In Depth Model Discussion, Analysis and Summaries

[Gibby]

Good evening. Here is the report of the 12z output from GFS, UKMO and ECM for tonight Friday December 21st 2012.

All models are showing a very unsettled picture right up to and including the two main days of Christmas. Low pressure and associated troughs are moving towards SW Britain carrying rain already into Cornwall and proceeding further NE overnight to reach all areas by midday tomorrow. Some heavy and disruptive rain is likely with further flooding issues developing by tomorrow. A drier interlude is then shown to cross NE through the middle of the day turning the rain light and drizzly before a further wave brings heavy rain back again later in the day and overnight tomorrow. Sunday looks like a better day as the UK lies between weather systems before Christmas Eve shows another system pulling in from the West with yet another band of rain crossing West to East through the UK. Over Christmas Day and Boxing Day the weather is shown to turn somewhat colder as a more showery couple of days move in from the West with air cold enough for some wintry showers in the North but with some welcome respite from recent continuous rains with even a few sunny intervals in places.

GFS then takes us out of Christmas with next Thursday being another day of rather cool and bright conditions away from showers around windward coasts. Towards New Year a new deep depression wind's it's way NE to the NW of the UK with gales and rain sweeping NE over the UK, this time heaviest in the NW. A broad Westerly and rather mild flow in the South takes us over the New Year with further rain at times, though less heavy than recently. Through FI tonight the trend is for a colder snap for the far North with a few wintry showers before a return to high winds, rain and rather milder weather returns later.

The GFS Ensembles show the wet period is likely to be maintained for some while yet with things turning somewhat chillier for a while before a return to somewhat milder conditions return before the end of the period. There is little prospect of anything seriously cold within the time frame of the perturbations shown.

The Jet Stream shows a continuation of the undulating West to East flow all the way from the States, across the Atlantic and into the vicinity of the UK for the reliable future.

UKMO for midday on Thursday shows a Low pressure area exiting NE England into the North Sea with a strong to gale Westerly flow over the South. Rain would clear East followed by showers. It would feel colder than of late, especially in the North where showers could be wintry.

ECM for the same time shows a similar synopses with Low pressure over the UK, clearing East though the day taking it's wind, rain and showers with it. Towards the end of the run the charts show no abatement in rainfall for the British Isles with the UK being the target zone for further deep Low pressure and further heavy rain and showers right out to the New Year. Temperatures will never be far from normal for most.

In Summary the weather looks like staying very inclement and unsettled with bands of heavy rain interspersed by short drier interludes lasting right through from now until New Year. Some of the rain will be heavy and disruptive with flooding issues continuing over the Christmas and New Year break without doubt and it may also be coupled by strong winds too at times. Temperatures will range from very mild at times in the South to a little on the cold side in the North on occasion with some wintry showers in between the more persistent rain bands. Low lying Britain is more or less guaranteed a green or water covered land surface rather than a white Christmas this year.

[Zenarcher]

Summary of the models this evening using the GFS, ECM, UKMO, GEM, NOGAPS, JMA.

This weekend - Now that we are in the reliable time where all the models agree on we can look at this weekends unsettled weather,

First of all the wind it will be very windy across most of the UK on Saturday morning where gales are likely,

Saturday night into Sunday morning for the far North of Scotland is where it will get stormy average wind speeds there around 55mph,

The rain is the real main concern for the weekend where we will see long lasting rain continue over a widespread area for 2 days,

Saturday

Sunday

Christmas Eve - All the models show a weak low now covering much of the UK around 985mb, winds will be lighter but rain during the morning will still be a problem for England,

Christmas Day - ECM snowfall maps still restricts any snowfall to the Scottish highlands while the GFS is a bit more kinder and gives us wintry weather over Northern parts of the UK so the models still uncertain where and if we will get any wintry weather for now.

Certainly doesn't look to be a mild Christmas though as the GFS still gives us low minimum temperatures,

Boxing Day - Some large changes in the models begin here they still show high pressure to the West of Greenland and low pressure to the East but it's the Atlantic lows that are causing uncertainty, most seem to show a low around just to the West of the UK. As for the UK it does still look cold with a NW wind.

144 hours and beyond - GFS keeps the Atlantic in charge but does end up building heights up over Greenland, ECM also shows Atlantic driven weather although the lows look weaker they would still bring in wet and windy weather, towards the end of the run it breaks PV up, NOGAPS gives us a very wet and windy outlook and JMA also shows Atlantic lows move in.

Overall - Don't have much time tonight to write up anything in better detail but the models show a very wet weekend and stormy at times in the far North. For Christmas time still unsure if we will get any wintry weather but the models do show cold temperatures. After Christmas the models show the Atlantic to move in and bring more wet and windy weather to finish off the year but the ECM and GFS both break up PV and build pressure over the Northern Hemisphere.

Edited December 21, 2012 by weathermaster

[Barry Reynolds]

Changing subject, can someone tell me what the Control Run is on the GFS ensembles? Also, the 850 mbar temp ensemble 'spaghetti runs' I see now and then, is there an ECM equivalent? Thanks.

[bluearmy]

Changing subject, can someone tell me what the Control Run is on the GFS ensembles? Also, the 850 mbar temp ensemble 'spaghetti runs' I see now and then, is there an ECM equivalent? Thanks.

On meteociel, its the blue line. On the ecm de bilt, its the broken blue line. We don't have access to ecm spaghetti.

[johnholmes]

copied from the model thread

7-weekly look on fri 21 dec 12.pdf

[Barry Reynolds]

On meteociel, its the blue line. On the ecm de bilt, its the broken blue line. We don't have access to ecm spaghetti.

