In Depth Model Discussion, Analysis and Summaries

[johnholmes]

copied from the model thread as it will quickly get lost

It also seems to sort out in my mind why the anomaly charts are showing less consistency over the past 24 hours. The idea of more cyclonic weather and the Atlantic trying to move NE seems totally feasible. Whether it does it as far north as the post from Ian F hints at is something I am sure they and all on here will be trying to work out over the next few days.

I do so hope that everyone on the model thread will read the Met O summary as they see it at the moment. It is about as good as we will get from any source and so wonderfully free of some the phrases so liked by some posters in the model thread!

UKMO view based on 00z data:

" 3. Days 8-10 - Friday to Sunday : WEATHER: S’ern, E’ern and some central areas are most likely to continue to see a mix of bright spells and wintry showers at first. However, signs are that temperatures may start to recover a little from the SW, with an increasing chance of more unsettled conditions starting to edge N and E across parts of the UK through this period, initially the far SW most likely to be affected. This may also lead to further significant snowfall on the boundary between the two markedly different airmasses. Mostly light or moderate winds at first, but perhaps turning windier at times from the SW. Temperatures widely below normal initially with widespread frost, and icy patches, but perhaps a gradual recovery towards nearer-normal temperatures from the SW.

4. Trend for Days 10-15 : Most areas probably staying colder than normal, but with unsettled weather more likely to spread N and E at times. Most unsettled conditions probably in the S and W. This leads to a risk of snow at times, especially, but perhaps not exclusively, on hills from the Midlands N’wards.

5. Discussion : Update based on 07/00Z data: Very similar signals. Increasing spread though slightly better overall ENS agreement for an increasingly cyclonic type and a possible transition to a slightly more progressive type. This implies frontal systems pushing up against the blocking pattern over western Europe with potential for significant snowfall though details very uncertain. Longevity of any change in type is also very uncertain and at this stage the trend is left mostly unchanged."

[Pennine Ten Foot Drifts]

Thanks John, and I've just picked out a few phrases:

"may also lead to further significant snowfall on the boundary between the two markedly different airmasses"

"Temperatures widely below normal initially with widespread frost, and icy patches"

"risk of snow at times, especially, but perhaps not exclusively, on hills from the Midlands N’wards"

"with potential for significant snowfall"

What's not to like ???

[bluearmy]

Ian's input is about as close as we can get to the NOAA updates for the usa. Its a shame that this isnt freely available to those that would understand it but whilst ian is allowed to keep posting it, we are so much better informed than would normally be the case.

Long may it continue, come rain, shine, heat and freeze.

[boyblue]

Just saying hello to All, this my first time posting on this forum, although I'm a long time viewer.

It amazes me at times to see the amount of work & time so obviously put in by some members with regard to their postings.

Many thanks for helping me to get a greater understanding of the intricacies of weather forecasting.

[Gibby]

Good evening. Here's my take on the 12zs output from GFS, UKMO and ECM.

All models show a similar pattern now out to the middle of next week. The current Northerly flow backs Westerly and decreases tomorrow. The remaining showers still falling in places will die out overnight with frost in places. By Sunday a new Low pressure slides SE towards Denmark pulling a cold front slowly South over the UK on Sunday changing the relatively mild Westerly winds to a colder Northerly. Then through the early days of next week high pressure takes control over the Uk with cold and frosty conditions developing and with a North or NE fetch to the east of the UK some sleet or snow showers are likely to occur through towards midweek.

GFS then breaks the cold weather down with Low pressure ganging up towards the West of Britain with wind and unwelcome rain becoming dominant over the UK in much less cold conditions. Transient snowfall would be a feature for only Northern areas in tonight's operational run. In FI a very unsettled pattern remains with further rain and strong winds a common feature. Once more the trend for colder is shown later in the run but I don't think too much credence can be placed on this since the turnaround of recent output.

The GFS Ensembles look very uninspiring for cold lovers after the brief cold snap early next week. With Atlantic domination making way for copious rainfall temperatures look like returning close to nomal from later next week. The operational was a cold outlier in its latter stages.

