Model output discussion - 5th December 2016 - Into Winter we go

[IDO]

13 minutes ago, West is Best said:

The point is that the colder air is pushing south on the day itself.

I'm certainly not able to forecast the timing with 5 days to go but the evening looks far from mild. It's just a little careless to describe the whole day as 'very mild' when there is forecast to be a temperature drop as it progresses. The timing will be interesting. 

Much synoptic movement, with serious storms ahead, mean even greater uncertainty about timings.

Hi

I was speaking IMBY and did qualify the further NW you are the earlier the cooler air will reach. Just checking my Met app and 11c still forecast for 9pm Christmas Day, so not the only one thinking a mild day for my area. But of course there is a spurt of colder air incoming and that should bring some wintry showers to the high ground favoured by a PM flow during Christmas & Boxing Day so very seasonal for that region.

[Summer Sun]

Maybe Christmas day won't be too bad after all

It could still be quite windy in Scotland as that low tracks east but any widespread gales look to be lower this morning

It could well be Chrismas eve sees the worst winds again more in the north rather than widespread

Post Christmas it's all about the high it's not likely to be in a rush to shift

 

[winterof79]

FI but serious cold developing over Greenland

[knocker]

The ecm ens anomalies consolidate the recent theme of retrogressing the Atlantic trough whilst building the positive anomalies to the SE of the UK thus a fairly amplified pattern over the Atlantic with some gentle south west zephyrs over most of the UK. This  initiate a period of quite pleasant dry weather with temps holding up very well

Looking further ahead out to T360 with the EPS no great change and in fact given the time scale an unusual emphasis on the continuation of the amplification with  the vortex well organized over northern Canada and a flat upper flow upstream. Quite a pleasant outlook.

Edited December 20, 2016 by knocker

[johnholmes]

Nothing encouraging on the 3 anomalies I use for anyone hoping for deep cold to develop. Just the revers really with the European high being shown pushing the Atlantic trough further west giving a S to SW upper flow into the UK out to at least 2 January.

[chris55]

A quick point on using the mean 850 charts as a stand alone forecast tool. When there is a large spread, as there is on the 00z GEFS, using the mean average alone can actually skew what is a low confidence data set.

loooking at the period from say 26-29th on the 00z we have a big spread in the ens, a cluster of members are actually trending colder, -5 to -10, while we also have those going milder up to + 5.

That is quite a large spread and unless we see some tighter clustering using the mean alone is pointless.

I also tend to think this important rule when looking at means in general, to often we get the mean chart anomalies posted and used as a forecast tool in isolation. The clustering of the individual members is what is most important, 

5 mild vs 5 cold will give you a mean of average conditions whereas cold and mild are equally as likely and the average conditions are not actually forecast at all!!!

The clusterings are the most important part of any ensemble forecast, without studying the individual members using the mean alone is futile. 

 

 

Edited December 20, 2016 by chris55

[Summer Sun]

GFS still seems to be the worst for Christmas day

Edited December 20, 2016 by Summer Sun

[Kentish Snowman in Yorks]

6 minutes ago, chris55 said:

A quick point on using the mean 850 charts as a stand alone forecast tool. When there is a large spread, as there is on the 00z GEFS, using the mean average alone can actually skew what is a low confidence data set.

loooking at the period from say 26-29th on the 00z we have a big spread in the ens, a cluster of members are actually trending colder, -5 to -10, while we also have those going milder up to + 5.

That is quite a large spread and unless we see some tighter clustering using the mean alone is pointless.

I also tend to think this important rule when looking at means in general, to often we get the mean chart anomalies posted and used as a forecast tool in isolation. The clustering of the individual members is what is most important, 

5 mild vs 5 cold will give you a mean of average conditions whereas cold and mild are equally as likely and the average conditions are not actually forecast at all!!!

The clusterings are the most important part of any ensemble forecast, without studying the individual members using the mean alone is futile. 

 

 

I'm actually quite shocked at that small cluster of runs heading south of -5 post Christmas.  A couple even breach the -10 threshold.  What setup is bringing about those kind of uppers?

