Winter Model Discussion - Cold Hunting -12Z 30/12/12

[Grimsby Snow Lover]

Morning all

My first post on NW - it's my birthday on the 15th and having done some research on the charts for that day over the years, it's remarkable how often we get an anticyclonic period around the middle of the month (about one in three over a 50-year timeframe). The output points to that anticyclonic period albeit still at the extreme edge of FI.

I don't know enough about the physics of SSW to comment on its possible impact but historical research and life experience tell me that the key period for "winter" is basically late January to early March. All we are seeing is the first outriders of what may or may not be "something". I also find it strange how quickly people have forgotten last winter's memorable European cold wave which fringed the UK and I well remember frantic study of output when it seemed as though the cold might reach us as well. Positioning and orientation of HP cells is or are the key and there's plety of time for that to be resolved.

Welcome to the forum Stodge! An interesting first post too

[mike Meehan]

http://www.meteociel...&ech=384&mode=1

http://www.meteociel...&ech=384&mode=0

Look's like a change mid month for a few days when we could have a bit of wintryness, though the Greenie high is not showing any sign of staying too long.

Still a long way ahead - anything could happen really.

Edited December 31, 2012 by mike Meehan

[Tuxedo]

I throw in a word of caution with regard to a possible patten change talked about on here and the strat thread. Remember in November we were saying there would be a pattern change end of month but the cold didn’t come despite model agreement albeit FI. Then it was going to be around the 20^th Dec but it never quite fell into place for us again despite all the chat and favourable signals. We are now seeing the same expectation from the models where in FI it looks like another possible cold shot/pattern change. I know there are favourable scientific signals that this may well happen but REMEMBER its 2 weeks away and any forcast that far away has a low probability of happening regardless of any spin of scientific reasoning. The weather will do what it will and defy even the best forcasters and models amongst us. This post is targeted to those that do not have the years of experience to realise that discussing the likely weather we will have 2 weeks away is subject to unexpected changes when it comes into a reliable time frame (3 days). Just emember the probability rapidly reduces when we are looking at 240+and even noting trends at this timescale is subject to large changes until it becomes within the 3 day to max 5 day period when the probability of it happening rapidly increases and we can either start prepping sledges or dusting off the BBQ. Its easy to get carried away with the models, the expertise (of which there is a huge amount on here) but always remember it’s the weather we are dealing with that is not driven by a computer or scientific data. I hope I haven’t said anything out of turn and no offence intended, I just think it should be said as a reminder and a word of caution particulary to newcomers to this fascinating forum..

[Froze were the Days]

? But there's a greater number of EC and NCEP EPS members showing blocking to NE into trend period... where was a notion EC wasn't in tune with this?

Have to agree with you on this I was only referring to the medium term on the 0 & 12z ECM model and not the members.

[Panayiotis]

Ensembles for my area, interesting too, they show the cool down trend which has been shown to happen for a couple of days now, but also I have noticed everyday that the mean decreases every run in Fi (past the 14th) now it's around -3C so there must be much more support for a colder outcome than a warmer one,right?

Edited December 31, 2012 by Panayiotis

[Summer Sun]

A very settled UKMO run this morning with high pressure establishing its self over the UK giving us all a welcome break from the rain

The ensembles haven't been this dry in a long long time

There is also good agreement on a cool down from around mid month but we'll just have to wait and see if it comes to anything

Edited December 31, 2012 by Gavin.

[Frosty.]

The metoffice continue to dangle the carrot of a marked change to colder spells towards the back end of january and before then it looks like temps would be trending cooler, back towards average after a mild or very mild start. It pretty much looks like something similar to the Gfs 00z op run, very loosly of course but that type of trend towards a cold and blocked outlook soon after mid month but the next 10-15 days look like delivering a northwest/southeast or north/south split with the southern half of the uk becoming drier than average whereas the north/northwest continue to have some unsettled but mild weather with winds backing sswly to swly. All the cold potential is beyond T+15 days.

[johnholmes]

The metoffice continue to dangle the carrot of a marked change to colder spells towards the back end of january and before then it looks like temps would be trending cooler, back towards average after a mild or very mild start. It pretty much looks like something similar to the Gfs 00z op run, very loosly of course but that type of trend towards a cold and blocked outlook soon after mid month but the next 10-15 days look like delivering a northwest/southeast or north/south split with the southern half of the uk becoming drier than average whereas the north/northwest continue to have some unsettled but mild weather with winds backing sswly to swly. All the cold potential is beyond T+15 days.

Ian F quoted from the media discussion this morning about that.

[Frosty.]

Ian F quoted from the media discussion this morning about that.

Yes I know, i'm just adding my spin on it, sounds promising later although how we get there is still unclear but northern blocking to take hold again after mid month looks likely. Let's hope our potential second bite of the cherry is more successful than the first, which was a let down, at least next time we won't have a cold strat to contend with.

