Model Output Discussion - Mid Summer Onwards

[MattStoke]

11 minutes ago, Djdazzle said:

A question: whyare upper temperatures of 20C only translating to 26C / 27C? I know it's October, but you'd expect a bit more than that. Even in Paris, it's only showing 27C.

@knockerput up a chart yesterday showing that there is a bit of an inversion being projected which may limit surface temperatures and make 850hpa temperatures a less reliable guide for surface temperature projections.

[mb018538]

16 minutes ago, Djdazzle said:

A question: whyare upper temperatures of 20C only translating to 26C / 27C? I know it's October, but you'd expect a bit more than that. Even in Paris, it's only showing 27C.

29.9c was achieved under this set up on October 1st 2011 at Gravesend.

If you look at the forecast for Saturday, you'd think that with a much warmer airmass we'd be seeing similar temperatures. Airmass just probably isn't dry enough this time around with more of a SW component. Makes all the difference with lapse rates etc. Humidity is still above 50% in most of the SE.

[Man With Beard]

53 minutes ago, Djdazzle said:

A question: whyare upper temperatures of 20C only translating to 26C / 27C? I know it's October, but you'd expect a bit more than that. Even in Paris, it's only showing 27C.

Not sure really, I thought it was winds coming from Biscay but upon closer inspection they are coming off the continent

I've studied other historical charts and a 10C-12C increase upon uppers should be achievable at this point in the year in optimal conditions, which are usually light winds, continental draw, sunny skies, build up of warmth, etc - all of which would appear to be in place?

This was the hottest chart I could find in the ECM ensembles - 26C on Sunday near Cambridge as a raw maximum, so given usual adjustments could result in something like 28C. But nothing higher than that, and in general a couple of degrees less. 30C appears off the table.

Mind you, the date record for Sunday is 26.1C, so we could achieve that.

(EDIT: just seen other posts above which may provide better answers than I've given)

Edited October 3, 2023 by Man With Beard

[richie3846]

32 minutes ago, Man With Beard said:

Not sure really, I thought it was winds coming from Biscay but upon closer inspection they are coming off the continent

I've studied other historical charts and a 10C-12C increase upon uppers should be achievable at this point in the year in optimal conditions, which are usually light winds, continental draw, sunny skies, build up of warmth, etc - all of which would appear to be in place?

This was the hottest chart I could find in the ECM ensembles - 26C on Sunday near Cambridge as a raw maximum, so given usual adjustments could result in something like 28C. But nothing higher than that, and in general a couple of degrees less. 30C appears off the table.

Mind you, the date record for Sunday is 26.1C, so we could achieve that.

(EDIT: just seen other posts above which may provide better answers than I've given)

I wonder if the forecast temperatures may also be affected by the rarity of the warm spell, for the time of year? There isn't much past experience, several date records for this stage in October, date back over a 100 years. 

[knocker]

The ecm ens do vertical profiles out to t120 and this Saturday 1200 for Reading

Edited October 3, 2023 by knocker

[Djdazzle]

31 minutes ago, richie3846 said:

I wonder if the forecast temperatures may also be affected by the rarity of the warm spell, for the time of year? There isn't much past experience, several date records for this stage in October, date back over a 100 years. 

And temperatures in warm / hot spells often seem to get upgraded as the time approaches.

[alexisj9]

1 hour ago, mb018538 said:

29.9c was achieved under this set up on October 1st 2011 at Gravesend.

If you look at the forecast for Saturday, you'd think that with a much warmer airmass we'd be seeing similar temperatures. Airmass just probably isn't dry enough this time around with more of a SW component. Makes all the difference with lapse rates etc. Humidity is still above 50% in most of the SE.

Great really love humid weather, not.

[Alderc 2.0]

Thankfully those silly charts showing single figure maximum through the middle of next week have been replaced with mid twenties until the 13th in the south

16 minutes ago, alexisj9 said:

Great really love humid weather, not.

It’s really not a humid airmass.

