In Depth Model Discussion, Analysis and Summaries

[Interitus]

Quite surprised not to see much comparison being made between this year and 2006.

Both years featured a January SSW leading to a vortex split, which was followed by highly similar trends of NAO, AO, and CET anomalies as shown in the graphs below. In particular the AO correlation is 0.80 since the SSW.

The zonal indices are the usual NCEP figures and the graphs are 5 day running means centred on the day number on the x-axis, with the central date of the SSW being day 59. This year is red, 2006 is blue.

March 2006 featured some persistent northern blocking leading to some cold northerly and easterly outbreaks, much like we have at present and potentially in the near future, so it will be interesting to see how long the similarity between these years remains.

Of course there is little if any relationship between late winter weather and the summer, but boy what a summer 2006 was!

Edited February 22, 2013 by Interitus

[IanR]

Quite surprised not to see much comparison being made between this year and 2006.

Both years featured a January SSW leading to a vortex split, which was followed by highly similar trends of NAO, AO, and CET anomalies as shown in the graphs below. In particular the AO correlation is 0.80 since the SSW.

The zonal indices are the usual NCEP figures and the graphs are 5 day running means centred on the day number on the x-axis, with the central date of the SSW being day 59. This year is red, 2006 is blue.

March 2006 featured some persistent northern blocking leading to some cold northerly and easterly outbreaks, much like we have at present and potentially in the near future, so it will be interesting to see how long the similarity between these years remains.

Of course there is little if any relationship between late winter weather and the summer, but boy what a summer 2006 was!

Summer 2006 produced some of the hottest days I have ever known, I walked out of the house one afteroon and was overwhelmed by heat and hot sunshine, very rare to feel like that in northern England!

[It's just wind...]

Speaking of 2006, I am not entirely sure what these pretty pictures show, but I was struck by how this year resembled 2009, 2006, 2004 and 1987 (albeit with an earlier start to the pattern)...

I don't have my CET anomalies to hand now, but I remember seeing that the nose of the yellow pointed to a cold March which was followed by a warm April and a cool May. What do you think?

ps, am i posting images correctly? Any other way than URL?

Thank you,

IJW

Edited February 22, 2013 by It's just wind...

[Interitus]

Each of those charts shows a SSW as seen by the anomalous warmth at high altitudes (low pressure levels) towards the left hand sides - the dates roughly being 6/1/2013, 24/1/2009, 21/1/2006, 7/1/2004 and 23/1/87. After this can be seen some recovery of the stratospheric vortex with the colder blue and purple temperatures, but the 'nose' of yellow shows the lasting effects of the SSW at the lower levels of the stratosphere into the top of the troposphere which may have led to the cool March.

Later on in April comes the final warmings of the stratosphere as the vortex weakens and reverts to an anticyclonic state over the summer. How this warming takes place can affect the conditions in April and May (but I've not examined these years in detail to say just how).

Edited February 22, 2013 by Interitus

[Gibby]

Good morning. Here is the latest 00z report on the output of GFS, UKMO, GEM and ECM for today Saturday February 23rd 2013.

All models show a very cold start to the period today with High pressure over Scandinavia dragging bitterly cold NE winds across Southern Britain. Large areas of cloud will persist with outbreaks of light snow or snow showers in places, especially in the East and NE today and SE tomorrow, The coldest of the weather will gradually release it's grip as we go through the working week due to High pressure movingWest over the UK and a little South eventually cutting off the cold feed over the South. It would stay dry and chilly rather than very cold for the middle and end of next week with lighter winds, still rather a lot of cloud and patchy frosts where skies clear as High pressure recedes further towards the West of the UK by next weekend.

GFS then shows the static rather non-descript conditions continue with the far North receiving some rain from a cold front edging down from the North with snow on the hills. High pressure then re-establishes over Scandinavia with a cold ESE flow developing again over the UK though not as cold as currently. It would still be laegely dry at this juncture though rain does reach the South with time and extend North over most areas as winds slowly turn towards the South or SW and decrease with milder air in tow.

The GFS Ensembles show a quick return to nearer to normal uppers for all areas as we move into next week and the cold feed is removed. A period of sustained quiet and settled benign type conditions are shown through next week before the usual spaghetti type split between members is shown, eventually giving rise to rain at times as Low pressure becomes factored in.

