In Depth Model Discussion, Analysis and Summaries

[Paul]

And anyway, maybe a good time to agree to disagree so this thread isn't taken off on a tangent to somewhere it doesn't really want to be?

[lorenzo]

Good to see some passionate debate happening... usual outcome from debates like this is that we all learn some more.

Looking at the Jet, Damians Law mentioned in the model thread the tendency for increase in December was a notable singularity. Wonder if GP can shed any light on the latest GWO phases and where they might be heading, each time I read the Weickmann and Berry paper it bakes my noodle, are there any NH analogs for the phases, it mentions phase 1 being transitional.

Edited December 18, 2012 by lorenzo

[johnholmes]

I think it needs saying that nothing should be ignored in meteorology, be it Stratosphere effects or anything in the Troposphere.

The longer the forecast predicted time is ahead then the more likely it needs both those in.

Shorter time scales 3-7 days possibly out to 15 days do not generally need other than the Troposphere data apart from with the longer time scale an understanding of what is/may be happening 'up top' so to speak.

[BLAST FROM THE PAST]

Looking forward to seeing some more Jan ideas on here, I can't at this stage see Jan as being as cold as has been sugggested, just like Dec really. Its going to need some big event to push it into coild category IMO.

BFTP

[Weather-history]

. Its going to need some big event to push it into coild category IMO.

BFTP

How can you make such an assessment when it is still 13 days to even the start of January?

[MR EXTREMES]

Not really beacuse the rest of the indicators this Autumn pointed towards a weaker jet- ..

If you read my post above I said the cold stratosphere is muted out the otherwise good signal........... & its a very general forecast based on back of fag packet probabilites-

S

to be honest steve i think this is a very valid point something else has muted out good signals.

and i think there was a massive cooling stage the strat went into around or mid novemeber.

but if u went back to the 80s and even 2010 the greenland heights were amazing!

the nao was record neg for a fair amount of time and the ao aswell,

so the conclusion ive come to is this period and recent weeks have show heights around scandi infact the northern hemisphere at one point was blocked all over the place!

problem is it didnt do us no favours with the vortex spawning fairly strong low heights which didnt really do us" and is still not doing us any favours right now".

now with the strat warming!!!!!!!

the only thing thats getting me worried is good outputs being shown with some incredible warming but there not coming any closer,

my worry is if warming happens to late then it will be pointless if blocking sets up in a favoured area in march.

[Bristawl Si]

now with the strat warming!!!!!!!

the only thing thats getting me worried is good outputs being shown with some incredible warming but there not coming any closer,

my worry is if warming happens to late then it will be pointless if blocking sets up in a favoured area in march.

Good point.

The model runs have flipped/flopped over the last couple of weeks showing almost every possible scenario at some point, which i feel vindicates, to some extent, my scepticism of their worth past 5 days anyway.

So why should any computer generated prediction of warming events some time in the near future be deemed any more worthwhile, valid or likely to verify....and more importantly, have much effect on the UK's maritime-influenced weather?

[Great Plum]

If I can copy what Weather History put on the strat thread - in reply to Blast - the warming is coming!

So a test period coming

1. Forecast warming, how good will the forecast be in coming to fruition [seems to be forever, t240 but that may be just misjudged perception

BFTP

Well here's 0 hour

http://nwstatic.co.u...56f810961f94de;

And here's 120 hour

http://nwstatic.co.u...56f810961f94de;

And here's 180hrs

http://nwstatic.co.u...56f810961f94de;

You can clearly see the warming even at 120hrs.

So it is definitely getting closer and not always on the edge of the horizon.

Edited by Weather-history, 46 minutes ago.

[Gibby]

Good morning folks. Here is a look at the 00z outputs of GFS, UKMO, GEM and ECM for today Wednesday December 19th 2012.

All models show a pattern of Low pressure troughs moving in from the SW to affect all areas at some point or another over the coming 4-5 days. The SW will see the most rainfall from these but other areas too could see plenty of rain as the troughs stagnate over the UK thanks to the persistent cold High pressure block out to the NE. Temperaturees will range from mild in the SW at times to rather cold in the NE where it may be cold enough for a time for some of the rain to fall as snow on higher ground. No major problems though are likely from this for most with the warmer air in association with the troughs mixing the air sufficiently to maintain rainfall. Flooding issues are more of a concern as the cumulative effects of days of rain manifest by the weekend, especially in the SW as further fronts and Low pressure swing in from off the Atlantic.

