Model Output Discussion - 1st - 7th January

[I remember Atlantic 252]

If we cant have snow, lets have high pressure over us, good agreement on all models for things finally drying up, could even be very cold due to inversion, although for a time with HP to the SW can be miserably wet for my area

[mountain shadow]

Yup, a dire run for coldies. What a difference 12 hours makes.

http://www.wetterzentrale.de/pics/Recm1921.gif

12 hours ago the ridge was way up past Iceland. Not good from the ECM for the second time this winter.

[Nick F]

There shouldn't be any surprise that 12z ECM wasn't going to follow the 00z run though. Beyond t+144 will often change anyway. Given the stubborn deep vortex over Greenland and the continuing strong jet across the Atlantic, any ridging building to the east is under alot of pressure. It doesn't even offer GFS's fairly cold northerly toppler next weekend either, rather a half-hearted NW'erly, though more amplification upstream coming through than suggested by ECM tonight could change this.

[Cheese Rice]

Interesting weather

Monday

Throughout Sunday night into Monday we see a brief PM incursion. 850's projected by the NAE to be around -5/-6

The colder 850s will promote rapid convection across the Irish sea. These showers will affect the areas highlighted on the PPN map above, so most western areas of the UK. Showers will fall as snow inland with a wintry mixture towards the coast, temporary accumulations expected across Northern England with several cm's over North West/West Scotland. Winds will be westerly with a south westerly tilt as the day continues, meaning areas that usually see snow in PM incursions may miss out due to the South Westerly element (usually winds from the North West).

Tuesday

During the early hours of Tuesday morning a deepening area of low pressure will track north of England, with the center of the low over Scotland.

Previous runs projected a slightly deeper area of low pressure, current projections suggest between 970MB-960MB (as seen on the ensembles above). The main cause for concern in the strengthening winds and large rainfall totals.

Winds gusting up to 60 knots (70 MPH) across the areas highlighted in red. Heavy rainfall will lead to localized flooding across Wales and North West England. Previous GFS runs projected exceptional totals of 50 mm for a 12 hour period. This has been downgraded to 28 mm for wales, 23 mm for North West England and 26 mm over the Lakes. There still remains a high risk to disruption to travel. A wet ground creates instability in the soil thus increasing the fragility of trees. When subject to high winds trees can easily topple. Expect disruption to road, rail, and electricity, with some trees falling.

Amazingly the NAE projects snowfall across large parts of Scotland and Northern England when the front arrives. I can't see any snow except transient snow across the highest ground over Scotland, 850s as seen above are not supportive in the slightest.

Wednesday

During late Tuesday the associated mild sector will quickly leave followed by colder 850s. Setup is very similar to Monday, with colder 850s promoting convection. Any showers falling as snow with a wintry mixture across the coasts.

Edited January 1, 2012 by Cheese Rice

[Cecil Hogmanay Melchett]

Yup, a dire run for coldies. What a difference 12 hours makes.

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

12 hours ago the ridge was way up past Iceland. Not good from the ECM for the second time this winter.

i wouldn't say dire,although the northern arm of the jet is still far to active to allow stable northern blocking at the moment.

Too much energy going North aided by the mind numbingly stubborn PV.

If we consider Dec Jan and Feb as winter months that damn PV will have ruined half the winter soon enough with the majority still waiting for their first snow letalone lying snow.

I guess pateince really is going to be a virtue this time round..

[kold weather]

I wouldn't describe the 12z ECM as dire, its not as good as the 00z though thats for sure.

What i will say about the 12z ECM is the vortex remains quite stubborn this run, doesn't really weaken all that much, but it does start to shift further east, so hopefully we can get the building blocks for change in by the 10-15th...

[Stormyking]

Hmm a much different look to the ECM 12z. I would say it would be very dry with some frosty nights and fairly chilly at day time, which in my opinion wouldnt be all that bad, an improvement anyways to recent

Edited January 1, 2012 by Stormyking

[Geordiesnow]

I'm still struggling too see where we are going to get much in the way of significant cold air from in all honesty from the ECM output, I mean what happens if everything does goes to plan and we get an easterly with the -10hpa barely reaching us because Scandinavia is way above average at the moment, even the NW'ly toppler at 96 hours is moderated because of the persistant less cold air around the svalbard isles. As I been menturning previously, the Svalbard isles must be having one of its mildest first half of the winter on record and conditions on our side of the poles has been quite mild due to the frequent nature of Southerly winds from the Russian high and low pressure further west pumping warmer air on our side of the Arctic.