The Jet Stream shows a maintained split flow with the main thrust of energy well to the South of the UK. As the Northern arm gets a surge of energy from a temporary linking from the Southern arm the flow rides over the top of by then the UK High and down East over Europe. By the end of the reliable forecast for this the flow is split once more with a weak arm running East across Southern Greenland and Iceland to Scandinavia with the main arm still along way South over the Atlantic and Southern Europe.

UKMO shows High pressure moving WNW further into the Atlantic as we move into the latter part of next week maintaining a ridge over the UK. The dry spell will continue with some sunshine likely by day, light winds but with the maintained risk of overnight frosts and fog patches. It would be less cold than recently though, especially by day.

GEM shows a similar trend with a gradual transition to a NW flow for a time with cold Arctic air getting into the North with some wintry showers. Elsewhere largely dry weather would persist and with winds settling variable in the North and ESE in the South later a change to unsettled weather looks imminent from Day 10 perhaps with some transitional snow as Low pressure to the SW bumps into cold air over Northern Britain.

ECM finally looks to be on a similar trend though showing a different result from last night. It takes High pressure away from the UK out to the NW later next week turning winds into the North with cold weather with sleet or snow shwers for a time before a collapsing High pressure cell moves SE over the top of the UK killing the showers and giving a cold and crisp period of weather with severe night time frosts but fine sunny days to end the run.

In Summary the weather remains driven by High pressure this morning with changes of position and orientation of the High making fundamental changes to conditions at the surface. It loks fairly certain now that a retrogression of the High will move West over the Uk from the ENE and then NW over the Atlantic. Dynamic synoptics in the Atmosphere don't seem to support an otherwise straingth Northerly flow with snow showers as would normally occur from this movement. Instead a tenuous ridge lies over the UK with cold Arctic air held over more Northern locations with the South staying largely dry and benign. It does look feasible that in 10-14 days time High pressure will give way to a push from the Atlantic, possibly from the SW and with the main arm of the Jet flow a long way South some interesting scenarios could development upon engagement with relatively cold air over or near to parts of the UK

[Gibby]

Good morning. Here is the report from the 00z output from GFS, UKMO, GEM and ECM for today Sunday February 24th 2013.

All models show a relatively dry week to come. High pressure will dominate the weather over the UK through the period, transferring from Scandinavia to the UK though the week before pulling away towards the NW later on. Despite dry weather maintained for most some further light wintry showers can be expected today and tomorrow before these turn to rain as less cold uppers move into the UK from the NE. Nevertheless, the week as a whole will stay somewhat on the cold side with a keen breeze maintained across the South of the UK until the end of the week when it falls lighter and backs towards the North.

GFS then shows a fine weekend, especially in the South as a ridge from the departed High pressure is maintained over the South. In the North very cold air grazes these areas in association with Low pressure crossing East to the North. Some rain and hill snow would develop here through the weekend. Through the following week pressure falls across the UK with the risk of rain increasing for all, more especially as a strong and cold SE flow develops late in the week in association with Low pressure advancing from the SW. Snow would be possible over the hills for a time before milder Southerly winds move in from the South later with heavy showers and longer spells of rain too.

The GFS Ensembles show a warm up in uppers over the coming few days to levels close to normal for the majority of the coming week before a wide spread develops between the members, especially in the North. While in the South most support a maintained average level of uppers a few drop the UK back into very cold territory again, rather more so in the North due to a more Northerly injection of cold air progged. Precipitation levels are low until the end of the run when thing become more disturbed.

The Jet Stream show a split flow still with a temporary strengthening of the Northern arm as it receives an injection of energy from the persistent Southern arm over Southern Europe. With time the Northern arm weakens again and slips somewhat further South to our NE while the Southern arm continues to blow relatively strongly West to East over Southern Europe in a week or so.

UKMO for next weekend shows High pressure having pulled away NW from the UK leaving a ridge of High pressure across Southern Britain. The weather would remain largely dry and rather cold with with some rain into the NW moving slowly SE with wintry showers following to the far North.

GEM shows a slack pressure gradient over the UK next weekend with a lot of dry benign type of weather to be found with a lot of cloud. Through the period covering the end of the run High pressure slips away East over Europe with a strengthening SSE flow over the UK bringing cloud and rain North up the Western side of the UK, though the far East would likely stay dry, cloudy and windy with near average temperatures by then.

