Model Output Discussion - mid Autumn

[Cambrian]

An elegant symmetry to the 12z GFS ensemble mean anomalies. 

The build of heights out of Canada, through the Atlantic and then eastward into Scandinavia from days 1-8.

Then the build back west to Greenland during days 8-16.

Several days of an easterly flow sandwiched between two northerly spells early and late.

Those looking out for a generally cooler and drier than average theme, with some pleasantly seasonal mid-autumn weather (avoiding the fatigue-inducing prospect day after day, week after week of constant damp, not seeing the tops of the hills and not even the bottoms of the mountains), can’t really lose if we maintain this oscillating pattern.

With glowing respect to the great contributions on here, which as ever I’m thoroughly enjoying and learning from, I think I’m going to dispense for just a little while with being overly concerned about which flavour of northern blocking might ultimately best stress the stratospheric PV, particularly when the Arctic hasn’t undergone a fraction of its seasonal cooling yet, and instead just enjoy the moment! 

[Metwatch]

Tonight's GFS run only, but check out those blues at the end of the model below the 300 hPa level, those are easterlies not westerly mean U component winds! (at 60N latitude)

 

The eddy heat flux, not really confident what it fully is, but looping through the run, to me it does seem interesting. Some reds (positive anomalies) which moves east to west over at our longitude, from 60-80N. Both diagrams from this site: http://www.weatheriscool.com/

Edited October 12, 2023 by Metwatch

[Mike Poole]

GEFS and ECM mean at T240:

You can see where they differ, in terms of getting the low near Germany under the block, ECM ensembles less keen, but maybe getting keener, if you look at the spread, you can see an area of uncertainty in exactly that area (circled):

I read this as ECM and the ENS moving to GFS/GEFS on this one, but still work in progress…

[Lincs Observation]

59 minutes ago, Metwatch said:

The UK under a warm airmass on the ECM 12z, but huge contrasts again with the -10C 850hPa isotherm spanning right across western Russia to eastern Europe.

Such a blocked pattern, just imagine it was modelled to be like this 8 weeks from now! However long this may last, some weakening on the SPV if so.

Could this be the start of a recurring pattern as we move toward winter ?  

[ANYWEATHER]

Interesting synoptics nontheless,  whether the weather ends up being colder or milder next week is still up in the air , but the usual invigorating Atlantic firing up at this time of year ,looks like taking a breather! 

[Man With Beard]

ECM having a go at Indian Summer v3.0

The overall synoptic setup looks far less promising for this type of eventuality, though - this is absolute best case scenario for warmth from the forecast situation, and a stones-throw from something much, much colder. I wouldn't bet my house on this coming off.

[WYorksWeather]

I'm going to repeat the exercise from last night and have a look at where the GFS and ECM are differing.

Once again, not much difference at T+72.

 

By T+120, GFS and ECM differ in the strength of the low to the west of Spain, which is much deeper on the ECM than the GFS. GFS has a deep low in the mid-Atlantic, whereas on ECM the same low is centred closer to Greenland.

 

By T+168, these differences become very important. GFS builds a 1030mb Scandinavian high centred over Norway, while the ECM has it just a little bit further east. The low to the west of Spain is still weaker on the GFS and fails to draw the mildest of the air into the UK, but the ECM manages it.

 

 

Finally, to round it all off, at T+240, the GFS has plunged us into a cold easterly, whilst the ECM is still milder than average.

 

Between those two frames, the ECM briefly goes exceptionally mild at T+192. 19C in the raw output is likely enough to get somewhere to 21C in practice, which is only a couple of degrees short of the date record. Meanwhile, the GFS at the exact same time has temperatures barely scraping into double figures.

 

All to play for beyond day 5 it seems at this stage. We need to watch the configuration of those two low pressure systems, and the position of the Scandinavian high. My money is still on ECM.

[Scorcher]

Does anyone seriously think the GFS is going to be 

1 hour ago, Mike Poole said:

GEFS and ECM mean at T240:

You can see where they differ, in terms of getting the low near Germany under the block, ECM ensembles less keen, but maybe getting keener, if you look at the spread, you can see an area of uncertainty in exactly that area (circled):

I read this as ECM and the ENS moving to GFS/GEFS on this one, but still work in progress…

The GFS 12Z op run has actually moved towards the ECM/UKMO at 144hrs:

I'm almost certain we'll be seeing the GFS back down more tomorrow.

[WYorksWeather]

2 minutes ago, Scorcher said:

Does anyone seriously think the GFS is going to be 

The GFS 12Z op run has actually moved towards the ECM/UKMO at 144hrs:

I'm almost certain we'll be seeing the GFS back down more tomorrow.

It is small margins. And it is exactly these sorts of scenarios where you'd expect the ECM to have an advantage, with its better resolution. Spotting exactly how deep a low is going to be, or the precise position of a high.

[Rain All Night]

The GFS has definitely got a friend in Google!

EC46: Euro heights to gradually return as the high-lat block slips back west beyond Greenland? (Sorry, I'll get me coat...)

