Jump to content


  • Content count

  • Joined

  • Last visited

Everything posted by stodge

  1. Evening all Well, I'll be in the minority here and say if you want an extended cold spell the 12Z ECM is absolutely superb. If you want a snowy spell, I can appreciate your disappointment. Let's look at GFS 12Z OP at T+240: Yes, it's a wonderful snowy chart but the movement is south to north and the coldest of the 850s are going to be mixed out from the south so a short intense snowy spell before a thaw and plenty of rain under the trough and -4 uppers which in early March won't deliver to lower ground. ECM doesn't "fail" because of what happens early but how the HP is modelled. At T+168 all looks fine: You might expect or hope the HP would stay where it was or meander slightly west but the orientation and latitude are pretty much perfect to send the coldest air right across the British Isles but instead the HP moves SW through Scandinavia and to the NW of the British Isles: At T+216 MSLP is 1040MB for most of us which equals dry albeit with -12 uppers across the south so hopefully brilliantly sunny days and cold frosty nights but obviously for snow fans poor. At T+240 the HP retrogresses to Greenland and the 850s are uninspiring: The key though is the wind-flow is NE so no possibility of a mild breakdown from the south or west - the cold is with us and staying and with further retrogression wouldn't we see a renewed cold incursion from Scandinavia as the trough drops down there ? Frustrating of course for many if not most but here's where we may have the next trade off or stand off. On the one side, a short and intense snowy spell especially for the south but with milder conditions returning from the south or a protracted cold and dry spell. I know most on here would like to have their cake and eat it too and that's NOT off the table even with this one OP run. Let's see how the HP is modelled on the morning output - I mentioned in my previous how a number of the ECM ENS had brought the HP further south into southern Norway and I suspect this OP may be reflecting that. At least we are talking about the probability of cold and the possibility of snow which puts us well ahead of where we normally are at this time.
  2. Afternoon all A rare foray from me into the lion's den of the MoD at the weekend but this seems a weekend unlike most. UKMO at T+144 next Saturday: One of the concerns I've had looking at ECM ENS and some GEFS members has been the HP positioned too far south - more around Denmark - so the ambient air pressure over the UK is above 1030MB which wouldn't be conducive for the kind of snowfall many on here want to see. I like this chart because the MSLP across the south is 1015-1020 MB so if we are going to get some convection off the North Sea (Thames Streamer anyone ?) this is going to be a big help. GEM at T+144: Here are those little nuances that show how we haven't nailed this down at all YET, UKMO has the HP centred to the north of Scandinavia, GEM has a 1040 MB HP over Norway. The resulting MSLP over the British Isles is higher so it's drier and perhaps sunny to the west and north west. For all the later development, it's a case of close but not quite for snow fans - for cold fans, it's another hit. Here's the GFS OP at T+144: Somewhere between the two ? Well, I suppose, but the SW'ly tilt of the HP makes me wonder if the colder air will miss. However, the Ukrainian LP fills out over Denmark and the winds go lighter with the MSLP at 1015MB across the south so that looks good for snow as well. Here's your near ice day: Actually, no ice days for London on this but 1-2c on the last two days of the month won't feel warm at all. Plenty of opportunity for snow to lie to high ground and further north and even in lowland East London we might get lucky. Nothing lasts forever - 7-10 days of severe cold will be memorable and noteworthy in its own right but the GEFS are already, at the very edge of FI, sniffing round the next evolution. We'd all like to see the HP retrogress and ridge SE drawing in a NE'ly from Scandinavia with plenty of embedded troughs (P 17 from the 06Z suite) but that's far from certain and it's also possible a strong west-based NAO will set up taking us back to the milder side of the jet.
  3. Evening all A near ice day next Sunday for the east. Superb though this is, I'd put the 06Z a notch in front.
  4. Morning all Well, another day of twists and turns as the output oscillates from the stellar to the not-so-stellar. Before my daily analysis of the mid-term prospects, a thought or two on the evolution to a more blocked pattern and how it was going to happen. Originally, the models offered the Azores HP moving north then north-east to the west of the British Isles into northern Scandinavia. That then became the Azores HP ridging NE through the British Isles into Scandinavia and finally it was an area ridging SW from northern Scandinavia into the North Sea. Any one of these combined with the so-called "trigger" LP dropping south down the North Sea into Europe would pull in the fabled Easterly. Yet as of last evening, GFS and UKMO were moving away from any notion of height rises to the NE in spite of the MJO being in high amplitude phase 7. ECM< which had originally been reticent, had, however, come on board strongly (though to be fair its ENS had always been in support). So, three evolutions to bring height rises and all failing - why ? A thought for another day perhaps but let's see where we are now and where we might be going forward (with all the Shannon Entropy flying about for good measure) to Monday February 26th. Starting as always with ECM 00Z OP at T+240: The cold air is heading away north as the HP in Scandinavia slips SE but heights remains strong to the north at this time in the face of a deep LP in mid-Atlantic. After a period of snow the day before, much milder and wetter conditions moving up from the south. Note the lack of low heights over Europe but the jet remains focussed to the south so undercuts and sliders not off the agenda but the evolution looks milder at this time. GEM 00Z OP at the same time: A ridge from Greenland down SE into central Europe keeps most of the British Isles fine. Deep LP in the Atlantic is stationary and a secondary feature far to the south is in development but where will it go ? A secondary colder LP is tracking south over the Baltic States but whether the very cold air behind us can make any progress westward remains to be seen. It's a bit of a stand off between west and east to be honest. GFS 00Z OP at the same time: A very different evolution but not a million miles away from the 00z of yesterday. A piece of the PV detaches from the main vortex and moves east to the north of the British Isles allowing heights to rise over Greenland. HP is over the south west of the British Isles with a large slow-moving deep LP in mid-Atlantic so a fairly mild and benign outlook for most with perhaps any rain or showers restricted to the far north of Scotland and the Isles. Further into FI and the remnant PV lobe is shunted further west allowing pressure to rise over Greenland and the prospect of a mid-Atlantic block in early March with winds over the British Isles shifting more NW as colder air approaches. GFS 00Z Control at T+240: A mild or very mild SW'ly airflow covers the British Isles with HP over central Europe and weak areas of LP to the west and north running across Scandinavia. Further into FI and the unsettled theme continues with the jet edging south and the PV dissipating over Northern Canada. To bring us right up to speed, the GFS 06Z OP at T+234: A taste of spring rather than winter with a benign SW'ly airflow covering the British Isles with HP over Europe and parts of Scandinavia and LP tracking NNE on a northerly jet. Further into FI and there's very little change with a broad Atlantic domination and no sign of heights to the NE or NW even as the PV weakens and heads more toward the Pole. 00Z GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 A significant away from the easterly-dominated suite of yesterday morning though it's fair to say the easterly option is still there on a number of members. A growing number have eschewed height rises to the NE and keep the Atlantic in charge with deep LP heading toward Iceland. Further into FI and it's fair to say a growing number are showing heights over Greenland so that might be the next wild goose for us all to chase. 