General Model Output Discussion Thursday December 24Th:

[Rollo]

I would just say that opposed to past winters when anything that could go wrong ,did go wrong we finally seem to have changed all that to anything that can go right will go right,so with confidence I totally agree with ("eye's)prediction of the track of the low and a country wide snowfest.

Edited December 24, 2009 by Rollo

[Shiny_Bottom_1]

I actually think this is an interesting scenrio again for the GEFS/GFS. It predicted the latest cool down well in a long term period....will it do it again?

Run on run today, and day on day, the GEFS/GFS has been an upgrade. For Derbyshire, the op/ctrl run (from memory) runs -5oC 850hpa's of below from Tuesday next week for the rest of the run.

The air pressure ensembles look good as a general agreement too.

PPN as always is always going to be subject to change, but even at such a range, Tues-Thurs next week shows quite a few good days of both cold and PPN.

Something interesting to keep a watch on.

What I would say, is perhaps watch for the upgrades on the 850 hpa's, as per this period, followed by a possible downgrade as it gets further in to the mid term (however, downgrade to still possible snowy weather, and cold days).

Synoptically...all very good.

[cooling climate]

Great run again by the ECM, excellent actually but two very different t240 charts from this morning and now

the 12z this is all down to the movement of the vortex which may take until boxing day to resolve.

My punt would be n/easterly backing northerly after 3 or 4 days.

Not a bad outlook.

[Tn9]

Going to need a bloody big shovel if this comes off.

http://www.wetterzen...cs/Recm1921.gif

NE Scotland would take an absolute hammering with that chart.

would this be big enough,this is the size you might need sorry mods,could not resist it is Christmas eve

[TEITS]

JMA is equally stunning.

http://www.wetterzentrale.de/pics/Rjma1681.gif

If anyone is still confused about next week then here is a brief summary of what the models are showing.

During middle of next week a LP system is going to track E with the centre of the LP somewhere along the English Channel. This means parts of the Midlands/Wales could see rain turning to heavy snow. As we progress towards the latter half of next week the colder air floods further SW bringing the risk of snow to everyone. However for N England/Scotland they will remain cold all of next week with the risk of further snow especially in E parts and more especially towards the end of next week.

However my advice is don't worry about the track of this LP because its bound to change between runs. My advice is enjoy xmas and hopefully by the weekend we should have a better idea. Remember the ideal track is like that shown by the GEM/GEFS Control run and this isn't because I live in Cambs!!

Going to need a bigger shovel than that TN9.

Edited December 24, 2009 by THE EYE IN THE SKY

[Hairy Celt]

would this be big enough,this is the size you might need sorry mods,could not resist it is Christmas eve

Been there, done that, got the picture...

[nick sussex]

its all nice discussing this snow potential and stuff, but you seem to forget if this low comes too far south many people in north england and parts of midlands will not get anything. yes we have had snow, but it would still be nice to have some more too and also if the low keeps being forecast too south it may well just hang onto the very south like it has done before. There is many other parts who want snow too and not just the people in the southwest and wales.

Fi on gfs would deliver bags of snow. lets hope its a trend too

I understand what you're saying but bear in mind theres no bias from me here, not living in Sussex anymore and down here in France so i think i can be as objective as possible here.

Sometimes people view the output from different perspectives, in my case i look for the pattern but also what perhaps can derail this, the reason it's better if the low is further south is simply to allow for more leeway in case it becomes slow moving and fills, this would send the coldest air into the Atlantic and this then has a knock on effect down the line.

Of course in an ideal world for your location the low dumps lots of snow and then heads se but again its a risk reward thing here, personally i think the ukmo has this too far and in these situations building pressure to the nw often means we see the models track this further south.

Hopefully the New Year can deliver for everyone.

Edited December 24, 2009 by nick sussex

[Geordiesnow]

Remember the ideal track is like that shown by the GEM/GEFS Control run and this isn't because I live in Cambs!!

Yep, i agree with that and i don't live in the South!

If the low is further South, it introduces the ne'ly quicker and is less likely to go wrong, plus you are also likely to be in the colder upper air as less mild air from the south comes up if the low is further South. We also need the angle of the low to be right aswell, as Kold Weather says, the angle of the low on the E is not the greatest. Something more like the GFS will certainly do.

It's whether we can get this low in the right place or not will determine whether we get cold ne'lies or not. Of course there are other factors to consider but for those who just simply look at the charts, then keep an eye on that low pressure system.

[kold weather]

Great run again by the ECM, excellent actually but two very different t240 charts from this morning and now

the 12z this is all down to the movement of the vortex which may take until boxing day to resolve.

My punt would be n/easterly backing northerly after 3 or 4 days.

Not a bad outlook.

Yep two different runs from the ECM model today, one had the PV dragging way south, the other has strong enough northern blocking not to matter and also a much flatter flow indeed. The one over-arching trend however is for the Greenland high to develop quite strongly again, quite impressive to see how much stronger its become on recent runs from the models.

[Bristawl Si]

JMA is equally stunning.

http://www.wetterzen...cs/Rjma1681.gif

If anyone is still confused about next week then here is a brief summary of what the models are showing.