GFS then shows Christmas week with a strong Southerly flow over the UK on Christmas Eve with Low pressure close to the West with an array of troughs over the UK delivering further rain. Over Christmas Day and Boxing Day winds turn more to the SW and eventually Westerly as Low pressure migrates slowly Northeast to the North of Scotland with further rain followed by showers for all. Then up to the New Year and through FI the trend is to keep the unsettled theme going with milder air in the South as winds turn SW again with Low pressure pulling in close to the UK at the end with further heavy rain at times in basically near normal temperatures.

The GFS Ensembles show good agreement on a hike in uppers in the run up to Christmas with a fall off to normal thereafter. Rainfall is shown in abundance in all locations. There are a number of colder options later on in the usual large spread by then with the Control run notably dropping into very cold territory for a while. The operational run was very much on the warmer side of the pack in the second week.

The Jet Stream shows a continuation of the ridging and troughing motion over the coming week or so always in the vicinity of the UK or to the South.

UKMO for midnight on Christmas Day shows a comlex Low pressure area over Scotland and just to the West of the UK with a slack but unstable flow over all areas with showers or longer spells of rain scattered around in temperatures close to average.

GEM today shows a more mobile pattern over the UK with a very deep Low to the North over the UK moving away NE to be followed by another meaning the familiar pattern of windy spells with rain followed by showers remain the order of events over Christmas and up to the New Year in normal value temperatures.

ECM finally shows Christmas to be governed by a Low pressure to the West of the UK on Christmas Eve to move NE to the North of Scotland with rain and strong winds crossing East over the Christmas holiday followed by showers in the run up to the New Year. A brief ridge is shown to give a drier day on the 28th before further troughs move North and east on the 29th with yet more rain.

In Summary today the weather remains in a very volatile state with the Atlantic particularly active at this stage in time. The result of this over the Christmas and New Year period looks like very unsettled weather with copious rainfall giving rise to flooding issues at times with the continued cumulative effects of what will be by then days and days of heavy rainfall. Temperatures look like holding close to normal for most areas with little chance of a white Christmas in the highly populated areas of the UK with any chance reserved for the high ground of Scotland and the far NE of England over the next few days.

[WhiteFox]

Good point.

The model runs have flipped/flopped over the last couple of weeks showing almost every possible scenario at some point, which i feel vindicates, to some extent, my scepticism of their worth past 5 days anyway.

So why should any computer generated prediction of warming events some time in the near future be deemed any more worthwhile, valid or likely to verify....and more importantly, have much effect on the UK's maritime-influenced weather?

I'm not sure if archive charts exist for stratosphere temperatures. Anyway, would there be a tendency for warming to occur as we head towards late winter, hence why we tend to see more blocked conditions in February? I know that SSW is often heralded as the harbinger of colder conditions earlier in winter, and there seems to be some evidence that this assists in weakening the PV, but does the same not normally happen more slowly as we progress from late January through to March? More questions than answers, because I do not know!

[Bristawl Si]

I'm not sure if archive charts exist for stratosphere temperatures. Anyway, would there be a tendency for warming to occur as we head towards late winter, hence why we tend to see more blocked conditions in February? I know that SSW is often heralded as the harbinger of colder conditions earlier in winter, and there seems to be some evidence that this assists in weakening the PV, but does the same not normally happen more slowly as we progress from late January through to March? More questions than answers, because I do not know!

Haven't got a scooby - not my expertise that's for sure!

My Q was really around the realibility of computer-generated output.

[WhiteFox]

My Q was really around the realibility of computer-generated output.

I think I can answer that: The reliability tends to decrease as the time from the forecast initiation increases!

[BLAST FROM THE PAST]

How can you make such an assessment when it is still 13 days to even the start of January?

Beacuse I can? No Kev, just don't see the pattern moving quick enough combined with Dec shortcomings and my way I see nothing too great in the offing just yet.

If I can copy what Weather History put on the strat thread - in reply to Blast - the warming is coming!

