Model Output Discussion: 12Z (20/11/12) And On...

[Backtrack]

Anyone know the dewpoints that the ECM forecasts ?

Or does it do dp's at all ?

I honestly think 850's of zero are fine under an Easterly, once dp's are low

Depends if freezing rain is your thing?

Without the cold upper air you'll find that any precipitation may start as snow high up in the atmosphere but then melt as it falls through boundaries of warmer air above the surface. It'll fall as freezing rain if there is surface cold already in place, so depending on the intensity of the easterly. Otherwise it'll be plain rain all the way away from the highest mountains.

Edited November 20, 2012 by Backtrack

[weather eater]

I have to say these conversations on the model thread along the line of, oh it’s not good enough because no snow is forecast absolutely do my head in, It’s not even December yet. We are in the process of a major pattern shift; we don’t know how things will develop over the next few days how about we just enjoy the synoptic evolution. As it stands the shift to blocking is still a few days away, never mind how long it will last and will we get the right conditions for snow.

Sound post from Daniel AKA WMD

Edited November 20, 2012 by weather eater

[xioni]

It's quite mild because we haven't seen any decent cold pooling over on the continent yet. When winter really does get going over there within the next few weeks you'll see a much colder air mass develop.

As someone has already mentioned, if this set up would of been happening in January rather than November, we would be in for a very disruptive cold spell to say the least.

I am sorry, but that's not the case. Even now both us and the continent can become very cold very quickly and we don't need cold pooling to our east.

This run mixes in a lot of warm air from the Med, London & Paris are 4-5C warmer on average next week compared to the previous run, which was quite cold.

[cold snap]

Very mixed info some say its bad some say its good I believe this quote

Charts have potential but they have to realize that potential

[london-snow]

This EC run wouldn't give cold conditions in any month, the air mass at the surface is not cold at all and it's actually quite warm for most of the near continent.

Also the way this run ends doesn't guarantee that cold air would come eventually as we end up with a trough southwest of the UK

I wonder if all this is happening due to a much faster MJO progression, most models now predict convection over the Indian Ocean around the turn of the month, while until now we were supposed to get a nice, high amplitude phase 8 for early Dec.

More runs needed obviously but a very worrying EC12 run

Hi xioni.

How can you view the 12z and call this a worrying run?

The pattern change to cold is nigh on nailed ( Below Average ) and we have a real chance of something brilliant further down the line as highlighted by the 240 ecm which shows bags of potential.

You sound like a very knowledgeable person but i fail to see how you have come up with that conclusion.

The main thing is to get the pattern change in place which looks very much form horse.

Edited November 20, 2012 by london-snow

[in the vale]

There has been bickering in this thread for around 4 weeks, discussing the likelihood of a pattern change that the wider range of signals (teleconnections to some) have been suggesting may occur at the end of Nov / start of Dec (ish). Now the major models have CLEARLY indicated a pattern change there is bickering over whether the 850s are going to be cold enough for snow. When the 850s are cold enough for snow (and they will be - follow the pattern run to run, look at what the ECM is hinting at from the NE) there will be bickering over whether it will snow in the north east or the west or in my back yard. Winter is upon us and the only guarantee is point scoring and bickering in this thread. The signals are pointing towards at worst a much better start to winter than last year, and at best a repeat of 62/63. I will happily just follow what the broad range of signals are telling us and bet on a pretty good winter overall. Stand back people and look from an objective viewpoint - it's looking positive. There really is no more useful information than that to be had from any source of predictive weather data.

[nick sussex]

Anyone know the dewpoints that the ECM forecasts ?

Or does it do dp's at all ?

I honestly think 850's of zero are fine under an Easterly, once dp's are low

JS it depends on the type of synoptics and how much embedded cold you have at the surface.

For frontal snow you can get away with 850's just below freezing but this is more likely on the Continental landmass.

I can tell you from experience of living down here that we can get snow with those values but any easterly or ne here isn't modified by any sea track.

For convective snow showers off an easterly you need 850's much lower.

[snowking]

Anyone know the dewpoints that the ECM forecasts ?

Or does it do dp's at all ?

I honestly think 850's of zero are fine under an Easterly, once dp's are low

I've got paid access to them

Nothing spectacular out at the time frames of the suggested easterly, around 0 to +1 daytime, 0 to -1 overnight.

That said, I honestly wouldn't pay attention to such details at this timeframe

SK

[Zakos]

I am sorry, but that's not the case. Even now both us and the continent can become very cold very quickly and we don't need cold pooling to our east.

This run mixes in a lot of warm air from the Med, London & Paris are 4-5C warmer on average next week compared to the previous run, which was quite cold.

Perhaps..., however I fail to see the logic in your post.

How can you say the ECM is a "very worrying" run. please elaborate

[bluearmy]

Some of you need to stop being so impatient. The last week of november was always bookmarked as the lead into a cold period. I think its panning out more wintry than expcted. The end of the ecm run is win, win, win. Undercutting southerly jet. Cut off retrogressing block. Negative AO pattern setting up to our ne. Either way we go proer cold after that run. Of course its unlikely to pan out quite like that but you wuld hope that one of the three scenarios will play out.

