In Depth Model Discussion, Analysis and Summaries

[Gibby]

Good evening. Here is tonights look from my perspective of the 12z output from GFS, UKMO and ECM for tonight Tuesday January 15th 2013.

All models are fairly much in agreement for just the next couple of days tonight. High pressure over Scandinavia is pushing a ridge SW towards Southern Britain holding at bay for now Atlantic fronts and depressions to the West. The weather will be cold with severe overnight frosts, especially over snow cover in the East where freezing fog could also form overnight. By day there will be some sunny spells with temperatures near to freezing or a little above away from snow cover or freezing fog. A few further snow showers could occur near the SE coast and along channel coasts tomorrow and Thursday as winds veer more to the SE and freshen somewhat in the West.

GFS then brings in a series of disrupting troughs from the SW into Southern and Southwestern Britain with widespread disruptive snowfall over Friday and the start of the weekend. Some milder weather will infiltrate into SW areas later as winds fall light and widespread fog forms over the snowfields. Snow will move North to other areas too but may not be so heavy as further South. Through the early days of next week the cold weather returns to the far South for a time before a renewed thrust of Low pressure from the SW brings the risk of further snow and sleet to many areas, probably turning to rain later across the South. Through the whole of FI in fact the pattern remains very knife edged between cold and snowy weather or less cold and rainy conditions with the difficulty being predicting where that boundary will be as Low pressure continues to move into the South of the UK and disrupts against the cold block further North and East.

The GFS Ensembles show a rather cold couple of weeks for many. The operational is very much on the cold side of the pack for Southern locations indicating more members have the boundary between the cold and mild rather further North than the operational shows. Northern locations continue to see tight agreement between the members on the run as a whole. Precipitation is shown for all areas from the end of this week indicating Low pressure being present.

The Jet Stream shows a slack Northerly flow down over the UK for a couple more days before a strong flow surge moves out of the States, across the Atlantic to reach Europe close to France later in the week and weekend.

UKMO for the weekend shows a cold and raw start to the weekend following a very snowy day on Friday in the South and West. After the first area of snow dies out a renewed thrust of energy moves NE into the SW by Sunday but this looks like being rain in the far South and West with a thaw setting in while areas further North and East have their turn for copious snowfall causing disruption in places. By Midday on Monday Low pressure is just West of Ireland with the cold and raw SE winds restricted to Scotland by then with a very unsettled and less cold regime with rain or heavy rain showers likely for much of England and Wales.

ECM shows a complex pattern of mild vs cold throughout the latter end of its run. It too shows a snowy Friday for the South and West as a trough slides SE over the SW carrying a significant period of snow for some. This might turn to rain before dying out later in the day leaving a lot of dull and foggy weather over the hills. Through the weekend a repeat performance looks likely of Friday though the rain to snow boundary would be slightly further North as shown meaning many Southern parts of Britain would more likely see rain rather than snow. Through next week the pattern persists with further disrupting Low pressure sliding SE over Southern England and maintaining a very bleak outlook for many in the North with major disruption from blizzards should these charts come off. The far South will also run the risk of some snow at times with some transient milder interludes with rain rather than snow.

In Summary the weather couldn't be more interesting over the coming week or so and possibly beyond. There is a strong chance of major disruption over the UK from Friday onward with blizzards a distinct possibility over many parts of the UK at various times of the output. There is a growing trend tonight from both ECM and GFS of the pattern of disrupting Low pressure crossing close to Southern Britain continuing for the foreseeable future with the path and position of these depressions as they pass totally responsible for the type of weather experienced at the surface. To the North of them would be cold and strong ESE winds while to the South a lighter SW flow would bring less cold air in at times, at least to the South. A couple of 100 miles further North or South for these Low pressures could totally change the weather in any one place over the coming week or so.

[Gibby]

Good morning. Here is this mornings review of the 00z output from GFS, UKMO, GEM and ECM for today Wednesday January 16th 2013.

All models show a continuing cold output this morning. The next few days show a cold and frosty spell with some sunshine in the East with some snow showers near Eastern coasts. In the West the weather will be cloudier for much of the time and consequently less cold with some light rain at times with some hill snow. On Friday all models show an active trough moving in from the West with widespread snowfall for many Central areas through the day, turning to rain in the SW later. Many Easternmost areas may not see the snow till late in the day either.

GFS then shows the weekend being one of continued cold weather with further snow at times, especially in the North and East while the SW continue to more likely see rain and sleet rather than snow. Through next week and FI the Atlantic does win through with showers or longer spells of rain rather than snow for many in strong and gusty winds at times too with any cold weather restricted to the far North and Northeast.

The GFS Ensembles show a slow rise in average uppers over the next few weeks but for much of the time but with a large spread later in the run in the South some colder options are shown late in the run as precipitation under Low pressure remains ever present from the end of this week.

The Jet Stream shows the flow strengthening over the Atlantic towards a position South of the UK where it remains for quite a while. There are signs of it wanting to lift North through the Atlantic in a week or so.

UKMO shows the weekend as being cold and unsettled as a trough moving into the UK on Friday disrupts and slips away SE over the weekend. Snow will continue for many into Saturday leaving cold and cloudy conditions into the latter end of the weekend. As we move into next week the model shows a further surge of Low pressure move in from the SW with further snowfall in Northern Britain while Southern areas become less cold and wet at least for a time.