The Jet Stream shows the flow moving SE towards Southern Europe for several more days before the flow weakens as a new strong surge runs from the West across the Atlantic towards the UK later next week.

UKMO for midday on Thursday shows a destabilising atmosphere as winds change the airflow to a Southerly over the UK. The day will be cold and probably quite grey for many before rain and hill snow begin to move into the UK from the SW later in the day.

ECM too shows a breakdown over next Thursday with rain and snow moving in from the SW late in the day, extending to all areas by Friday giving a transitory but appreciable snowfall for Northern and Eastern areas followed by less cold and unsettled weather with rain at times. This less cold pattern with rain from Atlantic Low pressure close to the NW of the UK lasts through to the end of the run with temperatures back up towards the seasonal normal for most.

In Summary tonight there has been a big change in upstream patterns leading to a quick breakdown to the recently predicted cold spell. There is an interim cold weather event lasting through to midweek with some snow showers for a while near the East coast. Beyond that the Atlantic bandwagon goes full steam ahead in ploughing through the cold air and pushing it well away back over Europe. In its place there looks to be a return to very unwelcome rainfall for still flood affected parts of the SW with a transient snow event as it arrives. Elsewhere too snow could be briefly troublesome before a rapid thaw brings a return to more traditional wet and windy winter weather. It really has been a big change to the chain of thinking from all the big models tonight underlined by almost total cross model support and backed by the GFS Ensembles. It really highlights with all the technological advances of weather prediction from big powerful computers they still know very little about predicting cold Winter blocking scenarios, especially when those blocks are over Northern Europe.

[J10]

Latest ski Blog now out.

[Gibby]

Good morning. Here is the report on the 00zs from GFS, UKMO,GEM and ECM for today Saturday December 8th 2012.

All models show a similar pattern between now and midweek. The weak Westerly flow over the UK will carry cloud and some light rain and drizzle into Northern Britain through the day as a Low pressure drifts slowly ESE to the North of Scotland. Southern Britain will see a dry and bright day with some sunshine and it will be somewhat less cold. Tonight and tomorrow will see the cloud over the North slip South to other areas preventing a frost for many with some rain sinking South through Scotland. Tomorrow will be a windier day as the Low slips further SE towards Denmark with a NW then North flow bringing colder and clearer conditions slowly South by Monday. The early days of next week sees High pressure build over the UK with frost and fog becoming widespread in cold weather with mostly dry sunny days save some wintry showers in the East for a brief while.

GFS then shows the Atlantic revving up later in the week with rain preceded by some snow replacing the cold conditions by Friday. The operational then takes us through the rest of the run with Low pressure up to the NW with High pressure well to the South and East of Britain with strong winds between SW and NW carrying spells of rain and showers in near normal temperatures all the way to Christmas.

The GFS Ensembles show that the operational was a milder option at times with the majorrity of the pack maintaining near average 850's after the 3-4 day cold period early next week. The weather looks like becoming unsettled with rai at times from Atlantic depressions for all with some snow innitially in places.

The Jet Stream flow shows the current North to South flow over the UK maintained over the next few days before the pattern breaks down by midweek as a strong West to East flow comes across the Atlantic at around 50 deg N making landfall near Northern France for the second half of next week.

UKMO for midnight on Friday shows a cold SE flow over the UK with low pressure out to the West and High to the NE. Disrupting Low pressure slides towards SW Britain carrying wind, rain and snow across Southern and Western areas through the day with other areas seeing the cjange in the days that follow.

GEM shows a potentially wet and stormy spell towards the end of its run with deep Low pressure to the NW with secondary features pummeling Southern areas at times with copious wind and rainfall in strong winds and near normal temperatures.

ECM shows a progressive pattern too with the cold weather swept away by Friday with strong winds and rain at times in association with deep Low pressure out to the NW with strong to gale SW winds.

