Winter Model Discussion - The Hunt For Cold -18z 17/12/12

[Methuselah]

Exactly, the pattern change over the Xmas period has changed alot. The upgrades for the reliable are good the AH is moving south as you say to allow the low pressure to move east. I wouldnt be suprised by the time the 18z roles out there will be a few suprises for Xmas day!

Indeed it has D82; it changes with each and every run, let alone each and every ensemble member. Which, with chaos & complexity being what they are, is just what we should expect - most of the time?

[latitude]

Exactly, the pattern change over the Xmas period has changed alot. The upgrades for the reliable are good the AH is moving south as you say to allow the low pressure to move east. I wouldnt be suprised by the time the 18z roles out there will be a few suprises for Xmas day!

Couldn't we just get stuck in this pattern with the AH just sitting in a position where the LP's just track East then North East? Shouldn't we looking for signs of proper high pressure appearing over Greenland with a AH link up to really block out the Atlantic?

With the odd LP pressure system going SE that might setup a very tempory colder shot, only for another LP to move in travel east then north east and bring back the milder air. A Greenie High is the best way forward to ensure proper Atlantic blocking and good chances of cold getting into the UK.

Why arnt we looking towards greenland....why so much interest in the track of LP's if theres only going to be another one right behind it taking a NE route.

I presume its because thats the only chance right now that some areas might see a little tempory white stuff.

Im only a newbie so obviously there might be a lot wrong with my post.

[TEITS]

For the period between the 25th & 29th I would say the chances of a cold, wintry spell are actually around 50%. Now because of the ECM/UKMO my odds should be 33.3% but personally because I feel the GFS is right with the trend of moving the LP E followed by colder N/NW,lys followed by further LP tracking E is what makes my odds stand at 50%. If the UKMO or ECM or even both come on board then my odds will certainly increase. Shall update my odds on each run.

[swfc]

phew!!!well id put the reliable time frame at 92 hrs at the moment?something seems to be throwing everything "even given the pv movement and predicted strat warming later in fi"out and making the model output odd indeed.Even between the 0z and o6z "in fi land"the pv is jumping around like a scolded cat!granted the low does go east on both runs but the diff in the model output between respective models is very very different at such a close time scale.im more confused than scooby doo but not nuch change there then!!!!

[Ian Brown]

Couldn't we just get stuck in this pattern with the AH just sitting in a position where the LP's just track East then North East? Shouldn't we looking for signs of proper high pressure appearing over Greenland with a AH link up to really block out the Atlantic?

With the odd LP pressure system going SE that might setup a very tempory colder shot, only for another LP to move in travel east then north east and bring back the milder air. A Greenie High is the best way forward to ensure proper Atlantic blocking and good chances of cold getting into the UK.

Why arnt we looking towards greenland....why so much interest in the track of LP's if theres only going to be another one right behind it taking a NE route.

I presume its because thats the only chance right now that some areas might see a little tempory white stuff.

Im only a newbie so obviously there might be a lot wrong with my post.

Yes, the problem with regards getting a cold spell is that at the moment there is nothing to suggest that we are going to get blocking to prevent the Atlantic train of Low pressure systems, I don't like to see the trend to build Canadian HP as this will do us no favours.

[latitude]

Yes, the problem with regards getting a cold spell is that at the moment there is nothing to suggest that we are going to get blocking to prevent the Atlantic train of Low pressure systems, I don't like to see the trend to build Canadian HP as this will do us no favours.

Thanks for the reply Ian. cheers.

[EML Network]

Well the 06z is a total disaster for those looking for cold and snow anyway, the cold ever so close, but always skirting us to the East, are we really going to have to endure 2 more weeks of what we're experiencing right now ?? ...I really thought there we're a few signs over the past few days runs that gave some hope between boxing day and new years...hopefully we'll start to see something different emerging in the models in the lead up to Xmas day and let's hope the GFS gives us a nice Xmas present so we can put the last few weeks weather behind us and look forward to colder days for the start of 2013

[Frosty.]

The only good thing about the Gfs 06z is it's not a mild run, fairly average for most apart from the far north of scotland and isles which are in colder air at times, especially above 60 degrees north which is the shetland isles, but for most it's around 7-9c, and that's what is shown for christmas day with a cyclonic spell, the only risk of snow for the scottish mountains but at least it's not a blowtorch southerly from africa on this run. Lots of wet and windy weather to come though, a little colder in the far north of scotland later this week into the weekend with a mix of rain, sleet and snow but then a little milder, most of the uk near average temps and some rain and showers with cyclonic winds.

[Iceaxecrampon]

MetO Cumbria:

Friday

Cloudy and unsettled with occasional showers, mostly over the eastern fells. These falling as snow over the higher peaks in the morning, but to lower levels later in the day. Light northeasterly winds becoming variable later. Freezing level 800 m falling to 400 or 500 m through the day.

Saturday

Mainly dry but cloudy to start with light winds. Winds soon strengthening bringing upland gales and wintry showers at times. Snow later in the afternoon with strong winds and blizzards. Freezing level dropping to low levels.