[Barry Reynolds]

Thanks bluearmy. But what is the Control Run, as in how does it differ from the operational and ensemble runs? It's name implies some kind of safety run.....?

[Gibby]

Good morning. Here is my report on the output of the big four, namely GFS, UKMO, GEM and ECM for today Saturday December 22nd 2012.

All models show a very unsettled period in the few days up to Christmas and the holiday period itself. There are numerous troughs and depressions swinging in from the West giving spells of rain and showers with just short drier interludes in between. It remains very mild in the South for a few more days before temperatures fall back to nearer normal values everywhere as winds turn more into the West over Christmas. There will be sufficient rain to give rise to further flooding issues almost anywhere as the ground remains saturated nationwide.

After Christmas GFS shows a very zonal pattern with Low pressure passing close by to Northern Scotland and bringing bands of rain followed by showers which in turn be followed by a drier 24 hours or so in an often strong Westerly wind. The heaviest of the rain will likely transfer to the North and West though all areas will see more than enough. Into the New Year and FI shows no real pattern change apart from a rather longer drier and colder spell in the South especially as a strong ridge moves East to the South following an equally brief cold NNW flow with wintry showers.

The GFS Ensembles show a slow decline in uppers over the two weeks after the next few days and more notably after a milder blip prior to New Year. There seems good agreement on rather colder conditions right at the end of the run with at long last a high pressure coming into play lowering temperatures and reducing rainfall. At this point the operational run became a mild outlier.

The Jet Stream shows an undulating West to east flow across the Atlantic towards the South of Britin over the coming week or so.

UKMO for midnight on Friday shows a ridge of High pressure moving away East ahead of a milder SW flow carrying rain bearing troughs NE over the UK in the day that follows.

GEM shows a very unsettled end to its run too with Low pressure well established to the North of Britain with a broad and unstable west or SW flow continuing to bring rain at times in normal temperatures in off the Atlantic.

ECM too shows this familiar pattern with the addition of strong and mild SW winds for a while with periods of rain in association with Low pressure to the North or Northwest.

In Summary there is little to say than what has been said already in that the UK is now set in a zonal train for some considerable time. Successive Low pressures will continue to feed bands of rain and showers East over the UK with some transient brighter, slightly colder and more showery spells mixed in too. Little in the way of frost, ice and snow is to be expected in the next 10 days or so with flooding continuing to be the most likely newsworthy event.

[Gibby]

Good morning. Here is the morning report on the 00z output from the big four, namely GFS, UKMO, GEM and ECM for today Sunday December 23rd 2012.

All models show the Christmas week to remain very unsettled and often windy with rain or showers at times. Today shows a respite in the rain with some sunshine in the Central swathe of the UK with continuing rain and sleet in the far NE and some light drizzly rain near the South Coast. Later today the front in the English Channel is shown to move North once more as a new wave runs NE along it bringing a return to rain and local flooding problems back to Southern Britain tonight. This will clear NE early tomorrow leaving in it's wake a West to SW flow with a further showery trough moving slowly East over the UK on Christmas Eve and Christmas Day with plenty of sometimes heavy showers in increasingly fresher and colder air with some wintry showers on far Northern hills. A NW flow is shown on Boxing Day with less showers and more in the way of sunshine. Later in Christmas week further unsettled is shown to advance in from the West with more rain at times in temperatures gradually moving upwards again as winds back more SW while becoming strong.

GFS then shows a mild and strong SW flow giving way to a cooler Westerly flow around the New Year as an active cold front moves East over the UK. Through FI the pattern starts quite zonal with further rain while later on the pattern sees a North/South split developing as High pressure moves in close to the South with dry if rather cloudy conditions developing here though still relatively mild while the far North staying mild and a little unsettled with these conditions shown to return to all areas by the end of FI.

The GFS Ensembles show nothing of interest for those looking for cold with almost a complete set of members going for a continuation of rather mild Atlantic based weather with rain at times and just brief slightly cooler spells. The operational was a milder outlier in the second half of the output.

The Jet Stream shows a continuation of the seemingly unrelenting flow across the Atlantic towards the UK with just undulating, wave like patterns drifting it somewhat North then South from day to day as disturbances pass by.

UKMO fro midnight on Saturday shows a deep depression just South of Iceland with a broad and mild SW flow affecting all areas. Rain will move NE on troughs over the UK, heaviest over the North and west with some welcome drier spells in the South and East.

GEM shows Low pressure closer in to the UK at the same time point maintaining more deeply unsettled and less mild conditions with further heavy rain and showers at times for all out until the end of its run.

ECM shows a very mobile pattern towards the end of its run with rain bands crossing East followed by showers as depressions run East just to the North of Scotland in temperatures which will stay close to normal or even a little above in the South at times.

In Summary the weather remains very unsettled with further rain at times over the coming two weeks. There are a few drier chinks of weather to come especially in the South with no cold weather likely anywhere through the period. The wettest weather may transfer to the NW later as something of a build of pressure to the South and SE carries the depressions and fronts further to the NW but this all looks rather tentative with the likely outcome seeing further substantial rainfall at times given the ground everywhere is so saturated. With high pressure down to the SE though ensures temperatures stay well up to or above normal at times.

[phil nw.]

The theme of of the 00z runs continue with the Atlantic pattern with plenty of unwanted rain in the offing over the next few days.