[Backtrack]

I am sorry, but that's not the case. Even now both us and the continent can become very cold very quickly and we don't need cold pooling to our east.

This run mixes in a lot of warm air from the Med, London & Paris are 4-5C warmer on average next week compared to the previous run, which was quite cold.

Without a cold source of air how are we going to become cold very quickly? That's like saying if we get a northerly in summer it'll be cold.. I really don't see any mixing going on here either really? The reason we're milder is because there simply isn't a cold air source to tap into.

We may get the surface cold due to the time of year weather dependent, i.e. sunny in the day, clear & frosty by night. Rinse and repeat and wait for the cold to come.

[Zakos]

There has been bickering in this thread for around 4 weeks, discussing the likelihood of a pattern change that the wider range of signals (teleconnections to some) have been suggesting may occur at the end of Nov / start of Dec (ish). Now the major models have CLEARLY indicated a pattern change there is bickering over whether the 850s are going to be cold enough for snow. When the 850s are cold enough for snow (and they will be - follow the pattern run to run, look at what the ECM is hinting at from the NE) there will be bickering over whether it will snow in the north east or the west or in my back yard. Winter is upon us and the only guarantee is point scoring and bickering in this thread. The signals are pointing towards at worst a much better start to winter than last year, and at best a repeat of 62/63. I will happily just follow what the broad range of signals are telling us and bet on a pretty good winter overall. Stand back people and look from an objective viewpoint - it's looking positive. There really is no more useful information than that to be had from any source of predictive weather data.

Excellent post. The bickering needs to stop. The cold will come eventually, if the block sets up as is currently predicted. End of story.

[xioni]

Hi xioni.

How can you view the 12z and call this a worrying run?

The pattern change to cold is nigh on nailed ( Below Average ) and we have a real chance of something brilliant further down the line as highlighted by the 240 ecm which shows bags of potential.

You sound like a very knowledgeable person but i fail to see how you have come up with that conclusion.

The main thing is to get the pattern change in place which looks very much form horse.

hi there, the pattern change and the beatiful blocking high are almost done (and it was a brilliant call by GP), but the cold weather is far from done yet.

Anyway, it's just one run and it could all change tomorrow and we shouldn't forget that unlike gfs the EC ensemble is rock solid for early Dec

[cfallon]

The bickering is starting to get annoying now! It's November the upcoming period is looking good and considering its early in the season I am more than happy! - some folks need to chill out! It's only the weather plenty of ups and plenty of downs and winter is always a roller coaster ride!

Ps - Crewe cold is still on a downer from last year as he got no snow! :-) lol!

Edited November 20, 2012 by cfallon

[Gael_Force]

Anyone know the dewpoints that the ECM forecasts ?

Or does it do dp's at all ?

I honestly think 850's of zero are fine under an Easterly, once dp's are low

You'll get the dewponts for a range of places in Holland on the WeerPlaza ensembles - still not indicative as there is no sea track to be taken into consideration in these locations.

http://www.weerplaza.nl/15daagseverwachting/?type=eps_pluim

[xioni]

Without a cold source of air how are we going to become cold very quickly? That's like saying if we get a northerly in summer it'll be cold.. I

It's called cold advection and you can go from 12C on one day to snow on the next one...

in this run the cold advection takes place in the wrong places and because of the shape of the trough there is sifnificant warm advection over France & Germany, which affects our air mass as well

[Paul]

And breathe...

Lets keep it friendly and on the topic of the models please all

For some closer range relief, lots of weather happening in the next few days - heavy rain, flooding, high winds etc - discuss those over here:

[Backtrack]

It's called cold advection and you can go from 12C on one day to snow on the next one...

in this run the cold advection takes place in the wrong places and because of the shape of the trough there is sifnificant warm advection over France & Germany, which affects our air mass as well

Again, I stress the need for a cold air source for snow. It can't just simply snow if the uppers are not cold enough man! I've been on this forum 4-5 years now and I've never heard anything like that.

[Whether Idle]

During the December 2010 cold spell., only rarely were -10 850s parked over us. The southern extremities were often under 850s of -4 or so, and it was a very cold month with plentiful snow even there,as we recall all too easliy. The ECM synoptics tonight are frankly stunning (esp the 1947esque 240 chart) and I think the charts will prove to be colder than is expected. Good times to be a model watcher - 10 days away and we're still in autumn!

[phil nw.]

Let`s keep things in perspective wrt colder air.

Next week has never been modelled for any real cold.The block would be firming up but the cold air is still away to the north east and was always thus.

I don`t think anyone has said any different we all know next week is currently forecasted near average.

We need to look into the new month for any chance of this if the block stays around.

[pyrotech]

Its quite humorous on here at times.

