Model Output Discussion - Into Autumn 2020.

[mb018538]

8 minutes ago, I remember Atlantic 252 said:

only really 1 warm day away from SE on EC on Monday, GFS 12Z? unsure of that cannot find it

Sunday isn’t bad - mid 20s

[I remember Atlantic 252]

10 minutes ago, mb018538 said:

Sunday isn’t bad - mid 20s

mainly a SE 'event' on GFS windy at 19 here

[Frosty.]

There’s some big swings in temperatures on the ECM 12z operational ( the duality of early autumn ) but high pressure / ridging predominates across southern u k meaning a good deal of fine weather and very little in the way of rain apart from perhaps some thundery activity associated with the hotter more humid conditions early next week.

Edited September 9, 2020 by Jon Snow

[Allseasons-Si]

1 hour ago, Griff said:

In layman's terms, how well do these verify or is it just for fun (pointing me towards tabular data or graphs at this point might make my head explode, one of those weeks here)?

Ta. 

I don't know the verification stats of the CFSv2 Griff but the trends is what i am looking for and yes @mb018538 i need my head testing hehe! but if they keep on showing then i will take notice,all fun and speculation of coarse,steady as she goes

Oh! and MERRY CHRISTMAS...

Edited September 9, 2020 by Allseasons-si

[Griff]

19 minutes ago, Allseasons-si said:

I don't know the verification stats of the CFSv2 Griff but the trends is what i am looking for and yes @mb018538 i need my head testing hehe! but if they keep on showing then i will take notice,all fun and speculation of coarse,steady as she goes

Oh! and MERRY CHRISTMAS...

I can't believe I'm already saying this and it's only September, but we're either going be collectively (as cold lovers) very excited or disappointed, but at least there is model interest... And the curse of the commentator.  

[mb018538]

BBC latest forecast Tuesday - 24c

MetO latest forecast Tuesday - 29c

Battle Royale!

Edited September 9, 2020 by mb018538

[Man With Beard]

You'd think the ECM op is a little on the progressive side

but exactly what will happen beyond Monday is still up for grabs.

[damianslaw]

A few notable changes in today's models, heights are quite likely not going to position themselves in a favourable place for any sustained warm period of note away from the SE quarter of the UK. Monday sees a shot of southerly warmth, but atlantic trough forcing will nudge heights to develop in a poor alignment to our east, with a quick reversal back to a atlantic flow for northern and western parts, then its back to square one, with azores high languishing to our SW doing its best to ridge NE, but coming unstuck against a very active atlantic. We have the vagaries of ex tropical storms to forecast, add these in the mix, and all I can see is a very active atlantic, heights will struggle to fend it off, low pressure systems probably wrapping up and over these heights with alternations between tropical and polar maritime air, with perhaps the SE holding on to more of settled warmer regime being further away from the atlantic influence.

Edited September 9, 2020 by damianslaw

[mb018538]

30 minutes ago, damianslaw said:

A few notable changes in today's models, heights are quite likely not going to position themselves in a favourable place for any sustained warm period of note away from the SE quarter of the UK. Monday sees a shot of southerly warmth, but atlantic trough forcing will nudge heights to develop in a poor alignment to our east, with a quick reversal back to a atlantic flow for northern and western parts, then its back to square one, with azores high languishing to our SW doing its best to ridge NE, but coming unstuck against a very active atlantic. We have the vagaries of ex tropical storms to forecast, add these in the mix, and all I can see is a very active atlantic, heights will struggle to fend it off, low pressure systems probably wrapping up and over these heights with alternations between tropical and polar maritime air, with perhaps the SE holding on to more of settled warmer regime being further away from the atlantic influence.

You can’t forecast anything with that amount of tropical systems. It could just as easily buckle the jet and amplify everything like we’re seeing now from the Pacific typhoons causing chaos. Nightmare time, don’t think I can recall 3 systems all close by in the same period like we might see in a week or so.

[Mike Poole]

Some talk of a single CFS run earlier, re winter.  CFS must be taken probabilistically to have any forecasting power at all, which means looking at a series of runs to try to identify a signal.  So here’s the last 4 runs z500 anomaly for December:

But this is only just starting to show on this model, so caution advised! 

 

[sheikhy]

8 hours ago, Mike Poole said:

Some talk of a single CFS run earlier, re winter.  CFS must be taken probabilistically to have any forecasting power at all, which means looking at a series of runs to try to identify a signal.  So here’s the last 4 runs z500 anomaly for December:

But this is only just starting to show on this model, so caution advised! 

 

Very good charts from ukmo and gfs this morning!!ukmo continues with the cut off low and extreme heat for the time of year and niw gfs cuts off the low as well and extends the heat a little more!!sunday to wednesday hot on gfs and more especially ukmo!

[mb018538]

UKMO is very warm/hot Monday and Tuesday, and still pretty warm Wednesday as the low cuts off and maintains the feed off the continent. GEM is remarkably similar, and has a patch of 18c 850 air moving up through Tuesday. It shows maxima at 28-29c for Monday, Tuesday and Wednesday. GFS not too far off, though not quite as warm as GEM by Wednesday. A lot will depend on how the low develops and where it ends up.

[mb018538]

ECM raw data this morning has a couple of small 30c patches in Norfolk on Tuesday, and stays pretty warm in the East on Wednesday too. Good to see it's come into line with the cut off low scenario too. Looks very dry too, with large areas of central and eastern England showing zero ppn out to day 9 on the ECM op.