00Z GEM ENS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=1&mode=1&ech=240 Plenty of cold and indeed very cold option still on the table. In summary, the arrival of the SSW has brought model volatility on an unprecedented scale. Some output seems to be ignoring it, some seems to be embracing it. So what appears to have gone "wrong" with what seemed a huge prospect for an Easterly (and let's not forget ECM is still very much playing that tune) ? Well, perhaps it's three strikes and we're out in terms of the three routes to Scandinavian height rises all of which according to GFS have failed. GEM keeps heights as does ECM so it's far from a lost cause at this time. The downgrade in the GEFS 00Z is worrying so what and why ? My only theory is the wave 2 attack on the Canadian vortex isn't causing its immediate disruption and re-location as many hoped and surmised but is instead causing a temporary strengthening as we've seen from vortex attacks in the past. The initial tropospheric response has been to strengthen the PV in situ for 7-10 days before it finally weakens and shifts away. Perhaps in all our excitement about the SSW we've forgotten the basic physics of the wave 2 attack and the initial reaction which seems, according to GFS, to be happening irrespective of zonal wind flow reversal. So, to annoy us even further, we have the 10-14 day lag from the initial SSW augmented by a 7-10 day lag from the wave 2 assault which would put us into early March which seems to correspond with both the GFS output (some of it) and Glacier Point's excellent analysis from a couple of days back. It's also worth noting some of the quality Hi-Res models such as ARPEGE are still bringing in the E'ly via Route 3 (northern Scandinavian HP building SW) as early as T+102 so it's a model standoff worthy of Bun-fight at the OK Tearooms and one or more is going to end up looking like a crazed omelette. If you have any nerves left prepare for them to be shredded further in the next 48 hours.
  5. I'm not entirely convinced. The snowfall of Easter 2008 came off uppers between -5 and -10: http://www.wetterzentrale.de/reanalysis.php?jaar=2008&maand=3&dag=23&uur=000&var=2&map=1&model=avn This set up on 11th March 2013 brought a near ice day to London http://www.wetterzentrale.de/reanalysis.php?jaar=2013&maand=3&dag=11&uur=000&var=2&map=1&model=avn That has most of the country under -10 uppers so it's not just the uppers, there are other factors to be considered such as Dew Points.
  6. Morning all Groundhog Day it would seem with more shattered nerves and thrown toys after the evening runs failed to live up to the expectations and hopes of a number of the more excitable participants. As usual, if the chart wasn't showing storm force easterlies and -20 uppers at T+6, people were "calling time" on the cold spell and having the useful half-baked whinging, whining and moaning which belongs in the other thread. Anyway, before I'm dispatched there, my morning summation of the medium term output which today takes us to Sunday February 25th or T+240 to its friends. Starting as always with ECM 00Z OP at this time: A very different evolution from previous days and I'm not sure why. Any attempt to build heights to the NE has been scrubbed and instead the Atlantic is firmly in charge with an LP pushing NE well to the north of the Faeroes and a mild SW'ly between that and heights over Europe. One thing worth noting from the Northern Hemisphere profile is it seems the LP has detached a part of the PV and while that doesn't seem able to encourage mid-Atlantic ridging it would like the residual vortex much weaker. That being said, it's a significant shift away from the modelling of previous days and it will be interesting to see where this sits in the ECM Ensembles. GEM 00Z at T+240: Very different from ECM and much more in line with what we've been seeing of late. A strong very cold ENE'ly airflow covers the British Isles with HP to the north and a classic LP over the Gulf of Genoa. -8 uppers cover the British Isles with -12 uppers approaching the East Coast so you can guess the rest. On then to the GFS 00Z OP at T+240: Yet another evolution. The HP develops over Scandinavia but the orientation isn't quite there at this time to fully advect the very cold air westwards so we have a SE'ly flow across the British Isles and the Atlantic LP systems are clearly slipping SE towards Iberia which would be a welcome sign for cold weather fans. However, that's not what happens in further FI - the Atlantic trough and the Ukrainian trough expand and meet across the British Isles producing some curious synoptics with, I suspect, a lot of rain for the south and snow for the north but the cold wins out and pushes the Atlantic back so by T+384 the cold is firmly in charge. GFS 00Z Control at T+240: Nearer the GEM than its own OP and a very solid chart for the cold weather fans with HP over Scandinavia and the colder air seemingly coming toward us. In further FI, the HP retrogresses to Greenland and the Scandinavian trough comes into play leaving the British Isles in a cold NNE'ly airflow with perhaps the coldest air more to the east but certainly still pretty chilly. The GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 Still looking very solid for the E'ly. If I was being picky, I'd certainly say 3-4 members had more Atlantic influence but no more. GEM Ens at the same time: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=1&mode=1&ech=240 Mean looks solid and while there's more Atlantic influence than on GFS it still looks a solid suite for fans of cold. I don't normally include the UK MetO charts because they go up to T+144 at best - yep. In summary, we are still a long way from cross model agreement though both GFS and GEM have maintained their consistency. ECM's morning output will be a huge concern for cold weather fans and I can't explain it at this time. I glanced through the ECM members last night and found a solid majority backing northern blocking but the OP refuses to come on board and that will be a concern and rightly so. Having GFS and GEM solidly on side is a big plus and this morning's MetO output will have got many quite excited and given its reputation deservedly so. The other point is the cold isn't being pushed back as some claim - as MetO shows the right evolution can get it in earlier but the timescale of the 23rd-25th has always been where I've looked and that remains on course for the majority of output this morning. I do think the longevity of cold has been improved this morning if that's any consolation. I'm not going to dismiss the ECM output even if it is an outlier - it's an important model with solid verification numbers and it may be right. IF it is, it will deserve all the plaudits but this is still a long way from being nailed and I'm afraid for all of us the roller coaster is starting up again. Buckle Up !!
