Model Output Discussion - The Start Of Winter

[Frosty.]

That's why in the UK we live in hope of a pattern change and certainly not expectation. Having said that, northern UK still looks favoured for some potent pm incursions between short lived milder, wet and windy weather spilling in off the Atlantic but further south it's generally average to slightly milder for much of the time..for now.

[knocker]

No surprise really Knocker.

If we are to see any changes it will be beyond that as i suggested.Those +ve height anomalies in the Atlantic on that second 384hrs mean towards Greenland are what we would need to develop and strengthen.

 

Be interesting to see what the ECM comes up with tonight as it was a bit more bullish about this than the GEFS on the extended this morning.

[phil nw.]

Be interesting to see what the ECM comes up with tonight as it was a bit more bullish about this than the GEFS on the extended this morning.

Yes if you have access to the ext ECM that would be good.I don't expect anything within the T240hrs range.

[Gavin Hannah]

Just looking at the GFS 12Z as it comes in, already, T.144 looking much better and at t.159, a very interesting HP cell located over western Canada, drifts east and looks to block off the Atlantic providing a very nice looking cold stream.

 

 

Edited December 15, 2014 by IBringTheHammer

[No Balls Like Snow Balls]

Just looking at the GFS 12Z as it comes in, already, T.144 looking much better and at t.159, a very interesting HP cell located over western Canada, drifts east and looks to block off the Atlantic providing a very nice looking cold stream.

 

 

The GFS P ends up different (horrifically different) from the old GFS, obviously that throws a big spanner in any potential shown by the old GFS.

Edited December 15, 2014 by No Balls Like Snow Balls

[Tim Bland]

Not a bad 12Z GFS overall.  Could be some wintry showers around on Xmas eve especialy in the north. By 28th (312hrs) a week ridg pushing up to iceland allows for a northerly with wintry showers in the North (esp North East) no sign of anything sustained though. Over to the GFS (P)

[Buxton Codge]

12z GFS still shows a cold period over Christmas. Potential White Christmas for favoured areas ( higher ground especialliy in the west)

[Gavin Hannah]

Very true NBLSB, however, at this range, I'm gona hold on these potential silver linings for Christmas. It may not be a snowmaggedon this Christmas but the flippity flop nature of the charts at this range suggest to me it's all to play for still. Plus, I going to be back in Scotland (Mwahaha!) for Xmas and New Year, so bring on the snow!

Edited December 15, 2014 by IBringTheHammer

[nick sussex]

It all looks very messy across especially the GFS P however my thoughts of earlier remain. Anything could happen around around Christmas, be it cold northerly or flatter westerly.

 

Too much doom and gloom has been rearing its head in here when the outputs are still working out the downstream effects of that troughing which digs south into the USA, this will tend to pull low heights away from Greenland and then its really down to how much amplification upstream to see if we can get a decent ridge to the west and northerly over the UK.

 

It's a shame that we're talking ten days away here, as we know a lot can happen and it could all go pearshaped very quickly, however I'm slightly more optimistic so far after the trends from both GFS's.

 

The key really is what happens over in the USA with that troughing and its interaction with low heights over Greenland, the pattern may well flatten out again later, it would be nice if the cards could just fall right to at least deliver some festive weather on Christmas and Boxing Day.

 

Anyway theres a lot of outputs to get through before we can even think of possibilities of a White Christmas for some areas of the UK.

Edited December 15, 2014 by nick sussex

[Ali1977]

It would be interesting to hear Ian Fs thoughts again, charts not particularly turning although GEFS have a few weak trends. Still a long way off, I think Xmas won't have much going for it apart from high ground in the North maybe.

[Iceaxecrampon]

Yes - messy indeed Yin and Yang.

 

T+192

 

 

T+147

 

 

Then a belter of a North - Northeasterly upstream at T+300 in cloud cuckoo land.

 

Ian

 

 

 

 

Edited December 15, 2014 by Iceaxecrampon

[Summer Sun]

GFS P shows a plunge of cold air arriving on Boxing day and it lasts for around 5 days

 

 

 

 

 

[knocker]

A very good run by the GFS and particularly the P. The ops has mainly above average temps and the P gets rid of that threatening low and and also moves the Azores HP  east bringing some interesting temps into the UK Xmas beach barby still on.

Edited December 15, 2014 by knocker

[Ali1977]

Knocker - what was very good about the GFS?

[MR EXTREMES]

Having been searching (rather desperately at times I’ll admit!) for some sign, any sign of a breakdown in the relentlessly progressive flow affecting us, no such sign has been forthcoming. The 500mb vortex over the W Atlantic is continuing to spawn LPs in the southern stream, destined for our shores, which has been added to at times by LP in the northern stream which have kept crossing Greenland, preventing any prolonged build-up of cold air, and thus HP there.

The GFS has been coming up with some intriguing long-term fantasies, but the short to mid-term has been fairly consistent across the models in the run up to Christmas, including the cold-lover’s worst nightmare – HP over France and Biscay!

However, I am with TEITS on this and feel strongly that a major pattern shift is gearing up for after Christmas and into the New Year. One of the first tentative signs of that today I think is the appearance of an upper high over W Canada, not much in itself but maybe an early sign of a trend to greater upper flow amplification, at least in the W hemisphere.

That flow does, I think, have a most peculiar look for mid-winter, with quite a number of fairly shallow vortices, showing little sign of moving. Indeed, between the vortex over the W Atlantic and the one over Iberia, that has done much to keep the Azores high firmly entrenched.