......can't see much to support blizzards.

Ian

Edited December 18, 2012 by Iceaxecrampon

[Frosty.]

MetO Cumbria:

Friday

Cloudy and unsettled with occasional showers, mostly over the eastern fells. These falling as snow over the higher peaks in the morning, but to lower levels later in the day. Light northeasterly winds becoming variable later. Freezing level 800 m falling to 400 or 500 m through the day.

Saturday

Mainly dry but cloudy to start with light winds. Winds soon strengthening bringing upland gales and wintry showers at times. Snow later in the afternoon with strong winds and blizzards. Freezing level dropping to low levels.

......can't see much to support blizzards.

Ian

LOL neither can I!

[nick sussex]

Regardless of the earlier disagreements the trend is to slowly edge the pattern east with the Russian high losing its grip on Europe, and I for one won't be disappointed to see the back of it!

Turns up hangs around promises much and delivers little! the upstream pattern just won't allow it to really influence things.

The GFS continues to advertise a little interest for the ne but isn't supported by the ECM/UKMO and thats not really the best of signs.

Thereafter the UKMO doesn't look too bad , the best perhaps we can hope for is that low pressure can track sufficiently south to keep the UK close to colder air to the north, seeing as theres little sign of low pressure taking a break from moving east out of the USA. Until we see much more amplification upstream and some higher latitude blocking then its hard to see a more prolonged period of cold.

But at this time I'd take a northerly toppler which is a great deal more fun for some parts of the UK than spending two weeks waiting for the Russian high to deliver.

Edited December 18, 2012 by nick sussex

[chionomaniac]

Have to be honest im not sure how you can base a forecast for xmas at the moment using the anomaly charts. As I posted earlier at +144 the placement of the LP is massively different on every model at +144 and of course xmas day begins at +168. If the LP is situation to the W or NW of the UK then obviously the outlook is mild SW,lys. However if the LP tracks E i.e GFS then you would pull in colder N/NW,lys around xmas day on the backside of the LP.

Those anomaly charts are useful when it comes to the overall pattern but you cannot use them to predict our weather on the surface of our tiny island.

ECM ensembles continue to show massive scatter very early on.

http://www.knmi.nl/e...E_06260_NWT.png

Those ensembles are for de bilt though.

De Bilt is sufficiently east enough to be in cold air whilst London is in a SW flow - so the scatter can be misleading here.

The London ensembles are far more accurate for here:

And out of the 70 joint ECM and NCEP ensembles there are about 5 that suggest cold air making it that far across. Even with my basic maths skills, I make that around a 7% chance.

I think I will go with the 93% here - though the period towards New Year looks more promising if the disrupted NH can just put us on the right side of cold.

[Frosty.]

I like how optimistic TEITS is but there is nothing to be optimistic about in terms of snow or cold as we hit the christmas period, near average or mild sums it up apart from maybe the far north of scotland where it could be a little colder at times with a little wintry ppn and a touch of frost.

Edited December 18, 2012 by Frosty039

[Ian Brown]

Regardless of the earlier disagreements the trend is to slowly edge the pattern east with the Russian high losing its grip on Europe, and I for one won't be disappointed to see the back of it!

Turns up hangs around promises much and delivers little! the upstream pattern just won't allow it to really influence things.

The GFS continues to advertise a little interest for the ne but isn't supported by the ECM/UKMO and thats not really the best of signs.

Thereafter the UKMO doesn't look too bad , the best perhaps we can hope for is that low pressure can track sufficiently south to keep the UK close to colder air to the north, seeing as theres little sign of low pressure taking a break from moving east out of the USA. Until we see much more amplification upstream and some higher latitude blocking then its hard to see a more prolonged period of cold.

But at this time I'd take a northerly toppler which is a great deal more fun for some parts of the UK than spending two weeks waiting for the Russian high to deliver.

Yes, the Atlantic pattern is not going to allow the blocking to back West, need to accept this and want to move on so that depressions can pass the Meridian. Beyond that we need to see the upstream amplification develop, perhaps associated with the Strat developments to promote the sort of blocking that bring a more meridional pattern.

[nick sussex]

Yes, the Atlantic pattern is not going to allow the blocking to back West, need to accept this and want to move on so that depressions can pass the Meridian. Beyond that we need to see the upstream amplification develop, perhaps associated with the Strat developments to promote the sort of blocking that bring a more meridional pattern.

I agree its just not going to happen and we need to say goodbye to the Russian high, very rarely does it manage to get sufficiently west, even last February with a strong signal to move west it only just about scraped the ridge into the UK.

Give me a small high located over Scandi anytime above the Russian high, it might not look as impressive on the charts but has a much better chance of influencing things for the UK and western Europe.

Edited December 18, 2012 by nick sussex

[mulzy]

Got this horrible feeling that the Azores/Iberian high will play a big role in our weather over the next 2 weeks.