ECM shows no real retrogression of High pressure next weekend, holding a centre close to the NW before sinking it SE across the UK allowing a strengthening chilly SE airflow to establish with some rain reaching Western and SW areas, edging slowly Eastwards with time.

In Summary there is still considerable indecision on the pattern of events following the dry and rather chilly pattern of the coming 5-6 days. In theory retrogression of a High to the NW and a Southerly moving jet would almost guarantee a Northerly for the UK but with Low pressure strongly centred out to the SW any retrogression is always going to leave a ridge of High pressure from it over the UK, especially supported by Low pressure to the North. As it stands we end up in a nomansland as regard to synoptics keeping things largely dry and benign until the Atlantic makes it's approach from the SW eventually as GEM and ECM show via a strong and slightly chilly SE flow. The options are very fluid though and will continue to change from run to run with colder synoptics rather than milder ones likely to be favoured over milder ones for some considerable time yet I would of thought.

[johnholmes]

The ECMWF-GFS 500mb anomalies this morning both show some changes which make me uncertain beyond about 3-4 March just what the upper pattern may look like. I don't think there is any doubt for the rest of February and into the start of March that a coldish pattern will remain in the upper air. The flow possibly from the ENE at first and becoming from WNW or even NW with time. But beyond those first few days of March then enough, especially if the NOAA outpt suggests something similar this evening, to start to have doubts how long this upper pattern may last.

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

[TonyH]

The usual regionally limited look ahead to the weeks weather:

http://forum.netweather.tv/blog/309/entry-4572-weather-guide-monday-25th-february-to-sunday-3rd-march-2013/

[Gibby]

Good morning. Here is the report from the 00z output of GFS, UKMO, GEM and ECM for today Monday February 25th 2013.

All models show a straightforward pattern of weather between now and next weekend as the UK continues to lie under the influence of High pressure which is currently moving from Scandinavia to be centred over Northern Britain by midweek cutting off the cold NE flow that's been plaguing the South for many days now but maintaining the dry if rather chilly weather with large cloud amounts floating around. It then sits around or just North of the UK for the remainder of the week and then weakens in situ or slides SE over next weekend as pressure falls over the UK to bring Low pressure closer ot both the South and North of the UK with a very complex pattern of synoptics next week gradually resulting in an increased risk of rain and wind through week 2.

GFS then pulls away it's UK High away SE setting up a slack SE flow as pressure falls away to the SW and NW with a trough edging slowly East over the UK with rain for all with time. Through the rest of the period a Southerly then SW airflow develops with troughs swinging NE with rain and strong winds spreading to all areas by the end of the run with near average temperatures.

The GFS Ensembles show a milder spell slowly developing at the surface as High pressure relocates to the UK and eventually moves away allowing milder SE then Southerly winds to develop with a breakdown in the fine spell towards the end of the run. There is good clustering around this sort of evolution but there are other options too with rather colder results especially towards the North of the UK. The spread between members is rather greater again this morning though from the end of this week out to the end of the run.

The Jet Stream comprises of two arms currently, one riding over the UK over the North of the UK while the Southern arm continues to blow East across Southern Europe. The flow to the North weakens late in the week and weekend as the Southern arm keeps blowing strongly across the Azores and Southern Europe.

UKMO for the weekend shows High pressure centred over the UK with the chance of rather brighter skies in light winds. Things stay a little on the cold side with some night frosts but dry weather with some welcome sunshine by day.

GEM shows High pressure too over the UK with the trend to collapse it away SE as Low pressure to the North and SW take control. Outbreaks of rain would eventually develop with temperatures close to or a little below normal.

ECM shows a similar projected view with High pressure declining early next week following a dry and bright weekend. Pressure than falls with the chance of rain arriving from the SW increasing as we move into the midweek period coupled with a chilly SE wind.

In Summary the weather will stay fine and dry this week as the Scandinavian High centres on the UK late this week and weekend with light winds and temperatures near or a little below average. Thereafter pressure falls on all models with a trend to rather more unsettled weather through a variety of options shown, though the favourite option to win in my mind would be a gradual transition to a milder South and SW flow as the Jet Stream pulls further North over Europe and over the declined UK high that will of moved to SE Europe by then in a week to 10 days or so time.