Edited October 12, 2023 by RainAllNight

[Mike Poole]

24 minutes ago, Scorcher said:

Does anyone seriously think the GFS is going to be 

The GFS 12Z op run has actually moved towards the ECM/UKMO at 144hrs:

I'm almost certain we'll be seeing the GFS back down more tomorrow.

GFS solution is clearly represented in the ECM clusters now, it is cluster 3 with 12 members (T192-T240):

Cluster 1 is the ECM op solution, and cluster 2 is somewhere in the middle.

[Don]

27 minutes ago, RainAllNight said:

EC46: Euro heights to gradually return as the high-lat block slips back west beyond Greenland? (Sorry, I'll get me coat...)

Think you'll need a taxi after posting those charts.....

[Rain All Night]

Everyone is now showing the "trough to the southwest" solution at day 7, just with varying strengths to the low:

Back to being much messier again at day 10. GEM and JMA have still managed to bring a cold pool across from the east, GFS no longer has - it's let the high sink into the continent. ECM, on the other hand, barely changes between days 7 and 10, and keeps the high over Scandi strong:

Edited October 13, 2023 by RainAllNight

[ANYWEATHER]

15 minutes ago, RainAllNight said:

Everyone is now showing the "trough to the southwest" solution at day 7, just with varying strengths to the low.

Back to being much messier again at day 10. GEM and JMA have still managed to bring a cold pool across from the east, GFS no longer has - it's let the high sink into the continent. ECM, on the other hand, barely changes between days 7 and 10!

Usual caveats with this situation.  Models often overdo the energy building the Scandi blocking scenario  ,some under do the energy. Timeless situation in these synoptics. As per usual the gfs is again wobbling all over the place, so ecm may well be barking up the right tree!

[Howie]

If the southerly comes off, do you think that it could quickly switch around to an easterly?

[Lincs Observation]

interesting 

https://x.com/worldclimatesvc/status/1712522155403931655?s=46&t=FDRXB-PdoXSULLPenJr_eA

Edited October 13, 2023 by Lincs Observation

[Downburst]

1 hour ago, Lincs Observation said:

interesting 

https://x.com/worldclimatesvc/status/1712522155403931655?s=46&t=FDRXB-PdoXSULLPenJr_eA

This is no surprise to me given

https://climate.copernicus.eu/copernicus-september-2023-unprecedented-temperature-anomalies

[CoventryWeather]

1 hour ago, Lincs Observation said:

interesting 

https://x.com/worldclimatesvc/status/1712522155403931655?s=46&t=FDRXB-PdoXSULLPenJr_eA

Not really a surprise to be fair. 

An interesting JMA run this morning, not a model I really use but seems popular to an extent on this thread. Here is the chart for 180 and 216. 

It kinda fits with what the professionals are saying will happen later this month, for the high across Scandi to retrogress westwards towards Greenland. There is limited support from other OP runs (slight extent of GEM), but most ensembles have a cluster that is similar to that of JMA - the ECM seemingly the largest ones, and even the UKMO ensembles have one, even if it's a small weak cluster.

Still a fair bit of uncertainty regarding what happens with the lows to the south west, whether they stall against the high and bring an easterly, or whether they move north, giving us a fresh wind from the continent albeit warmer moist air. 

Maybe a mix of the scenarios, with the North having the fresher easterly, and the south west/east having the warmer air, but I'll leave others to discuss that. 

[Daniel*]

A lot more of EC ens going for cooler continental undercut.

12z > 00z

 

 

[Shaunado]

2 hours ago, Lincs Observation said:

interesting 

https://x.com/worldclimatesvc/status/1712522155403931655?s=46&t=FDRXB-PdoXSULLPenJr_eA

I wonder whether, with the projected increase in northern blocking, the area of -5 hpas will be considerably more widespread this current month, (albeit less intense), perhaps a little closer to average?

[Rain All Night]

1 hour ago, Daniel* said:

A lot more of EC ens going for cooler continental undercut.

12z > 00z

 

 

For the south coast it's giving some serious consideration to a second consecutive weekend cold snap, this time from the east rather than the north:

[Battleground Snow]

A very early first post of the season for me, but this would have a been cracking chart for snow streamers if it was November and not October.

Edited October 13, 2023 by Battleground Snow

[Kasim Awan]

I can see ICON producing some wet snow next week down to this elevation. We'll be at a significant advantage if we start the Winter season with this level of tropospheric disturbance, which should help modulate the trop pv going into Winter.

[summer blizzard]

UKMO has the second low at day 7 at 970mb so its likely to fail. 

GEM succeeded in pushing through by day 9 with the second low as the Scandi Ridge moves towards Greenland. 

GFS0z was a horrid halfway house, it pushed the second low through but the low was already at our lattitude so we don't get the fresh continental air (recipe for 10C and cloud all day and night).

GFS6z was a fail, the Atlantic wins by day 10 (ignoring FI afterwards).

Euro is a fail overall although only just.

 

[Jeremy Shockey]

I'm up in the North of Scotland for a long weekend.

Could get interesting on the hills.

high res WRF NMM 12z

 

ARPEGE 12z

regards JS