Model output discussion - here comes the beast!

[Eastnorthwest 215]

Still time for slight changes for the positives for Thursday onwards, if the incoming low track on a slightly more southerly track and more to our east the whole situation will be completely different come next weekend with all that cold to the north sinkongsouth

[bluearmy 42,602]

After a few runs where the direction of travel is now abundantly clear (btw, watch the cold pool make it into the Atlantic, see the Azores ahead of it, slam the brakes on and head straight back to the Arctic!), it comes down to us needing the pattern adjusting a 150 miles. That’s all - not a big ask is it!   I would be surprised to hear that MOGREPS is as bullish on the systems not getting north of the channel on today’s runs. 

in the meantime, bundles of the white stuff around for many of us this week. No doubt there will be the usual ‘snow shields’ in operation but we should make the most of sypnotics that we perhaps won’t see again for many years. 

[Jayces 473]

19 minutes 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.

Funny, a week ago it was game over for the whole country when the cold pool was shown to be heading into France and then 24 hours later it all changed.

I think there should be a caveat for this thread that any discussion about the models use the words if or potentially rather then making statements suggesting that something will happen 100% guaranteed 7 days away.

Yes I agree there is a warm up being shown but it's less today then yesterday and the MET update is still saying a cold March which suggests it's (potentially) game on?

@Bring Back1962-63 has written some excellent posts on why he believes the low on Friday will behave differently and @Weather-history has provided evidence showing how what the charts show won't necessarily result in the weather we would expect (IE snow instead of rain).

The trend is a winter storm on Friday, just where it hits and how severe is still too far out.

Also I'm no expert but don't those ensembles show a wide spread from the 2nd of March but the majority with negative temps meaning it will still be cold?

Edited February 25, 2018 by Jayces
Spelling corrections

[bluearmy 42,602]

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. 

[Weathizard 4,668]

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. 

[Evening thunder 1,800]

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.

[s4lancia 9,901]

Truly fascinating stuff this. Put your emotions aside, enjoy the coming week and wait see what Friday brings. 

To those trying to learn... Anybody who states Friday is nailed is frankly talking out of their backside. End of.

I’d say this morning the charts, as a whole, are definitely a bit better. The beauty about living on the south coast is expectations are so low anyway, that when it rains instead of forecasted snows, we just shrug and accept it as the norm ?. So it’s just fantastic that that won’t be the case regards any PPN falling from Monday to Thursday. No marginality there at least.

Ive spent quite a while looking at the charts this morning, specifically the Northen Hemisphere ones, to try and get a grip on next Friday and what happens next once that low is detached from the jet. I am surprised how many charts are deepening it as much as they are. And then of course the model drives it more Northerly. Very few are disrupting / significantly filling it. I just wonder if there is a void and the potential, not showing, of a surface high over Norway to develop.

I’m on the fence as to whether the models have this right or not right now, as always, time will tell!

Edited February 25, 2018 by s4lancia

[Summer Sun 48,566]

UKMO extended has some precipitation it the north and west drier the further south and east you are

[Paul 21,502]

16 minutes ago, Weathizard said:

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. 

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. 

[Jon Snow 79,531]

The GEFS 00z mean has definitely backtracked from its milder 18z trend last night..an increasingly bitterly cold and snowy week coming up and then it stays cold, indeed very cold further north with an ongoing risk of snow according to the mean!..hopefully once we're in the freezer, at least most of us will stay there!!

Edited February 25, 2018 by Frosty.

[BLAST FROM THE PAST 12,917]

5 hours ago, The Eagle said:

So....I take it ICON is once again the darling model?

 

Navgem is a very good run too and GFS not too distasteful.  For me there is a movement on models and I’m standing by my thoughts that BENELUX area is where the LP heads......that would keep the wintry theme in place.....well into March.  The weekend is not nailed on, I think we’ll see more changes as we go through this highly wintry week.

 

BFTP

[Summer Sun 48,566]

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

[Paul 21,502]

For those getting frustrated by the breakdown chat, and wanting to talk more about the closer range stuff, we do have a short range model thread which has been fairly underused since we started it. Maybe now is the time to head over to that and chat about the next few days, if that's what's taking your interest.

https://www.netweather.tv/forum/topic/89089-short-range-model-discussion-into-2018/

 

[AWD 8,357]

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;

 o

[Weathizard 4,668]

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.

[Paul 21,502]

5 minutes ago, Weathizard said:

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.

Well, it's happened a lot of times before, I can assure you. Just because the largest cluster on the ensembles is going for one scenario, it doesn't mean that the other options shown aren't possible. It's just a guide to the confidence you may be able to place in an outcome at that point in time. And at 120+ hours, and particularly when it comes to the track of a low, nothing is super high confidence enough to be 'staggered' should it change. 

[Weathizard 4,668]

2 minutes ago, AWD said:

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;

 o

Look very similar to me.

[stotm 48]

 

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

 

[radiohead 2,956]

It's been a long wait. But the -12 uppers are now at hour 15 on the models. It felt like we were seeing this at hour 150+ for so long...

[Stuie W 1,858]

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.

 

 

[radiohead 2,956]

06Z ICON 120

[Weathizard 4,668]

11 minutes ago, radiohead said:

06Z ICON 120

GFS 0z shows this also, turns back to rain readily then onwards though as the mild air is introduced

Edited February 25, 2018 by Weathizard

[Quicksilver1989 5,670]

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!

[Summer Sun 48,566]

06z ICON showing the potential major snow event for some southern counties on Friday

 

 

Edited February 25, 2018 by Summer Sun

[Richard Waugh 44]

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.