Winter Model Discussion 18Z 13/1/13 onwards.

[lorenzo]

Re Request for charts, hopefully this image helps..

12z > 18z

[Wayneywoo]

It seems to me the GFS has too much of a westerly bias. I remember situations before where the GFS was keen to move a block off east only for it to hang around and not go anywhere. I think this is where the UKMO and to a maybe slightly lesser extent the ECM are giving slightly better outputs and consequently better verification stats.. Maybe this is why the UKMO is leading the way at the moment. Handling the upper atmosphere dynamics much better.

Someone said earlier it seems with very run the cold hangs around a little longer...

Edited January 13, 2013 by Wayneywoo

[If Wishes made Weather]

Undercut tastic towards 144 or will that low just stall?

Looks like stalling, just, but the heights in mid Atlantic are decaying al little perhaps giving a little room for it to go through. One way or another though all models are showing a fierce depression for Friday or so. Its just they dont know where to put it.

[frozen bluebird]

thankyou lorenzo

[BarnetBlizzard]

Weird, the GFS yesterday showed a non snow blip into the south and London.

Tonight it has appeared again. Wonder what is causing that to show up.

the mild sector

[Timmytour]

The cannonball low is stalling and drifting north.....but now it's going to be undercut itself by another one!

[chionomaniac]

See the purple blob southwest of Greenland - that's the Canadian section of the polar Vortex!!!!

It's going south on holiday!

Otherwise a good undercutting trend compared to the previous run.

[cyclonic happiness]

Looks like stalling, just, but the heights in mid Atlantic are decaying al little perhaps giving a little room for it to go through. One way or another though all models are showing a fierce depression for Friday or so. Its just they dont know where to put it.

That low is way too deep to be taken seriously, it wasn't even really there in the previous runs, FI must be getting alot closer?

[Cloud 10]

18z going for some deep low craziness,and is that part of the polar vortex on holiday

in the western atlantic.

lol chiono!

Edited January 13, 2013 by Cloud 10

[LomondSnowstorm]

Some positives on this run are the better jet angle and therefore the negative tilt of the trough:

There's just slightly too much energy going north combined with the low being a bit overdone to undercut properly. However, given the 'trend' over the last week or so to shunt everything southwards and to overestimate the Atlantic influence this is a promising run on the face of it.

[Tim Bland]

A step in the right direction (toward ukmo) with jet going south. Good for northern areas. Hopefully a growing trend

http://www.meteociel.fr/modeles/gfse_cartes.php?ech=150&code=0&mode=5

[bluearmy]

Weird, the GFS yesterday showed a non snow blip into the south and London.

Tonight it has appeared again. Wonder what is causing that to show up.

Look at the gfs hr 0.5 chart. Much clearer.

Booo. - the day 5 fax is ecm rather than ukmo

[nick sussex]

Making us wait for the day 5 fax. Looking at the T96, methinks it will be modified somewhat.

Good spot BA, the UKMO have modified that 120hrs.

Although to be honest these fax charts are pointless at the moment as they change so often that key detail re snow potential lasts max 12hrs.

Whether the easterly in terms of convection amounts to much remains to be seen, the current trend is to keep narrowing the window for that.

The continual haunting of the UK by shortwaves near Iceland shows no sign of stopping, that really is a nuisance for getting a better easterly.

As for the later output, more clueless nonsense and the current dismal continuity remains.

The ECM postage stamps at 96hrs show just why trying to make a forecast even that far ahead is liable to be wrong.

[pages]

See the purple blob southwest of Greenland - that's the Canadian section of the polar Vortex!!!!

It's going south on holiday!

Otherwise a good undercutting trend compared to the previous run.

Can the vortex undercut in theory?

[georgiedre]

i wonder when rjs was saying about a bit of a mild blip and cold from a different direction could it be the west as the low moves west to east?? some realllllllllly cold air coming into atlantic if the 18z is to be believed. any experienced folk able to advise on this please thanks.

[If Wishes made Weather]

By 156 the whole bit of the Candian vortex is tanking off over the Atlantic with - and I think that I am reading this right - sub 490 air, and presumably pressure to make your ears bleed.

[Jason H]

Wow, that's a ludicrous run. The PV over Canada is coming at us across the Atlantic. About as likely as the UKMO solution at T120. The fax chart looks a more sensible outcome. But in these confused times, who can tell which one is correct?

Edited January 13, 2013 by Jason H

[Froze were the Days]

Yet again the whole of the Atlantic taken over by LP - a wee bit like in mid-December (strange we had heights close to Scandy then as well). GFS showing permutations on the same theme really in the mid/long term and that is gradually trending unsettled and somewhat milder. errrr!

[Jason M]

Within the uncertainty some trends have emerged in my view. Firstly the longevity of the cold spell is being extended over time. The second and less welcome trend is that severity is being gradually eroded. We are now looking at a fairly ordinary mid winter cold spell IMHO.

The signal for a more notable cold spell has been really watered down both in the medium and short term. The killer is the PV as usual as it has taken up residence in a poor position for us. As always it may change but I actually think the model variability is starting to settle a little and whilst detail is changing a way forward for us seems to be emerging slowly from the mists.

Of further note is that the Scandi High is poorly aligned because energy is going over the top of the high. This means that we will eventually run out of cold pool and I suspect on current modelling the cold spell will end with a whimper.

It may well all change again, and of course UKMO till looks very good tonight. We just can't get the northern block we need regardless f the pressure anomalies indicating high pressure to our north.

Lets see what the ensembles bring.

Jason

[pages]

Lol at t186 west of Ireland has snow and -6 uppers from a westerly

[nick sussex]

i wonder when rjs was saying about a bit of a mild blip and cold from a different direction could it be the west as the low moves west to east?? some realllllllllly cold air coming into atlantic if the 18z is to be believed. any experienced folk able to advise on this please thanks.

Its very unlikely , any westerly flow has so much modification that its exceptionally rare to see decent snow and cold off that type of set up.

You'll never get ice days or decent lying snow on low ground unless its from the north round to the east.

[lord stratus]

i wonder when rjs was saying about a bit of a mild blip and cold from a different direction could it be the west as the low moves west to east?? some realllllllllly cold air coming into atlantic if the 18z is to be believed. any experienced folk able to advise on this please thanks.

Not from the atlantic, the temps are too modified!

[Chris D]

It's not that often you see the PV take a holiday though.

[If Wishes made Weather]

Lol at t186 west of Ireland has snow and -6 uppers from a westerly

Never seen this - snow approaching the west Irish coast from the Atlantic!

[ChartViewer]

GEM 120...Has this been seen yet?...sorry if it has too many models...im cracking up

144

Edited January 13, 2013 by ChartViewer