Frustrating output for cold lovers and for once I have to admit its hard too see where a significant cold spell will come from. I'm not ruling out any cold set ups because the models are hinting at what would usually be cold set ups(like the NW'ly toppler at 96 hours) but due to the weather patterns so far, every cold set up so far has been moderated by the lack of cold air!

[TonyH]

My take in this weeks weather specific to west Wales and the central Midlands:

Weather guide Monday 2nd January to Sunday 8th January 2012 (west Wales and central Midlands)

Headline: More rain and showers; drier end to the week. Quite mild on the whole.

West Wales could do with a break from the rain! December's total at Llanwnnen was 212mm (8 1/2 inches), and it rained on every single day of the month at some point. On the other hand, a bit of a respite from the exceptional dryness for the Midlands last month, with Coventry at least reaching average with 60mm in December.

2011 was the second warmest year on record, even though the Summer was rather cool. No real cold to come this week either.

Some rather cold air is over us for a change during Monday. Showers moving into west Wales later tonight may be of sleet and hail perhaps leading to icy conditions first thing on Monday morning. Further showers at times through the day, some heavy with hail, a smidgen of snow on the hills perhaps too. Only a few showers extending east into the Midlands, so a mostly dry and bright day here.

Monday night into Tuesday, an intense low crosses northern Britain, so it looks like gale force SW to west winds could cause damage in places. A very wet night too, and with possibly over an inch falling on west Wales, localised flooding could cause problems on the roads on Tuesday morning, so something to be wary of along with the wind. The rain should have cleared most by midday, but with more showers following in the afternoon, these again heavy with hail at times, with some even getting into the Midlands as the the wind turns more north-west through the day.

Further Atlantic troughs cross the country on Wednesday bringing some more rain and wind but milder.

Thursday onwards is difficult to pin details on but pressure should try to build in from the south-west, so that it will turn somewhat drier at last. Winds will be coming around the high from the west or north-west, and temperatures will be just above normal to mild, maxima from Thursday to Saturday between 7 and 10c, and no more than the outside chance of a touch of frost or two. GFS brings in colder air next weekend on its latest run, but I would be inclined to largely discount this just now, although a trend to cold may be emerging in the models for following week.

So, although probably mostly dry to end the week, and for next weekend, the odd shower or spell of light rain cannot be ruled out at this stage, but certainly not the deluges we have seen here in west Wales over recent weeks, and will see again early this Tuesday.

.

For supportive charts see the Welsh thread:

http://forum.netweat...48#entry2201048

Edited January 1, 2012 by TonyH

[nick sussex]

The ECM 12hrs is a continuation of its morning theme but with the pattern a little further south and with the GFS giving support in the higher resolution output theres a decent chance of this verifying.

Looking at the broader picture of the NH it is however a step backwards with the PV showing no sign of moving away from Greenland and still very strong.

Even if the models manage to edge the pattern further north giving a stronger continental feed the jet will eventually sink any high, at this point a surface inversion is as good as it gets with the PV where it is.

[kumquat]

Agreeing with Cheese Rice, the NAE seems to like over-egging the snowfall chances this time around. A couple of years ago it seemed very much the model of the moment - nowadays it does seem to overdo the 850 temps with no regard for variables from the surface.

[Harsh Climate]

I think people calling the ECM 12z run dire need help in interpreting the charts.

We are never going to go straight to a raging easterly with -15hpa crossing the country in one outbreak/change!!

The pattern change that seems to be evolving from around 7/10 days is going to be a slow burner, and may take a few failed attempts before any major cold possibly comes in

A few days ago we were staring at endless mild and a possible bartty, now we have the first building blocks falling into place, some strat cooling finally allowing high pressure to build to the east and for the PV to the north to weaken/split somewhat.

This chart is good and I can only see the high retrogressing again! Perhaps further north than before and probably even colder air down the line spreading into eastern europe. These are the first building blocks, in what could be a very cold end to january.

What we also want to see coinciding with this is low pressure being sheared up the eastern seaboard of america, this would drag up WAA (the final ingrediant) into greenland reinforcing our retrogressing high, allowing for a major cold spell to develope

Edited January 1, 2012 by Harsh Climate

[Cecil Hogmanay Melchett]

The ECM 12hrs is a continuation of its morning theme but with the pattern a little further south and with the GFS giving support in the higher resolution output theres a decent chance of this verifying.

Looking at the broader picture of the NH it is however a step backwards with the PV showing no sign of moving away from Greenland and still very strong.

Even if the models manage to edge the pattern further north giving a stronger continental feed the jet will eventually sink any high, at this point a surface inversion is as good as it gets with the PV where it is.