ECM today shows the snow of Friday dying out slowly over Saturday as the energy from the front slips away SE and decays. It would stay cold and cloudy for most areas. By Monday as per UKMO a new surge of Low pressure moves in from the SW with a further area of snow and strong winds moving NE over the UK turning to rain in the South as less cold air moves slowly North. The change is temporary with the cold air flooding back South over the following days with further cold and wintry weather for all before a UK High brings cold and frosty weather to end the run with somewhat milder SW winds in the far NW.

In Summary the UK battleground is set for Friday. Most areas will see some snow and some areas, particularly in Central districts could see a lot with drifting and major disruption for many. Through the weekend and beyond the cold continues its battle over the UK with further snowfall in places, more likely in the North and East while Southern and Western areas see less cold air with rain at times rather than snow. There is still plenty of variability between the models and I have deliberately kept the details on specifics to a minimum as the details can and will change still over the coming days.

[Gibby]

Good evening. Here is tonight's report on the 12z output from the big three namely GFS, UKMO and ECM for tonight Wednesday January 16th 2013.

All models are agreed for the next 48 hours though even at this range the specific detail differs between them. A weak front lies close to West Wales in a cold and slack pool of air over the UK over the next 24 hours. Tomorrow night sees an active frontal system moving into the West of the UK with and area of rain, readily turning to snow inland across Western areas by morning. Through the day the front decelerates as it moves East and the energy gradually slides SE late in the day. Widespread and in places heavy snowfall will occur, heaviest in Central and Western areas away from the far SW. Late in the day as the front slides away and weakens the snow will ease down and die out in most places over Saturday.

GFS then shows a quieter day or so with much of the UK under snow cover with cold conditions prevailing as a weak ridge develops briefly. By Monday further sliding Low pressure over the SW renews the risk of further rain and snowfall before towards midweek the Atlantic breaks through with rain and strong winds developing a rapid thaw of lying snow. The rest of the run shows a changeable pattern with another brief colder incursion through FI while on the whole there would be plenty of wind and rain on a milder wind flow blowing from the West.

The GFS Ensembles show the operational run was one of the milder options tonight though one can't ignore the slow trend to nearer to normal conditions as we move through Week 2. There are plenty of precipitation spikes on offer too indicating that rainfall would be commonplace as the Atlantic Lows push in and over the UK later.

The Jet Flow shows a flow weakly blowing SE over the UK. In a day or two the flow markedly strengthens as it steams across the Atlantic and crosses Europe well to the South of the UK. Eventually the flow ridges over the Atlantic and down over the UK in a week or so time.

UKMO tonight shows Low pressure filling and moving SE over France over the weekend with the legacy of Fridays snow dying out slowly over Saturday. Sunday should be a dry and cold day with a lot of cloud over the snowfields. On Monday a further area of rain and snow moves in from the SW with snow once more disruptive for some although rain is possible in the SW. Through the remaining early days of the week there will be further rain, sleet and snow in places as Low pressure close to the South of Britain fails to make inroads into the cold block over the UK.

ECM tonight shows a very wintry spell indeed with a widespread snow event on Friday subsiding away East and South over the weekend leaving cold and grey conditions for many though in any overnight clear skies some very low temperature values can be expected. By early next week a re-run of Friday seems possible as further Low pressure moves in close to the SW and on down into France by Tuesday. A bitter and strong East wind would develop on this second Low's northern flank with drifting of lying snow a major hazard should this setup verify. Through the middle of the week cold, snowy weather persists especially in the South as Low pressure is slow to move away East to the South of Britain. The end of the run shows the weather finally settling down as High pressure develops over the UK but in very cold air and countrywide snow cover some record breakingly low night time temperatures would be possible.

In Summary tonight the weather looks like staying cold through the reliable part of the output and most likely beyond too. The battleground will continue to be the UK for the next 5-7 days as successive attempts of mild air from the Atlantic try to displace the cold over the UK. The resultant copious snowfall remains a major feature of the weather with some very difficult travelling issues likely over the next week. Longer term various options are shown with GFS taking us on a milder route along with its ensembles while ECM looks like a pattern reload in the closing frame of its operational as the cold block remains to the NE, reaching across to the UK still. With pressure falling to the West the Jet is seen to be travelling South again with more disrupting troughs sliding SE over the UK likely in the days that would follow.

[Thundery wintry showers]

Copied from the main model thread:

Certainly some classic snowy synoptics showing up on tonight's model outputs with Atlantic weather systems having a real struggle making progress against a Scandinavian blocking high which is forecast to increasingly ridge across to the north of the UK. Many parts of the country are thus in with a major shot at frontal snow while the easterly component to the wind direction should bring a fair number of snow showers to the east of high ground to the north of the fronts. Chances are some areas, most likely the western half of Scotland and the far south-west, will miss out, but the majority of the country should get at least some lying snow by the end of the weekend.

As others have noted the models are increasingly placing the main frontal belts further south and west as we get nearer the time- this means that the chance of frontal snow over the north and east of England is diminishing, but this does also mean increased chance of those same areas getting a significant supply of convective snowfalls off the North Sea, while the chance of snowfalls penetrating to low ground over much of Wales and south-west England is increasing with each run. At present a belt extending from Merseyside SSE-wards to central southern England appears to be in the firing line on Friday.

There is no definite end in sight for this cold spell- the Atlantic will probably get in eventually but it looks unlikely to happen before the middle of next week now, at least away from the south-west. I think it is unwise for snow lovers to worry too much about any breakdown as we have a lot of cold and potentially snowy weather to get through before then, and the UKMO and ECMWF both keep the UK in the freezer beyond then.

