Model Output Discussion 12hrs. 01/10/13

[johnholmes]

The EPS members, as ever, give a bit more insight into the potential model trends than the ensemble mean and show that, whilst support is quite low, there are a few amplified solutions not too dissimilar to the UKMO this morning - so it is not a complete outlier any means

 

 

The overall agreement is for high pressure dominance, and hence the straightforward look to the ensemble means, but the exact positioning and orientation of the high pressure has taken on a little uncertainty with the trough to the north east looking sharper and likely to pull down further south from the Siberain side of the arctic than was initially modelled. This means that colder uppers seem likely to advect through north eastern, and eastern/central europe at least. It is the westward extent of this airstream that will determine conditions under the high pressure close to the UK

 

This positioning and orientation of the high will be critical as to conditions at the surface in terms of cloud cover, wind source, amounts of sun etc etc. So its one of those situations where the closer detail actually shows that the upcoming high pressure may not mean straightforward warm autumn sunshine by day after misty mornings.

 

The probabilities remain low that the more amplified solutions will not verify, but it does seem possible that at least for a short time a slight north sea influence may mean that some north eastern parts may become cooler and rather cloudy before the high migrates slightly eastwards as the jet stream flattens the high somewhat and we start to pull in more south easterly continental sourced air once more.

 

So a settled outlook for sure, but the exact detail a little uncertain with some subtle variations from day to day quite possible

 

Have to agree with those general sentiments there Tamara. It makes little difference which type of model we look at providing we take care to try and see the bigger picture so to speak. So to ignore the Met O T+144 pattern is not sensible. One has to look at all the available data we can get hold of, assess it and then use that to try and predict what may happen in the 5-15 day outlooks. Sometimes we get it right sometimes not but it is both interesting and more objective than simply taking any single model and a single output and using that alone.

[Richie V]

Hi frosty, looking at those Fax charts you've put up, there seems the very real risk of any HP's been flattened out south and eastward by the Lp strings in central and northwest Atlantic. I have seen this countless times in late autmn, early winters past it hurts! A few suprises in 5 days or so as northern lattitudes continue to cool prehaps? Maybe just a hunch but likewise, I have seen it too many times before. Those faxes made me sit up and take notice!

Ric

[johnholmes]

NAEFS spread at 240 hours;

image.jpg

Strong signal for high pressure just to the east of the UK with a warm easterly/south easterly flow. And at 384 hours;

image.jpg

That signal and pressure anomaly is still there. Could we be looking at an exceptionally dry October coming up? That's one strong Scandi high, oh if only it were 8 weeks later!

 

I keep saying I will start to regularly check NAEFS outputs with the other 3 anomaly 500mb charts but have yet to start doing it. If I can remember I will use the 10 day (T+240 h) from today and see how it compares to the other two over a long period. I'll let folks know how it goes-give me a reminder now and then please!

[Frosty.]

Hi frosty, looking at those Fax charts you've put up, there seems the very real risk of any HP's been flattened out south and eastward by the Lp strings in central and northwest Atlantic. I have seen this countless times in late autmn, early winters past it hurts! A few suprises in 5 days or so as northern lattitudes continue to cool prehaps? Maybe just a hunch but likewise, I have seen it too many times before. Those faxes made me sit up and take notice!Ric

Hi Richie, I don't see it that way, I think once we get into next week the high will take over completely and the north will join the south in a warm and sunny outlook.

[Summer Sun]

Encouraging met office update today for the next 2 weeks with only north west Scotland prone to any unsettled weather else where many places should be dry with some sunshine

 

Edited October 4, 2013 by Summer Sun

[Frosty.]

The bottom line is, this looks a very anticyclonic pattern on the way and it will probably last a long while, I expect today's met office update to finally jump on board properly for the first time.

And it has finally happened

Edited October 4, 2013 by Frosty.

[No Balls Like Snow Balls]

Encouraging met office update today with only north west Scotland prone to any unsettled weather else where many places should be dry with some sunshine

It mentions northwestern parts of the UK and northwestern Britain. How do you then take what is written in front of you and then change it to just northwestern Scotland?

[Frosty.]

It mentions northwestern parts of the UK and northwestern Britain. How do you then take what is written in front of you and then change it to just northwestern Scotland?

It's the northwestern corner of the uk although I think it will be the whole of the uk enjoying the warm and sunny weather as next week goes on, the ens mean charts and op runs show high pressure slap bang over the uk so how could nw britain be unsettled?...It's a summery outlook relatively speaking.

[Frosty.]

The GEFS 06Z mean is looking very anticyclonic with fine and warm weather for most areas, just the far northwest corner looks a bit breezier with a slim chance of occasional fronts brushing around the top of the anticyclone but overall it's a very nice looking outlook for many of us, if not all of us, cooler nights and fog patches will probably become more of a problem as time goes on but it should thin and clear to give sunny afternoons/evenings with temps well into the 60's F and closer to low 70's F for the south & east, it's a cracker..very much as the Ecm 00z ens mean, there is nothing on here to suggest a pattern change whatsoever.

[Summer Sun]

The latest long term met office update to November 2nd doesn't hint at any end in sight from this prolonged mild weather especially in the south

 

 

UK Outlook for Saturday 19 Oct 2013 to Saturday 2 Nov 2013:

 

Through the rest of October and the first part of November the most likely scenario is for northern and western parts of the UK to remain the most unsettled with slightly above average amounts of rainfall.

 

Remaining parts of the UK are likely to see more average rainfall amounts. However, there are indications that temperatures may well remain close to or above normal throughout, especially in the south, meaning that the risk of frost may be lower than normal.

