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Model output discussion - Post SSW - Will it turn cold?


Message added by Paul

Please only post model discussion in this thread. 

For more general chat and banter, or moans and ramps loosely around the models, please head to the banter thread:
https://www.netweather.tv/forum/topic/86721-model-moans-ramps-and-banter/

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:
https://www.netweather.tv/forum/forum/142-regional-discussions/

Thank you!

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Cold - Yes Instability - Yes Prolonged - Yes I just wet myself - Yes!

I quite often agree with your sort of sentiment, as I'm one who opts to look at the most likely solution to fit the signals rather than the preferred one But, equally impartially and with intended

Sorry, I just thought I’d walked into the moans threa.. oh wait. <passes around a big bag of grips> No sooner do we get a cold spell within sight it astonishes me that time and time again some p

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1 hour ago, Quicksilver1989 said:

Yup snow for the many and not the few hopefully! 

Still trying to keep myself grounded, I don't want a conservative cold spell under a strong and stable high....

The chart of Catacol for the same date shows a different set up to mine, (preceding post) though a similar set of circumstances but it is an example of how the models can vary. 

gem-0-240.png?00

 

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2 hours ago, John Badrick said:

Please no repeat of "that ECM" a few years ago when everything was a dead cert, even down to t48 and then... well we know what. Can remember even the met, bbc etc were certain. Is this set up Any different? Are we in a better position? Or could it all go horribly wrong again?

As I recall, although the Model output at the time was pointing to a coldish outlook, the ECM (and most of it's ensemble set) went for a very extreme outcome for 1 run.

There is far more model agreement this time, both in terms of cross model consensus and consistencies between runs for the same model. Add this to the background teleconnections as a result of the SSW and things look a lot more solid this time round.

It should be noted that there are still 4 or 5 ensemble members on the 06z GFS that don't really ever get that cold, so a complete collapse is I suppose possible until we see those blues and purples heading over the North Sea and the low countries at +72 or so.

What would concern me more based on 15 years or so of model watching, would be that some historic cold spells have shown similarly epic output in the 8-14 day range only for very incremental downgrades to occur in terms of severity or longevity (or both) which has resulted in a bit of a watered down version when the spell actually arrives, albeit with some noteworthy snow events on occasions. The two instances that I can recall the event being as severe as the models were December 2010 and March 2013, the latter event offering some hope to us here as that was also a SSW event.

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20 minutes ago, Daniel* said:

What we seem to be looking at predates the internet era, a classic easterly has been in deep hibernation like a dormant volcano. I won’t mention Feb 2009 that was very fleeting, it goes to show how rare synoptics like this are, when in Greater London we had the most disruptive snowfall since 1991 - 18 years.

And 2005 not really memorable not on level with may come. Last reference points has to be 1991 and this looks ruddy good if better, mean drops to -10C in London at day 8 looks like beast wants to pay a visit I think it’s coming... been a long time since. Exciting! 

B9492140-CE86-4B07-97A5-A7DFD0D45DC4.thumb.gif.bafce07b96f7c03462802bcb8a58d578.gif

 

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22 minutes ago, Daniel* said:

What we seem to be looking at predates the internet era, a classic easterly has been in deep hibernation like a dormant volcano. I won’t mention Feb 2009 that was very fleeting, it goes to show how rare synoptics like this are, when in Greater London we had the most disruptive snowfall since 1991 - 18 years.

And 2005 not really memorable not on level with may come. Last reference points has to be 1991 and this looks ruddy good if better, mean drops to -10C in London at day 8 looks like beast wants to pay a visit I think it’s coming... been a long time since. Exciting! 

B9492140-CE86-4B07-97A5-A7DFD0D45DC4.thumb.gif.bafce07b96f7c03462802bcb8a58d578.gif

Yep spot on as ever Daniel these set ups are very rare like the sudden severe weather set ups

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28 minutes ago, Daniel* said:

What we seem to be looking at predates the internet era, a classic easterly has been in deep hibernation like a dormant volcano. I won’t mention Feb 2009 that was very fleeting, it goes to show how rare synoptics like this are, when in Greater London we had the most disruptive snowfall since 1991 - 18 years.

And 2005 not really memorable not on level with may come. Last reference points has to be 1991 and this looks ruddy good if better, mean drops to -10C in London at day 8 looks like beast wants to pay a visit I think it’s coming... been a long time since. Exciting! 

B9492140-CE86-4B07-97A5-A7DFD0D45DC4.thumb.gif.bafce07b96f7c03462802bcb8a58d578.gif

If my recollection is correct, the build up to 2005 was quite similar, although by the time it actually arrived the uppers had got watered down quite a bit. I lived and worked in Central London at the time and got zilch, although it did deliver for quite a few as I recall. The cold pool looks more robust this time round, so a bigger threat would probably be a geographical deviation with the cold pool either missing us or not quite making it. here.

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4 minutes ago, Stu_London said:

If my recollection is correct, the build up to 2005 was quite similar, although by the time it actually arrived the uppers had got watered down quite a bit. I lived and worked in Central London at the time and got zilch, although it did deliver for quite a few as I recall. The cold pool looks more robust this time round, so a bigger threat would probably be a geographical deviation with the cold pool either missing us or not quite making it. here.

Yeah I remember 2005 well, I was so excited for the spell, told all my relatives and friends what was coming and how biblical it was going to be and the closer it got the less the impact was forecast to be. I also remember on the 27th (I think) that the dewpoints were too high and the snow had turned to wet drizzle and I remember being gutted!

 

That is one of the many reasons why I will not get excited about this until it's right on the doorstep, and I am certainly not telling anyone to stock up on essentials as I've been burned by that far too many times before! That said, even if it a watered down version of what's being modelled it'll still be a notable event.

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1 hour ago, Catacol said:

Agreed. This is still a risk. I'm slightly concerned the models may not yet be seeing the full impact of the SSW... and if anything that storm track might drop further south. The wailing and gnashing of teeth that would follow if Paris was buried and it was sunny in Portsmouth would be hard to bear!

That's interesting, and certainly one of the two biggest risks, but I think it may be the lesser one.  My gut feeling is that the second warming in the strat will only strengthen the block and the bigger risk is that the block will maybe drift too far north, GFS 0z run exemplifying this evolution?  

Having said that, there's very little in the output today to suggest that either of these risks are significant, quite the contrary, it's just that there are some days to go and things can always change.  At least I think the risk of the Atlantic breaking through is negligible.

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1 hour ago, supernova said:

By a considerable margin the best set of ENS I ever remember seeing for the Eastern counties. Am gonna see if I can unearth the ensembles for 2009/10 when I get time later - be interested to compare - but honestly I'm not sure they were ever this good.

graphe3_1000_296_42___.thumb.gif.ae7b47b1277fb73fc8459f48a9753a8c.gif

Could u please provide ME with a link to Kent ensembles thanks 

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1 minute ago, bluearmy said:

a week away from the deep cold onset and plenty of shortwaves to run under the bridge in the meantime. The cold pool just leaving Siberia. A warming currently under way in n America which could change the modelling again. 

Should that American warming really have much bearing on the European cold which is already in motion? As for shortwaves few have been modelled and some of them have been beneficial.

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