[Scorcher]

I'm taking it the GFS is having another wobble? It's been all over the place for the weekend while the ECM has barely shifted at all.

[legion_quest]

Typical, had a nice bit of cold on the models showing, and now that gets watered down but the heat verifies. 

 

[alexisj9]

6 minutes ago, legion_quest said:

Typical, had a nice bit of cold on the models showing, and now that gets watered down but the heat verifies. 

 

Looks like it 

[Don]

21 minutes ago, legion_quest said:

Typical, had a nice bit of cold on the models showing, and now that gets watered down but the heat verifies. 

 

As long as the same doesn't happen in a couple of months, I'm not too bothered at this stage!

[legion_quest]

5 minutes ago, Don said:

As long as the same doesn't happen in a couple of months, I'm not too bothered at this stage!

I think this is the new normal. Much more chance of heat earlier and later each year, lots less cold. 

Global warming for you! 

[*Stormforce~beka*]

19 minutes ago, Don said:

As long as the same doesn't happen in a couple of months, I'm not too bothered at this stage!

The annual snow for Christmas day hunt will begin soon lol

[Cambrian]

Aside from the great discussion regarding the precise temperatures we might expect (it will be very warm that’s for sure!), perhaps it’s fitting to celebrate such a stunning performance from the Atlantic trough in terms of pushing up the heights, and pumping up such a handsome ridge in time for the weekend, here at 96h on the 0z EPS height and anomaly chart.

Often when we see a sustained Atlantic trough being persistently (and correctly) modelled, we associate it with very changeable weather, often resulting in a conveyer belt of systems from the southwest running up into northwest Europe. 

On this occasion, it’s a particularly fulsome, elongated trough with a broad base that, importantly, digs a long way south of the Azores. This, combined with the exceptional residual heights from the summer to the south that the trough is able to engage, sends its partnering ridge cresting through the UK and Ireland with notable geopotential heights - that’s 585 dam running through the south, and 570 dam running through the north of Scotland.

The T850s appear to peak through Saturday at 12-14 degrees above normal for early October (staggering!) with surface temperatures around 8-12 degrees above average for many, here on the respective anomaly charts. Locally no doubt these will be higher still.

 

Our warmth friendly trough is ultimately broken through its middle by a strong build in heights to the west leading in to day 7,

its base forming a proper cut-off low over the Azores, with heights lowering to our north and northeast, for a very different feel by day 8, the combination of strong Atlantic ridge and a trough extending southwestwards into the Norwegian Sea bringing a northwesterly flow along the heights contours into northwest Europe.

 

So going by the EPS (at least), it’s still all change by day 9, below average T850s for all of the UK and Ireland.  Two very different faces of autumn in the same week. 

[Addicks Fan 1981]

1 hour ago, legion_quest said:

Typical, had a nice bit of cold on the models showing, and now that gets watered down but the heat verifies. 

 

Think @Alderc 2.0is right and any cold that appears will get downgraded.  Never a great idea to just look at op runs in isolation as if they are not supported that they don't come off.    

[legion_quest]

Woohoo, new models showing cold! 

Now to see how that plays out over the next 9 days! 

Cant wait for the models showing any snow and watching that disappear too! 

[Methuselah]

24 minutes ago, legion_quest said:

Woohoo, new models showing cold! 

Now to see how that plays out over the next 9 days! 

Cant wait for the models showing any snow and watching that disappear too! 

I do hope not, LQ. You're not Eon's CEO, are you? 

[Metwatch]

Looks like GFS and to an extent ICON, wants things to be a bit more westerly for the upcoming warm spell, more so than the rest of the other model's operational runs for the same time this weekend, perhaps due to stronger heights over Greenland, and so a stronger low next to Iceland, squeezing down on the Euro high on Friday - Saturday.

A sharp north - south split setting up, but where the fine line is between warmth / sunshine, and cooler wetter conditions doesn't seem fully set in stone yet. From what I see is that the further south you are, the drier and sunnier it will remain through the next 7 days, with central and southern England having the best chance for that.