In Summary the weather having turned cold for a while in the first half of next week turns back milder again later on as the Atlantic pushes back the cold block to Europe by the end of the week. It's bad news for the sodden areas of the SW this morning as renewed flooding and disrution from water could well develop should some of this morning's charts verify. With regard to cold weather the UKMO model is the only crumb of comfort this morning as it does show at least show some resistance to the inevitable in its 144hr chart this morning with a messy period of sleet and snow ahead of the milder weather waiting in the wings to affect more areas in the days after Friday. IMO I think the cold will hang on rather longer than some of the models show but I think a postponement of 34-48hrs is the more likely outcome rather than a cancellation. Time will tell in the coming days.

[johnholmes]

just posted in the model thread and copying the input from Ian F late last evening below

Posted Yesterday, 23:51

POPULAR

Just in from Ops Centre; analysis sent a few minutes ago: abstracted from detailed briefing & output summary re Tuesday-Thursday next week. It's a much improved story compared to yesterday re lessening any concern over disruptive potential, thankfully, but clearly we've some way to go between now and eventual outcome! (Sorry I can't share the varied figs cited below)-

" The ensembles seem to confirm the idea that snow showers will only affect eastern coasts and will not be especially heavy. Neither MOGREPS nor ECMWF has any signal for 5 cm or more. The 1cm signal from MOGREPS (fig 7) and ECMWF (fig both hug eastern coasts with little inland penetration..... WBFL (fig 4) of around 400m on eastern coasts may mean that (right on the coast) showers may be rain or sleet. However, the GM is underdoing the effect of overnight radiative cooling, which will depress WBFL below 200m and any showers (just inland) will be snow. With weak winter sunshine and widespread overnight frost, daytime temperatures will struggle to get above freezing, and it will be cold everywhere. UKPP max temps for Tuesday (fig 5) and Wednesday (fig 6) confirm this."

So, we'll clearly be mindful to how this influences NHS Cold Weather Alert status, but hopefully without any major snow issues (at that juncture at least!) to add to the mix. Later in the week & weekend, the spectre of flood vulnerability will again become a point of concern, plus any transient snow, but at least a few days now of dry weather for flooded areas - notably Somerset Levels - will be welcome news.

I would add the link to my post in the model thread with detail following later this morning

http://forum.netweather.tv/topic/75207-model-output-discussion-12z-runs-7th-december-onwards/page__st__480#entry2438444

best to admit my view that the Atlantic would not get through was wrong last evening when looking more closely when stone cold sober!

Edited December 8, 2012 by johnholmes

[johnholmes]

this later copy also from Ian F needs dropping in here

" 2. Days 6/7 – Thursday/Friday : WEATHER: S’ern, E’ern and some central areas are most likely to continue to see a mix of bright spells and wintry showers at first. However, signs are that temperatures may start to recover a little from the SW, with an increasing chance of more unsettled conditions starting to edge N and E across parts of the UK through this period, initially the far SW most likely to be affected. This may also lead to further significant snowfall on the boundary between the two markedly different airmasses. Mostly light or moderate winds at first, but perhaps turning windier at times from the SW. Temperatures widely below normal initially with widespread frost, and icy patches, but perhaps a gradual recovery towards nearer-normal temperatures from the SW. EXTREMES COMPARED TO CLIMATOLOGY: Generally nil.. CONFIDENCE: Moderate for change to cyclonic SW type. Low for precipitation detail (including snow). 3. Days 8-10 - Saturday to Monday : WEATHER: Unsettled in all areas with outbreaks of rain, perhaps heavy at times in the south and west. Risk of snow at first, locally heavy, although gradually becoming confined to Scottish mountains. All timings very uncertain. Temperatures near normal, although cold in the north and east at first. EXTREMES COMPARED TO CLIMATOLOGY: Nil CONFIDENCE: Moderate for cyclonic SW type. Low for all other detail.

4. Trend for Days 10-15 : Most areas probably rather cold. Unsettled weather more likely to spread N and E at times. Most unsettled conditions probably in the S and W. This leads to a risk of snow at times, especially, but perhaps not exclusively, on hills from the Midlands N’wards."

[johnholmes]

to me that last copy from UK Met is the most likely to occur.

