Model Output Discussion 4th Dec.2013-12z onwards.

[Tom Jarvis]

A Scandinavian high... Only 336 hours away... What could possibly go wrong???http://www.wetterzentrale.de/pics/Rtavn3361.png

it was so close to being a easterly but it was a case of so close but not close enough  

[TSNWK]

White Christmas anyone gfs ends the day with a little cheeky teeze. Although the signs were in evidence from around 240 onwards with the vortex stretching out a tad and heights starting to build north of Finland.

Anyway a little virtual eye candy for the next 6 hours.

Night

[SMU]

Well the kernals of a trend from the models tonight-

 

15 days to Xmas eve is enough to get through 8-9 days of poor weather & 5-6 days of ridge & cold building

 

Also worth noting that extreme cold uppers are not required for widespread snowfall

 

-2 air & sub 10 theta E Air from the continent

http://modeles.meteociel.fr/modeles/gfs/runs/2013120918/gfsnh-1-336.png?18

http://modeles.meteociel.fr/modeles/gfs/runs/2013120918/gfsnh-6-324.png?18

http://modeles.meteociel.fr/modeles/gfs/runs/2013120918/gfsnh-2-336.png?18

 

 

S

[Duane S.]

it was so close to being a easterly but it was a case of so close but not close enough

but potentially an interesting twist as we haven't seen many op runs like this building heights ne for a while. FI or otherwise.Interesting to see if hints shown by the ECM and 18z GFS are continued tomorrow.

[Severe Siberian icy blast]

After last week's near miss with the Arctic plunge, largely due to the upper flow being too flat, NOW it decides to turn meridional, with a sharpening upper trough over much of the central and eastern Atlantic, with a corresponding upper high over and to the SE of the UK, probably the worst arrangement for those of you who are on the look out for snow and cold.The models are showing little variation in output; HP gradually easing away E and the GFS bringing LP ever closer to us with typically increasingly stormy conditions associated with ever deeper lows, getting into the N and W.The latest 500mb suggests little in the way of change for some time yet:hemi1_00hr09122013.pngHowever, there is always the possibility that we will gradually see the jet taking a more southerly track, with heights starting to rise between Greenland and Scandinavia. In fact, at the end of 12Z GFS, with a very intense LP over much of the N Atlantic, such situations have, historically, led to the last and most intense LP spiralling SE as pressure builds to the NE of us, gradually bringing the air from the Continent.With such a sharp upper trough to our W for a while to come, it could also help build heights over the E US/Canada, up towards Greenland, perhaps encouraging surface pressure rises to our N. One other possible indicator for future developments does I think lie in the fact that some pretty intense cold air has dug in over much of the US, which has been around for some days now, this could be a factor in taking the jet further south, as the upper trough there digs ever further S and SE.However, in the meantime, mild, quiet weather gradually turning more unsettled and stormy seems to be the general message from much of the model output, but the jet location needs watching. It's early days yet for wintry weather!

Well I think you must of installed the 18z program yourself OMM ??

[R.P. McMurphy]

Exactly, a record breaking cold spell could be around the corner for all we know. But people seem to think they can write months off. The famous Winters didn't get going until after Christmas. Also It's not as simple as saying 'the pv is strong so we can't get cold', what an easy job it would be for forecasters if they thought 'lots of purple on this chart, Winter's going to be mild!'

While is it obvious there are many factors to determine a weather forecast, there is also a significant link between a strong Polar Vortex and mild winters. A strong PV during winter is the most common form, but when this becomes pertubed or becomes weaker, the flow of the air becomes weaker, and thus it generally goes north and south rather than east and west. This allows cold air to spill into areas, such as Europe, while warmer air is carried into the Arctic, and thus allows generally stormier weather, wetter weather, and with the cold, generally means snow for areas, again, such as Europe.

