Model Output Discussion - Mid Summer Onwards

[Rain All Night]

16 minutes ago, CoventryWeather said:

Clusters 264hrs+ are lovely. Bank that one in Dec/Jan. 

Hmm, are they actually that good? Here are the representative members for each...

[Rain All Night]

2 hours ago, RainAllNight said:

This morning, the GEFS is now more willing to follow the other two models and get that block up to a higher latitude and more quickly, but it still finds a way to get at least some of us wet (thinking of myself here) by letting lows dig down past us to the southeast.

Days 7, 10, 13:

And it seems that the ECM ensemble agrees with this, as the clusters posted by @CoventryWeather had suggested. A middle ground has been found.

Below are the suggested conditions for my south coast location with the time points of my three charts above highlighted: the dry spell brought in by the earlier northerly seems to end from the second chart onwards.

Edited October 10, 2023 by RainAllNight

[Daniel*]

Not sure what some are failing to understand we’re expecting a much colder than average air mass. It’s more than slight deviation. The likelihood of frost into next week is high it’s only cloud which can prevent this.  

[Addicks Fan 1981]

1 minute ago, Daniel* said:

Not sure what some are failing to understand we’re expecting a much colder than average air mass. It’s more than slight deviation. The likelihood of frost into next week is high it’s only cloud which can prevent this.  

According to the Exeter update they suggest below average temps to start with but above average temps to finish off.   We have to keep our eyes on Scandinavia to give us our next dry bit of weather.   

[Redbull165]

Oh look what have we here...

 

Edited October 10, 2023 by Redbull165

[Froze were the Days]

Hope that ECM 0z det run doesn't come off, cyclogenisis towards Greenland almost completely wipes out any form of a northerly getting going...will no doubt be colder (that's not difficult at the moment) but will soon be counting down the days before milder Tm air sets in place again if this run comes to fruition. 

[seb]

41 minutes ago, Daniel* said:

Not sure what some are failing to understand we’re expecting a much colder than average air mass. It’s more than slight deviation. The likelihood of frost into next week is high it’s only cloud which can prevent this.  

For 1 or 2 days which is exactly what you are showing; and which is in line with MetO, and with what I (and others) have said. It's also not "much colder than average".

London October average night time temps are 8 degrees and average daytime temps are 14. Even on Sunday which so far looks to be the "peak" of the "colder" air, the low for London is 5 degrees and the high is 14 degrees. Add to that the ECM more often than not underestimates night time temps and it could well be 24 hours with bang on average temps.

As for frost - a few areas north of Manchester on Sunday morning and the same area (roughly) again on Monday morning (unless you want to take the ECM for Monday morning at face value where some patches show up across the central parts of country... but this is of course not supported elsewhere). 

[Tim Bland]

Good news for European ski resorts if this happens …

[Cambrian]

The ECM is providing a clear set of signals and a consistent message for the next few weeks, albeit broad-brush at this range.

Yesterday’s regimes forecast shows a NAO+ signal and changeable for the rest of this week, eventually culminating in a northwesterly flow orchestrated by the Scandinavian trough, here on the heights and pressure weekly anomalies. Week 1, to 16 Oct.

 
 

Then we come under the influence of the Atlantic ridge for a few days of chilly, dry weather, which moves over us beginning to middle of next week, 0z ECM day 7 mean;

 

as currently modelled, it’s a cold high - EPS temperature anomaly, 5 day average, days 6-10 (12z yesterday).

before a consistent blocking pattern takes hold with high pressure over Scandinavia; Week 2. 16-23 Oct.

 

that currently shows good signs of persisting through to the end of the month. Week 3. 23-30 Oct. 

 

It’s a strong, persistent signal, and one that the other models are picking up on too.

[Metwatch]

15 minutes ago, Tim Bland said:

Good news for European ski resorts if this happens …

Quite the snow event modelled for north east Spain at the end. 

I know there's decent widespread elevation of above 1000m west and south of Zaragoza, but even so would be unprecedented after the seemingly endless heat they've had for the last few weeks.

Could be possible if the Scandi high brings the cold air far enough through to central Europe, then the high moves back over the UK trapping a trough into Iberia with cold air on the northern side.

If only most of England was on a plateau at 3000 feet above sea level, wouldn't need to worry about marginal frontal snow events

[CoventryWeather]

2 hours ago, RainAllNight said:

Hmm, are they actually that good? Here are the representative members for each...

I couldn't access those as I'm at college, so thanks for attaching! Seems like models are struggling to see how amplified it gets - something that briefly gets cold air to the UK from the east could be a rather small cluster then? 

[Quantock]

28 minutes ago, seb said:

For 1 or 2 days which is exactly what you are showing; and which is in line with MetO, and with what I (and others) have said. It's also not "much colder than average".

London October average night time temps are 8 degrees and average daytime temps are 14. Even on Sunday which so far looks to be the "peak" of the "colder" air, the low for London is 5 degrees and the high is 14 degrees. Add to that the ECM more often than not underestimates night time temps and it could well be 24 hours with bang on average temps.

As for frost - a few areas north of Manchester on Sunday morning and the same area (roughly) again on Monday morning (unless you want to take the ECM for Monday morning at face value where some patches show up across the central parts of country... but this is of course not supported elsewhere). 

The ‘airmass’, (presumably 850hpa temps) will be much colder than average as currently modelled on the ensembles charts.  Whether that translates to lower/higher than average 2m temperatures is a rather different matter and will not become clearer until nearer the time or sometimes on the day/night itself.

[Addicks Fan 1981]

According to this our cooler interlude is brief before temperatures 🌡 rise again.  