I am puzzled though why almost everyone, professional and amateur was so misled by whichever model type we were using. What has caused, in my area, the anomaly charts to change so dramatically in 48-72 hours? The other drivers all, or most of them appeared to support the view of the cold remaining?

All very interesting and the posts from both chio and Steve M show just how frustrating we all find it.

I do believe as chio posts that the upper air is the driver not the surface although obviously everything as I have often commented is inter linked. The problem is no one has yet been able to get the links correct all the time!

What is worrying assuming the newer outputs from all the models at time intervals out to 15 days is the threat of more spells of rain for those areas already so badly affected. Let us hope the models are wrong again!

Edited December 8, 2012 by johnholmes

[johnholmes]

another post from Ian, some of it seems identical to the last one but the latter part is new

Comments from Exeter based on 00z ensembles:

2. Days 6/7 – Thursday/Friday : WEATHER: S’ern, E’ern and some central areas are most likely to continue to see a mix of bright spells and wintry showers at first. However, signs are that temperatures will start to recover a little from the SW, with an increasing chance of more unsettled conditions starting to edge N and E across parts of the UK through this period, initially the far SW most likely to be affected. This may also lead to further significant snowfall on the boundary between the two markedly different airmasses. Mostly light or moderate winds at first, but probably turning windier at times from the SW. Temperatures widely below normal initially with widespread frost, and icy patches, but probably a gradual recovery towards nearer-normal temperatures from the SW. EXTREMES COMPARED TO CLIMATOLOGY: Generally nil.. CONFIDENCE: Moderate for change of type to cyclonic SW. Low for precipitation detail (including snow).

3. Days 8-10 - Saturday to Monday : WEATHER: Unsettled and often windy (increasing risk of gales) in all areas with outbreaks of rain, perhaps heavy at times in the south and west. Risk of snow at first, locally heavy, although probably gradually becoming confined mainly to Scottish mountains. All timings very uncertain. Temperatures near normal, although cold in the north and east at first. EXTREMES COMPARED TO CLIMATOLOGY: Nil CONFIDENCE: Moderate for cyclonic SW type. Low for all other detail.

4. Trend for Days 10-15 : Most areas probably rather cold. Unsettled weather more likely to dominate with active systems likely to spread N and E at times. The most unsettled conditions probably in the S and W. This scenario still suggests a risk of snow at times, especially, but perhaps not exclusively, on higher ground from the Midlands N’wards. Also risk of heavy rain and gales.

5. Discussion : Update based on 08/00Z data. Latest ENS have maintained a strong signal for a transition from a quiet, cold/blocked type to a less cold windy cyclonic SW’ly. This appears to be a relatively quick transition too; around Thursday/Friday; but operational models like the GM have been showing quite marked run to run variations in the detailed breakdown of the blocking ridge and postage stamps are still showing quite a spread of solutions through Thursday/Friday. Thereafter in the trend period the ENS suggest the bias for mainly SW’ly winds is maintained but with an increasing spread in cyclonicity. However comments below still apply. Interestingly too around a third of EC ENS members still suggest a risk of very cold E/NE’lies at least in northern parts in the trend period.

[johnholmes]

the promised look at the 500mb charts-right or wrong as far as I can check them?

Were the 500mb charts incorrect over the past week.pdf

[bradymk]

Afternoon all,

First of all, thanks Oldmetman, great post as always and hopefully that will lift a few spirits.

Now for my amateur look today. Its been an exhausting few days model watching but the fun never stops. I see "mild" being mentioned for the next few weeks by a few people on here today but is it really going to be mild? GFS Ens all over the place at the moment and I also think that along with the GFS and ECM, are a bit too progressive with the breakdown next week. Even after the swift breakdown being shown by GEFS, although the mean for 850hPa temps will rise to around 0/-1c mark for the rest of the run

, the surface temperatures are a different story. There is a lot of scatter but the mean rises after the early week cold weather to the 6c mark but then drops slightly to 4/5c and stays very similar for the rest of the run. Now i know the scatter will affect the mean but even if we have a swift breakdown in the coming week, I can't see this "mild" "zonal" weather that a few have been on about today.