[Johnp]

8 minutes ago, chris55 said:

A quick point on using the mean 850 charts as a stand alone forecast tool. When there is a large spread, as there is on the 00z GEFS, using the mean average alone can actually skew what is a low confidence data set.

loooking at the period from say 26-29th on the 00z we have a big spread in the ens, a cluster of members are actually trending colder, -5 to -10, while we also have those going milder up to + 5.

That is quite a large spread and unless we see some tighter clustering using the mean alone is pointless.

I also tend to think this important rule when looking at means in general, to often we get the mean chart anomalies posted and used as a forecast tool in isolation. The clustering of the individual members is what is most important, 

5 mild vs 5 cold will give you a mean of average conditions whereas cold and mild are equally as likely and the average conditions are not actually forecast at all!!!

The clusterings are the most important part of any ensemble forecast, without studying the individual members using the mean alone is futile. 

 

 

Good post Chris - unfortunately the usual 2 or 3 suspects have been  told this over and over and seemingly either do not want to learn, or want to continue being wind up  merchants.

I find either of those stances baffling, but yet it still goes on.

[A.J]

here's a thought.....rather than clog up the thread with "Your post was amazing, super, brill etc etc etc" type posts, how about just 'liking' it and/or sending the poster in question a nice pm instead?.....also rather than posting words to the effect of " stop quoting long posts as they clog up the forum etc etc etc etc" how about just sending the poster a quick pm?.....it would stop the thread going off topic and also save the mods/hosts time in having to reply with posts like this........food for thought 

[sunnijim]

23 hours ago, Kentish Snowman said:

I'm actually quite shocked at that small cluster of runs heading south of -5 post Christmas.  A couple even breach the -10 threshold.  What setup is bringing about those kind of uppers?

Had a glance at the gefs esembles this morning, over half are trending towards a deep low Christmas day/boxing day sliding down the North Sea or Scandinavia,  Some baloon the azores high in the Atlantic as it pulls away.A NW airflow develops over the UK in the lows wake for a little while.

Could be a new trend?

Edited December 20, 2016 by sunnijim

[stewfox]

1 hour ago, IDO said:

Hi

I was speaking IMBY and did qualify the further NW you are the earlier the cooler air will reach. Just checking my Met app and 11c still forecast for 9pm Christmas Day, so not the only one thinking a mild day for my area. But of course there is a spurt of colder air incoming and that should bring some wintry showers to the high ground favoured by a PM flow during Christmas & Boxing Day so very seasonal for that region.

The GFS 0z has delayed the 'cooler' air xmas day, lets see what the GFS 6z brings , updating now.

Clearly if we do hit 10-13c on the day itself I'm not going to argue that if it turns colder at 10pm that doesn't count re xmas day being mild or even very mild.

We have seen consistent PM in the mix on the GFS over last week up to and just beyond Christmas, just some variations on timing and area as you would expect.

 

[bluearmy]

The gfsp might have raised a few eyebrows in fi if it had been the op

not a million miles away from the evolution of the eps control

[bluearmy]

9 minutes ago, frosty ground said:

That helpful 

It's flippant but it's all you need to know really! 

The GEFS members recently have been all over the place - what is noticeable is the number with weak trop vortex polar profiles in the mid to long range. 

[Ali1977]

3 minutes ago, bluearmy said:

The gfsp might have raised a few eyebrows in fi if it had been the op

not a million miles away from the evolution of the eps control

That is an awesome FI blue, reload anfter reload and a prolonged big freeze IF it were correct - chances on that no doubt near zip unfortunately!! 

[Nick F]

00z EC ensemble mean and normalized standard deviation chart for day 10 suggests good confidence (greens) in a ridge building N over UK. So looks like the days of Atlantic influence are numbered, but still a long way from getting some sustained cold and wintry weather.

[bluearmy]

5 minutes ago, Ali1977 said:

That is an awesome FI blue, reload anfter reload and a prolonged big freeze IF it were correct - chances on that no doubt near zip unfortunately!! 