The modelling of the Greenland vortex and Azores high just locks the UK into the ongoing westerly pattern bringing some tropical maritime air north east and creating further bands of rain as it moves across the the country.

http://nwstatic.co.u...204f96b4c27f3d;

http://nwstatic.co.u...204f96b4c27f3d;

http://nwstatic.co.u...204f96b4c27f3d;

Looking at the mean outputs there`s no sign of any change for the next week or 10 days at least

http://modeles.meteo...-21-1-240.png?0

http://www.meteociel...1-240.GIF?23-12

with any signs of ridging in the Atlantic quickly flattened by the next approaching low.

Unfortunately not the seasonal outlook many of us were hoping for but until we see some upstream amplification in the jet profile any of the cold air to our north will have little chance of affecting the UK.

[Zenarcher]

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

Christmas Eve - Will be mainly cloudy and wet with mist or fog being wide spread as well. The wind will be mainly calm all day but a strong breeze will be over Southern England so Santa may have trouble landing at night where gusts around 40mph might catch him out. Temperatures will be cold although may reach double figures in the far South of England.

Christmas Day - Temps are expected to be below 7c for most of the UK but the SE of England may see double figure temps again. A white Christmas is looking unlikely now it will be a cloudy start with showers around and later on becoming more sunny in Western and Southern parts. Highlands may see some snow during the evening though. Wind will be mainly calm but in the evening and night gales moving in over Ireland and the Irish sea.

Boxing Day - All models show a low around 985mb just to the West of the UK, the low is expected to move in later, it will bring a heavy band of rain across the UK with heavy snow across the Scottish Highlands. It will bring gale force winds across much of the UK and severe gales over Ireland.

96 hours Thursday - The models show a low pressure sitting over the North of the UK but they all show it differently but agree on more unsettled weather. Out in the Atlantic we have 2 other lows every model has it's own idea but the ECM and UKMO show something very similar here where two lows are expected to meet like shown in the image,

Are the models finding the zonal weather easy to model? I don't think so still big differences seen at 96 hours.

120 hours Friday - ECM, UKMO and JMA show a strong low in the Atlantic around 970mb moving NE like this,

This would bring more unsettled weather to the UK.

However the GFS, GEM and NOGAPS place this low a lot further West in the Atlantic,

144 hours Saturday - GEM and GFS make things a bit messy lows and shortwaves,

The rest of the models disagree and go for something more simple and place one large low near or over Iceland,

All in all they still agree on a unsettled set up.

168 hours and beyond the changeable outlook - GFS keeps the Atlantic weather rolling in all the time. JMA brings some stormy weather over the far North of Scotland then builds up pressure in the Northern Atlantic and sends the Atlantic lows more South, NOGAPS similar to the GFS keeps Atlantic in charge and the ECM at first unsettled in the North but calms the Atlantic down then builds pressure up from the South into the new year.

Overall - Christmas should be calm although for some it will be wet at times. After Christmas the models show a unsettled period of weather to finish off the month and year. Into early January the models show either a unsettled theme continue or high pressure building in.

[Gibby]

Good evening and welcome to the evening look at the 12z output from GFS, UKMO and ECM for today Sunday December 23rd 2012.

All models show a continuation of the unsettled spell of weather in the reliable time frame tonight. Another wave depression looks like moving NE overnight amalgamating with an occlusion drifting in from the West tomorrow with further rain and showers for all in the next 24 hours following the brief drier spell today. Late in the day clearer air will move in from the West with some heavy showers at times near Western coasts. Christmas Day will see a sunshine and shower weather type in many places with lower temperatures and lighter winds on the big day itself. Some of the showers will be heavy and slow moving giving some large rainfall totals again locally. Boxing Day sees fewer showers as something of a ridge is shown to move across from the West. It will be rather chillier with temperatures near to normal. On Thursday an active front moves East with heavy rain moving West to East over the UK with a short showery spell following before winds back SW and milder air floods back NE over the UK behind a warm frontal band of rain on Friday, preceded by some snow again on the Scottish mountains.

GFS then shows next weekend as being very unsettled with Low pressure crossing East over the UK with rain and showers, heavy in places over all areas in temperatures close to normal. The unsettled theme continues into the New Year with a very zonal flow developing with a sequence of Low pressure moving into the UK delivering rain and wind, followed by spells of rather colder weather with showers falling as snow on Northern hills. It will remain very windy for much of the time.

The GFS Ensembles show a continuing unsettled Atlantic based theme with rain at times throughout as depression after depression approaches, centres over then exits to the East of the UK with undulating temperatures between very mild days and rather chilly days in always rather windy conditions. No real wintry weather is hinted at in any trend tonight.

The Jet Stream shows a continuation of the undulating pattern across the Atlantic towards the British Isles for the foreseeable future.

UKMO for midday on Saturday shows a deep depression to the NW of Britain with a strong to gale SW flow over the UK. Fronts would carry rain NE over Britain to be followed in turn by sunshine and heavy showers, especially near Southern and Western coasts. Temperatures would remain close to the seasonal average for most.

ECM shows an equally unsettled spell next weekend with strong West or SW winds bringing rain at times for most. Towards the end of it's run a brief pattern change is shown again tonight as a cut off Low down to the SW allows a High pressure cell close to the UK to bring a drier and more settled phase in 8-9 days time, though it doesn't look like lasting long beyond day 10 as pressure from the NW causes it to sink away SE into Europe over the days that follow the end of the run.

In Summary it's more of the same in the reliable time frame with rain at times with only brief drier intervals. The rain distribution may shift towards greater quantities falling in North-Western areas later. Temperatures will never be far from normal with some milder than average days in the South at times. The incidence of frost, ice, fog and snow all remain on hold tonight as this zonal train continues. ECM does offer some crumbs of comfort for a drier spell but other than allow for a few transient frosty and misty nights it doesn't look like hanging around long or setting up in any position where a more sustained cold spell could setup or evolve.

