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DiagonalRedLine

Model Output Discussion - The Run In To Christmas

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ECM op was a bit of an outlier for 2m temp last night at D10: post-14819-0-99009200-1418887474_thumb.g

 

To be honest, from recent performances I have come to expect that from the op and rarely pay any attention after D8 to the ECM op. At D12 on the GEFS 15% do not have some sort of Atlantic Ridge/GH, down from the 12z 30% so the ensembles continue to move towards the GFS hi-res. The control was closer to the op at D12 but we ended D16 with a UK MLB:

 

D12: post-14819-0-54013400-1418887697_thumb.p D16: post-14819-0-53319800-1418887729_thumb.p

 

Multiple clusters at D16 but most are HLB to MLB so a good sign of a continuation of the amplified pattern into the New Year. The spread at D12 remains clear:

 

post-14819-0-32701200-1418887830_thumb.p

 

So a lot of firming up on this potential upcoming cold spell. 

 

As far as I can see the trigger for this ridge is the splitting of the jet at around D5 as heights exit the US, This cuts off an upper level low in the Atlantic and it will act as support for WAA to build a Greenland High:

 

post-14819-0-81042100-1418889064_thumb.p  This looks solid on the GEFS at the moment.

 

The difference in the development of the GH between the GFS op & P is where the initial WAA is sourced from:

 

post-14819-0-44571300-1418889198_thumb.p post-14819-0-34487800-1418889209_thumb.p

 

Looking through the GEFS only one member was very close to the P, and the outcome was similar, with three reloads of cold air keeping us in a cold pattern till D16:

 

post-14819-0-07225600-1418889479_thumb.p  post-14819-0-99106900-1418889489_thumb.p

 

So the GFS P looks the most extreme solution and I think we will be very fortunate if that verified.

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BBC not buying into any prolonged cold spell. 6-10 day forecast from Darren Bett has just said milder air again on boxing day! I sincerely hope he is completely and utterly wrong!!

It would be interesting to hear from Exeter in the shape of Ian Fergusson this morning. Ian regularly posts on here and I wonder whether he can shed some light on Bett's analysis. Bett would no doubt be the first to admit he has a mild preference although I am not saying that would necessarily change the emphasis of his forecasts. Little evidence in the models to support his view from the publicly available NWP. Indeed GFS p wants to put us into the freezer over the holidays.

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Can we finish with the Darren bett stuff. It's out of date. It was based on yesterday's advice.

I know the ecm day 10 is not worth analysis (yet the gfsp at the same timescale apparently is) - however, it does produce a cut off s greeny block with the jet running below. How dreadful!

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Think until the ECM comes on board we should be very sceptical. The gfsp should in my opinion ignored this morning it just looks totally out of kilter. ECM seems to be following a west based nao which isn't great for the uk. Maybe the gfs gfsp will move towards the ECM towards the weekend.

If the GFSP was showing Blowtorch South westerlies, I bet you would Not be saying ignore it...

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Good morning TEITS my old friend. You, forecasting an easterly? Well I never.

 

Only teasing. I think you could be right with the blocked set up: there's a hint of it at the end of GFS P.

Morning matey.

 

To save time I just copy and paste my posts :laugh:

 

GEFS SLP mean for Iceland is now nearly 1020mb which is an increase of 20mb compared to last time I checked. Also worth noting is the GFS continues to be colder than the mean. In my experience when this occurs the rest of the ensembles follow.

 

http://max.nwstatic.co.uk/ensimages/ens.20141218/00/prmslReyjavic.png

http://max.nwstatic.co.uk/ensimages/ens.20141218/00/t850Cambridgeshire.png

Edited by TEITS

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You're spared my ECM tirade this morning because its at least moving in the right direction, the GFS P is the standout output but I would say that type of synoptic evolution is incredibly difficult to achieve , not saying it won't happen but its one of those rare set ups where you get everything working together to deliver that great output.

 

It's evident that any evolution to cold could be made alot more complicated by low pressure in the Atlantic and this at the moment is the variable that we could do without however you can see the marginality of the situation because if you get the pattern further south low pressure runs to the south of the  UK producing some significant snowfall on its northern flank, so the ECM this morning is a couple of hundred miles away from causing pandemonium in here.