It does look wet though, especially for the west which is a big concern as conditions here are still very saturated and further rainfall is not what they want at the moment. The met office 6-15 day also reinforces that average to below is the theme after the breakdown so I think a mobile westerly theme will be the story from next weekend for a time but not mild and not cold, average to below average, rainfall highest in the West with some hill snow in the North.

Just something else out of interest, the GEM caught my eye this morning at 240. Will be interesting to see on any other future outputs whether that high ridges further north and the low to dive south eastwards. A few GEFS perturbations also showed some good charts in the latter stages with some showing northern blocking towards Greenland and some with another Scandinavian high. A long way out i know and some will say its FI etc, but there is still plenty of potential for cold in the longer term especially if we can get the MMW that GP has been eluding to.

An improvement on the GFS 12z for the breakdown if its a snowier breakdown you want and it may be Tuesday before we know exactly what may happen regarding any breakdown.

Also wanted to add the JMA 30 day that was updated yesterday. For days 9-15 it still shows strong heights to our North with low heights to our south and a strong jet through Iberia. Completely different to what the models have been showing as this chart would still show the potential for NE and E winds into week 2. Not sure about this though, looks on its own but it has been good recently.

Have a good evening,

Matthew.

Edited December 8, 2012 by bradythemole

[Gibby]

Good evening. Here is the latest review from my perspective of the 12z output from GFS, UKMO and ECM.

All models agree on the longevity of the upcoming short cold snap with similar synoptics from all models up to next Thursday. A light West to NW flow with some clear spells over the South at first tonight will give way to cloud cover later in the night to join all other areas in a breezy and slightly milder WNW flow tonight and tomorrow. Through the day though tomorrow as a Low pressure area slips SE over Europe winds turn towards the North and brings colder and clearer conditions slowly South to all areas later tomorrow. pressure is then shown to build strongly over the UK for the first half of the week with temperatures below normal with sunny crisp days but very cold nights with extensive frost and the odd wintry shower towards the extreme early in the week.

GFS then shows Low pressure sweeping in from the Atlantic pushing the cold air quickly away. In the process a short spell of snow could occur in the North before rain and strong winds push North and East to all areas to end the week. The weekend would be quite stormy in places with heavy rain in the form of bands or showers falling into areas that least need it. Through FI the pattern remains unstable and relatively mild though with some quieter frosty interludes particularly towards the end of the run when the European High pressure which lurks too far to the East throughout the run makes an attempt to push back.

The GFS Ensembles show a cold snap early this coming week before temperatures retun to near the long term mean for the rest of the run with very few members supporting the colder evolution at the end of the run that the operational run above shows. The period will be low pressure dominated especially in the North and West with rain at times.

The Jet Stream shows the flow currently moving South or SE over the UK before a weakening of the flow occurs briefly before a renewed surge comes storming across the Atlantic towards the UK in a week or so.

UKMO for midday on Saturday shows a squally and showery Westerly flow over Southern Britain while Northern Britain are likely to see further persistent rain following on from that of the previous days. Temperatures would be near normal but it will feel cold in the strength of the wind.

ECM tonight shows a broadly similar setup to UKMO at 144hrs with Low pressure out to the NW feeding the UK with showers or longer spells of rain for all. It would feel cold in the wind with some snow likely on Northern hills at times. Late in the run Low pressure remains close to or over the UK with the Continental High tantalisingly close with the threat of rather colder conditions developing soon after 240hrs as the Atlantic winds down and Northern blocking slowly develops once more.

In Summary a wet spell is to come later in the week. After the first few days of the week being cold with widespread frost only a transitory snowfall looks likely for the North and East over the hills while in the SW the charts from all models show some worrying conditions for areas in the SW once more that have not yet recovered from the last bout of flooding. Heavy rain looks to be widespread and heaviest in the SW with strong winds to boot. There are some glimmers of hope for coldies in the late stages of the ECM run I feel and the consolation of losing the Easterly is that the large Continental High remains tantalisingly close through the entire output of all models. However, any true wintry weather is looking increasingly unlikely anywhere this side of Christmas if tonight's output verifies.