[TonyH]

Severe weather guide (Midlands and Wales specific):

http://forum.netweather.tv/blog/309/entry-4546-weather-guide-severe-weather-update-thursday-17th-to-sunday-20th-january-2013/

[Gibby]

Good morning. Here is the report of the 00z outputs of GFS, UKMO, GEM and ECM for this morning Thursday January 17th 2013.

All models show a similar synopses between now and the start of next week. Through this time there are likely to be two attacks of milder air trying to move in from the SW both of which are unlikely to succeed in any major way. Today shows a freshening SE wind with an active trough approaching the UK from the West later today and tonight. Most areas will be dry today and very cold. For the most part it will be dry with a lot more cloud about than yesterday with a few light snow flurries here and there. Tomorrow will be cold and cloudy and an area of snow with rain near the coasts extends NE through the day to most areas. The snow will be heavy and disruptive for many especially in Wales and NW England. Through Saturday the trough will weaken as it slides away SE into Europe leaving a cold and raw East wind with cloudy and grey skies for most. Early next week sees a repeat performance as a new surge of mild, moist air attacks the cold block over the UK on Monday but pulls away SE again over Tuesday.

GFS then shows the midweek period as being quiet but very cold as pressure builds from the NE over the UK. Over the snowfields some very low night time temperatures are possible through the latter end of the week. The cold anticyclonic weather is then shown to last throughout the FI period today as High pressure remains over or to the North of the UK. With time the severest of the cold would slacken with a slow thaw of lying snow through the daytimes though still frosty at night.

The GFS Ensembles show a steady rise in uppers as we move through the forecast period today with the long term average being reached for many areas by the end of the run. There is some precipitation shown, particularly earlier in the run though no excessive quantities are shown once the current breakdown of the cold is shown.

The Jet Stream shows the flow strengthening from the West over the coming days and crossing Europe over France and Northern Spain. Little general change is shown thereafter through a slow retreat North later is possible.

GEM shows a slightly less cold interlude in the far South early next week behind a period of snow turning to rain. Later pressure is shown to build too with some fine and frosty conditions for several days before the pattern resets to some degree late in the run as further Low pressure disrupts again to the West in response to the cold air over the UK.

UKMO for midnight on Wednesday shows Low pressure over Brest with a cold Easterly breeze over the UK. Some rain, sleet or snow could still be expected with the rain most likely in the South.

ECM shows a cold spell continuing through the middle of next week with some snow possible here and there. It becomes drier towards the end of the week as a ridge of High pressure slips South with a sign of rather milder air moving gently in from the West late on as the High drifts away SE.

In Summary the cold spell continues on for the next week or so at least. there will be snow opportunities for tomorrow and the start of the weekend and again early next week though then the snow might affect more Northern areas while the South sees less cold weather briefly. Later on in the output a dry, very cold and quieter spell looks likely with some very cold nights before a relaxing of the cold shows it's hand later in the outputs.

[Gibby]

Good evening. Here is the report on the 12z outputs from the big three forecasting models from GFS, UKMO and ECM for tonight Thursday January 17th 2013.

All models show a continuation of the cold theme for the time being. The front currently moving into the SW has reinvigorated an old front towards the East with some snowfall here this evening. Later in the night a much more active front moves in from the SW carrying rain turning to snow across all SW areas of England and Wales by morning. The front carries on East before pivoting back South over Saturday with the potentially disruptive snowfall of tomorrow sinking away South through Saturday. A short period of rain may accompany the snow for a while later tomorrow in the far SW and near Coastal strips. after a drier day on Sunday though still very cold a new Low approaches from the West sliding SE close to or over the SW early next week. The path of this second feature would be crucial to the events in any one place with on current trajectory snow for many but with UKMO showing a more Northward path milder air will infiltrate all of Southern Britain South of the Midlands for a time should that models verify. In any event snow would move NE again over the UK with snow turning to rain later on Monday.

GFS then shows a gradual relaxing of the cold weather as we move further into the week with Atlantic winds gradually extending over all areas by the weekend with rain moving East and introducing a steady thaw. Through FI tonight the weather shows a much milder pattern with Low pressure crossing to the North of the UK with troughs sweeping East with wind and rain at times for all areas to end the old month and start the new.

The GFS Ensembles show a further week of cold and wintry weather before uppers move much closer to the long term mean as the Atlantic gains supremacy over the UK in the second half of the run.

The Jet Stream shows the flow piling out of the States and crossing the Atlantic to the South of the UK. This process looks to continue unabated with just a slow lifting of the flow North in the Atlantic in 7-8 days time.

UKMO for midday on Wednesday shows a receding Low pressure to the South of the UK with a cold ESE flow over the UK with High pressure still over NW Scandinavia. Once rain and snow clears from the South earlier in the day the likelihood is that the rest of the day would be dry and cold though NE coasts would be prone still to some heavy wintry showers.

ECM shows the cold weather continuing well into next week too with further snow chances as the pattern remains of High pressure to the Northeast and low pressure to the South and West. Later in the run the Atlantic eventually wins the day as High pressure slips SE over Europe allowing the Low pressure to the West pull milder Southerly winds in with cloud and rain into the West and North later.

In Summary the weather shows signs of becoming less cold in the longer term. In the mean time though there is plenty more cold and unsettled weather on offer with a continuing snow risk, especially early next week as further disrupting Low pressure slips SE close to or over Southern Britain. With time the High to the North shows signs of weakening with the Atlantic gradually taking a more conventional route across the UK, a process that GFS brings in much quicker than ECM.