Not zip Ali, but less than 10% according to the NH eps probs. Funnily enough, despite Steve's excellent post showing greeny height rises are pretty well not possible within the next four weeks, I wouldn't be dismissive of any solution post week 2. 

[LRD]

11 hours ago, stewfox said:

In the reliable we have a lot of PM around with max temps below freezing on Christmas eve in parts of Scotland and potential storm force or above winds for Christmas day when folk sit down to their Christmas dinner in Scotland. I don't call that nothingness ? . FI T168

 

I was commenting on Ian's update mate. It indicates a 'nothing' pattern going forward with high pressure in exactly the wrong place a la 1988-89. I wasn't commenting on the Xmas weekend. Your response is talking about a completely different timescale to what I was referring to. In fact in an earlier post I do refer to this weekend being of interest but there has been a lot of nothing before that and Ian's update indicates a lot of nothing after

This morning's ECM and FI on the GFS does look more promising this morning, however

Edited December 20, 2016 by LRD

[Weather Boy]

3 minutes ago, bluearmy said:

Not zip Ali, but less than 10% according to the NH eps probs. Funnily enough, despite Steve's excellent post showing greeny height rises are pretty well not possible within the next four weeks, I wouldn't be dismissive of any solution post week 2. 

Well, exactly.  You may well be right that the colder ensembles referred to above "won't verify".  However, what they do tell you is that uncertainty (i.e. FI) is at pretty close range with +192, or even close, up in the air right now.

[Sky Full]

37 minutes ago, ajpoolshark said:

here's a thought.....rather than clog up the thread with "Your post was amazing, super, brill etc etc etc" type posts, how about just 'liking' it and/or sending the poster in question a nice pm instead?.....also rather than posting words to the effect of " stop quoting long posts as they clog up the forum etc etc etc etc" how about just sending the poster a quick pm?.....it would stop the thread going off topic and also save the mods/hosts time in having to reply with posts like this........food for thought 

As one of only two posters who commented in this way (unless other posts were removed) I think this message is directed at me.  There were only four posts relating to the quoted post which doesn't really amount to 'clogging up' the forum but in the past I have seen many many posts publicly thanking the four or five outstanding members whose contribution is acknowledged to be head and shoulders above every one else.  I therefore didn't think it was inappropriate to make such a comment publicly given the quality of what was posted but I will refrain from doing so in the future.

Back to the models:

Both the GEM and the GFS are promoting a potentially quite violent storm for northern Scotland, unfortunately on Christmas Day.   

  

In in the days that follow, happily, the same models both agree on a more settled period leading up to the New Year.

  

No snow for almost everyone in this short term outlook but at least the prospect of further damaging storms is also unlikely In the reliable timeframe.  It is still quite possible that we will see some really cold air from Eastern Europe drawn our way in early January which has often been the best period for our winters to really get going.

[Nick F]

 

Storm Barbara has been officially named by the Met Office for the low arriving to north of Scotland on Friday, the north bearing the worst of the winds, their yellow and amber warnings suggesting 60-70mph gusts widely across northern areas, 80-90mph across northern and western Scotland. Strong gusts along the cold front but strongest gusts reserved for far NW closer to tight gradient beneath SW side Barbara passing to the north, though GFS wind gusts don't look quite so severe as the warning suggests away from the far NW.

Then hot on Barbara's heels, I guess it looks likely Xmas day's low maybe named Conor, which anything, looks worse than Barbara atm on GFS, with the low centre passing further south between Orkney and Shetlands

Edited December 20, 2016 by Nick F

[West is Best]

The Christmas Day storm is pretty worrying

[Summer Sun]

GFS shows a stormy Christmas eve and day then settling down from boxing day

[Seasonality]

I think the 06z is following the theme of the 00z in the mid range. A re-amplified pattern again apparent. European uppers cooling nicely. Hope it can be directed West to the UK as suggested by some of the overnight output.

[Summer Sun]

4 minutes ago, Seasonality said:

I think the 06z is following the theme of the 00z in the mid range. A re-amplified pattern again apparent. European uppers cooling nicely. Hope it can be directed West to the UK as suggested by some of the overnight output.

 

Doesn't look like its going to happen for the UK on this run