[Glacier Point]

With the modelling congretated on a persistent zonal theme for the forseable, and people extraploating out from that into March, seems like a good idea to take a look at the positioning of the global synoptics.

Total angular momentum has plumetted of late and is now running well below average thanks to sustained scrubbing of westerlies over the tropics and Asia.

The strong flat northern arm of the jet and low heights being offered by model guidance is very consistent with this type of synoptic. However, I suspect we are in a very similar place to where we were in late October and early November so the next 10-14 days should provide some interesting viewing of the models as they are likely to overdo one signal and the hit the reverse gear as they realise something's going on.

Analysis of the low points of angular momentum confirms the addage, what goes down must come up. A forward projection puts our low point in angular momentum in the next week. That suggests that there is unlikely to be any quick turnaround in the outlook before New Year.

However, with frictional torques basically saying to the atmosphere 'I'm not with you', and the emprical reasoning of a low point being reached and natural rise theresafter, I would suggest that we are heading for another large uptick in angular momentum early in the New Year. The recent rise in temperatures in the western Pacific should aid this process in lending oceanic support to the atmospheric rally.

With increasing tendency in relative angular momentum we should see a spike in the GWO towards phase 4 which teleconnects to anomalous mid latitide (Scandinavian in this case) ridges, possibly more westward in extent towards Iceland around 10th January. That's a handy date as it corresponds with the possible first rapid response to the upcoming warming of the stratosphere which in itself should alter the global synoptic and stress the U-fields allowing for increasing westerly winds and a further rise in total angular momentum further down the line.

Basically, there are times when a vortex looks like a vortex and is a vortex which is sustained. There are times when a vortex isn't a vortex but looks like one. This is one whose chirade will soon be exposed. In contrast to many a recent year, we go into the Christmas period with cold hanging on but ominous signs developing into New Year. This year quite the opposite I think.

Edited December 23, 2012 by Glacier Point

[damianslaw]

GP - a good post above, yes the vortex isn't a robust strong affair at the moment, it has fragmented and weakened but decided for the time being to hang around our neck of the woods.

As you say, we are probably at the 'lowest point' with regard to chance of cold weather occuring this winter but this low point looks relatively shortlived - and into the New Year we should be looking at a very different more favourable picture for colder conditions as the 'vortex' really shows its weaknesses, just a pity this low point has coincided with the christmas period, could have done with these synoptics a couple of weeks back..

[Gibby]

Good morning. Here is the Christmas Eve a.m. report on the 00z output from GFS, UKMO, GEM and ECM for Monday December 24th 2012.

All models show the Christmas Week as remaining very unsettled with rain at times for all areas. It is not going to be a white Christmas this year away from the highest hills and mountains of Scotland. Today sees yet another wave depression moving NE over Southern Britain enhancing rainfall and flooding issues once more. This clears away slowly East later today with showers following on behind. Christmas Day will see somewhat fresher conditions as Low pressure tracks slowly East over the UK with plenty of potentially heavy and thundery showers moving slowly East through the day. These continue into Boxing Day when a new sytem of troughs run East in the flow with yet more rain, heavy in places though with a strong wind on the back of it the front should move through more quickly followed by a return to squally showers on Thursday. A brief drier interlude is shown then as a ridge crosses East before winds freshen to a gale South-westerly at the end of the week bringing mild weather back NE to all with fronts carrying rain NE, heavy and most prolonged in the Northwest.

GFS then takes us into next weekend with a very windy spell with gales ahead of an active cold front swinging East later with a band of heavy squally rain moving West to East. A fresher spell of windy and showery weather then mves swiftly East before further Low pressure leads us into a mild and windy New Year with rain at times rushing NE at times in the flow. The rest of the run shows very mild conditions continuing with windy weather and further rain at times, especially in the North and West with colder weather bringing wintry showers on Northerly winds shown right at the end of the run.

The GFS Ensembles show a continuation of the mild and unsettled conditions with the ensemble pack averaging above the long term mean for much of the time in a long fetch SW flow and frontal rain continuing to hinder any improvement in the environmental flooding conditions. There are a few very mild members while cold ones are restricted to the odd one or two, one of which was the operational in the far reaches of FI.

The Jet Stream shows the flow continuing to pump East over the Atlantic in the vicinity of the British Isles for the foreseeable future.

UKMO for midnight on Sunday shows a deep depression to the North of Scotland and a strong Westerly flow over the UK with squally showers and sunny intervals following a previous band of rain East with the heaviest showers in the West.

GEM shows a very turbulent spell of weather over the New Year with gales adding to the rain problems of recently as trough after trough swings their way quickly across the UK in the flow delivering rain followed by squally showers although conditions do improve a bit in the South later as High pressure moves over France.

ECM shows a very turbulent spell too over the New Year with gales and periods of rain interspersed by showers the weather pattern likely, with it too showing slightly improved conditions for the South by Day 10. though still windy if mild.

In Summary the pattern remains locked in a totally Atlantic dominated set of outputs this morning. There will be further rainfall events for all regions over the coming few weeks not helping the flooding risk at all and next weekend sees the addition of severe gales in places as very deep Low pressure winds up close to NW scotland next weekend. The far outlook does show a long fetch SW flow possible in association with a build of pressure over France which would serve to direct the worst of the rain towards the NW while at the same time bring very mild temperatures to the lee of high ground in the East. For cold weather fans I can offer absolutely nothing of cheer today.