[Gibby]

Good morning from a very snowy West Country. Here is the latest look at the 00z output from the big four forecasting models of GFS, UKMO, GEM and ECM.

All models show a continuation of the cold and unsettled weather in the short to medium term. The current weather front lying NW to SE over the SW will move a little further NE through the day before becoming disorganized later as Low pressure slips from Ireland to the South of the UK in 24 hours time. The heavy snowfall over the west Country and Wales will extend to other areas of the South and Central Britain through the day, gradually becoming less intense. Tomorrow will see a cold east flow with a continuation of heavy snow showers for all Eastern Coastal counties and some further snow flurries scattered about elsewhere. By Sunday away from the East Coast a lot of the snow will of stopped falling but all areas will stay very cold with lying snow unlikely to thaw by any great degree. By Monday a new area of rain turning to snow looks like spreading NE over Southern and Western areas again with further disruption very likely. It may turn to rain later in the day as milder air nce more attempts to infiltrate the SW for a time. Then through the middle of the week the weather looks like staying cold but less snowy with frost and freezing fog likely to be a hazard by night.

GFS then moves forwards with milder air steadily winning through towards the end of next week with spells of rain and westerly winds causing a thaw and a return to more normal conditions. In FI the changeable pattern persists with spells of rain and showers with snow at times on the hills with slightly more settled weather turning up at the end of the run.

The GFS Ensembles show another week of cold and unsettled conditions before the trend for less cold but still unsettled conditions take shape. there is a lot of spread though between members in the second half of the run but little support from members on anything as cold as currently shown.

The Jet Stream shows the flow continuing East to the South of the UK for the time being before a ridging of the flow North over the Atlantic occurs in association with the milder airflow later next week.

UKMO for midnight on Thursday shows a col area over the UK with cold and frosty conditions likely at that juncture. Later through the day a trough approaching from the SW will slowly bring cloud and snow, probably turning to rain later in the day as it moves NE over the UK.

GEM shows a continuing story of disrupting SE over the UK on occasion. Periods of rain and snow will affect all areas at times with the emphasis of the snow shifting towards the North with time with less cold air reaching the South.

ECM shows that the pattern remains locked right out to the end of next week and beyond with further risk of snowfall as Low pressures slip SE over the UK and into NW Europe. High pressure remains in close proximity to the NE maintaining the cold air over Europe. if anything at the end of the run High pressure appears to be rebuilding to the NE with a bitter flow travelling West over Europe.

In Summary in the short term little change is expected to the current cold and unsettled pattern as further Low pressure areas along the boundary of mild atlantic air disrupts and moves SE over the South of the UK. Some temporary mild incursions will affect the SW at times but overall even here cold weather will rule the day. Later on GFS shows its normal progressive nature in FI as has been by default of late while the Euros seem far more dogged in holding the cold over the UK for longer.

[Gibby]

Good evening. Here is the latest report from me on the 12z output from the big three models of GFS, UKMO and ECM for today Friday January 18th 2013.

All models continue to show a cold and unsettled spell of weather, agreed by all models up until the middle of the week. Todays snow band will weaken overnight in situ with the heaviest snowfall then reserved for NE Coastal Counties as heavy snow showers drift in off the North sea. It will stay very cold for all with widespread ice and compacted slush and snow. Through tomorrow will see a cold and raw East wind with a lot of cloud and patchy snow blowing through on the breeze now and again. On Sunday a new snow area will move up from France affecting may SE areas and potentially areas further west and North too. By Monday yet another area of snow could be thrown NE over the South while all this time the cold air aloft remains firmly locked in place.

GFS then moves towards the middle of next week with a steady change to milder and changeable weather with a thaw setting in, especially in the South. Through the remainder of the run the weather becomes very unsettled and potentially stormy for a while as intense depressions cross the Atlantic and over the British Isles with gales and heavy rain followed by wintry showers, these especially in the North. There will also be some periods of more generally colder interludes when wintry precipitation could turn up in areas further South at times.

The GFS Ensembles show a pattern that has been reflected in several runs previously with uppers on the rise over the coming week to levels close to the long term mean with time.

The Jet Stream pattern continues to blow East across the Atlantic and over Southern Europe for some time to come with the trend for the flow to lift North over the UK in a week or so time.

UKMO for the early and middle days of next week show cold wintry weather persisting with a cold pool of High pressure to the NE remaining in place while Low pressure continues to threaten Southern areas at times with further snowfall.

ECM tonight also shows a cold and unsettled theme continuing well on into next week and indeed on to the end of the week and beyond with continuing disrupting Low pressure in maintained cold air over the UK. Sleet or snow at times would continue to be a major threat for the UK, probably more likely in the North and East while the South and West continue to flirt with brief milder spells with some rain.

In Summary its the Euro's vs the Americans again tonight in the output. The American model seems in a hurry to bring milder weather over the UK as we go through next week with rain and strong winds at times thereafter, also supported for the most part from its ensembles. ECM and UKMO show the current pattern persisting throughout with much cold air locked over or in the vicinity of the UK. With Low pressure continuing to slip SE over the South of the UK and NW Europe further sleet and snow looks possible throughout next week, once more more likely in the North and East while the South and West see rain at times as milder interludes brush by but snow cannot be ruled out here either.

[Gibby]

Good morning. Here is the report on the 00z output of GFS, UKMO, GEM and ECM for today Saturday January 2013.