Quite Nick,we can see there is far to much energy spilling off that damn vortex to allow any blocking high to establish itself in afavourable location.

With no end in sight to the intense cold over the Pole one has to start to wonder what on earth is going to cause it to shift.

Until we see a relaxation of the Greenland low brief PM shots is the only crumbs the UK is going to get.

Nothing at the moment to be optimistic about but good things come to those who wait,i hope!!

[A Winter's Tale]

It's quite amazing how quickly an entire mood in this thread can change! Every run from every model seems to be taken so seriously. Come on, the models will chop and change over the coming weeks. There's still plenty of time left for the breakthrough for proper cold and snow.

The Model Thread, The Bi-polar thread? Certainly, I'm keeping an eye out for snow by polar maritime air in the coming days.

[Geordiesnow]

I think people calling the ECM 12z run dire need help in interpreting the charts.

We are never going to go straight to a raging easterly with -15hpa crossing the country in one outbreak/change!!

The pattern change that seems to be evolving from around 7/10 days is going to be a slow burner, and may take a few failed attempts before any major cold possibly comes in

A few days ago we were staring at endless mild and a possible bartty, now we have the first building blocks falling into place, some strat cooling finally allowing high pressure to build to the east and for the PV to the north to weaken/split somewhat.

This chart is good and I can only see the high retrogressing again! Perhaps further north than before and probably even colder air down the line spreading into eastern europe. These are the first building blocks, in what could be a very cold end to january.

What we also want to see coinciding with this is low pressure being sheared up the eastern seaboard of america, this would drag up WAA (the final ingrediant) into greenland reinforcing our retrogressing high, allowing for a major cold spell to develope

The chart you posted is an awful one really, reletively mild air toppling over the Azores high and the PV locked into Greenland and in actual fact the models(GFS in particular) is hinting at a severe cold spell for parts of America at that timerange so I'm not sure where the WAA is going to come from after that chart really I'm afraid.

The potential is sort of there for a cold set up to develop but we just don't have much in the way of cold air to tap into so even if a cold set up occurs(whether its a Northerly/Easterly) then its going to be so moderated that any snowfall will probably be limited.

The deep low pressure system at the start of the run is the only interesting thing about this evenings output, yet another deep low heading our way! Certainly is making up from the past few winters thats for sure.

[Stormyking]

The chart you posted is an awful one really, reletively mild air toppling over the Azores high and the PV locked into Greenland and in actual fact the models(GFS in particular) is hinting at a severe cold spell for parts of America at that timerange so I'm not sure where the WAA is going to come from after that chart really I'm afraid.

The potential is sort of there for a cold set up to develop but we just don't have much in the way of cold air to tap into so even if a cold set up occurs(whether its a Northerly/Easterly) then its going to be so moderated that any snowfall will probably be limited.

The deep low pressure system at the start of the run is the only interesting thing about this evenings output, yet another deep low heading our way! Certainly is making up from the past few winters thats for sure.

Come on Paul, you know anything can happen in the weather, everyone should know how quickly it can change. I think all is needed is patience, The models have been getting better lately and I believe the building blocks are there. It will take time, just got to give it chance we are not going to get a very cold spell over night, but the potential is there and just need some patience .

[Harsh Climate]

The chart you posted is an awful one really, reletively mild air toppling over the Azores high and the PV locked into Greenland and in actual fact the models(GFS in particular) is hinting at a severe cold spell for parts of America at that timerange so I'm not sure where the WAA is going to come from after that chart really I'm afraid.

The potential is sort of there for a cold set up to develop but we just don't have much in the way of cold air to tap into so even if a cold set up occurs(whether its a Northerly/Easterly) then its going to be so moderated that any snowfall will probably be limited.

The deep low pressure system at the start of the run is the only interesting thing about this evenings output, yet another deep low heading our way! Certainly is making up from the past few winters thats for sure.

I disagree, the chart I posted

A

Is far better than what we have been seeing over the past 6-8 weeks, this chart some's up this period pretty well (gfs 12z 24h)

B

I don't know how anyone can say chart 'B' is better for prospects of deep cold/blocking than chart 'A'.

The reason I say that is because in the first chart I posted, look how far north the azores high is. It wouldn't take much for it to retrogress into greenland from that position. In the second chart I posted, it is very flat and would strongly be dependant of a ridge exiting eastern america joining up with it, before it would have any chance of retrogressing northwards.. Not very likely!