[Zenarcher]

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

Christmas Day:

Scotland: Mainly cloudy with showers around, heavy rain around Southern parts in the morning. Drying up in the evening. Wind calm for most of the day but gales will develop over the West and South in the evening. Lowest temps ranging from 0c to 4c.

England: Either clear and sunny or partly cloudy and sunny also dry but the North of England looks cloudy with showers and mist. A strong breeze will be widespread across England with gale force winds in the Channel and Southern coasts. Lowest temps ranging from 2c to 5c.

Wales: Cloudy with showers to begin with but becoming sunny in the afternoon and staying clear later. Strong breeze for most of the day and coastal area's will see gales in the evening. Lowest temps ranging from 3c to 6c.

Ireland: Cloudy with showers to start with but becoming sunny in the afternoon but returning to cloudy in the evening and night. Gale force winds for much of the day getting stronger as the day goes on. Lowest temps ranging from 2c to 5c.

Boxing Day: Cloudy for most and showers affecting almost all parts. Gale force winds all over the UK apart from Eastern Scotland. Temps still cold ranging from 0c to 4c for inland area's in the morning and at night.

72 hours 27th December: The models agree on a weak low over the UK this will bring further wet and cloudy weather to many places, the GFS and some others show very strong winds across Southern Ireland and England like this,

96 hours 28th December: All models apart from GEM show a deep low to the West of the UK it is travelling North East, some models like the ECM showed this yesterday so good consistency from them, this low brings very wet and windy weather over Western area's.

The above image is what most models show and agree on but GEM goes for a low that is weaker, it would still bring unsettled weather although not as severe,

120 hours 29th December: All models apart from NOGAPS place a deep low over Iceland some models have it down to 945mb although most place it around 955mb, Also yes the GEM model does place a deep low around here as well despite not being similar at 96 hours.

NOGAPS did make the low in the Atlantic at 72 hours be a lot further West than what any other model goes for and now it's beginning to show what difference that makes, it places the low just to the West of the UK, this would bring severe gales across pretty much all of the UK,

144 hours 30th December: All models apart from GEM show a low pressure system to the North of the UK working it's way down South but at the same time it weakens this would bring further strong winds and rain.

GEM for the second time remains on it's own and places just a weak low to our North again this would be less unsettled,

168 hours and into early January: NOGAPS keeps a unsettled theme going, GFS like yesterday showed the Atlantic weather weakening and high pressure to our South tries it's best to rise up but the very North of the Atlantic stays too strong for anything to get set up. JMA shows PV weaken at least to our North and shows high pressure also trying to build in from the South and the ECM also does the same thing and tries to build pressure up from our South.

Overall: All the models show a very unsettled theme ending the end of the year, expect more wet and windy weather for the time being. NOGAPS has struggled over the last few days it seems to always be behind on things at the moment and the GEM run today has little support apart from them two the rest have good decent agreement and the ECM and UKMO have shown consistent runs over the past 24 hours. In the longer term the models aren't too sure what to do yet just a few days ago they were showing a unsettled theme continue into the new year but now they seem to have picked up on that high pressure wants to rise from the South the only question is will the Atlantic let it? Time will for now.

I won't be doing any more updates until later in the week so everyone have a Merry Christmas!

Edited December 24, 2012 by weathermaster

[Gibby]

Good evening and a VERY MERRY CHRISTMAS TO YOU all. The reports will continue through the holiday in a shortened form which in view of the continuing unspectacular weather for most will probably be appropriate. Thanks for all the support you give me over the year with supplying these reports. Anyway for those who can bear it here is tonight's look at the 12zs from GFS, UKMO and ECM for Christmas Eve Monday December 24th 2012.

All models show a continuation of the very unsettled weather persisting through the Christmas period and on up to the New Year. Tomorrow (Christmas Day) will be showery with some heavy showers in places migrating East through the day. Boxing Day sees more fronts rushing East across the UK with rain followed by a return to showers again for Thursday. By Friday a strong and mild SW flow carries rain NE through the UK with a drier and very mild interlude possible for the SE at that time. A cold front then runs East over the Uk over the weekend before a rinse and repeat looks likely as we enter the New Year.

GFS then shows a very mobile pattern with fronts followed by ridges bringing rain followed by drier interludes across the UK in quite respectable temperatures for the time of year. it is likely that due to the fast moving nature of the rain belts less disruption is likely to occur as time goes on.

The GFS Ensembles show a continuation of the generally mild conditions with rain at times in blustery winds mostly from the SW or West. Despite continuing wet at times there will probably less copious rainfall totals as we enter the New year especially in the South as pressure builds over Southern Europe.

UKMO for midday on Sunday shows Low pressure North of Scotland with a strong Westerly flow over the UK bringing squally showers and bright intervals for all.

ECM shows the same with a further surge of Low pressure and wind and rain to greet the New Year though pressure is building to the South directing the worst of the rain further North at the end of the run while keeping things quite mild everywhere.

In Summary a typically mild and unsettled Christmas and New year is shown from all the models tonight. there is no sign of anything remotely wintry for cold weather lovers with, if anything the chance of even milder conditions developing into the New Year if High pressure is allowed to develop to the South of the UK as shown by some of the output.

And on that note...*****HAPPY CHRISTMAS TO YOU ALL*****

[Gibby]

Good morning. Happy Christmas to you all. Here is the Christmas Day look at the outputs from GFS, UKMO and ECM.