[Gibby]

Good morning. Here is today's look at the 00z output from GFS, UKMO, GEM and ECM for today Tuesday February 26th 2013.

All models support the continuation of the UK being governed by High pressure over the rest of the week and weekend. The positions of the High will shift about a bit day to day creating small but subtle differences in amounts of cloud and wind day to day but with it's centre continuing to be over or near the UK throughout this period. Pressure is then expected to fall as we move into next week as the High makes it's move away Easy across Europe early next week with a freshening SE flow developing over the UK. In the meantime the weather will remain largely benign with the cold and cloudy conditions in the South lasting for a while longer before a better chance of clearer conditions occur the weekend when all of the UK become largely dry and bright by day but with frost and fog patches by night.

GFS then shows a chilly and freshening SE breeze developing next week but despite Low pressure edging slowly up from the SW the ingress of any rainfall will be slow with many places staying dry even out to the end of the week especially in the North and East with High pressure building back down from the North later with a return to rather cold weather with the chance of frosty nights returning by the end of the run with winds maintaining an East or SE component.

The GFS Ensembles show a huge spread developing between members fro a weeks time with the operational one of the milder options in the South out to just before the end of the run. In the North the spread occurs even sooner with the dry spell shown to come to an end some when next week.

The Jet Stream shows a continuation of the split pattern with the Southerly arm the most pronounced part of the flow. The Northern arm sinks South and weakens further next week as the UK High slips SE into Europe.

UKMO for the weekend shows High pressure well established over the UK but weakening by the start of the new week as it begins its slide off into Europe. A dry and fine weekend for many looks likely, though rather cold, especially by night when frosts are likely but some compensatory bright days with some sunshine.

GEM today also shows High pressure slipping away East and a chilly and strong SE wind developing by the end of next week. With pressure falling rain will move slowly NE across at least the South and West of Britain by the end of the week with some snow possible on the highest ground further North.

ECM too shows a similar progression through next week with it too showing rain and strong winds into the South and West by late next week as pressure falls over the UK and weak High pressure lies over Scandinavia.

In Summary today this week and weekend looks agreed by all members to see High pressure maintaining a fine and settled theme for all with variable cloud cover and temperatures at the surface near or a little below average. Next week becomes much more complex and although the pattern is agreed by all members that a push of the Atlantic into the UK from the SW looks likely, it's the engagement that has with somewhat colder conditions over the UK and much colder air to the North and NE that is yet to be decided. It could be with a Southerly Jet that the cold bottled to the North has pushed enough cold air down into the UK that could offer a more wintry scenario than that what's currently shown over the next few days. Don't be surprised if there aren't some rather interesting scenarios shown in the output concerning this period over the coming days.

[johnholmes]

a view of what the upper pattern may be in 6-15 days time?

the upper air pattern in 2 weeks-26 feb 13.pdf

[Gibby]

Good morning. Here is the latest report from the 00z output of GFS, UKMO, GEM and ECM for today Wednesday February 27th 2013.

All models show a fine and settled spell lasting through until about Tuesday or Wednesday of next week. In the mean time the UK will be governed by High pressure innitially centred over the North or just to the NW of the UK. Over the weekend it moves SE over the UK and away into Europe with an increasing SE wind next week. Through all this period all areas spare a few outbreaks of light drizzle would be largely dry with often large amounts of cloud but some brighter and sunny intervals too. Patchy frosts would occur at night should skies clear sufficiently and it will be rather cold generally, especially in the South.

GFS then brings fronts NE into the UK by midweek extending to all areas by the weekend with rain at times in winds slowly veering towards the SW with rather milder conditions than of late. Through FI today the weather stays unsettled and windy with rain at times and average temperatures before High pressure moves East behind a depression settling things down again at the end of the run, at least in the South.

The GFS Ensembles show a milder spell is on the way although despite higher uppers over the South through the next week things might not be realised at the surface under often extensive cloud cover and a cold breeze. Beyond that an unsettled spell for all regIons is shown with near to average temperatures trending rather colder again later, especially in the North where there is a lot of spread between members from later next week. The operational was something of a milder outlier for Scotland for a time next week.

The Jet Stream shows the split flow continuing for another week with the main thrust of the Jet held well South of the UK down over the Southern North Atlantic and Southern Europe before it starts to ridge North in the Atlantic towards the back end of next week.