During middle of next week a LP system is going to track E with the centre of the LP somewhere along the English Channel. This means parts of the Midlands/Wales could see rain turning to heavy snow. As we progress towards the latter half of next week the colder air floods further SW bringing the risk of snow to everyone. However for N England/Scotland they will remain cold all of next week with the risk of further snow especially in E parts and more especially towards the end of next week.

However my advice is don't worry about the track of this LP because its bound to change between runs. My advice is enjoy xmas and hopefully by the weekend we should have a better idea. Remember the ideal track is like that shown by the GEM/GEFS Control run and this isn't because I live in Cambs!!

Going to need a bigger shovel than that TN9.

Now that's what i call a snow situation!

It's uncanny isn't it how the models are shaping up like winter 78/79?

Merry Xmas to you all

[snowfish]

JMA is equally stunning.

http://www.wetterzen...cs/Rjma1681.gif

If anyone is still confused about next week then here is a brief summary of what the models are showing.

During middle of next week a LP system is going to track E with the centre of the LP somewhere along the English Channel. This means parts of the Midlands/Wales could see rain turning to heavy snow. As we progress towards the latter half of next week the colder air floods further SW bringing the risk of snow to everyone. However for N England/Scotland they will remain cold all of next week with the risk of further snow especially in E parts and more especially towards the end of next week.

However my advice is don't worry about the track of this LP because its bound to change between runs. My advice is enjoy xmas and hopefully by the weekend we should have a better idea. Remember the ideal track is like that shown by the GEM/GEFS Control run and this isn't because I live in Cambs!!

Going to need a bigger shovel than that TN9.

Very exciting times! I will now enjoy Christmas - the blessing has got to be that loved ones can travel from A-B more safely - I am of course, interested in the charts that are unfolding for the 29th Onwards! Would certainly be more intense and prolonged if it were to manifest! Merry Christmas EITS!

Snowfish

[Frosty.]

Fast running out of superlatives for the model output since early this month. Run after run of winter wonderland synoptics just over 3 weeks into winter with the second bitterly cold spell coming slowly into focus for next week, a relatively milder blip coming up for a few days after tomorrow but that gives time to prepare for the next round of snowy disruption and there will be plenty of widespread disruption if charts similar to the gfs & ecm 12z verify, potentially it would probably be more severe than the current icy spell which is now on it's last legs in england and wales until early next week.

[Wales123098]

http://news.bbc.co.uk/weather/forecast/4

Why is this so mild:S

[nick sussex]

Hi nick - a happy xmas to you

The GEM 12z is excellent and looks to me like everyone in the south would get snow from that - none of this M4 corridor nonsense lol! Then there is the NE'erly coming in behind so frost over the snowfilds as well as further snow showers coming in off the north sea. Purrfection for me!

The UKMO has the low furthest north as you say and is the worst output so far - no snow anywhere south of the Midlands there, plus I don't like the way the low appears to be slowing and preparing to drag its heels across the UK. This definitely would delay the cold air and I think if there was a t168 it might show areas still on the wrong SE side of the low. GFS as you say is inbetween, but still clears the low away eastwards with an epic prolonged northerly to follow..

Long way out to worry about the UKMO anyway - and it often doesn't verify too well at t144 anyway.

Evening Tamara and Happy Xmas

Yes I think the GEM would be great for your location, what we're looking for is the elongated low sending shortwaves into europe, in a nutshell for the newer members round low pressure not great, elongated or sausage shaped much better this suggests the low or trough disrupting with pieces of energy or little shortwaves running under the block.

http://news.bbc.co.uk/weather/forecast/4

Why is this so mild:S

Don't take any notice of those 5 day forecasts, they're utterly useless, why the bbc weather site would allow such rubbish on their site is beyond me.

[kold weather]

Fast running out of superlatives for the model output since early this month. Run after run of winter wonderland synoptics just over 3 weeks into winter with the second bitterly cold spell coming slowly into focus for next week, a relatively milder blip coming up for a few days after tomorrow but that gives time to prepare for the next round of snowy disruption and there will be plenty of widespread disruption if charts similar to the gfs & ecm 12z verify, potentially it would probably be more severe than the current icy spell which is now on it's last legs in england and wales until early next week.

Well the models certainly have been a pleasure to see recently. The models all seem to agree on a broadly -ve NAO but the other parts to the puzzle still not really well agreed on at all. As I've said a lot the PV's exact location/s and strength is going to make a massive difference between a 3-4 day feed of deep cold followed by some sort of toppler or the real deal.

The 12z ECM IMO has the looks of shaping up to be a 10-15 day cold spell with the whole PV heading down towards Scandinavia.

[mesocyclone]

Evening all and merry x mas!

The charts are looking like a x mas present to us all i think. I really like everyone wishing the low south as I'll probably get battered with blizzards! Hopefully our collective consciousness will effect the mild, your not wanted!

A big thank-you to everyone who contributes to the thread(my favorite read) and helps make sense of it for the ones not so educated yet. I'm learning bit by bit what the atmosphere is all about and I'm loving it.