  7. December 1981-January 1982

    I was living in Denmark at the time and remember the snowfall of mid-December which dumped feet of the stuff on the country in 36-48 hours. Yet nothing stopped working or running and the roads were cleared. I was due to head back for Christmas and travelled on the train from Aarhus to Cologne and then on to Ostend where I was due to get the overnight ferry back to Dover. The trains were freezing and I lived on coffee and bockwurst for hours. At Ostend I got on the ferry but the crossing was hellish - there was a huge storm, people were throwing up everywhere - it was the same storm which claimed the Penlee lifeboat. We couldn't land at Dover because of high seas and so went to Folkestone where I got off about dawn, walked up the hill into the town, found a café, had breakfast and then went on to Folkestone Central to catch the train home. I remember it being a snowy Christmas and I was due to fly back on the 7th from Gatwick and miraculously I got to the airport and the plane went. I remember looking out the window as we climbed out of Gatwick and seeing southern England under a blanket of white.
  8. Interesting to have a look at the temperatures which seems of particular interest and concern to some. Today a range of 3-7c would represent mid-afternoon values for many so chilly but not especially so. The GFS 06Z keeps most of the country close to or below average until the end of the weekend with Monday getting to double figures in some areas. No especially low minima either at this time. By Thursday only Sidney's environment remains on the milder side while much of the rest of the country has slipped back below average: The maxima for Friday 23rd about where we are today followed by a sharp overnight frost. So the sequence, as reflected in the 500 and 850 numbers, is a cool/cold spell through to Friday and then a warming over the weekend peaking on Monday with some places getting to double figures followed by a gradual cooling through next week with the really cold area not present until the following weekend. For those looking at March temperatures, the epic Monday March 11th 2013 is the yardstick - many places had an ice day with -12 uppers widely across the country. In London, we crawled up to freezing point with significant wind-chill. On that basis, if you're looking for an ice day at the end of February into the first week of March, you're going to need -10 to -12 uppers in my view so something like this perhaps: That's an ice day chart and no whingeing and whining about "marginal" from that. You don't get days of that even in midwinter unless you get something like an anticyclonic inversion in the south. Further north is quite different and for Scotland in perhaps the charts offer a prolonged spell of colder weather going into the new month.
  9. Morning all Well, it's fair to say this site went through the emotional mangle yesterday. Stellar morning output followed by what seemed to many as huge downgrades but then discovering the Ensembles were even better than before. Nonetheless, with volatility in abundance and nerves on edge, it all got a bit fraught so where are we this morning ? Whilst being totally aware of the volatility issues, I'm still going to take my medium-range look at the morning's output. So I'm looking to the end of next week - Saturday February 24th to be exact - and as always I'm starting with the ECM 00Z output at T+240: Not as strong for fans of snow as yesterday but the evolution to a Scandinavian HP remains albeit with less favourable positioning and orientation at this stage. A strong SE'ly flow across the UK so you'd think settled and reasonably mild (0 to +4 uppers suggesting temperatures well into the teens) but there's much colder air over Europe and heading our way. GEM 00Z OP at T+240: A complete change from yesterday. The attempt to push the Azores HP across the British Isles and into Scandinavia never gets started and instead LP develops over Scandinavia. There is strong HLB but it's currently too far away though there is a sign of a ridge building from the south to meet the ridge further north. There's a shallow LP in the North Sea so cold and damp conditions down the east coast and across Scotland but becoming more settled in the west. It's a dog's dinner of an evolution this morning and I'm far from convinced. GFS 00Z OP at T+240: This will have calmed a lot of frayed nerves this morning. The evolution is simple - the HP cell from the Azores north and then NW as northern blocking sets up based on Greenland. The E'ly is in place and the colder air is arriving - by T+240 -4 uppers across the country as a whole and -8 uppers crossing the east coast so much colder with the possibility of snow showers further south. Further into FI there's a chance of very snowy weather for the north while the cold lessens slightly and briefly in the south before a new pulse of colder air as the winds switch more NE. GFS 00Z Control at T+240: Another very strong chart for the fans of cold. It's slightly different to OP with more heights over Scandinavia but the jet is very far south. Further into FI the output remains stellar with the core of the HP retrogressing to Greenland and a hint of a disturbance developing in the Norwegian Sea and heading SSW toward the British Isles. Looking at the GEFS for T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 That's a very strong and solid GEFS in support of the OP and Control with just two or three keeping the Atlantic in place. The lack of spread at this time is noteworthy. By contrast, here's the GEM ENS at the same time: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=1&mode=1&ech=240 Much more variety. In summary, the morning GFS output will have steadied nerves somewhat and the confidence in the GEFS behind the evolution is striking but, that being said, cross model consistency remains elusive. GEM OP goes a very different route and its ENS still have many options on the table including long fetch S'lies and SW'lies. ECM is in a different place again this morning albeit with HP over Scandinavia and colder at the gates so I'd say two steps forward for the coldies this morning with the consistency across the GFS a huge plus. GEM OP sits and looks an outlier while ECM may or may not be indicative. Within the overall trend of volatility it's not a bad start to the day for cold fans though not as good as yesterday but a long way from some of the OP-led despair of last evening. Buckle up, I suspect the ride is just about to start again.
