[Teleconnections - Interactions and Impact]

21 hours ago, knocker said:

The links between the Madden-Julian Oscillation and European weather regimes

Abstract

Skillful weather forecasting on sub-seasonal timescales is important to enable users to make cost-effective decisions. Forecast skill can be expected to be mediated by the prediction of atmospheric flow patterns, often known as weather regimes, over the relevant region. Here, we show how the Grosswetterlagen (GWL), a set of 29 European weather regimes, can be modulated by the extra-tropical teleconnection from the Madden-Julian Oscillation (MJO). Together, these GWL regimes represent the large-scale flow characteristics observed in the four North Atlantic-European classical weather regimes (NAE-CWRs), while individually capturing synoptic scale flow details. By matching each GWL regime to the nearest NAE-CWR, we reveal GWL regimes which occur during the transition stages between the NAE-CWRs and show the importance of capturing the added synoptic detail of GWL regimes when determining their teleconnection pattern from the MJO. The occurrence probabilities of certain GWL regimes are significantly changed 10–15 days after certain MJO phases, exhibiting teleconnection patterns similar to their NAE-CWR matches but often with larger occurrence anomalies, over fewer consecutive MJO phases. These changes in occurrence probabilities are likely related to MJO-induced changes in the persistence and transition probabilities. Other GWL regimes are not significantly influenced by the MJO. These findings demonstrate how the MJO can modify the preferred evolution of the NAE atmospheric flow, which is important for sub-seasonal weather forecasting.

https://link.springer.com/article/10.1007/s00704-020-03223-2

https://confluence.ecmwf.int/display/FUG/Section+8.2.6+Madden-Julian+Oscillation+Output

[Teleconnections - Interactions and Impact]

The links between the Madden-Julian Oscillation and European weather regimes

Abstract

Skillful weather forecasting on sub-seasonal timescales is important to enable users to make cost-effective decisions. Forecast skill can be expected to be mediated by the prediction of atmospheric flow patterns, often known as weather regimes, over the relevant region. Here, we show how the Grosswetterlagen (GWL), a set of 29 European weather regimes, can be modulated by the extra-tropical teleconnection from the Madden-Julian Oscillation (MJO). Together, these GWL regimes represent the large-scale flow characteristics observed in the four North Atlantic-European classical weather regimes (NAE-CWRs), while individually capturing synoptic scale flow details. By matching each GWL regime to the nearest NAE-CWR, we reveal GWL regimes which occur during the transition stages between the NAE-CWRs and show the importance of capturing the added synoptic detail of GWL regimes when determining their teleconnection pattern from the MJO. The occurrence probabilities of certain GWL regimes are significantly changed 10–15 days after certain MJO phases, exhibiting teleconnection patterns similar to their NAE-CWR matches but often with larger occurrence anomalies, over fewer consecutive MJO phases. These changes in occurrence probabilities are likely related to MJO-induced changes in the persistence and transition probabilities. Other GWL regimes are not significantly influenced by the MJO. These findings demonstrate how the MJO can modify the preferred evolution of the NAE atmospheric flow, which is important for sub-seasonal weather forecasting.

https://link.springer.com/article/10.1007/s00704-020-03223-2

[Winter 2023/24 Chat and Discussion]

Lubbly jubbly to end the week

[Winter 2023/24 Chat and Discussion]

Just had a quick scamper through the Mod. thread and I know not why but “Other than that Mrs. Lincoln, how was the play?” flashed into my mind. 

[Winter 2023/24 Chat and Discussion]

I can't remember the last time I've seen so much frenzied .......

[Model Output Discussion - Into Winter]

9 minutes ago, alexisj9 said:

Low gets squeezed out perhaps?

But yep certainly looks odd for sure.

It is because the low deconstructs as the jet hits the buffers of the block to the east and rapidly veers

[Winter 2023/24 Chat and Discussion]

Shortwaveitus - an endemic disease that tends to proliferate in winter months. There is no known cure but can be treated with copious amounts of Diazepam and plenty of bed rest.

[Winter 2023/24 Chat and Discussion]

Sacre bleu.......we are on course for possible the shortest winter on record  

[Model discussion highlights]

Put simply the ecm next week has intense trough development in the Atlantic driven by a strong jet which at the same time amplifies the Euro ridge which  effectively mixes out the colder air in the west, including the UK and isolates the colder air to the east.