Have a great x mas

Meso

[Barb]

http://news.bbc.co.uk/weather/forecast/4

Why is this so mild:S

It's a very sharp temperature gradiant so 50 miles further south next run and it could be 1c.

[pyrotech]

Well another fantastic trend towards another cold spell. Do not even care which is more likely this far out from the models, like the last spell lets get the cold in and let the snow follow.

To put the last cold spell in perspective, i took the kids sledging today ( Christmas Eve) I can not remember the last time i could go sledging on xmas eve or day. Probably back in 1980 something. The models all picked up on this trend very early and have again now for the next. There will probably be a few wobbles ovr xmas with the data being less so do not choke on your turkey as you peek ovr next few days. Here in cardiff it is still very icy and snow still about so not as warm as met predicted a few days ago.

As for the upcoming battle with transition of the low, i am not even going to worry about it this far out, It looks good and some places will get snow by the bucket load.

for those who say get a life with your family - im on a 15hr night shift tonight and tomorrow night, and if i have time to come on here it means that my srvice is not needed which is a good thing. Looking forward to the 18z

merry xmas and a freezing cold new year to you all

[Wales123098]

just hoope that forecast changes for Cardiff. Even if its 10c in Cardiff it would only be 6c here and thats not going to be low enough for the snow!

[snowlover2009]

It's a very sharp temperature gradiant so 50 miles further south next run and it could be 1c.

yes utterly dire the night temperature is the same as the max and it wouldn't even be showery rain too. i agree they are utterly useless. tomorrow it will end up being 1c lol.

anyway ecm is just an absolute corker, making this cold spell just a very small taster of whats to come, compared to the charts we are seeing at the moment.

One thing i have to ask is, people saying that many parts would get a hammering and need a massive shovel to get out of the snow. don't we always usually say that and yet it only turns out to be a few inches lol. even with this cold spell. Will those ecm charts actually bring snow like the 70s? i am not dissing the snow we have already had, but i wouldn't want a repeat performance of this cold spell, i want this next cold spell to show what uk winters are all about. but judging these charts they would just show how severe they can get. Am i right?

just hoope that forecast changes for Cardiff. Even if its 10c in Cardiff it would only be 6c here and thats not going to be low enough for the snow!

Double figure temperatures are likely to be on the very extreme south coast. It will be a massive temp gradient though, the north likely to be below 0c or around that.

[mezzacyclone]

Classic "70`s style" rain to snow dump anyone post xmas prezzy?

Lots of fun on the cards regardless next week with a toppler becoming lesser plausible?

[Craigers]

yes utterly dire the night temperature is the same as the max and it wouldn't even be showery rain too. i agree they are utterly useless. tomorrow it will end up being 1c lol.

anyway ecm is just an absolute corker, making this cold spell just a very small taster of whats to come, compared to the charts we are seeing at the moment.

One thing i have to ask is, people saying that many parts would get a hammering and need a massive shovel to get out of the snow. don't we always usually say that and yet it only turns out to be a few inches lol. even with this cold spell. Will those ecm charts actually bring snow like the 70s? i am not dissing the snow we have already had, but i wouldn't want a repeat performance of this cold spell, i want this next cold spell to show what uk winters are all about. but judging these charts they would just show how severe they can get. Am i right?

The difference here is that the upper temps will be more potent meaning more convection with a solid stream and what happened last Thursday was different as that pesky low pressure caused a gap with the showers and i was in that gap as this location usually does so well in proper NE winds.

[snowlover2009]

The difference here is that the upper temps will be more potent meaning more convection with a solid stream and what happened last Thursday was different as that pesky low pressure caused a gap with the showers and i was in that gap as this location usually does so well in proper NE winds.

what is convection? sorry i have heard a dozen times, does it have something to do with snow potential or something.

[swilliam]

Well the models certainly have been a pleasure to see recently. The models all seem to agree on a broadly -ve NAO but the other parts to the puzzle still not really well agreed on at all. As I've said a lot the PV's exact location/s and strength is going to make a massive difference between a 3-4 day feed of deep cold followed by some sort of toppler or the real deal.

The 12z ECM IMO has the looks of shaping up to be a 10-15 day cold spell with the whole PV heading down towards Scandinavia.

Hi Kold,

I am not as convinced as you about the PV sliding South and prolonging the cold on the ECM. Looking at NH chart it seems the PV cannot move much further South due to the HP block which cannot go anywhere due to the LPs propping it up. I think the most likely evolution would be for the HP block to extend SE and for Mediterranean air to come NW towards us. I think I prefer the GFS set up at 240 for likley continuation of the cold spell.

Of course we know what happens with GFS evolution which does prolong the cold but I am not as convinced by the ECM. I think I would prefer the PV to stay to the West of our block giving a stable upper air pattern. It might not be as cold as if the PV sunk South but it would be cold enough I think!

[Craigers]

what is convection? sorry i have heard a dozen times, does it have something to do with snow potential or something.

basically convection is when the warmth is drawn out from a warm sea and rapidly builds heavy/beefy showers due to very cold upper temperatures!

Edited December 24, 2009 by Craigers