So a test period coming

1. Forecast warming, how good will the forecast be in coming to fruition [seems to be forever, t240 but that may be just misjudged perception

BFTP

Well here's 0 hour

http://nwstatic.co.u...56f810961f94de;

And here's 120 hour

http://nwstatic.co.u...56f810961f94de;

And here's 180hrs

http://nwstatic.co.u...56f810961f94de;

You can clearly see the warming even at 120hrs.

So it is definitely getting closer and not always on the edge of the horizon.

Edited by Weather-history, 46 minutes ago.

Ta G Plum, like I say maybe misjudged perception

BFTP

Edited December 19, 2012 by BLAST FROM THE PAST

[LomondSnowstorm]

Haven't got a scooby - not my expertise that's for sure!

My Q was really around the realibility of computer-generated output.

Essentially the processes going on in the stratosphere are far simpler and subject to less volatility than the troposphere, so forecasts are usually pretty accurate even out into FI.

[Gibby]

Good evening. Here is the evening report on the 12z output from GFS, UKMO and ECM for today Wednesday December 19th 2012.

All models are agreed now on the pattern between now and Christmas Eve. A succession of Low pressure and associated troughs will continue to feed NE over the coming 5 days. There will be some drier and brighter interludes, the most noteworthy of these over Friday. Rainfall amounts will be large for many with flooding no doubt making the headlines again between tomorrow and Christmas as the weather remains deeply unsettled. There may be a little snow on the high ground of the far NE and a lot of snow for the mountains of Scotland as the SE flow carries some cold air in from Europe for a while. Temperatures elsewhere will remain well up to the seasonal normal but it will feel cold in the wind and rain.

GFS shows Christmas 2012 as a wet and soggy one as Low pressure remains over the UK for much of the time with heavy rain continuing to occur with frequency in the normal temperatures and winds from the West. As we approach New Year and beyond the unsettled weather persists with the heaviest of the rain transferring to more Northern areas while the South become rather mild at times.

The GFS Ensembles show a lot of precipitation over the coming two weeks, especially in the South. The temperatures though averaging near to normal on tonight's graph shield the fact that there is a lot of colder options shown with the operational very much on the milder side of the pack. In the second half of the output there is a huge spread between +6C 850's and -10C 850's indicating that the pattern is still very fluid.

The Jet Stream shows a continuation of the sine wave pattern to the flow for the next 5-7 days before the flow flattens West to East close to Southern Britain thereafter.

UKMO for midday on Christmas Day shows a green Christmas for the UK with Low pressure stretching from Norway to the Hebrides with a relatively mild and unsettled SW flow with rain or showers through the day.

ECM shows a deep Low to the North of Scotland with a colder and showery day shown following the Christmas Eve rain. There could be some snow on Northern hills and mountains from the showers with the risk of more prolonged rainfall in the South. In the days that follow something of a North/South split in temperature develops as the North stays rather cold with some wintry showers while the South stays cloudier and milder with some further rainfall creeping slowly Northwards at the end of the run.

In Summary tonight there is very little to say other than it looks like the weather is trying it's hardest to give disruption over the UK over the holiday period. Unfortunately for many it's likely to be disruption from rain rather than snow as the weather is stuck in a rut with Low after Low impacting on the UK with prolonged rainfall in temperatures close to normal for most. There will be a few drier interludes but they will be brief and fleeting and there may be some rather colder air at times in the North but away from higher hills and mountains there will be very little if any sustantial snowfall for any low lying areas of Britain in the forecast period.

[Zenarcher]

This evenings model summary and comparison using the GFS, ECM, UKMO, JMA, GEM and NOGAPS.

72 hours - Between all the models we have good cross model agreement with most things it's just really the Atlantic low or lows we have crossing over and heading towards the UK where the large differences are at this short time frame,

The UKMO, NOGAPS and JMA show a low around 980mb or 985mb crossing the Atlantic like this,

The GFS and GEM disagree and have two lows and they are much closer to the UK as well,

Then on it's own the ECM it's sort of in between, it places just one low where the GFS and GEM place it but it's just one low at a similar depth as the UKMO etc,

We have disagreements here where you wouldn't normally expect them everything else seems similar between them just the lows.

