[Model Output Discussion - Into Winter]

00z and now 06z GEFS H500 mean by day 10 quite bullish to push Atlantic troughing east across NW Europe

00z EPS H500 mean at day 10 more blocked - with a ridge just to our west .

Be interesting to see if GFS backtracks on its keenness to bring back the default unsettled Atlantic zonal train or whether EC is wrong.

More closer in time, now Thursday's low looks off the menu, there looks to be a brief window for wintry showers, perhaps falling as snow inland, to affect eastern areas Thursday night / Friday morning in the strong NEly wind, before winds back northerly later on Friday and into the weekend, with most places becoming dry away from coasts. ARPEGE below Friday morning:

No widespread snow event on the horizon, far north and east likely the best place to be to catch a flake, drier and sunnier in the west.

[Model Output Discussion - mid Autumn]

Looks like GFS has dropped the far N Atlantic / Griceland block idea, but still toys with a southerly tracking jet with wedges of high pressure to the north of the jet to delay any attempts of a milder breakdown from the Atlantic. Still no concrete signs of a return to mild zonal, ignore the mild SW'erlies in FI ... for now.

[Model Output Discussion - mid Autumn]

Morning. I see that low from the Azores, that I thought wouldn't be a player, returns on the scene & moves toward S England Thursday, bumping into cold air - to bring a potential snow event somewhere.

Too far off to have confidence on this event, due to uncertain track of this low, could well end up missing us and tracking into France like previous runs. GFS doing its usual blowing the low up too much, so probably too far north in track.

Still the chance of wintry showers in the NE flow that follows, especially for eastern areas.

[Model Output Discussion - mid Autumn]

Another EC det blocked and cold through to day 10. The T850s don't look particularly cold, as in will produce convective wintry showers, but imagine if the flow is slack the cold will build at the surface.

Hard to pin down features that may bring some snow at the moment, but looks like the Azores low will not be a player, rather a low dropping south over Ireland before heading east close to the south mid-to-late week could bring some precipitation, perhaps wintry, to the west and south. Also low pressure over the North Sea could bring some wintry precip to more eastern areas later in week.

[Model discussion highlights]

Morning. So, we have a low near the Azores on Monday tracking NE towards NW Europe during next week - which wants to put a spanner in the works for clean cold air advection from the NE around low pressure over central Europe. Danger is it gets too far N or NE and pulls in milder air from the south.

What coldies need to see is the block that also develops to the north and northwest next week, in response to amplification of upper trough upstream over Canada, further south across Iceland rather than Greenland, as this will keep that low from the Azores further south and all of the UK in the cold air. But, too far off this low coming up from the SW to be resolved yet. So wouldn't be too concerned yet.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4956878

[Model Output Discussion - mid Autumn]

Not a bad GFS ensemble mean to start December on

[Model Output Discussion - mid Autumn]

Morning. So, we have a low near the Azores on Monday tracking NE towards NW Europe during next week - which wants to put a spanner in the works for clean cold air advection from the NE around low pressure over central Europe. Danger is it gets too far N or NE and pulls in milder air from the south.

What coldies need to see is the block that also develops to the north and northwest next week, in response to amplification of upper trough upstream over Canada, further south across Iceland rather than Greenland, as this will keep that low from the Azores further south and all of the UK in the cold air. But, too far off this low coming up from the SW to be resolved yet. So wouldn't be too concerned yet.

[Model discussion highlights]

An interesting thread by Eric Webb on x / twitter explaining the unusual and unexpected developments over Europe next week, especially the -NAO. He suggests recent tropical forcing and strong strat PV would normally be unfavourable for the -NAO pattern we are seeing evolve and that it is more 'local' in situ forces that are shaping it rather than teleconnections to what's going on further afield. Reflects what I mentioned earlier but he has far more knowledge on such matters.

Quote

These kinds of "in-situ" type -NAOs are more common in El Nino winters like this (esp mid-late winter).

Admittedly, these "in-situ" -NAOs can often be harder to forecast because you're relatively more reliant on "local" processes from individual cyclonic wave breaks/"storms" to develop a -NAO. 