[chionomaniac]

Yes, the Atlantic pattern is not going to allow the blocking to back West, need to accept this and want to move on so that depressions can pass the Meridian. Beyond that we need to see the upstream amplification develop, perhaps associated with the Strat developments to promote the sort of blocking that bring a more meridional pattern.

I have to say Ian, that they are my thoughts exactly as well - though we may need tropospheric help here as well to achieve any amplification. And the MJO, does not look in the most helpful of moods presently. No MT activity to report either. I think that for this period of winter everyone was always going need patience and that is proving correct!

[nick sussex]

Got this horrible feeling that the Azores/Iberian high will play a big role in our weather over the next 2 weeks.

Even I'm not that pessimistic!

The Azores high is only ridging ne within 144hrs as a result of the phasing upstream between a shortwave and troughing to the west of the UK.

Start worrying if you see a strong PV over Greenland, certainly don't worry over some GFS nonsense showing up well into FI.

Edited December 18, 2012 by nick sussex

[Frosty.]

The latest metoffice update confims the worst but it does sum up the ens mean and most of the operationals, temps close to average or a little above is the theme with spells of wet and windy weather punctuated by clearer, showery weather. The far north of the uk is slightly different in that it will be rather colder than elsewhere at times with some occasional wintry ppn, but even the far north of britain looks like becoming somewhat milder towards mid jan, for central and southern britain the risk of cold and snow is low to non existant according to the latest metoffice update, they are basically writing off january already which seems absurd at this range, especially when you factor the strat warming into the overall equation..it looks grim for cold weather fans at the moment.

[TEITS]

And out of the 70 joint ECM and NCEP ensembles there are about 5 that suggest cold air making it that far across. Even with my basic maths skills, I make that around a 7% chance.

I think I will go with the 93% here - though the period towards New Year looks more promising if the disrupted NH can just put us on the right side of cold.

Considering the vast difference in the operationals and the relatively short time frame the ensembles you posted are pretty useless in my opinion. Even at +48 we are seeing differences between the models.

So my possible outlook of turning colder between Xmas day/Boxing day with cold NW/N,lys followed by possible further wintry outbreaks via LP tracking E still remains at 50%. Obviously Scotland/ N England most at risk as they could remain on the N side of these LP systems.

Certainly going to be interesting to see who is right, my instinct Vs ECM/ensembles.

[LomondSnowstorm]

The latest metoffice update confims the worst but it does sum up the ens mean and most of the operationals, temps close to average or a little above is the theme with spells of wet and windy weather punctuated by clearer, showery weather. The far north of the uk is slightly different in that it will be rather colder than elsewhere at times with some occasional wintry ppn, but even the far north of britain looks like becoming somewhat milder towards mid jan, for central and southern britain the risk of cold and snow is low to non existant according to the latest metoffice update, they are basically writing off january already which seems absurd at this range, especially when you factor the strat warming into the overall equation..it looks grim for cold weather fans at the moment.

I wouldn't say they've 'written off January', it looks more along the lines of there being no strong signal either way in the 16-30 day range with cyclonic conditions favoured up to the start of January in some form or another.

[WhiteFox]

The latest metoffice update confims the worst but it does sum up the ens mean and most of the operationals, temps close to average or a little above is the theme with spells of wet and windy weather punctuated by clearer, showery weather. The far north of the uk is slightly different in that it will be rather colder than elsewhere at times with some occasional wintry ppn, but even the far north of britain looks like becoming somewhat milder towards mid jan, for central and southern britain the risk of cold and snow is low to non existant according to the latest metoffice update, they are basically writing off january already which seems absurd at this range, especially when you factor the strat warming into the overall equation..it looks grim for cold weather fans at the moment.

Meh. I'd put about as much faith in the Met Office forecasts for January as I do in the ECM 32 day forecasts. At best they are experimental which I guess is why the Met Office doesn't trumpet the longer range outlook very highly. Given the accuracy of previous updates, and the fact that they are placed in terms only slightly more specific than thos used by astrologists, I'll stick to the shorter range models for now!

[andy100]

Who cares about the snow? It's all about the severe gales

[Frosty.]

Meh. I'd put about as much faith in the Met Office forecasts for January as I do in the ECM 32 day forecasts. At best they are experimental which I guess is why the Met Office doesn't trumpet the longer range outlook very highly. Given the accuracy of previous updates, and the fact that they are placed in terms only slightly more specific than thos used by astrologists, I'll stick to the shorter range models for now!

They did very well in the build up to the Dec 2010 freeze but I agree there is still a lot of model uncertainty and I really don't know how they can be so dismissive of cold air affecting more of the uk in the next 10-15 days.

[syed2878]

with all due respect guys the met has access to mor data to what we have here at nw. Also don't the met have a new computer that forecasts the status of the strat? From chios and gp's posts in the strat thread it sounds good, how ever it seems that reading u guys posts here the met r not buying into the strat warming. The question is y? If they bought into the strat warming they wouldnt be riting off jan. I would be entrested to heare your thorts chio and gp.