  10. Morning all As the old song has it "there are three steps to heaven" and the same is true if considering the path to a very cold and snowy outlook so let's look at the three steps: 1) Build the block - some runs a few days ago had the Azores HP ridging north to the west of the British Isles and then NE into Scandinavia. This was, to paraphrase another song, "the motorway to cold". A more scenic route has the HP moving NE through the British Isles and into Scandinavia and that was advertised widely in last evening's output. 2) Get it in the right shape - HP over Scandinavia only works in terms of cold if it is positioned and oriented correctly. It's perfectly possible to have a HP oriented so feed warmer SE or S'ly winds across the British Isles so the right shape (aided by lower heights over southern and central Europe) is a necessity. 3) Find the cold air and bring it in - it's no use having an E'ly if there is no cold air to advect and that's the important part. Ensuring the HP is far enough north so the cold air is not advected too far south and making sure we are drawing our air source from a cold rather than warmer SE source is the most important aspect of the evolution. So is heaven on the horizon this morning, close at hand or is it going to be purgatory for the coldies with France in the freezer and Britain balmy or chilly ? Today I'm looking out to February 23rd and starting with ECM 00Z at T+240: The Azores HP builds across the British Isles and over to Scandinavia and draws in an increasingly strong and cold E'ly feed through next week. One suspects the blast of colder air might dissipate as the HP looks to be orienting slightly more to the ESE but not much. GEM 00Z OP at T+240: A slightly different evolution from GEM which moves the HP core to Iceland so more of a ENE'ly flow. The first puch of very cold air passes just to the south but the weave of frigid air approaching from Scandinavia looks to have our name on it. GFS 00Z OP at T+240: More anticyclonic and perhaps not as cold. A large HP sits to the NE covering the North Sea and a noticeable SE'ly flow covers southern and western England but it's dry at this time. Further into FI, the HP trends NW toward Greenland and forms a substantial HLB. There is one pulse of very cold air which crosses the British isles but at the very end of FI more than a hint of something much warmer. GFS 00Z Control at T+240: Very anticyclonic but with the coldest air just passing to the south of the British Isles. The evolution further into FI is a coldies' nirvana - the HP retrogresses to Greenland and an LP moves east into northern France drawing in some very cold air from the east. The GEFS at T+240 are one of the strongest for cold I've seen for a long time: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 Life has moved on and we now have the GFS 06Z OP at T+234: Very anticyclonic but with the coldest air just to the south of us at this time. The evolution into far FI is more complex with a slackening of cold air and a more SE'ly flow. GFS 06Z Control at T+240: Not much for fans of cold to complain about. The evolution into far FI is frankly as good as it gets if you want cold or snow. In conclusion, one of the strongest suites for cold I've seen for a long time but to stress a) it's not a done deal and b) for fans of snow there are still hurdles to jump. Some evolutions are more anticyclonic initially so the journey to snow is delayed further while others bring in colder air more quickly. It's hard to see how this can upgrade much further so it's now about consistency, severity and longevity. Some keep any cold air short-lived and return to a much milder SE'ly airflow while others are much more bullish about a 7-10 day severe spell.
  11. Afternoon all Well, it seems the SSW is now upon us and is likely to be of a considerable scale so that will have impacts. Fair to say a rollercoaster of emotion over the weekend with the Highs and Lows creating some highs and lows of their own. On the basis we can see a 10-14 day between the SSW and any tropospheric response, it's entirely possible any response is still at the fringes of the model outputs. I'd also like to mention Tamara's excellent post last night offering an explanation of why continued La Nina forcing might yet blunt the QTR (Quick Tropospheric Response). It remains to be seen if the SSW will overwhelm that as some expect and I have to say looking at last night's ECM EPS there were plenty showing northern blocking late into the month. So to today's outpourings which take us to Thursday February 22nd: Starting with ECM 00Z at T+240: ECM has stood four square against a QTR since the end of last week and continues this morning. The Azores HP ridges NE at the end of the week promising a sine and mild weekend but at this point there's little sign of a ridge into Scandinavia. Low heights over southern Europe are encouraging but the Atlantic still seems strong at this time though the PV does look elongated and under pressure. Fine conditions for many from this chart and just the hint of an E'ly for the south and Channel Islands. Strangely it's a chart that reminds me more of July than February. On then to GEM 00Z at the same time: A very different evolution though from a similar start. GEM sends the Azores HP across the British Isles and into Scandinavia and then moves back slightly westward so we have twin centres over the Faeroes and southern Norway. The Atlantic is weaker with the northern arm running to the far NE and there's an E'ly across the far south though with the coldest air passing over France. Could it correct further north ? Who knows ? With -8 850s clipping the SE it won't be warm but could be quite pleasant over Scotland and Ireland. GFS 00Z OP at T+240: A taste of spring with a S'ly feed over the British Isles The Azores HP tries to ridge into Scandinavia but topples into Europe instead with the Atlantic held at bay. The HP is oriented north-south over Eastern Europe so the cold air is sent far to the east and most of Western Europe enjoys/endures (delete as preferential) a warmer feed from north Africa. Further into FI and slightly counter-intuitively, the HP heads north into Scandinavia and builds a ridge further west toward Greenland. The airflow switches to a SE with a sharp contrast between colder air approaching from the east and milder air over the British Isles and to the west. GFS 06Z OP at T+234: Subtle differences as you might expect. The HP is oriented more NW-SE so a SE'ly flow with a stronger jet profile to the NE. Further into FI, HP is never far away and while the synoptics are confusing, one thing is clear - there's no Atlantic dominance. GFS 06Z Control at T+240: Anticyclonic though it's worth noting Scandinavia is more dominated by LP. An E'ly across the south but is retrogression the name of the game here ? Not quite but the tune is firmly anticyclonic with a SE'ly ruling the roost though, it has to be said, not especially cold. On then to the GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 Have to say the ECM evolution looks in a minority as GFS is looking at disrupting the Atlantic and strongly promoting HP but where ? There are any number of options and the placement and orientation of the HP will be crucial in determining whether we get a final blast of winter or a first blast of spring. To conclude, after a final unsettled spell in the early part of the week, the models are agreed on a push of HP from the Azores at the end of the week but whether that ends up as a blip or something more substantial is far from resolved.