 

That said I'd rather it just dropped this more western based negative NAO, overall this morning it looks like a cold Chrstmas Day but snowfall wise still too early to say.

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Just my two penneth on the ECM and BBC forecast by Darren Bett...

1) The ECM day 10 chart is highly unlikely to verify

2) It looks like being a mild outlier at that time frame in terms of conditions on the ground

3) If it does verify it is not that bad a chart and would certainly keep things seasonal with great potential for cold to lock in further down the line

4) The Darren Bett forecast sounds like it is the one I saw at 10pm last night and so will be out of date

5) As has already been mentioned this morning Carol on the BBC is now mentioning the possibility of some colder weather developing from Boxing Day onwards

More runs required as ever but nothing at all to get despondent about at this stage. Indeed my expectation of a cold snap / spell beginning on or just after Christmas Day has increased this morning having viewed the 0z suite if runs.

Keep the faith coldies!

Edit - sorry my error regarding point number 2) above. My comment was based on last night's 12z run.

Edited by Kentish Snowman

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It seems clear that Xmas day will see a cold north westerly flow developing .

What follows after that is open to debate.

At least we are seeing some interesting charts- pretty much the whole of lowland England has not seen anything in the way of snow since march 2013 . The charts in the 8-12 day period definitely offer some potential for snow in this period

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Can we finish with the Darren bett stuff. It's out of date. It was based on yesterday's advice.

I know the ecm day 10 is not worth analysis (yet the gfsp at the same timescale apparently is) - however, it does produce a cut off s greeny block with the jet running below. How dreadful!

 

The problem is its variability and because of that it's credibility at that range is questionable. The 12z was an outlier on several indices and again this morning its op synoptically it is out of kilter with its mean:

 

post-14819-0-58981400-1418891476_thumb.g That mean shows a stronger mean ridge than the GEFS at that time.

 

Its problems at the D8-10 range when their are potential changes are well documented on this site so it is fair to discount them if the ops look outliers.

Edited by i'm dreaming of...

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No 00z update from GFS P at 0.25° but the 18z shows widespread snow for the north, NI & ROI, the far south joins in eventually, a white Christmas for a lot of Scotland still looks a good bet at the stage

 

13:00 Christmas day

 

186-780PUK.GIF?17-18

 

By 13:00 boxing day the snow are is starting to spread further south

 

210-780PUK.GIF?17-18

 

By 19:00 on the 27th the snow has made it to the far south as well as widely covering the ROI and NI, parts of Scotland could have a foot of snow (12 inches) by this stage

 

240-780PUK.GIF?17-18

 

Very consistent from GFS P lately for the 25th and after lets see if it can make it to reality

 

giphy.gif

Edited by Summer Sun

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Unfortunately, there needs to be a recognition that if we share at *this tentative juncture* the exact nature of what we have as Ops Centre guidance, certain individuals will inevitably extrapolate/warp/skew it for certain newspapers... and we want to be 100% clear on key issues/likelihood of possible severe weather in public communication. I appreciate & sympathise how this is frustrating for genuine and well-meaning model-watchers, who can fully understand caveats, but we exist in an age where some very silly people repeatedly seek to scare folk through headlines before any high forecast confidence exists.

Sorry to continue off topic but...

 

I totally understand the met' o's stance,   Im sure this has been considered fergie, but could forecasts be issued with a confidence rating of some sort.   It may take a while but the public would eventually start to the view the forecast and the confidence rating ascribed to it?

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Unfortunately, there needs to be a recognition that if we share at *this tentative juncture* the exact nature of what we have as Ops Centre guidance, certain individuals will inevitably extrapolate/warp/skew it for certain newspapers... and we want to be 100% clear on key issues/likelihood of possible severe weather in public communication. I appreciate & sympathise how this is frustrating for genuine and well-meaning model-watchers, who can fully understand caveats, but we exist in an age where some very silly people repeatedly seek to scare folk through headlines before any high forecast confidence exists.

Ian,that provides total clarification of the way the media have to be drip feed to avoid mass over-reaction and is fully understood from my perspective.There is ample time to firm up on what are "possibilities" at present to probabilities over the weekend,

Many thanks for your time.

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Some nice charts beginning to be churned-out by the models and a more promising trend if you are looking for colder weather in UK.