All models show the cold spell persisting in place out to the middle of next week though some changes are afoot between some of the models thereafter. In the meantime the broad scale pattern of High pressure to the North and lower pressure out to the West and South remains with a cold and cloudy Easterly flow over the UK for today and tomorrow. A small Low will drift North towards the Low Countries tomorrow with snow affecting the SE for a time. Monday too sees the risk of further snowfall as further troughs move up from the SW, aad disrupt then weaken over Tuesday as the majority of the energy from this as before slides away SE into Europe. Frosts and ice will continue to be widespread at night.

GFS then shows several more days of little change to this overall pattern with the cold lasting through the week before early next weekend shows the Atlantic finally breaking through with rain and a thaw setting in. Through FI today the weather becomes very unsettled and still rather chilly in places for a while before the unsettledness eases later especially in the South with some temperatures reaching normal values at least towards the end of the run.

The GFS Ensembles show the trend as before of gently rising uppers over the UK in the coming two weeks. The operational was an exaggerated example of this later in the run but shared the general trend. With plenty of rainfall spikes on offer throughout the cycle Low pressure is going to remain dominant near the UK with rainfall more commonplace with time rather than snow.

The Jet Stream shows the flow well South of the UK with us being very much on the cold side of a strong Jet. Later in the coming week the trend is for the flow to move North towards the British Isles latitude later indicating the further incursion to more Northern latitudes of Low pressure.

UKMO shows the middle of next week remaining cold and unsettled with further rain, sleet and snow at times before signs of change from the Atlantic are knocking on the door by next Friday.

GEM shows a similar trend as the rest with a trend towards less cold conditions with time with the Atlantic becoming back in control over the UK as the cold High pressure is nudged further east through Northern Europe.

ECM shows the Atlantic breaking through to right at the end of next week with a large depression near NW Britain becoming a slow moving feature with a chilly Southerly flow with milder air for a time for all. It does look though that at Day 10 trough disruption close to the West will back winds towards the SE with the Eastern half of the UK becoming rather cold again soon afterwards.

In Summary winds of change are shown this morning. There are varying degrees of success shown between the models of how the Atlantic breaks through our cold block right at the end of next week as the Jet moves slowly north. GFS takes things forward in its usual progressive fashion from then on while ECM is much slower and brings a half hearted warm up with Low pressure blocked to the NW and cold air never far away to the East. The key to our cold weather persisting is the continuing factor of Low pressure in the Med allowing the disruption of Lows to the West slipping SE and merging down there maintaining and blocking the sinking of the cold if weak High pressure zone out to the North and NE. Various options to both support and oppose the pattern to break this pattern down will likely be shown between now and midweek next week before strong conclusions of a meaningful warm up over the UK can be guaranteed.

[johnholmes]

copied from the model thread-possible upper air pattern 6-15 days down the line and ? beyond?

9-500mb and the next 6-15 days on 19 jan 13.pdf

[lorenzo]

What a difference an SSW makes...

Here are a couple of charts simply for posterity to highlight where we were and where we are now.

Very simply last fortnight in December then first fortnight in January, remarkable change, sums up the obliteration of the vortex and the impact on the NH very well.

As for MJO also posted this in Strat. thread. Potential for Phase 8 entering February.

Tendency in GWO I think shows the mid latitude Jet energy crunched by negative anomalies, need a tutorial on these charts never get them, where it goes from here who knows need a GP for that !!

[Gibby]

Good evening. is it going to stay cold or is there a change on the way. read on for tonight's look at the 12zs from GFS, UKMO and ECM for today Saturday January 19th 2013.

All models programme a continuation of the cold in the reliable time frame of 4-5 days. The current overcast and snow grain type weather will continue for a time before a disturbbance moving North over France brings snowfall into the SE tomorrow, spreading slowly north. Near Eastern coastal areas of Scotland snow showers will continue with some brighter intervals in the West. It will remain very cold everywhere. Through the early days of next week things become more complex as Low pressures and troughs all in cold air move into the South of the UK again disrupting and slipping ESE. There would be some further snowfall developing at times with nowhere immune. By the middle of the week and Thursday somewhat drier but still cold weather looks more likely as a ridge or area of slack pressure develops over the UK with a steady reducing of the amount of snowfall over the UK in continuing frosty weather.

GFS then brings the Atlantic through with ease next Friday with deep Low pressure bringing an eventual change to windy and wet conditions is temperatures much closer to average. FI tonight shows a gradual warming of uppers further so that the UK comes under rather mild amd less wet conditions at times as High pressure to the South pushes Low pressure areas further North of the UK.

The GFS Ensembles show the slow rise in uppers that many runs have shown before with good support for a change in the weather late next week. The operational was a mild outlier in the second half of the run. With rain at times shown through the run the Atlantic will be reponsable for the milder uppers.

The Jet Stream shows the flow continuing South of the UK over the coming 4-5 days before the flow moves North to the vicinity of the UK by the end of next week.

UKMO for midday on Friday shows a SW airflow over the UK with milder air spreading to most areas with only the NE seeing any cold weather by the end of Friday. On these milder winds would be a change to rain at times rather than snow with a steady thaw continuing over the whole of the UK where snow still lies.

ECM shows a breakthrough from the Atlantic too by Friday with rain for all with a thaw too for areas covered in snow. However, it looks like a very stormy period would develop as a deep Low moves into the South with heavy rain and strong winds followed by a likely return to colder weather as the Low pulls away SE in response to a strong rise of pressure over NE Europe extending towards Scandinavia later.

In Summary a change to milder weather looks on the way late next week. All models now support this theory with all areas seeing a thaw and the return of wind and rain rather than snow next weekend. It may not last long as ECM shows us a quick route back to cold in the following week.