But what I am seeing as a possibility is for the slow but steady build-up of cold air and thus HP to the N, The Greenland HP would at last have a chance to intensify.

Many notable cold spells in the past have been preceded by a string of LPs heading across us from the SW, as cold air deepens to the N and NE, and the track of these has shifted slowly but steadily SE, finally allowing the cold air to break through. Here’s a spectacular example from 1978, a few days before a bitter E-NE flow set in.

archivesnh-1978-12-25-0-0.png

In one of its many end of run variations, the GFS actually showed such a development recently, not that it means much admittedly, but it must have come up with this idea from somewhere!

OK, a certain amount of straw-clutching you might think, but even in the face of current evidence, I am still inclined to trust my instincts here. If such a development is going to happen, then I suspect it will take a while for the models to catch on.

So if the current setup looks bleak, then look ahead and watch for the signs!

which happens to be a year thats been chosen on a lrf on an american weather site.

 

the problem is the azores heights is also well and truely at home to our south and could be there for weeks to come judging by the model outputs and could possibly move futher east setting up a bartlet type block.

 

theres lots of talk on the american sites of a winter storm dated around the 19th to the 21st of this month over the pond in the states.

and also talk of the vortex setting up like last year over there in the states,

so dare i say a return to a rerun of last winter ?

 

although id be very intrigued to how much effect this could have here,

 

i suspect a return to a more typical zonal that we are getting now,

but less intense than last winter as the vortex is not as strong as last year.

how weak is the vortex currently is there a chance of a strengthening vortex.

 

http://theweathercentre.blogspot.co.uk/2014/10/official-2014-2015-winter-forecast.html

Edited December 15, 2014 by emotional rollercoaster

[Ali1977]

GEFS look better again, defo heading in the right direction at T276 - lots off WAA heading towards Greenland on many ENS.

[MR EXTREMES]

GFS P shows a plunge of cold air arriving on Boxing day and it lasts for around 5 days

 

 

 

its dreaming of 1963 very unlikely with the azore heights so close the ukmo seems to be pretty much on the money and from the ecm this morning id say the gfs p is rather over excited.

 

im sorry to say a white christmas does not look likely with the grinch staying put for awhile yet.

[Severe Siberian icy blast]

which happens to be a year thats been chosen on a lrf on an american weather site.

the problem is the azores heights is also well and truely at home to our south and could be there for weeks to come judging by the model outputs and could possibly move futher east setting up a bartlet type block.

theres lots of talk on the american sites of a winter storm dated around the 19th to the 21st of this month over the pond in the states.

and also talk of the vortex setting up like last year over there in the states,

so dare i say a return to a rerun of last winter ?

although id be very intrigued to how much effect this could have here,

i suspect a return to a more typical zonal that we are getting now,

but less intense than last winter as the vortex is not as strong as last year.

how weak is the vortex currently is there a chance of a strengthening vortex.

You contradict yourself somewhat to be honest because on one hand you say it's the same as last year but yet on another you recognise the vortex is weaker .

You know that the background winter drivers are very different this year to last . And considering last year was the wettest winter on record really makes it even more unlikely.

If you mean we're heading for a zonal winter then I should be very wary of charts more than 150 hours away let alone t240 . A pattern change is emerging . -PDO , transportation of the vortex to the other side of the pole , very strong wave activity beginning Xmas week , all these things will force a pattern change , with the AO going negative along with the NAO , so I doubt very much tbh . Not sure whether you read Tamara's post earlier but if not I would really recommend it ?

Edited December 15, 2014 by Severe Siberian icy blast

[knocker]

Knocker - what was very good about the GFS?

 

Okay, I admit it could have been better,

Chart courtesy weatherbell

[IDO]

Okay, I admit it could have been better,

Chart courtesy weatherbell

 

 

Yes the direction of travel for around Christmas day has been for a warmer sector especially for the south:

 

 

Yesterday there was 50:50 mild or cold, the 12z looks like 66:33 in favour of a milder Xmas. ECM hinting that way as well:

 

Edited December 15, 2014 by i'm dreaming of...

[Tim Bland]

Does anyone trust in the GFS biased corrected run? If so it looks good for Christmas!

[ukpaul]

Does anyone trust in the GFS biased corrected run? If so it looks good for Christmas!

image.jpg

 

I asked this before to no response but is there anywhere that explains what the bias correction is and what it is designed to correct?

[nick sussex]

I asked this before to no response but is there anywhere that explains what the bias correction is and what it is designed to correct?

Theres quite a few good links here on the search results from the NOAA site:

 

http://search.usa.gov/search?affiliate=nws.noaa.gov&v%3Aproject=firstgov&query=bias+correction

 

Alot of its done by re-analysing historical charts and then comparing it to what forecast was given by the original GEFS, this way they can identify where any bias was found, they then add some formula to the bias corrected GEFS which lessons the overall error rate.

 

www.erh.noaa.gov/akq/workshop/winter/BiasCorrections.pdf

 

The above shows the differences in terms of error rate between the bias corrected and normal GEFS.

Edited December 15, 2014 by nick sussex

[Swave Snow]

A very good run by the GFS and particularly the P. The ops has mainly above average temps and the P gets rid of that threatening low and and also moves the Azores HP  east bringing some interesting temps into the UK Xmas beach barby still on.

 

 

Same as Russia, hey but they are freezing over there yippeee

Edited December 15, 2014 by Swave Snow

[The Eagle]

Lack of commentary on tonight's ECM tells us all we need to know really. A pattern change before the New Year looks increasingly fanciful.