Spain continuing with the heatwave conditions for what seems to now last endlessly, while a brief break for most of France, but the heat returns there properly from Saturday and central / southern UK likely joining in for a bit as well.

Edited October 3, 2023 by Metwatch

[raz.org.rain]

1 minute ago, Metwatch said:

Looks like GFS and to an exent ICON, wants things to be a bit more westerly for the upcoming warm spell, more so than the rest of the other model's operational runs for the same time this weekend, perhaps due to stronger heights over Greenland, and so a stronger low squeezing through next to Iceland on Friday - Saturday.

A sharp north - south split setting up, but where the fine line is between warmth / sunshine, and cooler wetter conditions doesn't seem fully set in stone yet. From what I see is that the further south you are, the drier and sunnier it will remain through the next 7 days, with central and southern England having the best chance for that.

Spain continuing with the heatwave conditions for what seems to now last endlessly, while a brief break for most of France, but the heat returns there properly from Saturday and central / southern UK likely joining in for a bit.

"North south split" always has me on edge, I'm not used to that generally meaning the borders!

[summer blizzard]

Pacific wave now forecast to be a little stronger than previously forecast meaning that the wave progresses further east through October. This may promote blocking to the north/east as we head towards the final third (hopefully we have a Polar Block to keep some retrogression). Also note that the Indian Ocean is now dead. 

[cheese]

18 minutes ago, Metwatch said:

Looks like GFS and to an extent ICON, wants things to be a bit more westerly for the upcoming warm spell, more so than the rest of the other model's operational runs for the same time this weekend, perhaps due to stronger heights over Greenland, and so a stronger low next to Iceland, squeezing down on the Euro high on Friday - Saturday.

A sharp north - south split setting up, but where the fine line is between warmth / sunshine, and cooler wetter conditions doesn't seem fully set in stone yet. From what I see is that the further south you are, the drier and sunnier it will remain through the next 7 days, with central and southern England having the best chance for that.

Spain continuing with the heatwave conditions for what seems to now last endlessly, while a brief break for most of France, but the heat returns there properly from Saturday and central / southern UK likely joining in for a bit as well.

GFS kind of looks like a one-day wonder really with the really anomalous warmth occurring on Saturday only, although the rest of the run still shows temperatures in the high teens/low 20s on many days thereafter. Certainly nothing that would threaten any date records though, and in Scotland/NI it never really gets warm at all.

Obviously just across the channel in northern France it's high 20s for days on end, nothing new there. The climatic gap between northern France and England seems to be getting bigger and bigger every year.

Edited October 3, 2023 by cheese

[chapmanslade]

8 minutes ago, cheese said:

GFS kind of looks like a one-day wonder really with the really anomalous warmth occurring on Saturday only. Obviously just across the channel in northern France it's high 20s for days on end, nothing new there.

Maybe in Leeds, but 5 or 6 days in a row over 20C is pretty amazing for October in the South of the UK

[cheese]

11 minutes ago, chapmanslade said:

Maybe in Leeds, but 5 or 6 days in a row over 20C is pretty amazing for October in the South of the UK

It's good, but still a big step down from what it was previously showing (widespread mid 20s, high 20s in parts of the SE with date records falling). It also wouldn't be unprecedented as London saw 5 days in a row above 20C in October 2018.

Hoping the ECM is on the money personally. Get the high moving further north so it's warmer for everyone.

Edited October 3, 2023 by cheese

[raz.org.rain]

25 minutes ago, cheese said:

GFS kind of looks like a one-day wonder really with the really anomalous warmth occurring on Saturday only, although the rest of the run still shows temperatures in the high teens/low 20s on many days thereafter. Certainly nothing that would threaten any date records though, and in Scotland/NI it never really gets warm at all.

Obviously just across the channel in northern France it's high 20s for days on end, nothing new there. The climatic gap between northern France and England seems to be getting bigger and bigger every year.

Story of the year really. So, so many downgrades to such promising outputs.