  12. Morning all On we go into February and with the vortex split now imminent and a possible SSW beyond that, more interesting chart watching ahead. This morning I'm going as far as Monday February 19th. Starting with ECM 00Z OP at T+240: Not a million miles away from yesterday's chart at this time and the rapid transition from a strong Atlantic to something much more blocked and amplified remains on course with this model. The Azores HP moves north than north east around the top of the British Isles and into Scandinavia opening the door to a cold ENE'ly flow. Wintry conditions for many especially in the south and east but cold and fine particularly in the north and west. The longevity of this pattern seems unclear at this stage. GEM 00Z OP at the same time: After yesterday's little diversion, it's back to more of what we've come to expect from GEM with little sign of an E'ly or anything cold. The Atlantic has slowed but the Azores HP has ridged NE to the east of the British Isles to link with heights to the north of Scandinavia. On the western side of that ridge, a mild SW'ly flow crosses the British Isles so a taste of spring rather than winter for many especially in the south and east but more unsettled further west. On then to GFS 00Z OP at the same time: A classic winter chart with LP to the north and HP from the Azores ridging across southern Britain and Northern France. A mild SW'ly airflow with the driest weather to the south while the north remains more changeable with occasional rain or showers. Further into FI and the evolution becomes increasingly messy and quite hard to fathom as the Atlantic slows. GFS 00Z Control at T+240: More dominated by LP than the OP but still an Atlantic-dominated chart. Control ends mild with rising heights to the south and the jet being pushed further north. Looking at the GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 Plenty of solutions on offer but only 2-3 offering an easterly component at this time. There's a cluster which build the Azores HP north forming an MLB close to the British Isles but others show the Atlantic still trying to come through and with the Azores HP ridging at the same time we get a milder flow over the British isles than seemed the case yesterday. That being said, by T+336, the number of GEFS with an E'ly component has increased markedly and more so by T+384. In summary, the new acronym on this thread has been "QTR" for Quick Tropospheric Response. Some have shown we are likely to see that QTR from the vortex split and the Wave 2 attacks on the daughter vortices. Perhaps and ECM this morning supports that but neither GEM nor GFS convince and suggest we could be looking at 4-5 days further before we see a significant pattern change taking us into the last week of February. I don't know - I do think proponents of QTR have taken a step back this morning and expecting the tropospheric response as early as T+240 from now seems unlikely but the wait may be worth it (or it may not). More runs are needed as always.
  13. The SSW of Feb 2018

    Afternoon all Thank you for the thread, MIA. I suppose I start from "what would be the indicators the world was warming ?" and logic dictates a warmer world would have a more turbulent atmosphere containing more energy as more heat is released from below to above. That "energy" would cause stronger PVs and by the same token stronger SSWs but would they be more frequent ? Among my other questions would be - has the PV always been in the same place on our side of the Pole ? I presume it's a product of the depression factory that is continental North America and in counterbalance to Siberia where the absence of oceanic current creates a cold, dry HP zone. Outside winters affected by other causes - 1815 being a good example - we have remarkable winters like 1683-4, 1739-40 and more recently the spells of 1947 and 1962-63 (the latter two more pronounced because of our greater civilisation and dependence on warmth and transport). All the accounts I read of 1739-40 suggest something far more severe but was that an early SSW ? One can imagine in an Ice Age with more land and less water a proliferation of cold stagnant HP - I suspect for example the traditional Ice Age image of Neanderthal man in hip-deep snow is overdone. I believe an Ice Age world was a much drier world. You'd think in a warmer world the "battleground" between sources of cold and warm energy would be more violent - stronger storms, tornadoes, hurricanes, blizzards - but what we don't know is IF the Sun is going into a prolonged quiet period what impact that might have. All I have are questions, no answers.
  14. GFS 06Z Control gets there in the end. Fascinating to see this develop at this stage and of course caution is required. As I've said repeatedly, the split vortex and the SSW buys us a seat at the table, not a winning hand. The modelling of the pressured PV is I think an area of uncertainty in extremis.
  15. Morning all A glorious winter's morning in lowland East London but one suspects the last of these for a while with a more changeable spell on the way. This morning I'm looking at the journey in the model outputs to the early hours of February 19th: Starting with ECM 00Z OP at T+240: A fascinating chart to start the day. A large and complex LP develops over SE Greenland over the weekend and dominates the week's weather keeping the British Isles in an unstable flow osciallating between colder and warmer airmasses as it moves first south and then east toward Scotland. By the weekend it is over or just to the east of Scotland but has filled considerably but is now drawing in a cold NNW'ly airstream so wintry showers for many with snow to high ground and some lower levels as well. Behind the LP strong signs of a rise in heights over Greenland propagating south into the mid Atlantic while the LP over Newfoundland meanders north perhaps bringinf some WAA over Greenland and re-enforcing the heights. GEM 00Z OP at the same time: Fascinating chart number two. The remnant LP off the SW coast of Ireland is all that remains of a large deep and vigorous LP which at one point was 945 MB to the south of Iceland but the LP has filled and disrupted in the face of heights to the NE and faded away to the south. A new pulse of cold air coming off the Eastern Seaboard of Canada is aligned negatively and a long way south but there is a growing cold pool over Scandinavia leaving the British Isles in a col. There's a SE'ly over the north but milder air hanging on in the SE. Could we see a big negative tilt to the trough ? GFS 00Z OP at the same time: And there's the hat-trick. As John Cleese would say "And Now for Something Completely Different". With GFS the LP doesn't get anywhere near the British Isles but disrupts far to the NW and so there's little to stop pressure building from the NE and we have a weak ESE'ly flow by this time with the HP centred over Norway. All I'll say about the rest of the OP run is I wouldn't look at it if you don't fancy cold. GFS 00Z Control at T+240: Not quite there but nearly. A more vigorous Atlantic with a final LP trying to spoil the party and it might as it draws up the Azores HP but the Scandinavian HP looks fairly robust. However, further into FI the Atlantic wins out so a huge note of caution that we aren't there yet by any means. Looking at the GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 The OP not without support but the problem is whether this final "tropical" LP heading NE will pull the Azores HP toward the UK and disrupt the E'ly flow. In summary, the pattern change induced by events in the stratosphere moves ever closer and into range this morning. How it is being handled is varying considerably with ECM, GEM and GFS all in different places by the end of next week. Suffice it to say something is happening and the signals are clear but the manifestation tropospherically is still being worked out. Whether we see the Atlantic disrupt far away to the NW or to our south the clear signs for blocking to the NE are evident but whether it is transient or longer lasting is still to be resolved. A fascinating time ahead for model watchers.