All models continue the very unsettled theme going way out into FI again this morning. Today will see a trough cross East through the day carrying some heavy showers across. These will die back towards Western coasts later as winds veer more towards the WNW. A chillier night tonight will be replaced by a spell of wind and rain through Boxing Day with gales in places for a time. The far North will stay rather colder with perhaps rain falling as snow on the hills. Showery weather will return through Thursday with further wintry showers on the hills of the North for a time before winds back SW and increase to severe gale force in the North and West with milder air with rain sweeping NE through Friday. Saturday sees a squally cold front race East across the UK in the strong flow returning showery weather to most areas with lower temperatures again with some snow possible in the showers on Northern hills.

GFS then takes us through New Years week with Low pressure continuing to dominate the weather with further spells of rain followed by showers in relatively mild and strong Westerly winds. Later in the week High pressure ridges up from the South with a quieter spell perhaps with a touch of overnight frost, especially in the South though weaker troughs than of late will still deliver some rain at times, especially in the North. By the second half of FI the pressure has become very high to the South with a North/South split developing with the North seeing most rain from continuing strong winds and troughs crossing over while the South sees lengthy dry spells with just occasional rain from weakening troughs as they move SE. Temperatures will remain near normal or above at times in the South.

The GFS Ensembles show a continuation of the zonal type spell of weather with temperatures at worst likely to stay well up to normal values for the time of year. Rainfall totals should reduce in the South with time as High pressure to the South steers the worst of the rain towards the NW. The operational was on the milder side of the pack towards the second half of the run.

The Jet Stream continues to flow West to East over the Atlantic towards the UK in peaks and troughs as various depressions pass by before a strong ridging of the flow in the Atlantic is shown in a week or so time.

UKMO for midnight on New Years Eve shows Low pressure to the SE of Iceland with a strong and broad SW flow across the UK with showers or longer spells of rain likely for all, chiefly in the North and West with near to normal temperatures.

GEM shows a further spell of wind and rain as another Low passes to the North on day 6 followed by a strong rise of pressure from the South thereafter drying things up for Southern areas at least with the North and West still more cloudy and mild with rain and drizzle at times.

ECM for day 6 shows an almost identical pattern to GEM with the depression around the New Year the last in the series before some respite develops from the South in terms of a strong build of pressure over France and Iberia with a warm front tracking NE over Northern and Western areas with rain and drizzle here.

In Summary the weather looks like staying unsettled and wet for some time yet as further Low pressures cross East close to or North of the UK maintaining the proximity of spells of rain and gales later over the UK. There is a growing trend for a pressure build from the South after the New Year to at least suppress the rainfall for many later away from the NW. There is no indication of anything remotely wintry still for many apart from the usual Northern higher elevations who may see a little snow in the showery interludes in polar maritime air between the rain bands over the coming week.

[Gibby]

Good evening. Hope you all have had a good day and here is the report on the 12zs from the big three tonight.

All models continue with the pattern as before in the period up to the New Year. The current showery flow will last overnight with some heavy showers in the West. Through Boxing Day a band of cloud and rain will sweep East over the UK before clearing again later. Winds will blow from the SW or West across the UK in temperatures close to normal. Thursday sees a mix of sunshine and showers in a fresh West wind with some wintry showers over Northern hills. On Friday and Saturday a couple of extremely windy days seems likely due to a very deep depression out to the NW of Britain pushing gale SW winds over the UK along with some very wet weather for all at some point. By the end of Saturday a squally cold front brings colder and more showery conditions back over the Uk with further wintry showers over Northern hills again. Towards New Year a further band of rain moves across the UK on further strong SW winds with New Years Day currently looking rather windy and showery as a cold front clears East.

GFS then shows High pressure building from the South as we move further into 2013 with drier and more settled weather in the South with less rain for the North too. Late in FI the High drifts a little towards the East still bearing influence on the weather for the East while the West see Southerly winds freshen with some rain.

The GFS Ensembles data shows a continuing unsettled pattern for the next week or so before High pressure to the South looks like trending things mild and rather less wet as we move into the second week.

The Jet Stream continues to undulate across the Atlantic to the UK unrelenting for the coming week or so.

UKMO for midday on Monday shows Low pressure to the North of Scotland with a broad SW flow over the UK with a trough out to the West approaching the West of the UK with rain later in the day.

ECM tonight shows an unsettled end to the year and start to the New Year with further rain and showers before High pressure builds from the South later next week though with the High in the position shown ther would be a lot of cloud moving round the High off the atlantic with weak fronts embedded bringing drizzly rain in places. It will generally be mild as we move into the New Year too.

In Summary there is another week of unsettled and rather windy weather with some heavy rain on occasion for all and some wintry showers on hills in the North in the brief showery spells. It then looks like becoming rather drier though still mild later next week as High pressure is shown to build from the South.

[Gibby]

Good morning. Here is my take on the 00zs from the output of GFS, UKMO, GEM and ECM for today Boxing Day Wednesday December 26th 2012.

All models are fairly agreed on the period which takes us through the beginning of the next year. Today will see another active trough running East over the UK with a spell of heavy rain for Southern areas through the day. Further North some scattered showers are likely which will turn wintry in the far North as colder air digs in. Tonight the rain will clear away East from the south with a showery day following tomorrow in a brisk westerly wind. Over Friday and Saturday deep Low pressure is seen to develop up to the NW with a gale or severe gale force SW wind developing for many along with further spells of potentially heavy rain. A cold front crosses East later on Saturday bringing a return to showery conditions for the seond half of the weekend before a further Low pressure and squally winds push Eastwards over the Uk to take us through the New Years Eve period and New Years day.

GFS then shows a gradual trend for the weather to improve from the South at least for a while in the FI period. How long it lasts is open for debate because on this morning's output after several pleasantly dry and mild days for the South and East before renewed Atlantic Low pressure bring a return to wind and rain later in the run.