[Zenarcher]

These are my thoughts on the Atlantic lows and how they are appearing different on the models,

96 hours = Both the ECM and UKMO place the lows much further West than any other model they place it to the SW of Greenland. The GFS JMA and NOGAPS all place it more to the South of Greenland and the GEM is on it's own while it places it much further East than any other,

Below is roughly where they place it,

120 hours = Despite NOGAPS and GEM going with the JMA and GFS at 96 hours we see them look more similar to the UKMO and ECM at 120 hours meanwhile JMA and GFS still agree. So most of them place the low to the South or South East of Greenland meanwhile the GFS and JMA do place it to the very far South East of Greenland.

144 hours = Here we see some more models changing over and agreeing, the ECM, UKMO and GEM show a deep low to the West of the UK this would certainly bring wet and windy weather across all of the UK. NOGAPS, GFS and JMA do show a low over the UK but a lot weaker it would still bring lots of rain and wind though.

Edited December 8, 2012 by weathermaster

[Gibby]

Good morning. Here is the morning review of the 00zs as seen through my eyes on the output from GFS, UKMO, GEM and ECM for today Sunday December 9th 2012.

All models show a NW flow over the UK turning Northerly late today as a Low slips SE down the Eastern North Sea towards Europe. Pressure builds strongly over the UK from the NW behind with High pressure encompassing the UK out until midweek. After some cloud and patchy light rain clears Southern Britain later today all areas will settle into a cold and settled spell with some wintry showers in Eastern areas tomorrow and Tuesday. With sunny spells elsewhere by day and clear skies at night frosts will me a marked feature overnight with some freezing fog patches too.

GFS then shows a SE flow deveeloping on Thursday and continuing through Friday as pressure falls from the West. The weather would stay cold with wintry showers in the NE and a band of rain preceded by snow moving slowly NE into the SW later Thursday and into Cental areas by the weekend with an appreciable snowfall possible for a time. Over the weekend the snow moves on towards Scotland where it would likely stay with some disruption possible while the South sees less cold but very unsettled conditions with rain and showers over the weekend. In FI this morning the operational shows the milder air winning out for all for a time before the block to the NE forces Low pressures to move SE into Europe with a tendency towards further rather cold and unsettled conditions with rain, sleet or snow at times to return by the end of the run. CHRISTMAS DAY on this run would show a rather cold day with rain and sleet about and a chance for some snow on the hills meaning some areas would see a white Christmas.

The GFS Ensembles show a less supportive chance of cold for Christmas with a trend to normal 850's quite early in the run in a cyclonic flow over the forecast period with rain or showers at times.

The Jet Stream forecast shows the flow tumbling SE over the UK at the moment into Europe. This part of the Jet weakens in a few days time as a strong arm pushes East out of the States across the Atlantic making landfall over France and Southern England late in the week and over next weekend.

UKMO for midnight on Saturday shows a strong High pressure over Russia with a weak link to Greenland. Low pressure from the Atlantic is disrupting as it approaches UK airspace with troughs ganging up down to the SW carrying bands of rain with some snow on the forward edge in the SW and more widely for Northern and Eastern areas through Saturday. On this run it looks like changes to milder air will be slower than recent runs especially for the North.

GEM shows a much more progressive pattern with the cold air pushed away more quickly NE out of the UK. In its plalce Low pressure to the NW brings spells of rain and showers to all before the Low weakens by day 10 as the embryonic signs of a block to the North and East sends Low pressure down into Europe later introducing colder conditions again.

ECM shows a spell of rain with snow preceding it moving staeadily NE over Friday and Saturday in a strong SE wind. By the weekend all but Scotland see less cold and rainy conditions as winds turn cyclonic South-westerly. Scotland maintains the cold and wintry theme longest before it too joins the rest of the UK in an unsettled and windy, milder spell with rain at times to end the run.