  16. Indeed and under midwinter anticyclonic conditions this has happened on numerous occasions but not recently. I can't remember the last truly anticyclonic winter spell with 4-5 days of HP over the British isles and a lovely inversion bringing fog, frost and ice days. It now seems we have a more mobile and turbulent atmosphere and a more powerful jet. I wonder why..
  17. Morning all Onwards and sideways into February we go. A very cold morning in lowland East London but is this winter's last hurrah or a sign of things to come ? This morning's medium term output takes us to Saturday February 17th: Starting as always with ECM 00Z at T+240: A typical winter chart (or indeed for almost any other time of the year). The LP just to the west of the Hebrides is trundling eastwards but filling rapidly having been 955 MB just 48 hours earlier. Frontal systems crossing the British Isles west to east with the mild sector over the SW at this time so cloud and rain for many with perhaps snow to Scottish mountains. Some signs of a slackening Atlantic and hints of pressure rising further west. GEM 00Z at the same time: A very different profile this morning and more akin to the pattern we've seen for much of the winter. The LP has filled and is disrupting SE into Europe between a much more prominent Azores HP and heights to the east and NE. The Atlantic is still strong with new LP coming and a very vigorous feature over the far NE of Canada but the vortex looks under huge pressure so the evolution isn't clear. GFS 00Z OP at the same time: A mild or very mild airflow over the British Isles between a deep LP just off Greenland and HP over Europe so a classic SW'ly airflow. Some signs of trough development to the SW which could presage rain for western areas but more than a hint of spring from that especially for the south and east. Further into FI and pressure builds strongly through the British Isles and to the north opening the door to a very cold E'ly airflow. If there was ever an example of very cold weather starting from very mild this is it. GFS 06Z OP at T+234: As you'd expect, not too different but the Azores profile is different with a larger HP area albeit a bit flabby in places (aren't we all ?). We get to a nice cold evolution for those who like that sort of thing but more slowly oddly enough. GFS 06Z Control at T+240: Subtle differences and more defined heights already in place to the NE with the SE already getting close to a continental feed but nothing spectacular. Further into FI and the Atlantic remains in charge albeit with the vortex looking severely weakened. Looking at the GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 It's a mess - plenty of options as you'd expect but many trying to handle the breakdown of the Atlantic flow - do we see an undercut here, a slider there ? Well, maybe but far too early to tell. Certainly at the far edge of FI there continue to be a lot of cold or very cold options. In summary, then, it remains a case of "as you were". Next week remains unresolved with some output suggesting an evolution to almost spring-like conditions while other suggesting more LP dominance and colder air over the British Isles. After mid month it's all to play for - GFS 00Z OP was close to nirvana for many cold fans and it's far from unsupported and perhaps more likely than a Greenland based HLB at this time but other evolutions are possible and in much of the output the Atlantic and the PV remnant are fighting hard to stay in control. As ever, more runs are needed.
  18. Afternoon all Another day, another chilly but sunny one here in London. Plenty of talk regarding the impact of the upcoming vortex split and the tropospheric response but a lot of weather to come in the medium term which this morning means Friday February 16th as T+240: Starting as always with the ECM 00Z: Continuing from yesterday, the deep LP near Iceland is slowly filling and moving even more slowly east with a large HP ridge from the two HP cells over Azores and western Russia across central and southern Europe so there isn't anywhere for the LP to go at this time. The British Isles is in a cool unstable airflow with showers or rain likely further north (snow to hills) and the likelihood of secondary features and troughs augmenting the rain at times further south. On then to GEM 00Z OP at the same time: Some differences. The Azores HP more prominent and a ridge on the way but for now a cool WNW'ly flow with showers for many. GFS 00Z OP at the same time: With the trough positively aligned, warmer air over the British Isles with a WSW'ly airflow. The :LP is well back over SE Greenland with a pronounced ridge from the Azores into northern France. Decent conditions in the south but windier and more unsettled further north. Further into FI and pressure continues to rise from the south leaving the British Isles in a col between LP to the NW and SE and HP to the NE and SW. GFS 06Z OP at T+234: Between a very deep LP over the southern tip of Greenland and HP over Europe a mild SW'ly airflow affects the British isles. Dry in the south and east but more unsettled with rain and drizzle to the north and west. Further into FI and perhaps the effects of the stratospheric shenanigans begin to manifest as the Atlantic stops to a halt and pressure rises strongly over Greenland leaving the British Isles in an increasingly cold ENE'ly flow spreading from Scandinavia. GFS 06Z Control at T+240: Not too far removed from the OP - mild or very mild conditions across the British Isles with the south and east drier than the north and west. Into FI and the Control opens the door to an early spring with pressure rising to the south and east. Not what cold fans would want but a perfectly possible evolution. The GEFS from 06Z at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 A mixed bag but only a minority showing an immediate tropospheric response. A number have LP disrupting close to or over the British Isles but clearly the medium term evolution remains far from clear. Once again plenty of eye candy starting at T+312 and points onwards but certainly a larger minority of members slower to kill off the Atlantic than yesterday. Worth noting others set up HP close to or over the British Isles but the OP evolution certainly not without support. In summary, little change from yesterday. Next week looks set to be Atlantic dominated and could get quite mild by the end of the week if GFS has it right. However, plenty of options for a windy spell of cool or cold zonality with rain or showers for many. Little immediate sign of trough disruption to the south but the very strong signal for a break in the Atlantic remains but whether that provides the coldies (and snowies) with what they want is far from clear at this time.
  19. I don't follow this at all. No one was expecting the cold air to come back west as early as mid month. The PV is under attack and a split vortex is still on course for the 9th-10th after which the two vortices will themselves be subject to strong warmings. It's a hugely significant event but its immediate tropospheric response isn't yet clear. We are going to have to endure a final Atlantic onslaught next week and all the models tonight have a very deep LP around or to the south of Iceland at T+240. From there, of course, there are any number of possibilities and as I've said from the start, the SSW doesn't guarantee cold or snow - all it does is buy us a seat at the table not a winning hand. I'm NOT going to say a SSW will lead inevitably to colder conditions over the British Isles - it COULD but I'm not saying it WILL. There is a lag as we all know - ten days from 9th-10th takes us to 19th-20th and the very edge now of GFS FI - look at the GEFS of T+372 off the 12z and you'll see plenty of interest. We may finish up with benign boring dross or we may not - it's going to be an interesting few days of model watching.