 

NAO continues to head positive as well which will help the UK to stay mostly settled

 

Edited October 4, 2013 by Summer Sun

[johnholmes]

The latest long term met office update to November 2nd doesn't hint at any end in sight from this prolonged mild weather especially in the south

 

 

NAO continues to head positive as well which will help the UK to stay mostly settled

 

 

I am not sure where the idea of a +ve NAO makes the UK settled. Maybe a quick read of its definition SS?

[Cloud 10]

Interesting comparison at 144 hrs between the UKMO 00z and the GFS 12z.

 

gfs 12z..  ukmo 00z..

 

 

Unusual to see such massive differences at that timescale.

[Frosty.]

I am not sure where the idea of a +ve NAO makes the UK settled. Maybe a quick read of its definition SS?

When do you think the settled pattern will break down John? It looks like a prolonged anticyclonic spell to me with superb weather for the time of year :-)

[johnholmes]

see my post way back up the page or the previous one frosty where I showed the various model outputs-nothing I have seen really suggests much change in the time scale I deal with, that is 6-15 maybe 20 days. By nothing much changing I am talking about the upper air pattern, the main trough around 20-30 west not moving all that much, maybe 5-10 degrees either side of that position which gives overall, other than brief and short lasting changes, a general 500mb flow from south of west.

[Captain Shortwave]

Day 5

GFS

UKMO

That's quite a big difference

And the GEM is completely different to both of them

Edited October 4, 2013 by Captain shortwave

[Frosty.]

I think the ukmo model has a few glitches today, completely different to the well supported trend.

PS. Cheers for your reply John, appreciated. :-)

[Summer Sun]

GFS shows the low breaking through later next week this afternoon

 

 

The GFS ens 00z and 06z went for pressure lasting a lot longer than what the 12z is showing so this may be an outlier we need to wait for the ens update shortly before we can take this 12z run further

[Frosty.]

Yeah Gavin I think it's typical default to zonal gfs rogue outlier...the outlook is warm and settled for the foreseeable future. :-)

[bluearmy]

the spreads on ecm 00z ens (not surprising given tamaras postage stamps) show the colder uppers making inroads into central uk from the ne as the trough heads se into scandi.  the 12z ukmo looks more reasonable than the 00z did but does show an option for next week which i think will gather some momentum over the next few runs from all the models. the end result may well be that the colder air doesnt quite make it as far west as the uk.

[Cloud 10]

It seems the 12z op runs are a complete shambles for next week so best stick with the ensemble mean.

 

 

I wonder how close this chart will be?

 

 

 

Anyone else having problems with meteociel?

Edited October 4, 2013 by Cloud 10

[Tamara]

the spreads on ecm 00z ens (not surprising given tamaras postage stamps) show the colder uppers making inroads into central uk from the ne as the trough heads se into scandi.  the 12z ukmo looks more reasonable than the 00z did but does show an option for next week which i think will gather some momentum over the next few runs from all the models. the end result may well be that the colder air doesnt quite make it as far west as the uk.

Yes I agree - and the UKMO this evening is not a surprise at all in that respect. Enough amplification there to create a wind off the north sea for a time for eastern UK and a suggestion that whilst the colder air will stay to the east, it will mean that the warm conditions earlier outlined would be tempered down, a least for a short while especially in eastern areas. The High as indicated on the UKMO would drift SE over the UK beyond t144 - assuming it verified, and hence something of the NW/SE split probably resumed thereafter as the anticyclone adjusts further SE'wards.

Edited October 4, 2013 by Tamara תָּמָר

[BlueHedgehog074]

I do perhaps think the UKMO may be being a touch too quick with the pattern with the way it seems really eager to try drop that Low Pressure system into Scandinavia, while seemingly trying to be really eager to amplify High Pressure to the West of us. (I mean I probably might be wrong, since maybe a pattern like that could evolve very quickly, although it still seems a tad too fast). I agree that the UKMO's Northerly idea shouldn't be completely ignored since it has been showing on two of its runs now.

Edited October 4, 2013 by DiagonalRedLine

[Captain Shortwave]

The UKMO is over deepening that low over Canada which causes the amplification require to retrogress the high and give the East of the UK a glancing northerly.

Just as a note the UKMO 12Z has downgraded that low by a good 10mb in this run but is still a good 10mb deeper than either the GFS or GEM.

Out of the three models run so far. The GEM I believe is closest to the mark and fits in with the metoffice outlook, though of course that doesn't mean much on recent history.

[Tamara]

I do perhaps think the UKMO may be being a touch too quick with the pattern with the way it seems really eager to try drop that Low Pressure system into Scandinavia, while seemingly trying to be really eager to amplify High Pressure to the West of us. (I mean I probably might be wrong, since maybe a pattern like that could evolve very quickly, although it still seems a tad too fast). I agree that the UKMO's Northerly idea shouldn't be completely ignored since it has been showing on two of its runs now.

The likelihood is that a compromise will be arrived at whereby there will be no northerly as such, just an anticyclonic circulation that briefly puts the UK just on the eastern flank of the High. But a more oval shaped High seems probable than anything over amplified at this time and it is likely to adjust east or SE'wards by next weekend

 

CS above describes the reasoning behind the more amplified solution of the UKMO very well

Edited October 4, 2013 by Tamara תָּמָר

[Dan the Man]

Slightly off topic, but its way too early to be looking at trends going forward to winter isn't it?

 

Didn't the temperature this time last year get up to around the 30C mark? And look what happened last winter; albeit belatedly.