Edited December 31, 2012 by Frosty039

[bradymk]

the CFS v2 weekly anomaly update today continues the trend from the last few days of heights to our N/NW into week 3 and 4. This model takes also takes stratospheric forecasts into account and shows huge +ve height anomalies over Greenland.

GFS last few ops have been consistent with blocking to our NW day 10-15 and both GEFS and ECM ensembles highlight a cooldown mid month however still a few mobile zonal runs in there but expected at this stage. For me, a definate trend developing here for colder weather mid month with more and more GEFS Perturbations trending cooler each run. Now for a bit of luck.

[bluearmy]

Although the cfs weeks 3 and 4 must be used with care, the week 4 tends towards daves concern that if the block is too far west, it may allow the atlantic trough to get far enough north to allow less cold air into the south. My own view on this would be that the way the reverse zonality is shaping up on the strat forecasts, if we get propogation (which cfs clearly sees to bring such a strong greenland anonmoy), i doubt TEITS concerns will be valid for a while once the cold were to set in. As time passes, any probable adjustment/ tweaks to the longwave pattern could allow a west base -NAO.

Rather think steve m might be back soon, especially as the trend of the ops is to verify his weekend research into propogating SSW's.

[Theresnoway]

The GEFS mean showing a gradual return to tomorrow's uppers (-3c) in 15 days time, after a relatively mild 6-7 days.

The OP is a cooler option in FI, but other members also hinting at it's trend:

So a settled period coming up with indications that the current synoptics are weakening, around D8. This I suspect is not due to the SSW and is probably just the ebb and flow of winter. This may of course help, when the strat warming starts to feed in.

The 0z control shows a cleaner Atlantic height's build, and something that looks more possible:

The GEFS mean also, at T300, shows a clear tendency for heights around the UK:

FI starts at around D7-8 and this looks like it will vary on the theme of amplification around the UK, so that is likely to chop and change, placement wise.

The strat signals are remaining strong so things are moving in the right direction for mid Jan onwards.

Hi,

Learning here, an answer to the below would help my understanding better...

What is meant by "when the strat warming starts to feed in"? Surley it is already fed in? Is it not these very models that are forecasting the strat warming?

Thanks

[IDO]

Hi,

Learning here, an answer to the below would help my understanding better...

What is meant by "when the strat warming starts to feed in"? Surley it is already fed in? Is it not these very models that are forecasting the strat warming?

Thanks

Hi

"when the strat warming starts to feed in" to the trop. Is what I meant.

I am not sure the strat warming has fed in yet, could have but only time will tell. Can take up to four weeks according to the more knowledgeable, but probably half that in reality.

[Geordiesnow]

The metoffice continue to dangle the carrot of a marked change to colder spells towards the back end of january

Yawn, according to this thread, we should of seen ice crystals by now, but unfortunately, the set ups just has not really fallen into place for anything prolonged or all even that cold, the -10hpa has not even touched the UK yet albeit it came close on the 5th December and as I said, it is amusing that the date for "something interesting" is getting put further and further back.

Besides, its mild and drier weather that is going to play ball from around mid-week onwards, still the potential for some rainfall across NW Scotland which is common in these set ups but unfortunately at this time of year, sunshine amounts could be limited to those that is sheltered from the hills. If any sunshine does break through, it will be interesting what temps we will record, especially in those areas that get the fohn affect.

[Theresnoway]

Hi

"when the strat warming starts to feed in" to the trop. Is what I meant.

I am not sure the strat warming has fed in yet, could have but only time will tell. Can take up to four weeks according to the more knowledgeable, but probably half that in reality.

Thanks for the reply.

So are you saying the models are forecasting the stratosphere to warm, but are not making any allowance for impact on the troposphere? Or are you saying the the models are so bad at handling the propagation, the true impact cannot be modelled so far out in the land of low resolution?

David

Edited December 31, 2012 by Theresnoway

[IDO]

Thanks for the reply.

So are you saying the models are forecasting the stratosphere to warm, but are not making any allowance for impact on the troposphere? Or are you saying the the models are so bad at handling the propagation, the true impact cannot be modelled so far out in the land of low resolution?

David

The real McCoys are here:

Interesting reading...

[Panayiotis]

Yawn, according to this thread, we should of seen ice crystals by now, but unfortunately, the set ups just has not really fallen into place for anything prolonged or all even that cold, the -10hpa has not even touched the UK yet albeit it came close on the 5th December and as I said, it is amusing that the date for "something interesting" is getting put further and further back.

Besides, its mild and drier weather that is going to play ball from around mid-week onwards, still the potential for some rainfall across NW Scotland which is common in these set ups but unfortunately at this time of year, sunshine amounts could be limited to those that is sheltered from the hills. If any sunshine does break through, it will be interesting what temps we will record, especially in those areas that get the fohn affect.