In Summary there is a little more resistance shown to the models this morning in holding the cold a while longer and permitting the chance of a wintry breakdown to affect more locations as we reach the end of the week. For areas in the South and West this period is shown as relatively shortlived while the North could see quite a bit of snow before the thaw sets in for all with rain and milder weather taking over all areas beyond next weekend. There is a tentative sign from some of the models namely GFS and GEM where the block tries to reassert authority late in there runs pulling Low pressure down into Europe and reintroducing a cold continental feed. Things remain very volatile on the model runs at the moment and I still expect to see quite a few changes run to run from model to model over the coming days until this breakdown zone has passed

[Thundery wintry showers]

At present, the GFS is showing a shortwave moving eastwards over northern Britain on Thursday- this brings some rain and sleet and introduces milder air from the SW, meaning that any frontal attack from the SW on Friday/Saturday would produce rain for all at low levels:

http://cdn.nwstatic..../96/h500slp.png

However, the ECMWF and UKMO do not have this feature and as a result the frontal attack from the S and SW would be likely to see rain turning to snow as the belt penetrates north and east.

http://cdn.nwstatic..../ecm500.096.png

The ECMWF operational run then has near-average temperatures sweeping in from a cyclonic south-westerly flow, but the UKMO keeps the cold continental air hanging on for longer over the north and north-east of Britain, so all of this is well work keeping an eye on. Meanwhile there remains the possibility of significant flooding particularly towards south-western Britain.

This morning's model outputs maintain a fair amount of northern blocking into the foreseeable future. A few days ago, I overstated the length and intensity of the upcoming cold snap (on the basis of the strong ensemble support for an east to north-easterly outbreak) but noted that in the long-term, high pressure would stay extensive to the north and probably retrogress towards Greenland, but with the caveat that the UK will end up relatively mild if we get a slow-moving trough in the eastern Atlantic. At present, it looks like this scenario will arise and any future cold snowy weather will rely upon the trough shifting from the position that it is currently shown at for the end of next week. As Gibby noted above some model runs are hinting at the possibility of the trough eventually sliding SE and re-introducing colder conditions, but the hints are quite tentative at present.

[syed2878]

entresting what ian f had to say in the swc thread latest comments from the met.

[len]

entresting what ian f had to say in the swc thread latest comments from the met.

Are we supposed to know what "the SWC thread" is......or is this just for a limited cogniscenti?

[jay1lk]

Are we supposed to know what "the SWC thread" is......or is this just for a limited cogniscenti?

south west regional thread

[johnholmes]

Hopefully Ian will start to repost into this thread rather then the other area which caused so much upset on both sides of the fence yesterday. I will be posting in here whenever there is something to add to a previous post. My last one was lengthy enough and nothing has changed on the 500mb anomaly area today nor indeed for 48 hours that would warrant another post.

[Gibby]

Good evening. Here is the evening look at the 00zs from the 12z output of GFS, UKMO and ECM for today Sunday December 9th 2012.

All models show High pressure building down over the UK from the North over the coming 72 hours. The weather will become cold and frosty with freezing fog in places overnight and wintry showers near to Eastern coasts.

GFS then shows from midweek a change to milder and unsettled conditions with periods of rain and showers preceded by a spell of snow for many Northern areas. A period of quite stormy weather will continue to affect the UK over the end of the week and the weekend with spells of heavy rain and thundery showers in a near gale WSW wind. By the start of next week things quieten down somewhat as Low pressure weakens to the NW and High pressure edges closer in towards the South with mild conditions likely here for a time. This quickly gives way to further wet and windy weather as Low pressure collapses SE into NW Europe with colder conditions returning slowly South over the UK with drier and more settled conditions. Further Low pressure then dives down across the UK from the NW to return rain and wind for all in near normal temperatures to end FI.

The GFS Ensembles tonight show a disappointing look for those after cold weather as after the next few cold days the weather becomes Low pressure dominated from the Atlantic with rain and strong winds in copious measure for the rest of the run. 850's average very near to the long term average with just a handful of members offering the usual recipe of rather colder options in FI.

The Jet Stream currently running SE over the UK currently, weakens in two or three days time as a new arm of the Jet steams across the Atlantic at around 50 deg N latitude on a direct West to East course across France and eventually further East into Europe.