If I was a betting man, I'd put my money on the METO (and Darren) being right about a relatively mild Boxing Day across most of the UK!

But, after that we could be seeing something much more wintry at least for a time!

 

 

Yep, just the other day the BBC Forecast said it will be grey, damp and gloomy all day for my part of the world. It could't have been more wrong, we had clear blue skies and light winds drying everything out! In fact December has been really sunny this year

 

I recall the Easterly that never was a few years back and that still haunts me to this day! So although these charts really get me excited and I am going to 'try' to remain cautiously calm. If however, they are still showing on next Wednesday (Xmas Eve) then I might just go a little crazy!  :crazy:

 

Apologies if slightly off topic mods! 

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Sorry to continue off topic but...

 

I totally understand the met' o's stance,   Im sure this has been considered fergie, but could forecasts be issued with a confidence rating of some sort.   It may take a while but the public would eventually start to the view the forecast and the confidence rating ascribed to it?

They do. If you watch the 9.55pm 10 day forecast they do highlight the main clusters. But with the general public on the normal forecasts they are more circumspect. A bit like most of us. I know to wait till much closer to a potential cold spell till I start ramping to friends and family, maybe a teaser in the early stages, but once bitten twice shy, so caution is now the watch word.

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Unfortunately, there needs to be a recognition that if we share at *this tentative juncture* the exact nature of what we have as Ops Centre guidance, certain individuals will inevitably extrapolate/warp/skew it for certain newspapers... and we want to be 100% clear on key issues/likelihood of possible severe weather in public communication. I appreciate & sympathise how this is frustrating for genuine and well-meaning model-watchers, who can fully understand caveats, but we exist in an age where some very silly people repeatedly seek to scare folk through headlines before any high forecast confidence exists.

Its a shame but its so true, in this modern world of journalistic excesses or any thing to sell a newspaper.

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Don't want to ruin the ride and excitement here, but realistically the evolution shown on that chart could happen, saying it needs to go in the bin sounds like you're basically wanting to discount it because it's not showing what you want. It's this sort of thing which leads to the massive disappointments when things don't come off.

ok but the truth be known of coarse any output is possible,

and to say it should be binned was rather silly.

 

because looking at it again it could very possibly move on to better and better or worse!

if low pressure systems are able to penetrate more south or southeast this would be great.

 

but i think seeing the upper +4 in place so rapidly sort of led me to think perhaps the ecm is being rather swift to clear out cold.

 

of coarse things are way to early  in its infancy of change.

but jan was ment to be the turning point so really its a rather nice suprise<

and im the first to admit i get gutted when i see cross model agreement yesterday and then the mighty ecm bring us coldies back to reality.

 

but the reality is the gfs has been leading the way in this change!

 

this is another reason why i felt the ecm today is rather erratic.

 

but then the gem has flipped from last night and the over all trend is still there,

but everything seems futher west and the neg nao looking a little to far west!

 

but its still an evolving pattern so i should know better than to get hung up over these outputs.

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That is something under discussion, as it happens. And you may have seen how with major events over past year or so we've begun showing special graphics highlighting competing solutions on-air (eg possible tracks of extratropical storms to UK; MCS development from S, etc).

NB Note possible issues of concern post-Xmas aren't solely focused on snow. This needs stressing.

Thanks Ian, I think that would be really valuable, it covers you guys as-well......if The Express do one of their famous hypes, at least your defence is there for all to see (i.e it was based on forecast that you stated was low confidence) 

 

As I said I understand the met o's caution, but like so much in this country its lowering standards to accommodate the lowest common denominator.

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A quick question for those who have a far greater understanding of this than I and apologies if this is not right forum for this question. Why is that America can forecast their Winter snow and weather (be it vast snow storms or just a harsh very cold period) a lot further ahead than us? Or like us, could their models be showing a raging snow storm (equivalent to our Easterly say) and then this get dropped within a very short window, like 72/48 hours. 

 

Thanks in advance  :friends:

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WOMD - I think the main reason America can forecast slightly easier at slightly longer range is that they are not a little island sat under the path of a jet stream.  I think the UK is guaranteed to get colder post Xmas, but the variables are huge and the slightest change in the Atlantic can have huge effects on our little island.

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