 

This is why we are best to look North and see HP forming in the Arctic, which most people will know it as NAO (Negative Arctic Oscillation) which allows cold Arctic air to flow into mid-latitudes of Europe and many other areas... If the PV is strong, it mainly confines the colder air to higher latitudes much closer to the Arctic and surrounding areas...

 

So in saying this, the PV has a huge role in determing a milder winter, to a colder winter, which is why if any cold synoptics are showing in FI, but the PV is solid as a rock, it generally won't come off, hence a couple of weeks back, where the milder air crushed the North flow to oblivion and confined it to a 15 hour event or so.

 

Had the PV been weak and pertubed, it would probably have been a different story all together, as much colder air from the Arctic would have fought hard against the Milder flow...

 

It's still early in winter, but.... At the moment, it's a strong PV = milder weather.... For now.

 

But I will stress again, there are many other factors that determine a cold flow, but the PV is a huge, huge part of it.

 

Edited December 9, 2013 by Glenn W

[legritter]

YES YES PLEASE Mr GFS ,certainly in a festive mood ,but more runs needed but signs are there .so off to bed ho ho ho .at least long last something of interest ,perhaps the vortex is about to BOW down, HOPE SO .

[bluearmy]

Having looked through the ECM extended mean/ anomalys plus various gefs output from today ( and the oft exuberant ops) there are some notes to make.

The Canadian vortex seems keen to drop a lobe towards sw Greenland which is a sure fire recipe for a strong Atlantic push. Yet the anomoly to our east doesn't want to give way. If this is the broad sypnotic, there are two ways out (assuming the status quo doesn't hold). Either the jet cuts se and sets up a nw/se flow which should allow weak heights to rise to our north or ne or the jet fires s/n and fires WAA which builds a scandi ridge further north than we've seen modelled of late. We could easily end up beneath the trough. Currently the modelling seems to want to hold any troughing to our west. At least some interest at the end of what looked like an uneventful day

[OldMetMan]

Well I think you must of installed the 18z program yourself OMM ??

image.jpg

Nah, I wouldn't know where to start!

The 18z seems to be continuing the 12z trend, with LP taking a more S track. In the past, from about this point in winter, I always keep an eye on cooling trends over N Russia, to see if increasing surface pressures are in evidence, in association with intensifying cold. The GFS seems to think this is likely to happen, albeit a long way off. On its own, it's not I think that significant. All too often, intense HP in that region just stays there with little influence on our weather. But occasionally, the cold air spreads further SW and W as the surface pressure builds with it, as had already been mentioned regarding what happened in Dec 1962.

The key item of interest right now as I see it is that deep cold over the US, pretty early in the season I think for those sort of temps. This has got to distort the upper flow, and could do so in our favour if, as I mentioned, the jet gets shunted further S.

Bear in mind too that the GFS likes to keep things zonal, especially in the long-term of each run, so this is quite an intriguing possibility it's showing. If it continues for a day or two, well, we might be in business!

[Barry12]

 

This is not always the case though, currently we have a cold stratosphere yet the US is very cold at the moment.

[Frosty.]

I see cracks starting to appear in the limpet euro highs attempt at destroying the early weeks of winter 2013 / 14, hoping the weather will be kinder to all us coldies seeking those magical snow flakes before and during christmas.

[R.P. McMurphy]

This is not always the case though, currently we have a cold stratosphere yet the US is very cold at the moment.

If you look where the PV is at the moment, it will give you a good idea why.

[Frosty.]

If I was a forecaster I would find it hard to motivate myself this week as the weather is as dull as dirty dish water but there is a good chance that we won't have to wait long for the first cold shot, ecm 12z is my pick at T+240...hoping tomorrow will see more damage inflicted to the limpet euro highs longevity. :-)

[Purga]

Blimey a post from Steve Murr!! Things must be looking up...

 

a downward trend from the ENS to average which is a start.

A very vague hope

[Great Plum]

Morning all,

I was worried when I saw the 0Z this morning...

Take a look at the ensembles - the op is well above the mean and appears to be 'off on one'

http://www.wetterzentrale.de/pics/MT8_London_ens.png

One to be binned?