The first signs of a fairly cold spell and many moan its not cold enough, worse still off members who are experienced enough to know that getting the block in place is the first step and then OFTEN the cold uppers have a chance to appear.

We also have the comments on GFS, if any one disagrees then fine but here is my take on it.

Its not the best performing model, but saying ignore all in fi is crazy .

Why even show any charts beyond 144hrs then?

To use any model beyond 168hrs i would suggest you study the feasability on how it gets there, then what its trying to acheive and why it tries to acheive it, also look for trend not actual synoptics.

Does the GFS pick up a pattern change correctly, SOMETIMES... you need to look at other factors and is it feasable, often its not, but intermittently it does pick a pattern change, i suggest it did this time. Will it verify? probably in some form, however we are not there yet.

The GFS is one tool to use in Fi , just one. Would i rely on its output alone, NEVER !

We may next week get to a place where percipitation is of interest, toys will be thrown out of the pram, guaranteed.

Yet again percipitation is only good at 24hours out in this situation, maybe a shortwave will appear in a northerly flow, just 36 hrs out, perhaps a warm sector that originates from way up North. Thats one that often catches people out.

The models are showing heavy percipitation this week, yet i bet where the rain falls heaviest will change by a few 10s of miles over the week.

Here we are at the first potential cold spell and on here the bickering really starts, however for me thats a sure sign that things are getting interesting on the weather models.

Forgot to throw in convective cooling, if something does come off then that will possibly come into play, it helped already once this winter for some fairly unexpected snowfall for some, with 850s above the magic -5

Edited November 20, 2012 by pyrotech

[london-snow]

hi there, the pattern change and the beatiful blocking high are almost done (and it was a brilliant call by GP), but the cold weather is far from done yet.

Anyway, it's just one run and it could all change tomorrow and we shouldn't forget that unlike gfs the EC ensemble is rock solid for early Dec

It just got to me how you come with that answer ' Worrying Run ' but never mind.

The thing we have to remember here is that we was never going to go straight in the freezer was we. It is a pattern change and trending on from the pattern change we could well go in the freezer however this depends on a number of factors. The main point is is that after the pattern change things will become very interesting indeed with the amount of blocking likely to occur as demonstrated by the 240 ecm this evening.

[Thundery wintry showers]

I don't know why everyone wants to snow immediately anyway.

A week or so of surface cold is FAR better in my opinion if we're seeing widespread night time frosts, it freezes the ground so when the snow finally does arrive there's a much higher chance it'll settle. IF BLOCKING IS IN PLACE, THE COLD WILL COME < It really is as simple as that.

ECM is perfect, the extend of Northern Blocking is something we very rarely saw on the charts last year, I'm very happy with where we are at the moment and really cannot understand the negativity! We live in the UK, not the Arctic.

The above post got a lot of "likes" but I think the ground temperatures are often overstated as a factor in the likelihood of snow accumulating and sticking around. They can make a fair amount of difference in marginal situations with light snow, particularly on concrete surfaces, but most of the time, when snow struggles to settle, it's because the air temperature and humidity are a bit too high, resulting in wet snow which melts on impact with the ground.

For snowfalls during the last few days of November, we would need the low pressure to be centred out in the North Sea bringing a northerly flow, as the southern Arctic Circle is currently colder than continental Europe. The ECMWF version has the low situated to the south which feeds in relatively mild 850hPa air from the east, and combined with surface cold from the continent, the most likely result would be stratus/stratocumulus trapped underneath an inversion- although from where we get to at T+240, most routes would lead to something snowy.

The GFS 12Z shows what will most likely happen if the trough hangs around in the North Sea, which has so far been the scenario shown by the ECMWF ensemble mean. A north to north-easterly flow with a mix of sun and wintry showers, and occasional troughs and organised belts of precipitation moving around the low pressure. With 850hPa temperatures around -3 to -5C, I would expect just rain/sleet showers near the usual north and east-facing coasts, but any troughs that head inland could potentially bring snowfalls.

Before that, as Ian Ferguson pointed out, we have some pretty serious rainfall totals to contend with in the west on Thursday, accompanied by a strong southerly wind, and the GFS has not backed down on its projections of strong to gale force winds for a time. Tonight's GFS run (and the GFS is quite reliable with precipitation outputs within 48 hours in my experience) suggests that Wales and SW England will be heaviest hit by the rain, while over western Scotland and NW England it passes through more quickly.

Edited November 20, 2012 by Thundery wintry showers

[phil nw.]

OK people let`s move on and simply discuss the model outputs and not what you think about other members.

All opinions related to what`s in the charts are welcome- but not bickering.

There`s a fine line between allowing this thread to flow and some unpleasantness creeping in.

A few are now getting close to that line and are liable to see any further instances deleted.

[Jason T]

Well with comparison http://www.meteociel...12&map=0&mode=0

http://www.meteociel.fr/modeles/archives/archives.php?day=30&month=11&year=2011&hour=12&map=0&mode=0

I know which output i would prefer.

Edited November 20, 2012 by Jason T