Edited January 1, 2012 by Harsh Climate

[nick sussex]

Quite Nick,we can see there is far to much energy spilling off that damn vortex to allow any blocking high to establish itself in afavourable location.

With no end in sight to the intense cold over the Pole one has to start to wonder what on earth is going to cause it to shift.

Until we see a relaxation of the Greenland low brief PM shots is the only crumbs the UK is going to get.

Nothing at the moment to be optimistic about but good things come to those who wait,i hope!!

Well putting aside the last few winters the coldest weather has often come late in the season and judging by the limpet PV thats a good bet this time around.

If you keep getting these strat warmings then the PV might finally decide it's time to move on and so I'm still optimistic. I'm sure though most members are losing patience but theres not alot we can do but wait for a NH pattern change.

At least though for down here the ECM isn't too bad, whatever snow falls in the Pyrenees is likely to hang around with that easterly flow but it would still be nice to see some snow here in the valley.

I think what this winter has shown so far is that snow in the UK is still relatively rare and that even if its just a few cms then thats great, a few good winters seem to have raised expectations.

Anyway lets see whether theres a bit more interest in the ECM ensembles.

[Geordiesnow]

I don't know how anyone can say chart 'B' is better for prospects of deep cold/blocking than chart 'A'.

The reason I say that is because in the first chart I posted, look how far north the azores high is. It wouldn't take much for it to retrogress into greenland from that position. In the second chart I posted, it is very flat and would strongly be dependant of a ridge exiting eastern america joining up with it, before it would have any chance of retrogressing northwards.. Not very likely!

Both charts are not great really and the only real difference between both of those charts is that chart 'B' has higher pressure over us but the overall pattern is still very flat and whilst you can't rule out any retrogression to Greenland, experience tells me 9 times out of 10 we get a half hearted attempt and we get a half hearted attempt of a NW'ly, sometimes they are just cold enough for snow in the NW though. The low heights over Greenland on chart 'B' means it will be difficult to get any retrogression unless some obvious pattern change occurs.

Stormyking - its the lack of cold on the charts that is a nuisence at the moment, the charts are not too bad reletively speaking but would'nt it be frustrating if we do get height rises and we get an easterly and its ends up being a half hearted attempt because Scandinavia is fairly 'mild' at the moment. The upper air temps don't reach -15hpa in most places and I see no indication of a deep PV dropping into Scandi giving us a better chance of something much colder.

Of course things can change but I'm finding it hard to see where we are going too see a cold snap that would be cold enough for lying snow for most areas.

[johnholmes]

It's quite amazing how quickly an entire mood in this thread can change! Every run from every model seems to be taken so seriously. Come on, the models will chop and change over the coming weeks.

oh so very true

[bluearmy]

as long as those aleutian ridges keep blasting away, the vortex will eventually fall. they are the one consistency from the past few days of modelling in fi. and we have plenty of evidence from winters past where they have 'done for the vortex'. reacting strongly to each run is futile. just keep watching the trend. cold runs and arctic highs in the T200/T300 timescale. unthinkable just a week ago to many of you. we now have more ens runs splitting/displacing the p/v than not beyond T300. enjoy the ride.

[Frosty.]

Colder weather is on the doorstep but being ignored for something that might happen beyond T+240 hours, absolutely typical. There will be wintry showers in some parts of the uk until thursday night and even some lying snow in parts of northern and eastern britain with cold showery weather at times but then a bit milder through fri/sat with pressure rising.

Edited January 1, 2012 by Frosty039

[Cumulonimbus Tower]

Interesting to see the NAE has the colder air undercutting the rain over Ireland on Tuesday noon. I wonder if some upland areas in the UK might have a few flurries before it clears?

[nick sussex]

Two separate clusters showing up in the ECM ensembles for De Bilt:

http://www.knmi.nl/exp/pluim/Data/PLUIM_06260_NWT.png

The operational run is the coldest right at day ten, before that the ensembles go their separate ways, you can tell by looking at the ECM ensemble maps at 168hrs which members have the best chance of bringing a colder continental feed into the UK.

For the UK as a whole member 37 gets my vote!

http://www.ecmwf.int/samples/d/inspect/catalog/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!168!pop!od!enfo!enplot!2009112700!!/

There is quite a spread of solutions regarding the placement of high pressure , still waiting for the extended ensembles to come out.

[Frosty.]

Thank you frosty you have presented this in a nice basic way . Totally agree with your own words.

Thanks sam, and the next 4 or 5 days are interesting with some polar maritime air at times bringing wintry showers but tuesday is looking very disturbed. I'm quite encouraged by some of the model output today with regard to how FI develops with some colder options.