UKMO shows the breakdown on Thursday as winds from the South become strong with heavy rain sweeping North and East over Britain with a spell of snow briefly in the North. Following the rain temperatures will return to normal values with sunshine and squally showers the nature of the weather as we start the weekend.

ECM tonight shows the breakdown too towards the end of the week with an intense depression sitting near the Irish Sea circa 965mbs on Friday with heavy driving rain with a brief spell of snow for the North arriving by Friday morning. The rest of the run sees the unsettled pattern continue with Low pressure out to the NW with relatively mild SW winds and rain or showers continuing unabated.

In Summary a pattern change will develop in the second half of this week. After several cold and frosty days all models show Low pressure slamming in from the West by the end of the working week bringing strong winds and heavy rain and just the fleeting spell of snow for some Northern areas briefly at the meeting point of the air masses. Thereafter, the unsettled weather persists with Low pressure close by and spells of rain or showers likely for all in temeperatures close to normal.

[Gibby]

Good morning. Here is the report on the 00z outputs from GFS, UKMO, GEM and ECM for today Monday December 10th 2012.

All models show remarkable consistency throughout their output this morning. With just small but subtle differences in synoptic patterns day to day. The High pressure area recently developed near to the Britis Isles remains dominant to the weather over the next 72 hours. The weather will be cold and settled with widespread night frosts and freezing fog patches up until Thursday with cold and sunny days. A few wintry showers will occur near to Eastern coasts over the next 48 hours with some light snow in places there.

GFS then shows a strengthening SE flow on Thursday with rain spreading quite quickly NE with some snow for a while in the North. For the remainder of the run the weather remains unsettled with spells of wind and rain mixed with a few drier, brighter and rather colder interludes. Christmas Day and Boxing Day on this run would likely be wet and windy days with the chance of snow reserved only for the higher mountains of Scotland.

The GFS Ensembles show an unsettled spell to come with copious rainfall at times for some. With 850's near or just below the long term mean most of the precipitation would be of rain but there is just enough scope for some wintry weather on the highest ground at times, chiefly in the North.

The Jet Stream shows the Southward moving flow over the UK currently giving way to a renewed arm streaming across the Atlantic towards Southern England and France by next weekend.

UKMO for midnight on Sunday shows a large High over NW Russia with Low pressure North of Scotland with an unstable Westerly flow over the UK bringing rain or showers to all areas through the weekend.

GEM shows a similar setup with Low after Low moving across the Atlantic and hitting the buffers of the large Russian High. The net result too for the UK is for wet and windy weather at times with just brief drier interludes in between with temperatures close to normal.

ECM finally completes the set with Low pressure never far away to the NW or West with rain at times for all with maybe a short drier interlude for the SE early next week. Temperatures here too would remain close to the seasonal normal at worst.

In Summary it's a very unsettled look to the UK weather later this week. After a few days of cold and frosty weather the Atlantic comes into the UK by Friday with stalling Low pressure areas remaining close by to the UK thereafter with bands of rain and showers for all with the renewed risk of flooding at times, particularly in the West. There seems little likelihood of snow of note for anyone once the unsettled spell arrives except from showers on the higher hills, moors and mountains.

[johnholmes]

no change in how the anomaly charts see things and it has been similar for 3-4 days now, deep trough over/close to the UK with a fairly strong W'ly across the Atlantic into the UK showing on the ECMWF version, NOAA similar, with GFS hinting at the flow being just north of west. 500mb heights are well north, NE or even further away.

[bluearmy]

the anomolys from naefs show something we've got used to this year - we're stuck under a mean trough throughout week 2. blocking waxes and wanes to our north - never very strong. the rising heights to our south in a weeks time retrogress into the atlantic. our trough is 'boxed in'. what is evident is the lack of any strong anomolys so there remains the opportunity for features to crop up and drive the pattern in a different direction. that could mean us ending up mild or cold. the odds favouring just below average in general. note the appetite to rebuild an aleutian ridge in the longer term and as a candaian vortex reforms, signs that it will remain split from the stronger siberian core. i wouldnt discount anything for week 2.