96 hours - Again all the models show a similar picture apart from the Atlantic low which is now expected to be either to the West of the UK or over the UK,

JMA, NOGAPS and GEM place a low to the West of the UK around 970mb,

Our three main models the UKMO, GFS and ECM place a low over the North West of the UK that's around a similar depth to what the other three suggest,

Whatever the outcome here the models do paint up a unsettled spell of weather.

120 hours - All the models apart from NOGAPS show something very similar here we have a weak low over the UK,

This is where things start getting interesting over Greenland and in the Northern Hemisphere we have pressure building there and we have PV pushing down the Eastern side of Greenland, of course exact details vary between the models but at this range it's expected the important thing is they all show a similar picture.

144 hours - It's Christmas day and not bad charts rolling out tonight for it, models agree on heights building into Greenland and a cold Christmas day the GFS gives minimum temperatures below 3c across much of the UK on Christmas morning. As with 120 hours and the same here there's no point getting down by any exact details shown here at this range the important thing is the models show this and are continuing to show it.

168 hours and beyond where big changes will happen - GFS does give PV a hard time here but seems to want to bring in the Atlantic weather for most of the time, ECM continues to keep the Greenland high going and makes the Atlantic weather weak, NOGAPS has high pressure over Canada and Greenland giving us a very blocked pattern and JMA keeps high pressure near Greenland and keeps the Atlantic weather away.

Overall - The models are still clearing struggling where you'd normally find them not to be, still big differences between the Atlantic lows but they all do agree on high pressure building in over Greenland at some point next week which could lead us to have a cold Northerly air come down in time for Christmas but at the moment it is good to see some consistent runs from them all now at this time range just a few days ago we never really saw anything like this but they seem to have picked up on something now that we are closer to the time.

[johnholmes]

the prediction for immediate post Christmas at 500mb from the anomaly charts today-take your pick which type would you like?

update wed 19 dec 12.pdf

[Gibby]

Good morning. Here is this mornings report on the 00zs from this morning Thursday December 20th 2012.

All models show a very wet pre Christmas spell between now and Christmas and well beyond. They all show a series of active troughs from Southern latitudes moving SW to NE over the period with Saturday and Christmas Eve the next wet days likely after today. Temperatures will range from mild in the SW to nearer to normal for NE areas with some snow on the mountains today. Some drier interludes look likely probably Friday and later on Saturday the most likely time for these.

GFS shows a wet Christmas with Low pressure over the North of the UK eventually moving ut into the North Sea veering winds towards the West then NW as the general rain gives way to a spell of cooler and more showery weather. Towards the New Year very little changes in the very unsettled pattern with further Low pressure sweeping bands of rain followed by showers over the UK from the Atlantic. Then as we move into the first week of the New Year there remains very little significant change at the surface with winds remaining for the most part between South and West with the close proximity of Low pressure staying put.

The GFS Ensembles show an interesting dip in 850's post Christmas between the members with the likelihood of colder West or NW winds for a while before uppers return to near normal as the Atlantic brings somewhat milder air back later. Throughout the run there is copious rainfall shown, especially in the South.

The Jet stream shows a continuing sine wave pattern to the flow moving West to East close to the latitude of the UK or just to the South.

UKMO for midnight on Boxing Day shows a complex belt of Low pressure stretching from Norway to the NE Atlantic witha West to NW flow bringing further showers or longer spells of rain in temperatures close to normal, though this wouldn't proclude the risk of some wintry showers on Northern hills.

GEM today shows an unsettled picture too with winds between Christmas and New Year blowing from between SW and NW with squally showers or longer spells of rain with snow on Northern hills in the showers.

ECM shows a Westerly flow with further rain at times with the heaiest maybe transferring more towards Northern Britain with some drier spells in the South but this is basic straw clutching and the overall pattern from ECM for the period between Christmas and the New Year remains wet.

In Summary there is little to say this morning other than we are in for a protracted spell of very wet conditions. Flooding is bound to be an issue in various parts of the UK from time to time with disruption to travel as well from this. Temperatures will range from mild in the SW to rather cold in the NE at first before more normal values of temperatures affect all areas later in the period. Snowfall away from Northern hills and mountains looks highly unlikely in lowland Britain anywhen in this morning's output range.