[Thundery wintry showers]

Copied from the main model output thread with minor modifications:

I feel that a change to milder and moist weather from the south-west is likely at some stage during the second half of January, but it may well only be temporary. The breakdown shown by the ECMWF operational run and the GFS 18Z is far from convincing now- indeed the GFS 18Z has most of Scotland and northern England in cold continental air right through until the end of next weekend.

Of significance is the tonedown of the milder 850hPa temperatures. Here was the GFS 06Z projection for 12Z on Tuesday:

http://cdn.nwstatic..../h850t850eu.png

...and now tonight's 18Z:

http://cdn.nwstatic..../h850t850eu.png

Although the UKMO/ECMWF have shown some movement towards this morning's GFS runs, it seems to me that the GFS has shown more movement vice-versa. This is important because it means that, on the evidence of current runs, most inland parts of the UK should have frontal snow tomorrow night followed by snow flurries for eastern areas late on Monday and into Tuesday, with sleet/rain largely confined to the far south of England and eastern coastal counties. For the latter areas, though, a period of raw sleety weather and slowly-thawing slush and ice may be on the cards.

Another frontal system is forecast to move eastwards on Thursday followed by more fronts straddling the country on Friday. These will turn conditions more marginal for snow the further south you are, but inland areas on the northern and eastern flank of the systems have potential to see yet more snow from them.

[Gibby]

Good morning folks. The third day of lying snow here with no thaw at all as yet. Will it stay intact for much longer. Here is the regular look at the 00z outputs from GFS, UKMO, GEM and ECM for today Sunday January 20th 2013 to find out.

All models show another 4-5 days of unsettled and cold conditions with rain, sleet and snow at times as the cold pool of air continues to circulate the UK with Low pressure areas and stalling fronts slipping SE over the South of the UK and down into Europe. Widespread night frosts will persist until the end of the week.

GFS then brings a change to milder weather by the weekend, first in the South and West and slowly on to more Northern and Eastern areas as the weak and blocking High out to the NE collapses SE. A thaw would set in and snow would turn to readily in most places as winds turn SW and become strong to gale force later next weekend as a powerful depressions sweeps across close to Northern Scotland. A rather cold and squally showery West airflow follows with wintry showers and sunny intervals with some further snowfall possible on Northern and Western hills. This weather type persists for several days as the parent Low slips SE, filling as it does maintaining a chilly and showery theme. Then further Low pressure moves in from the West with rain followed by showers once more wintry on Northern hills to close out the run.

The GFS Ensembles show another rather cold week to come with snow at times before the general consensus between the members this morning is for the Atlantic to win back supremacy with Low pressure spreading rain at times across the UK in more traditional January fayre with normal uppers. There is though quite a lot of spread later in the run with a few members wanting to keep rather cold conditions going. The operational was on the milder side of the pack at times but not by much overall.

The Jet Stream forecast supports the evolution above with the flow crossing the Atlantic and Europe well South of the UK currently rising to our latitude by the end of the week with a more sine wave like motion by then indicating more mobility West to East of the pattern.

UKMO shows the Arctic ridge finally giving way on Friday and collapses the cold block SE at the start of next weekend allowing milder SW winds to take hold with a thaw and rain at times likely over next weekend although the Jet Stream remains well South in the Atlantic.

GEM is more dogmatic than the other models this morning maintaining the cold and unsettled weather right out to the end of the run, maintaining the cold block to the NE longer and eventually allowing a pressure rise over Greenland late in the run although milder air will infiltrate Southern areas later the pattern would probably evolve in allowing cold weather back to all with time probably in terms of a Northerly.

ECM finally shows a slow ingress of milder air across the UK next weekend but progress is shown to be slow as the Low pressure disruption continues but over the British Isles rather than to the SW which allows at least Southern and Western areas to become milder and wetter while Northern and Eastern areas hold on to the colder and potentially wintry conditions longer.

In Summary this morning all models support a sneaking in of the Atlantic next weekend after another cold week this week with further frost, ice and snow at times. Sneaking though is a good word as it's progress is slow and messy with a certain amount of disruption still taking place to depressions as they reach the UK as per GEM and ECM to a degree. This means in real terms that rain and milder air will bring about a thaw though conditions in the North and East will be slower to give way to this weather type. How long such a milder interlude will be with ECM dropping last nights quick return to cold. However, there is a long way to go between now and the weekend in UK Winter cold blocking patterns so don't be surprised if there aren't more swings back towards cold shown again through the week as models struggle on how to deal with the detail within the synoptics.

[johnholmes]

I honestly cannot see that any major change in pattern prediction has occurred in the past 24 hours so I would stand by my post from yesterday, less cold and blocked yes into the end of the month, not mild. Beyond early February and again nothing looks to have altered from the data I looked at yesterday morning so a return to cold blocked is the form horse in my view.

In basics then yes some are going to lose their snow cover during the next 7 days, hillier areas from the Midlands north probably holding on to it. Frosts still likely in clearer slots beyond 7 days.

[Gibby]

Good evening folks. Here's the report of tonight's 12z output from GFS, UKMO and ECM for tonight Sunday January 20th 2013.