 

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4956640

[Model Output Discussion - mid Autumn]

An interesting thread by Eric Webb on x / twitter explaining the unusual and unexpected developments over Europe next week, especially the -NAO. He suggests recent tropical forcing and strong strat PV would normally be unfavourable for the -NAO pattern we are seeing evolve and that it is more 'local' in situ forces that are shaping it rather than teleconnections to what's going on further afield. Reflects what I mentioned earlier but he has far more knowledge on such matters.

Quote

These kinds of "in-situ" type -NAOs are more common in El Nino winters like this (esp mid-late winter).

Admittedly, these "in-situ" -NAOs can often be harder to forecast because you're relatively more reliant on "local" processes from individual cyclonic wave breaks/"storms" to develop a -NAO. 

 

[Model discussion highlights]

Following the trigger low moving SE into near continent on Monday, EC brings another low SE from Iceland mid-week which interferes with cold air advection from the E / NE. But, EC has been behind the curve with these lows, so don't feel too despondent yet.

Original post: https://community.netweather.tv/topic/99428-model-output-discussion-mid-autumn/?do=findComment&comment=4956440

[Model Output Discussion - mid Autumn]

2 minutes ago, CoventryWeather said:

UKMO and ECM very similar to each other at 168 so perhaps they are sensing something. 

True, need that ridge to build in stronger to the N and NW following the trigger low sinking SE, to prevent more lows dropping SE to maintain the cold NE flow.

[Model Output Discussion - mid Autumn]

Following the trigger low moving SE into near continent on Monday, EC brings another low SE from Iceland mid-week which interferes with cold air advection from the E / NE. But, EC has been behind the curve with these lows, so don't feel too despondent yet.

[Model Output Discussion - mid Autumn]

3 minutes ago, bluearmy said:

Will be interesting to see how the Google AI model has been dealing with this - as mere humans, we are closer to the AI model which (as I understand it) looks back at previous patterns to predict what is likely to happen.  we all know that deep cold to our east will make the modelling less accurate than usual. Presumably the AI is better at appreciating that too?? 

Yes, think AI weather models, with its machine-learning hindsight approach (think it looks back at 40 years of data) will be an important addition along with NWP, with it's physics approach. We'll soon be looking at the AI run as well as the operational run I guess!

[Model Output Discussion - mid Autumn]

Sometimes I think some are putting too much emphasis on tropical forcing / teleconnections to predict what will happen over our part of the world and not looking what's going on with the atmosphere on a less global scale, i.e. stubborn East European cold trough to the east and how this is causing the jet to buckle upstream to form blocking over Iceland well into next week. Was not long ago that some were telling us the blocking would be temporary and would quickly collapse to allow resumption of Atlantic zonal conveyor of lows, based on MJO / AAM forecasts. Clearly something else going on and more 'local'. Not saying that tropical forcing isn't having some say in the current patterns, but perhaps less influential than we think?

[Model Output Discussion - mid Autumn]

Looks cold on 12z UKMO for next Monday across SE England, T850s of -7 to -8C and temps struggling.

However, 12z GFS completely different with low pressure slap bang over the UK with showers or longer spells of rain and milder.

Lots of uncertainty after the weekend with regards to an upper level ridge building NE from the Atlantic towards and over Scandinavia. GFS makes a right dog's dinner of it, by quickly pushing in lows across the UK off the Atlantic as heights builds over iceland, Norwegian Sea and then Scandinavia.

[Model Output Discussion - mid Autumn]

2 minutes ago, Catacol said:

If that comes off Nick it would be a surprise. More likely to see the ridge collapse and the jet ride back over the top…but in recent times the weather has begun to confound and confuse perhaps more than in the past.

Certainly if we can see a high lat block gain traction when the pacific goes back into the IO and the vortex is still strengthening it would raise some significant questions regarding what happens later in winter when drivers are looking more theoretically aligned. I wonder how significant the Atlantic SST profile is in an analysis of relative weighting…

I'm surprised the EPS members are clustering to show a mean like this too, given the teleconnections / Pacific driving pointing to temporary block this weekend before a more zonal patterns resumes into December. 