[Gibby]

Good evening. Here is the latest report on the 12z output from GFS, UKMO and ECM for tonight Thursday December 20th 2012.

All models show a continuing spell of unsettled and rainy weather all the way through Christmas and to the New Year. Details between now and Christmas are fairly clear with some further spells of heavy rain on Saturday, probably Sunday and again on Christmas Eve. The rain will be heavy and disruptive at times with the continuing risk of flooding in various areas. In between there will be some brief drier spells. Temperatures will remain well up to the seasonal average with some mild weather at times in the South while temperatures will slowly recover from the rather lower levels than normal in the NE.

GFS then takes us out of Christmas with slightly cooler weather as winds turn more towards the West and a more showery period develops though this in itself is also brief as a further slide into deep Low territory in the vicinity of the British Isles as we move towards the New Year. The rest of FI shows somewhat drier conditions in the South with winds from the SW it could become on the mild side though rain at times will continue, especially in the North, though not as heavy as recently.

The GFS Ensembles shows a very wet spell still to come with copious rainfall for many. Later in the run the Ensembles show less disruptive rainfall totals as we move towards the New year. 850's peak in the next few days before they taper off to levels much closer to the long term mean as winds turn more Westerly through Christmas and beyond.

The Jet Stream shows a continuation of the flow pumping strongly East over the Atlantic to the vicinity of the British isles as we move through Christmas week.

UKMO for midday on Boxing Day shows a ridge of High pressure crossing East over the UK with showers clearing in the East. Elsewhere will be dry and somewhat cooler than of late with new Low pressure likely to affect the UK on Thursday.

ECM shows a ridge over the UK too on Boxing Day followed by a West, backing SW strong flow developing later in the week with troughs bringing further rain east over the UK, heaviest in the NW. Towards New Year the weather looks decidedly disturbed again as Low pressure winds it's way into UK airspace once more with heavy rain and squally winds in near normal temperatures for all.

In Summary there is very little change in the output from earlier that will be felt on the surface with wind and rain frequently battering the UK for the foreseeable future. The very mild conditions at times in the South will subside somewhat as a more Westerly flow brings a drop in uppers over the UK towards the long term mean. It will make little difference to the actual weather with further Low pressure off the North Atlantic bringing rather colder rain for many towards the New Year.

[Zenarcher]

Model summary using the GFS, ECM, UKMO, GEM, NOGAPS and JMA.

48 hours Saturday - We still have the models unsure on the low that will bring very wet weather and windy conditions this weekend most agree on something like this,

For the wind if the low is deeper and the Russian high pushes in more it will be more windy across the Northern parts of the country this is what varies between the models but they all agree on windy weather. What they can agree on is for very heavy and long lasting rain over the weekend as the GFS below shows,

Saturday Rain being very widespread across the whole UK,

72 hours Sunday - All models show a low around 975mb over the North of Scotland the GEM model is the only one that doesn't and places the low way out in the Atlantic. We see the models agree on very strong winds over the far North of Scotland average wind speeds there over 55mph, They also agree on the rain staying with us through Sunday as well,

96 hours Christmas Eve - The models agree on the low from Sunday starts to weaken and with it so does the wind but rain still stays around,

120 hours Christmas Day - All models show something along the lines of high pressure to the West of Greenland and low pressure to the East of Greenland this set up would give us a cold Northerly to North Westerly wind, the GFS shows cold minimum temperatures,

As for snow it's difficult to predict that even at short range so what the models currently show will change, the ECM snowfall maps restrict it to the Scottish Highlands and the GFS gives us some wintry weather across Northern parts of the UK.

144 hours Boxing Day - All models still show high pressure to the West of Greenland and low pressure to it's East as for the UK it heads into unsettled weather with some Atlantic lows moving in.

Overall - Models are still undecided on the low expected in 48 hours time but they all agree on a unsettled picture to end the week with plenty of rain and wind for much of the time, flooding is the main concern. After this the models show the low from the weekend weakening and later through the Christmas period they show a cold N to NW wind that I expect will give us cold temperatures but for where any wintry weather may fall is tricky to say at the moment. After the Christmas period the models show the Atlantic weather move in more and giving us a unsettled spell to end the month. GP today did say in the strat thread that he still believes warming to take place around the 7th/8th of January.