This should have been posted in the moan thread tbh. My cousins who live in Newcastle have had a couple of cm of snow, also here in Cardiff we have seen snow. Back at the start of December we had 3 consecutive days, where the max temperature reached 3C, thats 5C below average for where i live, but according to you, thats not cold enough? Edited December 31, 2012 by Panayiotis

[Panayiotis]

Thanks for the reply.

So are you saying the models are forecasting the stratosphere to warm, but are not making any allowance for impact on the troposphere? Or are you saying the the models are so bad at handling the propagation, the true impact cannot be modelled so far out in the land of low resolution?

David

The stratosphere is at a much higher altitude (~12km-50km), from where our weather takes place (0-12km) (troposphere), so far the models are predicting the strat to warm, at different levels, but for this example I will use the warming taking place at 30hPa which is at around 25km above sea level, this warming then takes time to filter down the stratosphere until hitting the troposphere, this is where the polar vortex starts to feel the warmth from the strat and starts to break down.

Im sure 'i'm dreaming of.....' wont mind me helping you, to answer your question,more answers, more knowledge!

Edited December 31, 2012 by Panayiotis

[Frosty.]

Yawn, according to this thread, we should of seen ice crystals by now

Yes but we have to believe we will have the first proper wintry spell with snow during the second half of jan or just throw in the towel right now. I think the model output (and the actual weather) over christmas has been dismal but there are a few signs emerging that from mid month it will be turning generally colder.

Edited December 31, 2012 by Frosty039

[swfc]

Yes but we have to believe we will have the first proper wintry spell with snow during the second half of jan or just throw in the towel right now. I think the model output (and the actual weather) over christmas has been dismal but there are a few signs emerging that from mid month it will be turning generally colder.

After admire your optimism frosty.yes there are signs of a change in a fortnight or so to a more blocked scenario but where that leaves the uk weatherwise is anyones guess.happy new year

[Snowman.]

The latest CFS anomalies for January shows a big lump (my technical language) of low pressure to our West with above average temperatures and rainfall around average, above average in the South. I think the CFS is useful to check for trends but obviously not to taken at face value but here it is.

Temps

I have never had much hope in that model changes to much.

[alexisj9]

I throw in a word of caution with regard to a possible patten change talked about on here and the strat thread. Remember in November we were saying there would be a pattern change end of month but the cold didn’t come despite model agreement albeit FI. Then it was going to be around the 20^th Dec but it never quite fell into place for us again despite all the chat and favourable signals. We are now seeing the same expectation from the models where in FI it looks like another possible cold shot/pattern change. I know there are favourable scientific signals that this may well happen but REMEMBER its 2 weeks away and any forcast that far away has a low probability of happening regardless of any spin of scientific reasoning. The weather will do what it will and defy even the best forcasters and models amongst us. This post is targeted to those that do not have the years of experience to realise that discussing the likely weather we will have 2 weeks away is subject to unexpected changes when it comes into a reliable time frame (3 days). Just emember the probability rapidly reduces when we are looking at 240+and even noting trends at this timescale is subject to large changes until it becomes within the 3 day to max 5 day period when the probability of it happening rapidly increases and we can either start prepping sledges or dusting off the BBQ. Its easy to get carried away with the models, the expertise (of which there is a huge amount on here) but always remember it’s the weather we are dealing with that is not driven by a computer or scientific data. I hope I haven’t said anything out of turn and no offence intended, I just think it should be said as a reminder and a word of caution particulary to newcomers to this fascinating forum..

I don't agree, there have been some small patern changes this month and three of them have resulted in small cold spells for parts of the country. The first produced an unexpected snowfall in the West Country, The second brought snow to the North and East Angela, and even to London and the southeast one morning. The last was a short wave that blocked the Easterly we were expecting, we still had a cold snap that brought snow to the North East and even to some places down south though those falls were very slight.

Sorry I think I misunderstood what you wrote the first time I read it. I do agree that althought the strat warming will eventauly change things, there is at this stage no real way of knowing if that will be good for cold for us or not.

Edited December 31, 2012 by alexisj9

[Snowman.]

Hi

"when the strat warming starts to feed in" to the trop. Is what I meant.

I am not sure the strat warming has fed in yet, could have but only time will tell. Can take up to four weeks according to the more knowledgeable, but probably half that in reality.

Takes over a weak after the initial warming.

[TEITS]

Wow only just seen the 06Z operational and yet again a similar trend continues Re blocking.

If anyone is wondering why the 06Z +384 chart is showing such low min temps when upper temps are only around -3/-4 then thats simply caused by lying snow!

http://www.wetterzentrale.de/pics/Rtavn38417.png

So based on recent GFS Ops it seems the period between 10th Jan to 16th is when a cold spell could emerge. Some of the GFS Ops have hinted at the 10th Jan when it all kicks off but this might be a little soon. My best guess at the moment is around the 14th Jan. Very soon the ECM comes into range and I shall particularly be interested in the ECM output from Wednesday onwards.

[TAFKAP]

Takes over a weak after the initial warming.

Takes over a weak what? A weak SSW?