With regards to Atlantic SSTs, interesting you raise that, a tripole has developed, similar to late Nov 2009 (which was also El Nino).

Current SST anomaly

30 Nov 2009

But in Nov 2009, the north Pacific was cooler

[Model Output Discussion - mid Autumn]

Interesting the EPS throwing an olive branch for a renewed Atlantic ridge build in the medium range joining up with the northwest Russian high shown well in the H500 mean but also support in the clusters

Keep UK in the cold at least, but potential that we could tap into deep cold from the northeast or east should the flow switch to favour this. Mean keeping us cold day 10.

[Model Output Discussion - mid Autumn]

4 minutes ago, Northern Lurker said:

Glad to see a pro summarise what I suspect 99% of readers here have witnessed over the last few days. GFS was first on the scene with a cold plunge mid last week, ECM wanted nothing to do with it at first but has now changed its tune & backtracked towards the sentiment of GFS.

I find the pro ECM narrative from Met4Cast bizarre & out of keeping with previous winters on here, all of the models get predictions wrong, so just call it as it is? They are only weather models & as far as I'm aware nobody wins on here wins any prizes for which one is best? 

I don't have statistics to back it up, but my experience of watching the models over the years I've found GFS is usually the best at picking up northerlies first of all models, though may tend to to overdo the depth and longevity of cold advection. GFS does not do so well with other synoptic evolutions though, tends to struggle more with trough disruption and often too far north with tracks of lows moving east, probably because it deepens them too much at range. All of the big three models GFS, EC and UKMO seem to have their strengths in certain areas. Though even these apparent strengths don't always play out. That's why it's always worth keeping an eye on how the operationals sit with ensembles.

[Model Output Discussion - mid Autumn]

Although GFS continues to be the most amplified of the models with the Atlantic ridge this coming weekend, thus keep the northerly going longer and colder, to be fair to the model, the EC wasn't interested in building the Atlantic ridge as recent as yesterday's 12z if you compare the two charts below, this morning it has an Atlantic ridge holding back low pressure moving east toward the UK:

12z EC (yesterday) for 00z Saturday 25th

00z EC (today) for 00z Saturday 25th

To me it seems the EC has done some backtracking, while the GFS is toning down the longevity and depth of cold of the northerly 

[Cold arctic air will try to move south by next weekend, but how far south remains uncertain]

After a mild weekend and temperatures close to or above average much of this coming working week, cold arctic air will try and spread south by the weekend, but some uncertainty how far south. Could be some snow for Scottish hills though.

View the full blog here

[Storm (Tempête) Frederico]

Some strong gusts on islands and in exposed parts of the coast of NW France - 142 kph / 88mph on Belle-Ile, 127 kph / 79mph gust at Point de Chemoulin on the mainland. 

Orange wind warning for Channel Islands 

 

[Despite the supercomputing power, weather models can still get it wrong - even at short range]

A look at how the weather models and the trillions of calculations they make a second from weather obs - they can still get the forecast wrong less than 12 hours ahead. A good example was today with heavy rain across southern England - which was poorly modelled.

View the full blog here

[UK Storm and Severe Convective Forecast]

UK Severe Convective & Storm Forecast - Issued 2023-11-13 23:28:22

Valid: 14/11/2023 0000 to 14/11/2023 23:59
THUNDERSTORM WATCH - TUES 14TH NOV 2023

Click here for the full forecast

[UK Storm and Severe Convective Forecast]

UK Severe Convective & Storm Forecast - Issued 2023-11-13 23:28:22

Valid: 14/11/2023 0000 to 14/11/2023 23:59
THUNDERSTORM WATCH - TUES 14TH NOV 2023

Click here for the full forecast

[Jersey tornado - Wednesday 1st November 2023]

A look at the Jersey tornado that ploughed a path of destruction across the east of the islands on 1st November and was rated T6 by TORRO, equivalent to an EF3 tornado. Also some quotes from a resident who experienced the full force of the tornado and Storm Ciaran's strong winds that followed.

View the full blog here