  20. Morning all One or two excellent comments last night to counterbalance the trolls. No one ever said the coming week was going to produce "feet of disruptive snow" and while my part of lowland East London is dry, very cold and clear currently, who knows what the day and the Thames Estuary might bring ? On then to the medium term outlook and this morning we're looking at where we might be in the middle of next week - Thursday February 15th to be exact. Starting with ECM 00Z OP at T+240: A deep and quite vigorous LP (960 MB) is approaching the NW of Scotland. The frontal rain bands have crossed the British Isles leaving us in an unstable PM airflow from the NW or WNW. The 850s aren't very low though so any wintriness in the showers restricted to hills but there would be plenty of convective activity in that flow. GEM 00Z OP at the same time: As is often the case, GEM produces a very stormy run and it ends with an LP right over the British Isles. This has developed as a secondary feature from the main LP which moved to the south of Iceland and has now filled with the remnant over SE Greenland. A new LP is forming in the Atlantic and you'd imagine that would join the party or head SE into western Europe. Plenty of rain and showers for the south and west, colder further north and you'd think snow for the mountains. GFS 00Z OP at the same time: Quite different. While both ECM and GEM have completely suppressed the Azores HP and the ECM has a negative tilt on the trough, GFS is ridging the Azores HP into Europe and the trough has a positive tilt so a much milder and more benign outlook with the LP still well to the west of Iceland. Settled in the south, perhaps less so further north but nothing exceptional. Further into FI and pressure starts to rise in mid Atlantic but it's slower than some of the FI output from the weekend suggesting the effects of the MJO and the splitting of the vortex appear to be lagging more than some might have hoped. GFS Control at the same time: Mild and benign for most especially in the south. Further into FI and Control also raises heights in mid-Atlantic and ends with southern England under a cold NE'ly airflow from an LP over the Low Countries. Looking at the GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 A number of members starting to hint at mid Atlantic height rises but that translates only into an MLB near the British Isles with too much strength in the northern arm at this time but as Chio said in his superb post last night, the energy displacement from the current wave of warming is vital to ensure the vortex split (still scheduled for next weekend) and the resulting warming on both remaining vortices, That may limit any cold spell we have now but opens the door for more opportunities later in the month. One note of further encouragement, the GEFS at T+312 are clearly showing signs of the Atlantic weakening and the jet amplifying and the OP is atypical at T+384 with almost all options having heights either to the NW or NE. In summary, and it's a repetition of yesterday's message to some extent, the "failure" (as some of the trolls have called it) of this week's cold spell is going to work to our advantage as the Atlantic energy which kills it will in turn start to split the vortex which leads to a sustained Wave 2 attack as we move through the middle of the month. The tropospheric response to that isn't clear yet but the overwhelming majority of options in GEFS FI beyond T+312 are going cold in some form. Will it be feet of snow for all ? Probably not but snow for many is likely and wintry weather for all very likely but nothing can be called yet. For now, GFS offers a mild and benign middle of the month but both GEM and ECM are keeping the energy close to the British Isles so a spell of cool if not cold zonality with wind and rain would be on offer. That medium term issue has still to be resolved but it won't interest the ultra-coldies that much. For them, all I can offer is patience in the short term.
  21. Afternoon all I don't often post in my "Home" thread. Here in lowland East London, we've had one fall of snow (a couple of inches) in December and two instances of falling but non-settling snow since so the best since 2013 by any measure. Living in the urban heat island, getting snow to settle is hard - watching it fall and not settle much easier. I'm not expecting snow to settle in my location this week but I expect to see it fall and I expect people who live further out and higher up to get a covering (and perhaps more). I also see the milder evolution has been pushed back again so if not the brutal cold some on here seem to want or expect (I think there could be some very cold nights) solidly below average this week.
  22. Morning all Certainty a variety of opinions and expectations regarding the coming week and so much of it is expectation and managing that. For some winter is about feet of disruptive snow lasting for days for others it's simply about cold, clear, crisp and very frosty weather. I'd love to see a good old foggy frosty anticyclone - ice days in London but no snow. Never mind, the weather will give what it gives and we take what it gives. Looking to the medium term as usual this morning and that means St Valentine's Day or February 14th if you prefer - starting with ECM 00Z OP at T+240: The ECM run is the classic sine wave of colder and milder interludes - indeed, a typical winter outlook. The T+240 chart is typical - pressure low to the NW and building to the SE with a weak HP over southern England and northern France. Could the HP ridge into Scandinavia or will the deep LP near Iceland continue east ? For the British Isles, it's fairly benign for most but with increasing wind, cloud and rain to the far north-west. GEM 00Z OP at the same time: Not markedly different. GEM has been dragged kicking and screaming to the upcoming cold spell and maintains a strong Atlantic profile with a 940MB LP over or just to the west of Iceland and a strong deep vortex back toward Canada. Pressure rising over Europe and a SW'ly airflow over the British isles so fairly mild and benign if breezy but the frontal rain is close and a clear transition to colder PM air on the horizon. GFS 00Z OP at the same time: For the normally most progressive of the models, GFS keeps the block and the colder air in situ over northern Europe far longer than GEM/ECM but the Atlantic is closing in with the very deep LP we've seen elsewhere so rising temperatures bringing rain and wind (snow on the front edge) to western parts and probably further east. Further into FI the jet slows and begins to disrupt south or SE offering some teases for cold fans. GFS 06Z OP at T+240 (6 hours further on): Very different, A stronger northern arm of the jet but a broad rise of pressure from the Azores through the southern part of the British Isles into Scandinavia so dry and increasingly cold with frosty nights for the south but mild with drizzle or rain further north. Into far FI and mosre eye candy is pressure rises continue as the Atlantic slows to a stop and we get into a colder scene with LP to the south and heights to the north. GFS 06Z Control at T+240: Control close to the OP at this point which is always encouraging for model continuity but the evolution from there is different with a large anticyclone setting up to the west of Ireland so nothing particularly remarkable in the outlook with any colder conditions restricted to the far south east. Of all the morning charts, this is perhaps the most informative of all: The 10HPA Strat temperature continues to tell the story of a split vortex from next weekend and repeated assault son the vortex remnants as the month goes on: The GEFS at T+240 also tell a story: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 It's a story of model uncertainty as the month moves on and it's little surprise with the strat developments. It's worth repeating - a split vortex doesn't guarantee us a winning hand but it buys us a seat at the table. The GEFS are sniffing at the possibility of a weakening Atlantic, a split jet (and plenty looking at sending the energy SE rather than NE) and various permutations of HP evolution and orientation many of which would draw colder air to the British Isles. The other part of the split vortex is the dynamic response which, as we've seen before with Wave 2 warmings, is not to immediately break the vortex but to make it tighter and colder. Tropospherically, we get what might be a counter-intuitive response as the jet fires up and we see the kind of deep LPs we are seeing at T+240 this morning. These can be and have been characterised as "the last hurrah" of the PV but the more immediate impact isn't on the PV but on the jet which slows, weakens and starts to amplify but where that will end up is impossible to know at this time. As the vortex itself begins to displace and fragment and the jet weakens further the opportunity for further amplification offers all sorts of possibilities whether from the north, east or both. In summary, whatever the coming week brings or doesn't bring, there will be a renewed Atlantic onslaught going into mid month which will likely see a transient return to milder conditions before the pattern change takes hold and we get what we get which may be cold but may not.