[johnholmes]

I try not to do 'knee jerk' reactions but the 6-10 NOAA this evening is something coldies, cold temps and possible snow lovers should hope is reality ?

http://www.cpc.ncep....10day/500mb.php

By the 8-14 it shows the flow at 500mb back to the coldish unsettled westerly that is probably the form horse from the anomaly charts for the past 5-6 days. However, all of them, do seem to be 'trying' to support the idea floated by the 30mb Tropsophere temperature on 1 December with its rapid rise above normal that a blocked type of pattern was a distinct possibility around Christmas Day, using the rule I have of a maximum of 25 days from the onset of the warm spike. For how long I have no idea but I would think colder rather than average to mild for 3-7 days?

copied into the cold search model thread for those who do not venture into here!

Edited December 20, 2012 by johnholmes

[Chris K]

I shouldn't be posting off topic really - but thought I'd say thanks to all these really good posts continuing. It's a godsend to pop out of the, at times, chaotic general MOD thread and read these in relaxed mode.

Keep up the good work Gents

[phil nw.]

The 00z outputs continue the very mobile Atlantic modelling out to 10 days at least.

A broad westerly flow and a flat looking jet profile-lows just to our north and that Azores high dominate the Atlantic pattern.

Any deep cold pretty much bottle up around the Arctic, on this side of the Atlantic, with only brief polar maritime incursions likely- in the far north that will give some highland snow.

Many parts will see more bands of rain or showers through the the period with strong winds at times.

The GFS ens graph for London

show temperatures never far from the average.

Unfortunately not the seasonal outlook many of us probably want but the type of pattern we often see at this time of year.

[Gibby]

Good morning. Here is the morning review of the output from the 00zs of GFS, UKMO, GEM and ECM for today Friday December 21st 2012.

All models continue to show unsettled weather unabated throughout their output this morning. In the short term a drier interlude today for many Southern and Central areas will be shortlived with renewed heavy rainfall sweeping NE over these areas through tonight and other areas tomorrow. Yesterdays rain and mountain snow has yet to clear from Northern and Eastern areas but here it will become lighter through today but will reinvigorate tomorrow as the new trough pushes in. Temperatures will stay above normal in the South while the NE will still be rather chilly. Sunday and Christmas Eve continue to show very unsettled conditions with further spells of rain in strong and gusty winds continuing the flood risk nationwide.

GFS shows CHRISTMAS DAY as a rather colder day with a slacker NW flow with rain or showers for most. It will be a green Christmas for most rather than white though some wintry showers will occur on Northern high ground with snowfall above 2000 feet in the showers. BOXING DAY shows further showers, wintry on hills give way to drier conditions through the day as a ridge crosses East from the West. Then between Christmas and the New Year the weather remains very unsettled with further spells of rain and some showers, wintry on hills all in association with the passage of successive Low pressures crossing East over Northern Britain. Into the New Year and there is no change with New Years Day itself showing as the only reasonable day as a weak transient ridge passes by before further rain returns from the West by the end of the run.

The GFS Ensembles show more than anything else a very wet few weeks to come as Low pressure remains dominant over the UK. Temperatures in the South especially will fall back to normal values or a little below in the North around the Christmas period for a few days before the trend shows a rise in uppers again later in the run as Low pressure migrates slightly further North with a milder SW flow becoming popular between the members.

The Jet Stream shows a persistent undulating pattern in the vicinity of the British Isles or just to the South for the next week or so continuing to carry Low pressure after Low pressure East in the flow.

UKMO for CHRISTMAS DAY shows Low pressure just to the North of Scotland with a slack SW flow ahead of a trough just to the West of the UK. The big day itself will see showers carried NE in the flow, heaviest near SW coasts and very few in the East. The trough to the West swings East later on Christmas Day with a band of heavy rain or showers for all before BOXING DAY sees rather colder conditions with some showers, wintry on hills in the North and West before cloud approaches the far West late in the evening on Boxing Day with further rain and fresh winds on Thursday. as a new Low pushes East towards Scotland.

