Winter Model Discussion 12Z 15/1/13 onwards.

[The PIT]

The breakdown delayed in FI land still at T159 and effectively pushed back a day on the GFS. As long as it stays out there we don't care do we. GFS also thinks about the slider shown in ukmo so fairly good agreement in FI land.

JMA leading at the moment on the 12 oz

Edited January 16, 2013 by The PIT

[bradymk]

UKMO sticking with the cold all the way to 144hrs giving us a channel low with heavy snow for the south, combined with the easterly dragging in cold uppers from Europe it will feel bitter!

Not sure about that, wouldn't give heavy snow for most of the South at 144, well from my experience anyway but as the low continues to move south eastwards then cold uppers will definately back westwards.

[R.P. McMurphy]

Chief Met Office Forecaster on Fridays event http://bit.ly/VK5zlg

[Severe Siberian icy blast]

Not sure about that, wouldn't give heavy snow for most of the South at 144, well from my experience anyway but as the low continues to move south eastwards then cold uppers will definately back westwards.

Far too far to be concerned with details but yes that chart would be a very snow affair , with dew points mega low, deep snow cover , cold 2meter temp, even if the 850's were -1 that would still be snow, but the uppers are more like -6/-8

[phil nw.]

Yes as Dave said an excellent UKMO for cold and snow and throughout to T144hrs.

http://www.meteociel...60-21.GIF?16-16

http://www.meteociel...20-21.GIF?16-17

a double whammy of snow if the modelling is anywhere near with even lower uppers in a bitter wind backing more easterly as the pattern continues to re aline itself-those heights gradually easing towards Iceland on this run.

GFS none to shabby for the weekend mind you but as ever some differences at T96hrs

http://modeles.meteo...gfs-0-96.png?12

more energy going north there see the pressure on the block.

Mean outputs from earlier GFS and other runs kept that energy going south east towards France with the gradual retreat of the Canadian Vortex

so i would be surprised if the 12z Op has the later frames correct.

Edited January 16, 2013 by phil n.warks.

[bradymk]

Far too far to be concerned with details but yes that chart would be a very snow affair , with dew points mega low, deep snow cover , cold 2meter temp, even if the 850's were -1 that would still be snow, but the uppers are more like -6/-8

Yes i know way too far out but i wouldn't say at 144 its snowy for all the south, your looking Bristol northwards (so i suppose most of the south ) but a brilliant chart for sure and yes the easterly direction wind would bring DP's right down so no need to worry about 850's so much, the low would continue south eastwards anyway so nearly everywhere would see snow by the time it clears. Edited January 16, 2013 by bradythemole

[Memphis snow]

GFS is nothing if not consistent.

Consistently saying for the last week that the block will last for another 120-144 hours and then collapse. It will eventually be right I am sure, but the question is when?

It will be right when the UKMO says so as well !!!!

[Wayneywoo]

I have little doubts the GFS is underestimating the strength of this cold block that is over Scandinavia feeding us the cold continental air, coupled with the LP that is stuck over Europe that is keeping the block propped up. 12z starts off well and then resets to default with the Jet running SW/NE and giving us mild SW'lys.

I'd like to think this is a mild outlier, we will see...

[LomondSnowstorm]

On Monday the GFS progged the breakdown as being Sunday (when it was noted that it seemed to put the breakdown back a day every single day):

Today the breakdown is forecast for late on Tuesday:

There's no reason to think it won't delay it yet again over the coming days.

[Methuselah]

On Monday the GFS progged the breakdown as being Sunday (when it was noted that it seemed to put the breakdown back a day every single day):

Today the breakdown is forecast for late on Tuesday:

There's no reason to think it won't delay it yet again over the coming days.

So long as it gets it right before June!

[weather eater]

Gem looking impressive as well, here’s 132hrs

[Brad lough]

Hi first time poster here I don't honestly understand the charts I am just a enthusiastic follower of the weather I just wondered if someone could tell me if the uk met model chart for t144 would mean any chance of snow for Cornwall many thanks

[Panayiotis]

Gem looking impressive as well, here’s 132hrs

By impressive you mean, heavy snow (+25cm widely), with +35mph blizzards and -10C uppers reaching the west? Edited January 16, 2013 by Panayiotis

[patrickshere]

Gem looking impressive as well, here’s 132hrs

Blizzards anyone?

[Jason M]

Crikey, that GEM is chart of the century. Just look up to the far NE to see what waits in the wings!!!

Gotta say, GEM has performed very well indeed of late as has the METO.

Jason

[LomondSnowstorm]

So long as it gets it right before June!

There was no real breakdown of the cold from the start of April to the end of July from what I can remember of last year

[Zakos]

Very exciting prospects for coldies continue, and I think the potential for repeated significant heavy snow events is now being realised

If things go right, the UK could endure a "snowpocalypse". IMO, the UK is in prime position to endure a very cold and significantly snowy, for a prolonged amount of time.

The precipitation chart above shows the areas that will be hit hardest by the snow from advancing weather fronts, however I feel all areas will see some snow at times,including ireland (expect perhaps South West extremities)

This is due to weather fronts moving west and stalling right over the UK, giving prolonged and heavy snowfall. The depressions then dive south east, only to replaced by another depression etc...

