (red) favoured over the other three, maybe declining towards the end of the runs, but look at the period early on that I’ve highlighted in yellow on the first plot!  This period has changed from favouring blue (+NAO) to red (blocking) to green (-NAO) over the last week.  Models have really struggled to get to grips with this period, and I’m not at all convinced there isn’t another twist to come…