 

Original post: https://community.netweather.tv/topic/99584-model-output-discussion-into-winter/?do=findComment&comment=4965504

[Model Output Discussion - Into Winter]

Put simply the ecm next week has intense trough development in the Atlantic driven by a strong jet which at the same time amplifies the Euro ridge which  effectively mixes out the colder air in the west, including the UK, and isolates the colder air to the east.

 

[Winter 2023/24 Chat and Discussion]

The dash to make a silk purse out of a pigs ear is now well underway 

[Model Output Discussion - Into Winter]

3 minutes ago, mountain shadow said:

That cold pool is saying NO to any Atlantic incursion.

And nobody was listening

[Model Output Discussion - Into Winter]

14 minutes ago, Downburst said:

Yes, further north is more behaved, Dublin for instance. I'd be looking at the mean here. And thanks @knocker for the reminder of looking at the expected conditions when looking at ensembles for a location to put the scatter into context, obvious but easily overlooked.

Yes when something looks odd the first question should be why?

[Model Output Discussion - Into Winter]

10 minutes ago, sheikhy said:

Yes and you could see that on the pressure charts on ecm with that slight bend to the isobars near the m4 corridor but still the ecm has not been great lately!lets see what the 12z brings!!!!icon about to roll out....

Surface chart

[Model Output Discussion - Into Winter]

14 minutes ago, sheikhy said:

Its ridiculous!!if ecm fails again at just 72 hours this evening then questions must be asked about the model!thats gona be 3 times in the last 10 days it has failed then!!!ecm has always been my go to model but its performance recently has been woeful!!!the spread is crazy at just 4 or 5 daya out!!!

I take it you do appreciate that currently the analysis has a warm front edging slowly north on Sunday into the cold air so the ens not too surprising

[Winter 2023/24 Chat and Discussion]

Well now  the moderate rain here has turned to moderate snow for a while this morning. A good example of evaporative cooling 

[Winter 2023/24 Chat and Discussion]

Game over.....just as well close the mod. thread for the rest of the winter 

[Teleconnections - Interactions and Impact]

A short summary of the MJO

MJO_summary.pdf

[Model Output Discussion - Into Winter]

Time to wheel out "Will it Snow" by John once again 

https://community.netweather.tv/learning/basics/will-it-snow-by-john-holmes-r96/

[Model Output Discussion - Into Winter]

15 minutes ago, bluearmy said:

Think it would be marg….inal  

Oh God............just when I thought things couldn't get any worse in here 

[Model Output Discussion - mid Autumn]

37 minutes ago, throwoff said:

The 'problem' with this thread is that is does pull out a cross section from ardent rampers to doom mongers. 

Sadly when the models are complex toys immediately go flying from multiple prams and the unstoppable force meets the immovable object.

FWIW the mods do a superb job, especially as the thread gets busier and busier.

There is a strong rumour doing the rounds that this thread is going to be renamed the gymkhana thread.

[Model Output Discussion - mid Autumn]

11 minutes ago, Met4Cast said:

Well, do feel free to provide some evidence and examples of when trop/strat coupling alone has led to high latitude blocking.. 

I didn't say alone and bluearmy has pre-empted my reply which i have made in more detail elsewhere

[Model Output Discussion - mid Autumn]

1 minute ago, Met4Cast said:

Surely strat/trop coupling make high latitude blocking even less likely? 

Not necessarily

[Model Output Discussion - mid Autumn]

4 minutes ago, Met4Cast said:

No, but Greenland highs and amplified patterns aren't just born out of thin air, I'm afraid. The most likely outcome for the 22nd-28th period has always been a mid-Atlantic high, despite the GFS best attempts to usher in a true Greenland high & winter proper. Without sufficient tropical forcing it's just not possible to get such highly amplified patterns. 

 

 

.

Not even with a strat/trop coupling?

[Model Output Discussion - mid Autumn]

43 minutes ago, TSNWK said:

Can you elaborate please on this strong assertion? Thanks

Because given the rather complex nature of the evolution minor changes with the energy flows can make a big difference as highlighted by the development and track of the frontal wave next Friday. Cryptic assertions like the one I responded to are absolutely no help to people trying to understand what is going on