[TSNWK]

Morning all,I was worried when I saw the 0Z this morning...Take a look at the ensembles - the op is well above the mean and appears to be 'off on one'http://www.wetterzentrale.de/pics/MT8_London_ens.pngOne to be binned?

phew! I took a sneek peep and thought hey MR GFS what have done with my white Christmas from last night can I have light blue please, that would have been nice to see

[winterof79]

A very good reason why every run,four times a day,should not be taken as a given

 

http://www.wetterzentrale.de/pics/MT8_Manchester_ens.png next.......

[MattH]

It's just been plotted wrong on wetterzentrale. Check out the GFS ENS on meteociel, 00z GFS Det is sitting much nearer to the ENS mean. Seems to be a wetterzentrale issue.

M.

NB: Every straw is worth a clutch at this present time but the synoptics behind the 18z GFS really are unlikely I'm afraid.

[Beaufort12]

HP building over Scandinavia t240 ECM  

[terrier]

Well been away for a few days. And to be honest things don't really look any better. The gfs 00z is classed as one of the best run of the days on the gfs. Think it's the 18z that's a outliner as it isn't supported at all. Think I will come back after Xmas and hopefully something more wintry will show up. Because at the moment it's a complete bore fests.

[Ian Brown]

The models continue to show more conventional zonality driven by the deep PV over Greenland. Increasingly wet, windy and unsettled, generally mild at times and likely to dominate for some time.

[IDO]

I know many of you have been hoping for the MLB to sink a bit so the UK can get into the zonal flow, in the hope that resets the synoptics. My experience from zonal flows is that once they start they can kill weeks of the Winter. Anyway this should make you happy, Christmas Day:

 

 Should be mild in the south at least.

 

Well the GFS is zonal from T120:  to T384: 

 

The Bartlettesque high remains omnipresent at the end of FI: 

 

It has just sunk enough for the UK to get the rain fest.

 

ECM looking like going that way with a flatter pattern, the energy at T240 looks like going over the transient Scandi ridge and the cycle continues:

 

 

 

So we now see how long we get stuck in this rut of westerlies; be careful  what you wish for.

Edited December 10, 2013 by i'm dreaming of...

[snowking]

Only have time for a brief post, but the overnight ECM32 generally sticks with the Westerly flow through December - signs of something a little more amplified in the Atlantic, and consequently cooler at 850mb for the UK as we head in to January.

 

SK

[Downpour]

I know many of you have been hoping for the MLB to sink a bit so the UK can get into the zonal flow, in the hope that resets the synoptics. My experience from zonal flows is that once they start they can kill weeks of the Winter. Anyway this should make you happy, Christmas Day:

 

gfs-5-372.png  Should be mild in the south at least.

 

Well the GFS is zonal from T120: gfs-0-120 (3).png to T384: gfs-0-384 (6).png

 

The Bartlettesque high remains omnipresent at the end of FI: gfsnh-0-384 (4).png

 

It has just sunk enough for the UK to get the rain fest.

 

ECM looking like going that way with a flatter pattern, the energy at T240 looks like going over the transient Scandi ridge and the cycle continues:

 

 ECM1-240 (10).gif

 

So we now see how long we get stuck in this rut of westerlies, be careful  what you wish for.

Not sure anyone wished for it. The key thing for me is to avoid the heavy rains of last year - plenty of time for snow this winter but I don't want my four year old boy cooped up. Charts of this nature make me splutter my coffee.

Edited December 10, 2013 by phil nw.
removed personal remarks.

[Frosty.]

The Ecm 00z op run has a similar look about it to the 12z last night with unsettled atlantic weather gradually breaking through the uk from the west during the weekend and especially into next week as the influence of the euro high slackens and then disappears over time, a nice wedge of 528 dam approaching from the west by T+240 hours and potential for colder zonality to follow during the immediate run up to christmas and beyond.