GEM shows CHRISTMAS DAY affected by Low pressure drifting slowly East over Southern Britain with rain at times with temperatures falling back to near normal levels in the South. BOXING DAY starts with a chilly NW flow and a few showers before cloud, wind and rain will move NE over the UK again late in the day. In the run up to the New Year the weather continues unsettled and windy with showers or longer spells of rain with temperatures rising above normal at times in the South late in the period.

ECM shows CHRISTMAS DAY with a slack Low pressure over all of Britain with rain at times in slightly colder conditions than of late. BOXING DAY looks like being rather colder in a NW flow with some showers, wintry on Northern hills. Thereafter, a very windy spell sets up with a SW gale and further rain at times, heaviest in the NW before all areas see Westerly winds and further rain at times for New Years Eve.

In Summary this is turning out to be a very disturbing wet spell for many parts of the UK, unwanted for most through the holiday period. All models show an unrelenting attack from the Atlantic with potent rainfall on the cards for all areas in occasionally, strong to gale SW or West winds. This will undoubtedly keep the weather very much in the news as the flooding issues are bound to enhance in the coming few weeks. Temperatures will fall back for a while in the South next week with some snow at times on the higher mountains of Northern England and Scotland but lowland snow looks very unlikely through the period.

[J10]

The Latest Ski Blog is out

http://forum.netweat...-december-2012/

Here is the Synoptic pattern extracted from it .

Synoptic Analysis

Starting with today's chart for a base point.

Sat 22 December -

The seemingly omnipresent Russian High is still in place (1044mb), this gives very cold weather for Russia Scandinavia and Eastern Europe, not quite so cold as you move further west. there is low pressure over Svalbard (988mb), with a surface High Pressure over Greenland (1036mb). There is High pressure over the western half of the Atlantic. Over the main part of the Atlantic there is a deep area of Low Pressure (980mb). Finally the Azores High is over Iberia and much of Southern Europe. This means a very mild flow into much of Western Europe, Due to the very mild air, this gives further very heavy rainfall for the UK. The Alps not for the first time in-between the weather systems, mild for western areas, cold further east but turning milder across the Alps.

Sun 23 December -

Since Saturday the whole pattern moves further east by around by several hundred miles. The Russian High Pressure a bit further east (1036mb) so still very cold over Russia and Scandinavia, deepening low pressure over Svalbard, with High Pressure building further over Greenland, the High Pressure block slight further east than yesterday. Still low pressure over the Atlantic, 980mb over Northern Scotland another centre 984mb over the Mid Atlantic. Not quite as unsettled over the UK, W/SW winds over the UK and Northern Mainland Europe. generally mild over the UK, very mild over much of Northern and Western Europe, including the Western Alps, while mild over Eastern Alps and generally much of Eastern Europe. The Azores High ridges into Iberia and gives some warm air here (+10 850Hpa)

Mon 24 December - The Russian High continuing to edge east, with the very cold air continuing to edge Northwards and Eastwards. Low Pressure over the UK (980mb), cool/mild here, with extremely cold Northerly winds to the North west of the UK with High Pressure over Greenland. To The South East of the UK, South West winds over much of Europe, with very mild or mild winds for most of mainland Europe including the Alps.

Tue 25 December - A continuation of the South eastward movement of the pattern. Surface High Pressure (1052mb) over Greenland, Deep low pressure over Svalbard through the UK and Scandinavia, pushes down some extremely cold air southwards. North West winds over the UK and North West Europe, cold over Northern UK, cool for much of the UK, mild over of Northern Europe. the very mild air in the far South East of the UK.

Wed 26 December - The Russian High for the first time in ages, largely out of picture. again very cold over Svalbard, but with more a zonal west to east flow further south, so the very cold air never reaching the UK. A generally flat pattern over much of Europe as well, with the Azores high in place. Very cold over Scandinavia, cold over Northern Europe, cool over much of Europe.

Towards Weekend - A bit of uncertainty at the moment, a Greenland High seems likely as does very cold unsettled air over the Svalbard areas, possibly again it looks as if the coldest air remains trapped over High latitudes.

The Current guidance is for. Low pressure over the Atlantic, with the UK on the South Eastern edge, as for much of Europe so mild SW winds with a Bartlettesque High Generally the further east you go, the colder it is, especially into Scandinavia and NW Russia.

Edited December 21, 2012 by Jackone