UKMO for early next week shows High pressure slipping away SE through Europe with a SE flow developing over the UK. Fronts are approaching from the SW though these will probably not reach anywhere spare the far SW through this period. Near to normal temperatures would prevail under the cool breeze.

ECM today follows the same route with rain bearing fronts slowly moving North and East across the UK through the middle and end of next week with a chilly SE wind for much of the time before things turn rather milder with time as winds begin to turn to a milder Southerly.

In Summary there is good agreement on the pattern of events over the UK through the next 10-14 days. Small but subtle differences do exist between the models but they all point to another week of benign and in places cloudy conditions before the atmosphere is stirred by an increasing SE breeze as the High that's governed our weather for so long finally slips away SE across Europe early next week. Low pressure lying well to the South of the UK then pushes it's fronts NE into Southern and Western areas by midweek and to all other areas later meaning some rain at times for all by the weekend with milder temperatures likely to follow on behind under winds turning more towards the South or SW.

[Gibby]

Good morning. Here is the report from the 00z output from GFS, UKMO, GEM and ECM for today Thursday February 28th 2013.

All models show good support for the sequence of events as follows over the next 7 days. High pressure lies close to NW Britain with a slack North flow over the UK carrying areas of cloud South over the UK at times. One such band in association with a weak cold front sinks South tonight and tomorrow bringing a little drizzle and freshening the NE breeze over the South of the UK again tomorrow making it feel cold. Through the weekend High pressure sits right over the UK though still with a lot of cloud trapped underneath it in light variable winds. A few sunnier breaks are possible and it should stay largely dry. Then through the first half of next week all models support High pressure moving away across Europe with a SE flow developing over the UK. Pressure will fall for all areas and troughs of Low pressure moving slowly North and East will reach the SW of Britain midweek with some rain in association with a depression down to the SW.

GFS then shows further pulses of rain from the South as the first attack fails midweek. This new pulse makes further inroads North into the UK than it's predecessor bringing milder Southerly winds across the UK for a time with further rain at times, especially in the West. Then through FI Low pressure disrupts to the West and slides across the UK and into Europe as pressure builds strongly over Scandinavia. This would mean rain with snow on Northern hills would develop as cold Easterly winds return pushing further South as the Low pulls away East. Towards the end of FI Easterly winds become established again, especially over the South with snow showers developing once more across the South and East to end the run.

The GFS Ensembles show that the operational above was a rank outsider with it's end of run cold snap with the general mood of the pack to keep things much closer to the seasonal normal though trending rather chillier with time in the North. Rainfall events peak towards the end of next week as the Low pressure to the SW takes hold before falling rather again towards the end of the run North and South.

The Jet Stream continues to show the main arm of the flow well South of the UK over southern Europe with little support for much of a shift to this in the coming week. A weaker Northern arm continues to blow slowly East across areas to the North of the UK too for some time yet.

UKMO for the middle of next week shows a SE flow over the UK with Low pressure to the NW of Spain. It would be generally rather cloudy and with troughs pulling slowly North and East into the UK the South and West in particular would see some rain at times developing. Temperatures would be close to normal generally in this set up.

GEM shows a fall of pressure too midweek under a SE flow with depressions ganging up to the Southwest. This model though holds them South of the UK backing winds off towards the East and bringing rather cold and dull conditions back across the UK late in the week with some cold rain at times here and a cold and strong raw wind from the East in the South.

ECM today shows Low pressure making more Northerly inroads up the Eastern edge of the North Atlantic tilting winds across Britain to a more Southerly point later next week with rain making good progress across many areas while introducing milder air too. However, late in it's run a return to colder conditions looks likely soon after the termination of the run as rising pressure to the North pulls Low pressure back slowly towards the South and SE with colder East winds returning South over the UK with time, reaching the North first, right at the end of the run and probably sinking South to other areas in the days following day 10.

In Summary today I don't see much sign of Spring showing in the charts today. There looks to be another 5-6 days of set fair weather with a lot of cloud around with all in all rather benign and uninspiring weather affecting many areas through this spell. Then a change to more unsettled conditions look like taking hold especially in the South and West later next week with rain at times. It's progress towards the North and East looks painfully slow with the chance that rising pressure to the North or Northeast later next week and the period that follows brings the chance of cold East winds back over the UK once more further into March. The depth and severity of cold shown by GFS at the end of its run has next to no support but it isn't the only Easterly evolution shown in the output this morning so we will have to wait and see whether further output shows this evolution as a growing accentuating over the coming days.