  23. Nick's comment (picked up by one or two others since) is completely on the ball. We often see the initial impact of a push on the PV as being substantially negative in terms of "cold" over western Europe as the PV tightens and the zonal winds increase in response. No one can be surprised if we have to enjoy/endure a 7-10 day period of Atlantic domination (and the best we can hope for within that is cool/cold zonality) before the tropospheric response to the stratospheric response becomes clear. Given the pressure on the vortex from now until the projected split next weekend and then renewed pressure on each of the vortices I'd anticipate a frustrating milder spell mid-month before we see where the pattern takes us later in the month. Without wishing to sound too downbeat, it's worth pointing out the vortex split offers us only a place at the table - it doesn't guarantee a winning hand of Easterlies. Still, 18Z Control offers one option which will be attractive to many: Everything I've seen today in far FI suggests a slowing weakening Atlantic and jet as we move past the middle of the month. Obviously, that offers some possibilities which may be from the NW or the East. We'll see.
  24. Afternoon all I won't do a full medium term model summation but irrespective of the next 96-120 hours which I'll leave to others, I've never seen much prospect of a continued cold period without any kind of less cold/milder interlude. That seems more and more likely in the form of a stormier and unsettled spell around mid month as the Atlantic stages what is, I believe, its last hurrah. So after this week's cold spell a general easing into mid month and then 7-10 days of Atlantic weather before the next big pattern change which is being well signalled in the MJO, the stratosphere and elsewhere. The manifestation of that pattern change isn't anywhere near settled but plenty of the GEFS in far FI are looking at height rises to the north and east. The key is or will be the decline of the Atlantic as the influence of the split vortex lessens. None of that guarantees cold weather or snow - we could easily finish up dry and cold or even dry and very mild - but we are much more in the game than if facing a relentless PV. One thing is certain - model watching won't be dull this month.
  25. Afternoon all Unfortunately it's all often the case that when the charts get interesting my life gets busy. As so many others, I've enjoyed watching this hopefully interesting cold spell emerge from almost nowhere earlier in the week. There's a lovely animation over on the Finnish Met Office website showing the HP developing from above the point where Finland, Norway and Sweden meet and growing from 1020MB to 1035MB in just 12 hours and extending SW. http://en.ilmatieteenlaitos.fi/marine-weather-and-baltic-sea While you're enjoying that, I'll take a look at the medium range model output which today is going to take us out to Monday February 12th. Starting as always with ECM 00Z OP at T+240: A cold- looking chart though uppers are only -4 for most. Of more interest is the block re-developing over Scandinavia and the movement NW to SE of LP areas and the hint this movement could retrogress further west. Unsettled with rain and snow to altitude for many. GEM 00Z at T+240: GEM has never bought into the upcoming cold spell and has been dragged kicking and screaming to the table in the past 24 hours. Even now, it's a short-lived colder blip before the Atlantic rushes back and this is a very mobile chart with rain or showers for most with a cold front clearing through the British Isles. GFS 00Z OP at the same time: GFS has always played the anticyclonic card and continues to do so here. A brief milder segment embedded within the WNW'ly flow but generally benign and dry for most part from far NW parts which could see a little drizzle. Further into FI and the HP remains in charge with retrogression to an emerging Greenland HP. GFS 06Z OP at T+234: A more mobile and colder pattern with a strong WNW'ly flow off a chilly Atlantic. A secondary LP approaching the SW Approaches threatens enhanced rain and snow to elevation with some cold HPAs (below -8 over Scotland) in place. A colder evolution into FI with a NE'ly over the south which looks set to draw in some very cold air. GFS 06Z Control at T+240: Not hugely different to the OP - a brief quieter spell under a transient ridge before more rain and wind from the west. The Control also ends very cold with a NE'ly flow setting up behind an emerging Greenland HP. Looking at the GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 My observation would be a good number of colder options especially where the British Isles is under a cold col between pressure systems to the east and west. That looks our best prospect for a continuation of colder conditions into the medium term. A number bring in vigorous LP systems where there are milder options as well. Just looking at the Ens further into FI, a growing cluster favouring much colder conditions and following OP and Control. To conclude, events in the next 4-6 days notwithstanding, the best prospect of maintaining the cold theme through the end of next week is to get the British Isles into a col between systems where stagnant cold air can be maintained. That said, there are other milder options on the table and I'm struggling to see the cold theme surviving by this timer next week. That being said, strong signs within GFS FI for a return to colder conditions after mid month with a renewed thrust of NE winds as pressure builds over Greenland. So it could be very cold, less cold, mild, very cold as a sequence for the next fortnight. My final caveat is given the dramatic model evolution of the past 72 hours and the varied evolutions shown by the main models, confidence in any medium term evolution has to be low. Developments elsewhere offer encouraging signs of possible pattern change (GFS 06Z FI ?) but we'll know a lot more as time goes on.