Time-longitudes diagram - Extended range forecast

CHARTS.ECMWF.INT

---

This is a time/longitude diagram (Hovmoller diagram) of 500 hPa or 1000 hPa mean height anomaly (contours) and spread (shading). The mean anomalies are derived from the ECMWF extended...

 

[sheikhy]

Beautiful gfs 06z if you like cold!!!bring the frost and cold temps on from this saturday im ready!!

[Addicks Fan 1981]

Just now, sheikhy said:

Beautiful gfs 06z if you like cold!!!bring the frost and cold temps on from this saturday im ready!!

Does the op have support from the control and the mean?    

[seb]

3 minutes ago, Addicks Fan 1981 said:

Does the op have support from the control and the mean?    

See for yourself...

 

 

Edited October 10, 2023 by seb

[sheikhy]

2 minutes ago, Addicks Fan 1981 said:

Does the op have support from the control and the mean?    

Seems as though it does!!!!!

[Addicks Fan 1981]

12 minutes ago, seb said:

See for yourself...

 

 

It has a very close tie with what Exeter are on about actually, the met office 6-15 day outputs are pretty reliable and offer information that is second to none.    

[seb]

31 minutes ago, Quantock said:

The ‘airmass’, (presumably 850hpa temps) will be much colder than average as currently modelled on the ensembles charts.  Whether that translates to lower/higher than average 2m temperatures is a rather different matter and will not become clearer until nearer the time or sometimes on the day/night itself.

Of course it is a different matter but that is exactly what doesn't seem to be understood. I don't know how much clearer I can explain it - there is currently nothing to indicate that there will be widespread out of the ordinary cold 2m temperatures. There may be two mornings where some areas will experience temps which are a little below average for this time of the year but even that is far from guaranteed. People seem to forget that we are an island which is 300 miles wide at its widest point. SSTs are still higher than they should be and that will affect 2m temps and is not accounted for by models.

Edited October 10, 2023 by seb

[seb]

10 minutes ago, Addicks Fan 1981 said:

It has a very close tie with what Exeter are on about actually, the met office 6-15 day outputs are pretty reliable and offer information that is second to none.    

Well quite. And the elephant in the room that so many don't want to see is that this isn't just shown on the most recent GFS run but also the previous one... and the one before that. And the ECM.

That's what I mean I say that there's wide confidence levels and that this is when you switch to probabilities of what is more likely on balance.

The mean is in sync with the LT average or above, apart from a very short period starting Saturday. The scatter is off the scale starting from Tuesday next week.

 

[Maz]

51 minutes ago, seb said:

See for yourself...

 

 

Rock solid on 4 days, from Saturday, below average 850s, and below by quite a margin.  Most likely either sunny with below average nights and almost average days, or cloudy/foggy, with nights nearer average but days cooler.

After that (Wednesday next week onwards) an interesting split.  Most ensembles see a warming of the airmass (presumably high slipping into central Europe and a toned down version of the current pattern establishing).  But a few, including both operational and control, remain cool (probably a Scandi high and easterly). 

The middle ground is "empty" on 20th October, so a half way house appears unlikely.  Probability favours the resumption of a milder pattern (the Met Office suggests this), but there is obviously a chance of remaining cooler.  I say cooler, as it is October, SSTs are high, the continent still warm, so it's not "winter".

[johnholmes]

This is the latest output from ECMWF, I'll leave you each to make your own minds up what it means in terms of weather and surface temperatures day and night for next week from Monday onwards

Just now, johnholmes said:

This is the latest output from ECMWF, I'll leave you each to make your own minds up what it means in terms of weather and surface temperatures day and night for next week from Monday onwards

Just to add, in my view, you may disagree, I find it usually nearer the actual at 500 and 850 MB than GFS at 6-10 days out, let alone inferences one may make for surface weather

 

[Addicks Fan 1981]

7 minutes ago, johnholmes said:

This is the latest output from ECMWF, I'll leave you each to make your own minds up what it means in terms of weather and surface temperatures day and night for next week from Monday onwards

Just to add, in my view, you may disagree, I find it usually nearer the actual at 500 and 850 MB than GFS at 6-10 days out, let alone inferences one may make for surface weather

 

I tend to support the ECMWF more than the GFS like yourself @johnholmesand find the ECMWF hovmoller plots very near to the mark.  Its a tough one of where our upstream activity will be and i will use a policy of using anomoly charts rather than op runs in isolation.     

[Daniel*]

2 hours ago, seb said:

For 1 or 2 days which is exactly what you are showing; and which is in line with MetO, and with what I (and others) have said. It's also not "much colder than average".

London October average night time temps are 8 degrees and average daytime temps are 14. Even on Sunday which so far looks to be the "peak" of the "colder" air, the low for London is 5 degrees and the high is 14 degrees. Add to that the ECM more often than not underestimates night time temps and it could well be 24 hours with bang on average temps.

As for frost - a few areas north of Manchester on Sunday morning and the same area (roughly) again on Monday morning (unless you want to take the ECM for Monday morning at face value where some patches show up across the central parts of country... but this is of course not supported elsewhere). 

Can you actually support that? GFS has maxes barely double figures on Sunday in London mostly single figures across UK.. similarly ECM not much higher. 

also lows forecast Monday AM a widespread air frost… this night is clearly going to be a frosty one, with a cold air mass, very light winds and clear spells. I think we should return to this once it passes.

 

 

[sundog]

8 minutes ago, Daniel* said:

Can you actually support that? GFS has maxes barely double figures on Sunday in London mostly single figures across UK.. similarly ECM not much higher. 

also lows forecast Monday AM a widespread air frost… this night is clearly going to be a frosty one, with a cold air mass, very light winds and clear spells. I think we should return to this once it passes.

 

 

Last week there were a couple of posters that were contradicting about the current warm spell. Now we have others  that are contradicting the coming cold spell