The GFS Ensembles show a continuation of temperatures near to or a little above normal everywhere with much unity between the members of the run. There will be rain at times for all but with a reduction in quantities in the South at least in week 2. There is still no sign of any significant wintry spell within the next two week period from what is shown here this morning.

The Jet Stream shows a peaking and troughing over the Atlantic towards the British Isles over the coming week or so ridging more strongly over the Atlantic by the end of next week.

UKMO for midnight on New Years Day shows Low pressure to the North of Scotland with a trough crossing East through the day delivering a spell of rain followed by squally showers from the West later. Temperatures will be close to normal.

GEM shows an unsettled start to the New Year with rather windy and damp conditions before a strong High is shown to move slowly up from the South bringing a welcome change to dry if rather cloudy conditions over the UK later with temperatures still quite close to normal.

ECM is less inclined to bring the High pressure North keeping it further South over Iberia and Southern France with a strong Westerly wind to continue with some rain at times in the North with the likelihood of ths extending it back South to other areas later in a continuing rather mild flow.

In Summary today the models are showing some good consistency between themselves today as the pattern as before is shown with the wet and windy weather continuing into the New Year before a change to somewhat drier conditions arrive from the South later next week. The extent and longevity of this improvement is a bit confrontational between the models but the likelihood of a drier spell in the South looks strong. Temperatures throughout look reasonable though Northern areas could see a colder few days early in the period perhaps with a little snow before the milder air extends to all later on Friday and beyond.

[lorenzo]

Interesting difference on the MJO phases UKMO more progressive than ECM, moving things round toward the more favourable set ups earlier. ECM follows a similar path to it's larger ensemble run but is slower, the GFS almost at a standstill in Indian Ocean phases.

UKMO ECM GFS

Main point here is all 3 very different on the evolution of week 2 in January and would not discount the UKMO solution at all have seen it take the lead on a couple of occasions on these plots, still some cross model agreement required from here.

Analogs display the variation on the theme, 3 GFS and 4 ECM for Jan especially pertinent concerning the elongated euro high.

3/4/6

UKMO encouraging as this places things ready to move to phase 7 by 8th Jan where the ECM ensemble run had this positioned out at final third of Jan. An interesting watch considering the differences within. Also the toss up between MJO and strat will be a good watch.

Phase 1 and 2 of MJO combined with Strat losing cold and blocking is a mouthwatering combination if it came off in favour of cold for UK could be special.

[Glacier Point]

Would add on to that analysis that we've seen a strong + global mountain torque in addition to strongly positive frictional torques which have added significant relative increase of westerly tendency to the atmosphere. Tendency in relative angular momentum is very positve.

http://www.esrl.noaa...ltaum.90day.gif

http://www.esrl.noaa...ltauf.90day.gif

http://www.esrl.noaa...d.sig.90day.gif

That's a solid signal for amplification in the 10 day timeframe and anomalous mid latitude ridges.

Worth keeping an eye on modelling of this high as it may well stick around long enough to work off the initial wave response in the atmosphere from the upper warming and adopt a higher latitude feature. In any event, that tells us that the atmosphere is attempting to add westerlies and repeat late October into November. There will likely be a second pulse of westerlies coming in 10 days which will also amplify the flow and the cumulative impact should draw the GWO into phase 5-6-7-8 orbit, maybe the third pulse in mid to late Jan the signal for higher amplitude GWO phases 5-6-7-8.

Edited December 26, 2012 by Glacier Point

[Gibby]

Good morning. Here is the look at the 00z output from GFS, UKMO, GEM and ECM for today Thursday December 27th 2012.

All models are in agreement this morning with just small differences between them. In the short term they all show further unsettled conditions for the coming 4-5 days as Low pressure remains the dominant feature to the North or Northwest of the UK continuing to bring wet and windy weather on troughs moving quicly NE or East over all areas in the strong to gale SW or West winds, especially windy weather for Friday and Saturday. The current cold weather over the Northern half of the UK with a little snow will give way to the mild conditions of further South tomorrow and up to the New Year with all areas seeing rather mild conditions at times mixed with spells of nearer to normal temperatures in any showery interludes when showers could fall rather wintry in the North. It's hereafter the New Year period when a pattern change finally develops.

GFS shows High pressure building from the South in association with a ridge from its centre moving into the UK behind the last depression in the series early next week. The weather will become dry and quiet with a lot of cloud drifting over the top of the High pressure and down over the UK. A slight frost may occur in places though as the ridge arrives. The High pressure stays over or close to the South of the UK throughout FI with some occasional rain in the North, possibly shown to move further South by the end of the run. Temperatures would remain close to average or a little above in the North for the most part.

The GFS Ensembles show a sustained spell of mild weather as the High to the South becomes dominant with warm Atlantic uppers drifting over the UK with less rainfall to at the surface but probably not much sunshine with mostly cloudy conditions dominant.

The Jet Stream continues to flow East over the Atlantic towards the UK before it ridges strongly North to a position well North of the UK as the High develops near the South of the UK late next week.

UKMO for midnight on Wednesday shows Low pressure West of Norway with a weakening WNW flow over the UK ahead of a ridge of High pressure. Showers would lessen through this time with drier air coming in from the West through the following day.

GEM shows pressure building from the South pushing rain bearing fronts and Lows well North of the UK with time and introducing dry and rather cloudy conditions with temperatures well up to normal or above.

ECM too shows the High pressure build but with it's axis a bit further West a few rather colder days could innitially bring frosts across the UK under a slack North flow before the High slips just to the South allowing the feed of Atlantic cloud to topple over the High and over the UK restricting frosts and slowly lifting temperatures to normal or somewhat above in the SW flow over the NW at the end of the run.