[sheikhy]

Massive upgrade on ecm!cuts off the low completely!some beautiful heat and sun on the way!!!last few mornings have been pretty chilly here!!can defo tell winter is on its way!!

[mb018538]

ECM Op pretty close to the mean this morning. A very decent spell of September weather on the way.

[Scorcher]

17 minutes ago, mb018538 said:

ECM Op pretty close to the mean this morning. A very decent spell of September weather on the way.

Looks like the wobble is over after yesterday's op runs- I was concerned the warm spell was going to disappear but this morning's runs look great.

[Frosty.]

2 hours ago, Scorcher said:

Looks like the wobble is over after yesterday's op runs- I was concerned the warm spell was going to disappear but this morning's runs look great.

Indeed..OMG what an upgrade compared to last evenings ultra progressive ECM 12z op!!!!..I think we can safely say another return of summer is safely in the bag now.!!!!!!.,Boom!... 31-32c for the sarf east..hats off to Tamara, who spotted this FIRST!!!!!

 

Edited September 10, 2020 by Jon Snow

[Man With Beard]

Impressive ensembles on the ECM - a very large number bring the 18C upper air line over the UK at some point - the marker of a major heatwave during summer months - and a couple even squeeze the 20C uppers line up to the south coast, which is quite remarkable for mid-September.

However, around 30% of ECM ensembles have some similarities to yesterday's ECM op from Tuesday onwards, so not quite there yet on heat lasting beyond Monday.

[Tamara]

1 hour ago, Scorcher said:

Looks like the wobble is over after yesterday's op runs- I was concerned the warm spell was going to disappear but this morning's runs look great.

Yes indeed - very much so. Back towards making more sense, set against the direction of travel of forcing within the tropics>extra tropics   The suggestion was made last week that the progress back to fine, warm spells on a more widespread basis would not be seamless in terms of how NWP handled it - with the tendency to try to shift rossby wave amplification back upstream and push troughs south east across NW Europe.    Customary modelling difficulties evident with the high frequency tropical convection wave negotiating the passage of the terrain of the Maritime Continent as it propagates eastwards a factor in this respect - leading to susceptibility to defaulting back to the La Nina standing wave across Africa and the Indian Ocean.

Quite a lot of SST warmth across the Maritime Continent and the Western Pacific, as the Eastern Pacific continues to cool further below average.

 

 

Possible makings of a (continued weak) central/eastern based La Nina which assists the prospect of MJO related tropical convection convergence perhaps setting up a little further east than a traditional La Nina heading through this autumn. Therefore maybe greater downstream amplification patterns to mix up the default La Nina-esque mid Atlantic ridge than might otherwise be expected, and hence Indian Summer potential for October as well

 

Edited September 10, 2020 by Tamara

[Man With Beard]

And now we have 20C upper air on an op run: GFS 06Z at T120. You have to look closely but it's there!

[sheikhy]

1 minute ago, Man With Beard said:

And now we have 20C upper air on an op run: GFS 06Z at T120. You have to look closely but it's there!

Yup upgrades flooding in now!!expect to see even more improvements on the gfs 12z!!seems to lose the plot on the 06z after 168 hours but thats gfs for you!!cant handle the cut off lows or energy distribution!!!i cant believe how dry its expected to be for the rest of september!!together with heat and sun it really does not get better than this at this time of the year!

[MP-R]

May just squeeze another sunny day on Tuesday, which would be fantastic given the 850s. Hard to tell what may or may not arise from a thundery point of view. Minor changes to the setup can have big results. Overall, still looking like more unsettled beyond the end of next week, but I'm certainly seeing the warmth prolonged until then. Impressive stuff for mid September - just imagine if we had had these synoptics from August 13th onwards, given what came during the first 13 days of that month. You could almost delete everything between then and now and continue where we left off.

 

[Premiere Neige]

17 hours ago, Griff said:

I can't believe I'm already saying this and it's only September, but we're either going be collectively (as cold lovers) very excited or disappointed, but at least there is model interest... And the curse of the commentator.  

Weak to moderate la nina, warm SST's off the east coast of Canada/USA and around Greenland, hurricane activity ramping........maybe.......just maybe!

[Man With Beard]

A look at this morning's clusters

13th September (T72) - A week ago we saw a marked split in the ensembles, with a very stormy option in the clusters. See below, from 3rd September when this date was T240.

  

Turns out both were wrong; neither saw the strength of an Azores High pulse into Europe

@Tamara or others who look at the background signals - any ideas on where the ECM ensembles had gone wrong a week ago? Was there a signal it was not picking up?

Onto next week

T132: Looks like 4:1 in favour of a hot Tuesday, with clusters 1 and 2 keeping the Atlantic low far at bay. Even the smallest cluster would see heat being pushed out during the day. 

Further out, T216/T300 - the majority view is that High Pressure will set up to the north, keeping the warmer uppers originally sucked up from the south in situ for some time - though moderating gradually due to the time of year. A breakdown far from certain and slow if that, as heights to the NE may be slow to move away from the UK.

[mb018538]

@Man With Beard most of the changes have come about from the Pacific. Typhoon moved north, severely buckled the jet stream (hence 36c to freezing in 48h in Colorado, and the ripple has continued across the Atlantic. Almost impossible to forecast that chain of events at that lead time.