[Gibby]

Good morning. Today is the birth of Spring 2013 (meteorologically speaking) and here is the first report of the new season from the 00z outputs of GFS, UKMO, GEM and ECM for Friday March 1st 2013.

All models show the UK still influenced by high pressure currently centred close to NW Britain with a chilly NE breeze over the South and a lot of cloud feeding down from the North or NE. Over the weekend the High transfers slowly SE and then more quickly away East early next week with a freshening SE breeze over the UK. The dry spell will continue and after another day or so of large cloud amounts there should be more in the way of sunshine as the SE flow brings drier and somewhat less chilly air NW over the early days of next week.

By midweek GFS shows troughs moving North over the UK with rain at times developing, eventually for all areas as winds turn more towards the South or SW in the South. Through FI today a Low pressure complex drifts slowly East over the UK maintaining the wet spell, leaving a cold Northerly flow in its wake with showers falling as snow over Northern hills for a time. Late in FI winds back West and SW and a return to something more normal in the way of synoptics develops over the UK with spells of rain at times, heaviest in the North and West with the best of the brighter drier spells in the South and East in near normal temperatures.

The GFS Ensembles show the pattern as before with uppers just above normal for the next 3-4 days but with an inversion keeping things at the surface a bit chilly for the time being. Then as the Low pressure systems take hold later next week uppers fall to nearer average conditions or a little below at times. There are a few very cold options on the table this morning creating a wide spread between the members in the end third of the run.

The Jet Stream shows no sign of the main arm moving to more Northern latitudes anytime soon. Instead it blows strongly down over Southern Spain and the Meditteranean for the next week or so.

UKMO for next Thursday shows very slack but relatively Low pressure over the UK with a parent Low well to the SW. Despite no real indication of troughing over the UK it is highly likely that some outbreaks of rain will be scattered about almost anywhere with the main rain areas down to the SW. Temperatures would be near to normal.

GEM shows a more vigorous SE flow later in its run meaning winds would be strong to gale force, making it feel cold. Areas of rain would move slowly north and East over Southern and Western areas perhaps falling as snow on the highest ground later as winds back towards the East. Late in the run High pressure develops from the North with cold and settled conditions returning steadily South.

ECM today shows a more Southerly aspect to it's wind flow later next week making things feel rather milder but at the same time carrying rain bearing fronts further North and East across Britain. Towards the end of it's run Low pressure becomes complex and centred over the UK with rain and showers for all in breezy conditions with temperatures no better than normal for early March.

In Summary the weather looks like changing next week. Progress will be slow but by the end of the week most places will have seen some rain with quite a lot possible again towards SW Britain as Low pressure becomes slow moving near Southern Britain. Temperatures look like being near to normal for most but in any stronger winds it will feel cold especially under the rain.

[Gibby]

Good morning. Here is the report on the output of the big four from their 00z runs for today Saturday March 2nd 2013.

All models show signs of a change on the way. This comes in two phases as the current benign and cloudy weather with a little drizzle here and there as well as a few brief sunnier or clearer breaks continue for the next 24-48hrs. As the High responsible for these conditions gradually starts to slide away SE tomorrow the first phase of change sees a milder SE flow pick up bringing both drier and milder air NW from France with more sunshine over Monday and Tuesday than of late. Secondly as the High moves even further away from the East pressure falls from the SW and rain will arrive int the UK on a Southerly breeze by then.

GFS then brings this rain across all areas later in the week reinforced by a deeper Low pressure running North close to the West Cast with strong winds likely for a time. Then through FI the operational brings a typical March mix of weather with spells of rain and showers in occasionally strong winds which blowing from mostly a Southerly or Westerly quarter ensures temperatures stay close to the March average for all areas for most of the time.

The GFS Ensembles show the warmer uppers in association with the current High pressure gradually giving way to more average temperatures aloft as Low pressure takes hold midweek. Rain at times is then shown to occur throughout the rest of the run with the usual spread of values later on. The operational was one of the milder options on offer though both North and South later though more especially in the North.

The Jet Stream shows reluctance to move North anytime soon preferring to continue to flow East across Southern parts of the Northern hemisphere in the absence of the dominance of an Azores High.