In Summary this morning a change is on the way. At long last a change to drier and quieter conditions will develop later next week as high pressure from Iberia moves North. It's position will be crucial to what weather at the surface develops but as shown this morning rather cloudy Atlantic air would move round the top of the High and over the UK meaning rather benign conditions for most in rather cloudy skies and temperatures well up to normal. In the North the Alantic maintains a stronger influence with occasional rain in a mild SW flow.

[Zenarcher]

Evening everyone hope you had a nice Christmas,

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

Friday to Sunday -

How the models struggled - Over the last few days the models have struggled greatly with the Atlantic low heading it's way to the UK for Friday night at first they had it too far East but later pushed things to the West, overall the model that remained consistent over the past few days with it is the UKMO well done to it.

Friday, Gale force winds across much of the country mainly in Western parts,

It's also going to be very wet over Ireland and Scotland in the morning,

Saturday, Very early hours of the morning Western and Northern Scotland will be hit by high wind speeds where gusts around 75mph is possible, elsewhere is likely to just see gale force winds,

Also a very wet morning on Saturday across England and Wales,

Also over Iceland on Saturday get very high wind speeds due to a very deep low some models have it down to 945mb, GFS has average wind speeds over 70mph,

Sunday, The low over Iceland now starts to move closer to the UK but as it does it weakens and so does the winds still it will bring very strong winds across the Northern parts of the UK,

Sunday morning severe gales across Scotland,

Later on Sunday evening more rain arrives over Ireland and parts of England and Wales,

Monday New Years Eve 96 hours - All models start to show a more settled outlook we have good agreement on high pressure moving into the Atlantic meanwhile weak lows are to our far North, still expect breezy conditions and showers though,

Tuesday New Years Day 120 hours - NOGAPS and GEM have an Atlantic low move in across Southern Greenland this stops high pressure building up in the Atlantic however the other 4 models send the low more into the SW of Greenland this lets high pressure build up better in the Atlantic. New years day does look settled though mainly dry with a North Westerly breeze.

Wednesday 144 hours - All models show high pressure move up from our South this has been a trend over the Christmas period and still continues this would bring in settled and dry weather which I'm sure those affected by flooding will be glad to hear,

168 hours and beyond - ECM continues to build high pressure into early January so gives us a settled outlook, GFS also brings in high pressure then eventually we see something interesting in the Northern Hemisphere in the strat thread there's been a lot of talk about a warming sometime in January so the long outlook on the GFS today is a positive thing, JMA agrees and builds up high pressure from the South and NOGAPS does build in high pressure although not as much and tries to keep the Atlantic and PV in charge.

Overall - This weekend will be very unsettled with wind and rain affecting a lot of area's mainly those in the West and North. New year looks more settled and dry and into early January most models show high pressure being in charge continuing a settled theme and then after that remains unanswered but positive signs are appearing in the stratosphere at the moment.

Edited December 27, 2012 by weathermaster

[Gibby]

Good evening. Here is the latest report on the 12z output from GFS, UKMO and ECM for today Thursday December 27th 2012.

All models show a weak ridge crossing East as I type being chased by a strengthening SW flow in association with a very deep Low pressure area moving NE to the NW of Scotland. A warm front will bring rain across the UK followed by a mild and strong SW flow with a cold front crossing East on Saturday bringing a band of heavy rain followed by squally showers for the latter half of the day and overnight. On Sunday the West flow backs Southwest again with a further spell of rain sweeping NE over the UK by New Years Eve before a change of winds to a North-Westerly direction and rapidly rising pressure brings a spell of sunshine and showers in rather colder air before the showers die out as we move into the second day of 2013.

GFS then shows a High pressure centre settling over or just to the South of the UK with dry weather for many with pressure in excess of 1030mbs for many. There will probably be a lot of cloud about especially if the centre of High pressure remains to the South but if it moves over the UK some clear spells are possible with frost and fog problems developing more. Later in the operational run the High gives way Southwards with Atlantic fronts and lows returning in from the West with rain at times extending to all areas again by the end of the run.

The GFS Ensembles show the up and down pattern in uppers continuing for a while yet before stability arrives as uppers settle above average from midweek next week as High pressure builds from the South. As a consequence rainfall amounts fall back in the South with far less than recently throughout the second half of the run, especially in Southern locations.

The Jet Stream shows the flow still running East over the Atlantic to the UK before a strong ridging in the flow carries it North of the British Isles as the high pressure builds North later next week.

UKMO for midday on Wednesday shows High pressure down to the SW of the UK with a moist West airflow over the UK with a warm front carrying rain across the UK from the West followed by a moist and mild West airflow with drizzle on exposed hills and coasts, but at least drier weather than of late.

ECM for Wednesday shows a warm front crossing East bringing rain and drizzle across with it before a continuing rise in pressure allows for High pressure to settle near Southern England by the end of the week with dry and bright weather away from North-Western coasts and hills where cloud and drizzle could blow in on the developing moist westerly flow. By the end of the run the High shows signs of sliding away East with the damp drizzly conditions gradually extending further South and East in continuing relatively mild conditions.

In Summary the weather over the coming two weeks can be split into two halves. In Week 1 the weather remains unsettled with further wind and rain blowing in off the Atlantic while Week 2 sees a High move up from Iberia settling things down for at least 4-5 days before signs of it sliding away South or East again later heralds the likely return to wind and rain once more. The bad news for cold fans it looks very unlikely that the High will get itself into a position to bring cold weather over the UK with anticyclonic gloom being the more likely outcome with temperatures near to or above normal throughout.