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Model output discussion - here comes the beast!

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:

For general weather chat including about the snow/cold chances around the country, please go to the regional threads:

We also have a special post SSW cold spell discussion open here:

Thank you!

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Early guidance forewarning of next weeks weather was issued earlier on, and this has been further enhanced with extended outlooks in bulletins. AFAIK (comms not being my area) public agencies and majo

Come on those looking for the breadown before the major cold and snow has begun You will be very lucky if that is the correct word to see this in ANY winter in the rest of your lives I would sugg

Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of nex

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2 minutes ago, mb018538 said:

Certainly no mention of a big mild fest on the meto update today...,maybe they aren’t buying it still.

We know that the last MOGREPS run wasn’t seeing quite the northern push that other models are. If the 00z run is the same then they will probably stick with what they have, adding a caveat or two re less cold conditions into the south of the uk.. I would be surprised if some of the ens members aren’t breaking ranks by now though. 

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1 minute ago, bluearmy said:

We know that the last MOGREPS run wasn’t seeing quite the northern push that other models are. If the 00z run is the same then they will probably stick with what they have, adding a caveat or two re less cold conditions into the south of the uk.. I would be surprised if some of the ens members aren’t breaking ranks by now though. 

That's my problem, it's all well and good people having the opinion that it may end up further south, I thought that yesterday morning! But since then there's near total agreement amongst GFS ops and ECM ops and the ensembles and for them to be so wrong at day 5 I would find quite staggering, if there was divergence I would be more hopeful but they are solid.

Besides this we all know the law of the sod means the models will be right when it comes to a warm up. 

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42 minutes ago, That ECM said:

Post the models that show what you are describing. 7c Friday 10c weekend. 


24 minutes ago, Weather-history said:

Looking at Friday, if you look at the archive of famous snow events of the past, the uppers are not that impressive.

The famous snowstorm of March 1891 which buried the SW of England, the uppers don't look that special in the area that was badly hit. 


Look at the uppers for the famous ice and snowstorm of late January 1940. You wouldn't think you would get anything from that just on that chart.


Bit of a side track, but I've wondered how accurate the uppers are on these charts for a long time ago? I assume they are a reconstruction/calculation as I doubt they had actual data for them especially in 1891.

I've have noticed significant differences in the 850's between the 'NOAA 20th Cen' and 'CFSR' archives on Wetterzentrale for some dates.

That's not to take away from your point in any way and I agree with it, just something I've wondered about.

With regards to the models this morning, ECM is still too far north for me in the far south/SW if I want to enjoy anything this weekend (as are all the main models). Better away from the south though and great for the north. Good old maritime Ireland will probably quite well again.
It still gives a good snow event, even a blizzard down here before it starts thawing before dawn for me though.

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London 18z ens v 00z ens


A few more colder runs have appeared this morning with the mean a fraction lower around the 5th

Overall it does look like becoming less cold still later in the week but a lot will happen before then with the potential for a major snow event in the south prior to a breakdown

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Is it me or does the 0z Arpege have the iberian LP a lot further south compared to other model output for the same timeframe;

arpegeeur-0-96.thumb.png.10a4a2b41790d52b7fde85b08b34f19f.png o

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7 minutes ago, Paul said:

Do you really think that models being wrong at 120/144 hours would be staggering? When it comes to placing a low pressure system, the typical scenario would be for the models to take pretty much right up to the event to nail down the precise track and intensity, let alone when it's a low taking the trajectory it's currently forecast to take. 

Look at the situation in the last week or so with the models too, we've had a massive amount of volatility, have a relatively unusual blocking situation, have just come out of the back of a major ssw etc. There's plenty to suggest that changes are more likely than not at that range. We'll see how it plays out, but I don't think anyone should ever be staggered if the models change at a range of 120+ hours, since they do it all the time. 

I wouldn't be shocked about an OP run being wrong at day 5, but given  they are backed heavily by the ensemble suites I would be extremely shocked if there was a big enough movement back at this stage to allow the southern half of the uk to get in on the act.

Sure, it's possible but it would be a pretty epic fail from the 2 major models ensemble suites, I'd really love to see then MetO model suite to see where it stands on the matter, will be keeping an eye out on twitter.

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Hi, with all the models about the same until 66 hours , the gfs assembles look very close too each other. Can any one tell me until we get to about this 66 hours we will not see if the lows progress is making inroads to the block more or less . So will all out put be wrong after this if models like gfs do not get blocking correct? Or am I not getting this wrong.Thanks


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I posted a few days ago that the JMA and GFS were showing this scenario of a greenie/Scandi block which was dropped but the GFS favours again.

That is a decent block still in place but also cuts off the cold feed. 

Yet another couple of days of interesting model watching, what wins out / manifests from Thursday onward is a big call but my glass is half full and the potential jackpot for snow lovers at the end of the week is still on the table.




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Right, had a look at a load of the ensembles this morning. Time to update the graph again, showing whether milder uppers move through the south by midday Saturday:


So a subtle further shift towards milder conditions by next Saturday but this is far from nailed. Indeed there are still plenty of very cold runs in there that have a full snow event with no marginality down here. I think some people again are just focusing on uppers only when there are plenty of scenarios with uppers just below zero that would have any precipitation falling as snow.

The ECM showed 9 runs with warmer uppers advancing north on saturday, 13 with colder uppers remaining over the UK. As it stands I make the return to milder conditions on saturday the slight favourite at the moment but I really wouldn't like to call it!

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1 hour ago, Weathizard said:

It's game over for the far south, pretty much unanimous agreement amongst the GFS and ECM ensemble suites for a fast warm up, I mean... anyone who can't see that in the GFS ensembles is in serious denial, people will say it's a 6 days away but we've seen once the GFS and ECM suites are onboard at this range they aren't often wrong.


Question for the more intelligent ones regarding the SSW, as it was a record reversal do you think to some extent that is what is shooting the coldest uppers straight through us at a vast rate of knots as the cold pool seems to move through us very fast, all things considered.


Not really there have been plenty of times when GFS and ECM have together "agreed" and it's gone a completely different way.  Think of all the times when GFS & ECM agreed we were going to be buried under 25 feet of snow 5 days out and then at T+24/48 the cold spell completely evaporates and we ended up warm instead.

If this was showing a snow storm and staying cold for 2 weeks everyone says its FI, could change etc but somehow because it shows a breakdown and 2 models kind of agree it's suddenly "game over"???  If that low tracks 100 miles south it's far from game over and that level of correction is probably well within margin of error for the models concerned.

Yes it's there and it's showing a warm up for some BUT it's not certain, it's not game over.

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