All models continue to show a cold and unsettled pattern over the coming two or three days. With Low pressure trapped in cold uppers engulf the UK there will be various pockets of snow floating about over the UK. The NE of Britain seems at greatest risk of disruptive snowfall over the coming day or so as today's snowfall in the SE and Midlands tracks slowly North overnight and tomorrow driven on by a strong SE wind. Elsewhere are at risk from snow or sleet at times too, especially in the SW of England around Tuesday as another surge of milder air attempts to break down the block and fails as it shears away SE to France on Wednesday. Towards the end of the week the models show pressure rising over the UK with some welcome sunshine by day and a slight thaw but with very cold and frosty nights with some very low temperatures over the snowfields.

GFS then shows that by next weekend a pattern change commences as Low pressure in the Atlantic will make a more concerted attempt at dislodging the cold pool over the UK. Cloud will move in from the West with a further spell of snow likely but with a more general likelihood of it turning to rain as milder air advances slowly across the UK from the West. Thereafter and through FI details are irrelevant but the trend is shown for milder Atlantic based weather with rain and strong winds at times for all.

The GFS Ensembles show a warm up in uppers at the weekend with things maintained near average thereafter with rain at times as the Atlantic gains momentum.

The Jet Stream shows the flow maintained South of the UK or the first half of the week before the flow moves North later in the week and beyond over the Atlantic and the UK.

UKMO for midday on Saturday shows milder Atlantic SW winds having developed on Friday with milder air moving in across the UK preceded by a spell of rain and hill snow for some.

ECM shows milder air reaching the NW on Friday while England and Wales stay cold and frosty but dry by then. Over the weekend pressure falls away everywhere and a band of rain preceded by snow in places crosses the UK leading into a milder and windy spell of weather with spells of rain and showers through the week that follows.

In Summary its a full house between the models tonight in that our cold spell will be coming to an end at the end of this working week. In the meantime there are a few more snow opportunities over the next 72 hours before a rise in pressure brings several days of cold, settled weather with severe night time frosts and freezing fog patches before milder air preceded by a short spell of snow crosses the UK next weekend leading us into a more traditional Atlantic mix of showers or longer spells of rain with strong winds at times in the week that follows with temperatures well up to the seasonal normal by then.

[TonyH]

A big headache this weeks guide to the weeks weather (Wales and the Midlands):

http://forum.netweather.tv/blog/309/entry-4550-weather-guide-monday-21st-to-sunday-27th-january-2013/

[Glacier Point]

Reasonable grounds for thinking that the global synoptic dynamical model is moving towards a third cold pattern this winter (the waning of this present one being well advertised) and the last few GEFS ensemble means have leant support to this idea.

Tropical convection has been focussed in the western Pacific in the last 10 days. This has introduced anomalous westerly winds to the tropical Pacific which in turn has helped lift tendency in angular momentum towards an El Nino type pattern.

Latest TOA Triton data indicates anomalous ocean heat content centred just west of the Dateline and encroaching anomalous westerly winds on the back of the MJO. Trade winds are also decreasing, which is typical of MJO progression towards phase 7/8.

The GEFS MJO forecast has come to life in the last day or so, suggesting a strong amplitude wave to develop in phase 8.This seems reasonable on the basis of favourable conditions for convection due to increased heat avalability and cooling upper atmosphere (especially lower stratosphere).

These tropical developments are beginning to take effect in the sub-tropics. A strong +ve mountain torque has occured and tendency in angular momentum is already postive and likely to spike very positive in the coming days. Overall relative angular momentum similar to November.

The shrewd will recognise that the last uptick in relative angular momentum heralded our first pattern change and cold trough in December, by about 2 weeks lead time as positive (westerly) wind anomalies are fluxed poleward introducing anomalous mind and high latitude ridges and circumglobal troughs (Pacific and Atlantic).

Meantime, our first downwelling wave from a very strong polar stratospheric warming (and sustained reversal in zonal winds) has matured. Stratospheric time scales are extremely long, and we can expect further downwelling episodes lower down in the atmosphere for the next few weeks. Based on Baldwin'c composite of weak vortex events, the next episode of increased eddy activity is due around 28th January although the timing of this is not exact.

The temperature anomaly section shows a reasonable time scale for 'nodal' type propogation extending into February, perhaps more towards mid February. A typical tropospheric response to this would be very similar to an MJO phase 8 projection, so its interesting the atmosphere choreographed in this way.

So teleconnectively we have a reasoned case for anomalous heights to our north end January into February. The timing of this highly problematic as the models were to a degree blind-sided by the first downwelling wave, only latching onto it 2 days before the warming took place. Were this happen again, a sudden turnaround in modelling could well occur.

The last five GEFS mean height anomaly for the extended range has 'hit the target' on all five occasions to varying degrees, which is interesting in itself. Todays GFS super ensemble mean height anomaly....

Putting this together, expect further cold pattern, becoming stronger probability the further we go into February but I wouldn't be suprised to see it pop up from 28th January onwards. Winds from the NE and E the favoured scenario.

[Robbie Garrett]

GP, am I right in saying very similar teleconnections to a la November 2010? MetOffice fully aware of this it seems for colder conditions and frequency of snow events to continue into February.

However, colder weather and below average temperatures then probably come to dominate once more towards mid-month. In terms of rain and snowfall, southern parts in particular will probably start wetter than average, but trend to nearer normal by mid-month, while the north will probably see drier than average conditions for much of the period. Meanwhile, the frequency of snow events during this period may be greater than average.

Edited January 20, 2013 by Robbie Garrett

[xioni]

Great post and I hope you are right, but I think you might be underestimating the risk of tropical convection returning to the Indian Ocean in early Feb with the AAM tanking/

In fact and despite the favourable stratosphere, I think there is at least 50% chance of the MJO progressing into phases 3-4-5 by mid-Feb, which would give us another spell of ~zonal weather similar to late Dec and early Jan.