This is as good as it gets for the UK. No other pattern will produce such a prolonged spell of repeated widespread heavy snowfalls

The chart depicts a classic battleground scenario. The UK is in the perfect position,right on the boundary between two air-masses.Unlike most battleground scenarios, the boundary looks like staying right over the Uk for a prolonged amount of time, rather than a typical snow-to-rain event.

This UKMO charts above illustrates how the depressions collide with the block, and are forced on a South-East track.

The Atlantic appears to be somewhat active, however the cyclogenesis only acts to enhance the cold spell, by producing significant snowfalls as it attempts to attack the block.

I see this pattern lasting a week at least. It could well last much more than this. My money is on the UKMO scenario.

Whilst we cannot discount the risk of mild air encroaching on the UK sometime next week, I think the GFS can be binned and is "defaulting". The block vanishes at a ridiculous speed, and we have South Westerlies right Across the whole of Scandinavia by Friday.

The scenario itself cannot be discounted, but the speed at which the Atlantic makes inroads is ludicrous in my opinion. Note how slow moving the fronts are at the beginning of the run, and then see how the front on Tuesday races across the UK giving a virtually snowless breakdown.

If we are to see a breakdown of the cold pattern next week, I think it will be a very complicated and much more snowy breakdown. The GFS is massively over-simplifying everything and has mild westerlies across Europe in a matter of days. Synoptical garbage as far as im concerned, but time will tell.

Edited January 16, 2013 by Zakos

[Zenarcher]

GFS is still keen on sending a low into PV much earlier and deeper than the rest of the models which explains why it has a large deep low to the South of Greenland that's it's third run now it's shown this. The UKMO, NOGAPS and GEM all disagree and send the low across the South of the Atlantic then it eventually moves down South giving us more cold weather. I've just checked the high res NAM model since it can pick up on this low now and I believe it shows something similar to GEM it has the low heading South like what most models are saying. GFS so far has little support at the moment.

Edited January 16, 2013 by weathermaster

[ChartViewer]

CMA72 Excellent charts up to T120 .......This mornings run....... (had a slight wobble last nite)

CMA T96 850's

CMA T120

CMA T144...Eastern promise

Edited January 16, 2013 by ChartViewer

[swfc]

Hi first time poster here I don't honestly understand the charts I am just a enthusiastic follower of the weather I just wondered if someone could tell me if the uk met model chart for t144 would mean any chance of snow for Cornwall many thanks

hi.i cant access the ukmo 850s but id guess being on the coast maybe marginal

hi I'm a real newbie and trying to look and understand the models .looking at them I can see a lot of snow for me Friday (Hertfordshire) but then I hear that by the time the low gets to me it will have fizzled out. am I reading the charts wrong??

the snow may well fizzle out but you should get a good spell of snow

[Frosty.]

The Gfs 12z op run goes pear shaped just before the middle of next week and then remains flat zonal with temps going back to normal or a little above but in my opinion it's going to be proven very wrong and cold will continue, tuesday gives us 1 last evening of deep freeze over the snowfields before milder air rolls in midweek..RUBBISH.

However this turns out, the severe spell is going to bring major snowfalls to a large swathe of the uk on friday, only the far north and northeast staying dry but cold, a very windy day with gale force SSEly winds, these backing more SEly by saturday with more sleet and snow, especially for the n and e and then winds backing Ely during sunday dragging even colder air from the continent with snow showers, not long after that the gfs defaults to zonal, the gfs charts later in FI are a joke compared to what the ens mean is showing with the uk still in cold blocked conditions.

[No Balls Like Snow Balls]

And the good news is.........

The London 12Z GFS ensembles go on the mild side of the run from 21st onwards

[Zakos]

GFS being overprogressive....how refreshing

I must say after the December debacle I was ready to bin the UKMO, but its redeemed itself big time of late. Its beginning to make me wonder if the only reason the GFS was the first to pick up on the December failure was simply because it was being its usual self and overdeveloping LP wherever it saw fit, and that this accidentally became the reality.

fully agree!

The GFS has embarrassed itself recently. Whilst being a very accurate model in the short term, it is pathetic at dealing with complicated scenarios beyond 120 hours in my opinion. It may be good during nominal westerly flows, but when things are synoptically unusual it continually reverts to default.

If memory serves me correctly, the ECM correctly predicted Hurricane Sandy to take an unusual path and head towards New York, whereas the GFS defaulted and sent the Hurricane out in the Atlantic, only to backtrack in the short range.

As we all the know the ECM was correct and the hurricane made landfall in New York. The ECM is much better at the GFS at long range predictions, and I fail to see any substantial evidence to suggest otherwise.

[snowice]

Any hope for us in Ireland on the ukmo 12z?on phone cant see charts! ps looks great for you guys in the uk!

[Panayiotis]

And the good news is.........

The London 12Z GFS ensembles go on the mild side of the run from 21st onwards

As predicted by someone on here earlier, the GFS is near to an outlier on this run (in the longer term). Edited January 16, 2013 by Panayiotis