UKMO for late next week shows Low pressure just to the west of Ireland with a cyclonic Southerly flow over the UK. It would of become steadily milder in the preceding days but cloud and rain would of already arrived by this point with some sunshine and heavy Spring showers the likely weather under this setup.

GEM today continues to want to keep a more SE airflow the dominant force later next week with rain held more into Southern and Western areas while the North and East see cool SE to East winds making it feel cold as well as cloudy. Late in it's run winds back further into the East bringing cold and dry conditions back later as High pressure shifts South down over the UK by the end of the run with the return of cold and rather cloudy weather with frost risk at night.

ECM too shows a similar evolution as GEM with High pressure re-establishing later in the run pushing down from the North and squeezing the Low pressure to the South of the UK away East and replacing the occasionally rainy conditions late next week with colder and drier conditions once more with overnight frost.

In Summary we are still on course for a change in the weather next week. The predominantly dry and rather chilly conditions will be replaced by a milder and wetter spell as Low pressure to the West and SW takes control for a while at least later next week. How long such a spell lasts is open for debate with GFS and UKMO looking like sustaining milder and unsettled conditions moving forward while GEM and ECM build High pressure back down from the North late in their output with the removal of rain from the South and a return to dry and rather cold conditions with night time frosts as we approach mid month.

[johnholmes]

An update on the 500mb anomaly charts

500mb charts on sun 3 march 13.pdf

[TonyH]

Latest weekly look ahead (and a bit of retrospective) for my regions of interest:

http://forum.netweather.tv/blog/309/entry-4576-weather-guide-monday-4th-to-sunday-10th-march-2013-west-wales-and-the-midlands/

[Gibby]

Good morning. Here is the report of the 00z output from GFS, UKMO, GEM and ECM for Monday March 4th 2013.

All models show the High pressure currently moving away towards the East with a SE breeze carrying milder air steadily NW over the UK in the coming days. Cloudy conditions too will be replaced by some much needed sunshine in places and despite the breeze it will feel considerably warmer, especially in the South tomorrow. Pressure will be falling everywhere though and cloud and occasional rain may reach the SW by Wednesday and spread to other areas too by the end of the working week with the heaviest rain always towards the South and West of the UK with temperatures returning to near normal in the North.

GFS then shows the weekend with Low pressure over Southern England with rain or showers at times here while the North maintain a SE to East wind and occasional rain where it will feel rather cold especially near the North Sea coast. Then through the start of next week a ridge extends SE from Greenland and dries things up for all for a time with rather cold conditions with night frosts returning before a return of less cold air from off the Atlantic moves East to the South of the UK keeping the UK on the cold side of this disturbance and enhancing the risk of some snowfall on hills in the South and more generally in snow showers further North. At the end of the run High pressure slips SE over the UK with much frostiness before milder air climbs over the top of the sinking High with SW winds to end the run.

The GFS Ensembles show good agreement on the milder wetter spell later this week and weekend before a change to colder conditions on the 11th in the South and somewhat before in the North. With unsettled weather still close by from most members later in the run with a Southerly positioned Jet and colder uppers someone somewhere will see some snow at times in the North from next week

The Jet Stream as mentioned continues to blow at Southerly latitudes through the coming week in association with the Low pressure to the SW edging towards Southern Britain late in the week.

UKMO shows an unsettled weekend with rain at times as Low pressure moves slowly in towards the West and SW of the UK. Winds will be mostly from the South or SE so away from North Sea coasts temperatures could well stay a little above normal, especially in the South.

GEM shows Low pressure over the South at the weekend exiting away SE early next week as it like GFS shows a ridge building SE from Greenland bringing a return of colder air for a time with frost at night and some snow on Northern hills from any showers. Frosts at night would return for a time before milder air moves slowly in at the end of the run.

ECM too shows Low pressure close to Southern Britain at the weekend with Low pressure more reluctant to leave the UK early next week hence the spread of cold air South being more limited due to Low pressure holding positions South of Iceland and keeping the coldest air away to the North. Rain or showers would continue to affect the UK at times.