[Gibby]

Good morning folks. Here is my take on how the models shape up this morning taken from the 00zs of GFS, UKMO, GEM and ECM for today Monday January 21st 2013.

All models show the cold weather lingering on for the whole of the working week. There will be various fronts delivering the risk of snow in places early in the week, notably in the NE today and tomorrow while Southern and SW areas may join in latr tonight, tomorrow and early on Wednesday as further Low pressure and associated troughs disrupt as they move SE over the SW then down into France. By midweek pressure will be rising and the risk of snow will be subsiding as a ridge of High pressure develops over the UK for a time bringing sharp night time frosts but brighter days with some sunshine. By Friday cloud and wind will be increasing in the NW as winds turn SW with milder weather with rain reaching these areas later. England and Wales will probably hold on to the dry and cold conditions near the ridge for one more day.

GFS then shows a change over the weekend as troughs cross East over Britain, especially on Sunday in a strengthening SW flow bringing about a rapid thaw along with heavy rain followed by showers, wintry on Northern hills. From then on through the remainder of the run the weather stays windy, relatively mild and unsettled with showers or longer spells at times in strong winds. Late in the run pressure rises over Greenland and the UK turns colder again with wintry showers right at the end of FI.

The GFS Ensembles show a warming up and the end of the week to nearer to normal uppers. Later in the run uppers do trend back downwards again to levels just below the norm. There are plenty of precipitation spikes, notably at the transition to milder weather with changeable conditions shown thereafter.

The Jet Stream shows the flow continuing East across Southern Europe for a few more days before it ridges Northwards to our West to latitudes of 50-55deg North eventually crossing the UK and turning SE through NW Europe by next weekend.

UKMO for midnight on Sunday shows milder weather well established by then with a fresh SW wind, continuing thaw and rain moving in again from the West through the following day.

GEM shows a less mild scenario through the latter stages of its run with a slower transition to less cold weather, especially in the East through the weekend. Nevertheless, the pattern of a thaw and a good deal of rain with strong winds is shown with snow reserved for Northern hills in its latter stages as Low pressures cross into the UK.

ECM shows an active Atlantic trough moving East through the UK on Sunday followed by a run of long fetch SW winds bringing ever milder weather with rain at times, most heavy and prolonged in the North and West with just shorted cooler spells with showers likely at times later as cold fronts pass by.

In Summary the change to milder weather at the weekend is well and truly programmed to occur now at the weekend and before in the NW. There will be a few more days for snow to occur over the UK before pressure brings a day or two of cold and frosty weather. The Jet Stream then rides over the top of the ridge sinking it quickly away SE and bringing milder and strong SW winds and rain at times and a rapid thaw of all lying snow over the weekend. The pattern then seems set for a while of a traditional Atlantic feed of strong winds from the SW, with rain at times and some brief drier interludes of sunshine and showers.

[Catacol]

Another great summary Gibby - thanks. Wish there was a dislike button though...

[Isolated Frost]

Here is an animation about the 7 days (20 Nov-27 Nov) that built up and extended into one hell of a cold and snowy spell.

The notes regarding it (which relate to the potential NE reload) is the retrogressive motion in the mid-atlantic and subsequent stalling of the jet (before retrogression fades towards the end of the animation), and the advancing upper cold pool from the NE, acting as an extended segment of the polar vortex.

This is the type of pattern that would be preferred over the next few weeks as the MJO shifts, and the stratospheric conditions move into northern blocking territory-

watch out for these prominent signals in order for a NE reload

[Gibby]

Good evening. Here is my take on tonight's 12z output supplied by GFS, UKMO and ECM for today Monday January 21st 2013.

All models show the cold weather lasting several more days with a change at the start of the weekend to less cold and windy weather. through tonight and tomorrow a trough over the North weakens slowly with snow gradually dying down and eventually dying out altogether. In the South a quiet night seems likely before low pressure slips along the English Channel tomorrow with a mix of rain, sleet and snow a strong risk for Central Southern England and the SW later tomorrow. Through Wednesday to Friday the risk of snow subsides as a ridge of High pressure delivers a period of very frosty weather later in the week. Over the weekend all models show a breakdown as South to Southwest winds bring less cold conditions in from the West with a rapid thaw of lying snow and rain at times in strong winds.

GFS then shows next week to be increasingly mild but very unsettled with spells of rain and showers in strong SW winds in association of deep Low pressure out to the NW. Later in FI this pattern breaks as pressure builds over Greenland sending Low pressure SE over the UK and NW Europe bringing about a return of colder and more wintry potential late in the run in the wake of the depressions.

The GFS Ensembles show a strong signal for a warm up at the weekend with rain at times in association with Low pressure to the North or NW of Britain. This pattern then appears to continue then for the remainder of the run.

The Jet Stream currently running East over Southern Europe rises North towards the vicinity of the UK in a weeks time.

UKMO for noon on Sunday shows a very deep Low to the West of Scotland with a strong to gale West to Southwest airflow driving bands of rain quickly East over the UK followed by squally showers.

ECM too shows a similar pattern with Low pressure too out to the NW with a strong to gale and increasingly mild airflow over the UK next week with showers or longer spells of rain becoming more restricted towards the North and West by the end of the run as pressure rises to the SE.

In Summary the weather is set to change at the weekend. After a few more days of ice and snow the weather becomes dry and frosty for a period late in the week before a total change to relatively milder conditions with rain or showers at times affects all areas by the end of the weekend with very strong winds too.