In Summary the weather still looks like turning steadily more unsettled as we move through this week with rain at times, especially in the South. Colder air then begins to engage in the Easterly flow over the North of the UK and this spreads slowly South early next week to bring colder conditions for all for a time. ECM today though holds rather more unsettled conditions over the UK for longer without the feed of cold from the North either which is a milder evolution that this model has been showing of late. With the GFS ensembles showing many different evolutions within it's pack this morning and such complex synoptics generally the pattern of weather for next week is far from nailed on and many more changes are likely from the output of the coming days.

[johnholmes]

looking at the outputs from NOAA last evening, its 6-10 and 8-14 outlooks for the upper air along with the ECMWF-GFS output this morning, I made the following comments

Ec-gfsEc-

gfs

They (ECMWF-GFS) both support the colder block type but the block on both is receding further north again with the impetus for colder air showing as a trough induced input-with gfs the stronger model for this

It is going to turn colder after a shortish milder unsettled spell but how cold and for how long is fairly uncertain I would say. The mega cold shown on ecmwf for 2 days seems pretty unlikely to me.

Noaa last evening did show more inclination to this idea than it has for the past week but it still does not look totally convincing and another day might make a decision on the cold spell more clear?

link to ec-gfs

http://www.meteo.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html

and link to NOAA 6-10 and 8-14 last evening

http://www.cpc.ncep.noaa.gov/products/predictions/814day/500mb.php

I will leave folk to make their own minds up

[Purga]

looking at the outputs from NOAA last evening, its 6-10 and 8-14 outlooks for the upper air along with the ECMWF-GFS output this morning, I made the following comments

Ec-gfsEc-

gfs

They (ECMWF-GFS) both support the colder block type but the block on both is receding further north again with the impetus for colder air showing as a trough induced input-with gfs the stronger model for this

It is going to turn colder after a shortish milder unsettled spell but how cold and for how long is fairly uncertain I would say. The mega cold shown on ecmwf for 2 days seems pretty unlikely to me.

Noaa last evening did show more inclination to this idea than it has for the past week but it still does not look totally convincing and another day might make a decision on the cold spell more clear?

link to ec-gfs

http://www.meteo.psu...0z/hgtcomp.html

and link to NOAA 6-10 and 8-14 last evening

http://www.cpc.ncep....14day/500mb.php

I will leave folk to make their own minds up

Thank you very much John for your excellent and measured insight - so looking a bit uncertain then!

[TEITS]

Those charts John posted won't tell you anything with regards to the outlook.

Our attention should not be on the blocking but the Low pressure.

The quicker and cleaner this moves SE the greater the chance of the UK seeing much colder weather with colder upper temps. The reason why we are seeing the differences in the operationals is like this morning the ECM develops a spoiler shortwave.

[Methuselah]

Those charts John posted won't tell you anything with regards to the outlook.

Our attention should not be on the blocking but the Low pressure.

http://www.meteociel...1-144.GIF?04-12

The quicker and cleaner this moves SE the greater the chance of the UK seeing much colder weather with colder upper temps. The reason why we are seeing the differences in the operationals is like this morning the ECM develops a spoiler shortwave.

And 'spoiler shortwaves' will? IMO, if the upper-air patterns are conducive to a 'clean evolutions' then that's what we'll get. If not, 'spoiler shortwaves' will be the inevitable result?

[johnholmes]

I think you should actually look at what they show Dave. I did not mention any areas of either -ve heights nor areas of troughs/upper lows but obviously they are all linked as ever in meteorology.

Again it needs to be stressed that surface low pressure cannot occur without the correct upper air pattern which is what the anomaly charts are all about. Upper air patterns.

7 days ago this pattern was not being shown, now it is, hence colder air is a stronger possibility than it was.

hope that helps you and maybe others.

[TEITS]

And 'spoiler shortwaves' will? IMO, if the upper-air patterns are conducive to a 'clean evolutions' then that's what we'll get. If not, 'spoiler shortwaves' will be the inevitable result?

My point was is currently we have two options being shown on the modes. One is a colder E,ly flow especially for N areas but without cold upper temps or a cold spell that brings snowfall via colder upper temps. Both options are currently shown on the ECM/GFS and my point is you cannot decide which is likely to be correct using the charts John posted.

[johnholmes]

You are perfectly entitled to that view Dave but your argument is flawed. By that I mean unless you understand how the upper air and surface features intereact then you will not truly understand why any model, such as the two you mention, arrive at the chart(s) you are discussing.

I am happy to set up a separate thread to try and explain this in more detail if you or any others wish?