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Showing content with the highest reputation on 01/03/18 in all areas

  1. 27 points
    A POSSIBLE HISTORICAL WEATHER EVENT - PART 3: PROS AND CONS In part 1 (buried on page 170) I examined the early set up and re-conditions to today's event and in part 2, I focused on temperatures and winds. In this part, I'll look at some of the other factors and consider the "pros and cons" on terms of what can go wrong, what can go right going forward from today and through to the weekend. I will do the first bit of this now and finish it off later today in part 4. Before I get going, I need to point something out that some of you might not realise. I just stated in my interim update this morning (on page 199) that the current (mostly light) snow is not the main event. It was part of the snow that pushed up over France yesterday and overnight well ahead of storm Emma. It then moved across the Channel and engaged with the remains of our Channel streamer. The whole band then pushed northwards. There is some additional residual moisture in the Channel now and the surface flow remains (more or less) easterly with the dense cold air still well in place. This recipe might beef up some of the Channel snow and sustain some more light snow during the next few hours. There are also a few other patches of snow moving north out of France that will top this "early" snow up. There may then be a lull for several hours. None of this is associated with the main event. Do not be surprised to see only a little more snow showing up over much of France during the day. Our "blizzard" will start to form much closer to us. The less cold air associated with storm Emma tracking northwards will (already has been for over 24 hours) will over ride the frigid surface flow ahead of it. As the frontal systems associated with Emma approach our cold block, snowfall should develop very rapidly and expand and intensify as it (at least initially) makes very slow and erratic progress northwards. It is this "mild over cold" air that generates the perfect conditions for exceptional snow events. The radar echoes may look quite benign even after midday. I believe that many of us will be gobsmacked by how rapidly things develop early this afternoon. I'll post the usual "key" live charts here to keep an eye on: I need to keep reminding a few of you that the colours in the (4th) "infra red" chart represent areas of thicker cloud, the reds and purples (and whites when they appear) being the thickest cloud. This does not always relate to precipitation but it's safe to assume that on this occasion it does. The strong under cutting remains intact. That is the frigid surface layers still in place under much of the upper flow from north-west France, the UK northwards and further west and then south-westwards right down to the west of Biscay. This is one mammoth battle will probably be fought out right over much of southern and south-west England over the next few days. We have merely seen the very early skirmishes so far. This takes me on to the main point of this post, the pros and cons. What Can Go Wrong and What Can Go Right? Many of us (including me) would imagine that with such a massive deep cold block in place it will be very difficult to displace and that it will put up one hell of a fight. Although the deep cold is an important ingredient, it is the pressure patterns and what drives them that are key. I will keep this very simple so that those of you who perhaps only take a passing interest in the weather can understand (and I am NOT an expert but someone whose lifetime hobby has been learning about some of the processes and studying maps and charts all the time and I'm not experienced enough to go into too much technical detail). You do not need to understand all of it to get a general idea of what's going on. This exceptional cold spell all started with a record strength sudden stratospheric warming event several weeks ago. This impacted on the Arctic and caused the flow at the surface to reverse with HP forming close to the pole and spreading out from there. These HLB "blocking" patterns then set up around the high latitudes of the northern hemisphere. Much of the Arctic cold was displaced towards the middle latitudes. On this occasion we had the almost perfect pattern for cold here in the UK. The Siberian HP extended westwards through Russia, Scandinavia and on towards Iceland and Greenland. The dense and very cold air over Siberia surged westwards right across Europe , the UK, Ireland and way out into the Atlantic. Such was the expanse of this dense cold air mass that it reached into much of central and southern Europe too with snowfalls in parts of Italy and Spain that rarely see them. The near record low temperatures that we have seen would be very unusual even for a mid January cold spell and today is the first day of meteorological Spring! The sheer depth of this cold is also exceptional. The upper flow has seen temps last night fall to below -14c over the entire country and below -16c in a few spots. Even in many of our severest winters we do not see values as low as this. i did a post on the MOD thread several weeks ago comparing this spell to previous winters and this one ranks around the tenth coldest. So, we have both deep surface cold and deep upper cold in place right now over the whole of the UK. So what can it take for this cold block to be displaced or to weaken? With a normal cold spell (without a pattern reversal) the jet stream usually changes course and strengthens and pushes much milder air straight through our country and well into Europe. The charts below show that the main branch of the jet stream has been pushing from west to east well to our south through southern Spain, the Mediterranean and even north Africa.. There is a very weak breakaway streak that's pushing up towards southern and south-eastern England. Just 48 fours later this has dissipated. To me this seems to be too weak to displace the block very far at all (but time will tell). GFS 6z T+6 for 1300, Mar 1st GFS 6z T+54 for 1300, Mar 3rd Now, we need to see the predicted surface pressure charts for the next couple of days. Pick any model or any ensemble chart and you'll find a huge range of solutions. This is the micro scale pattern that we're talking about over 2 days and simply demonstrated that this set up is the most complex one with such enormous opposing forces, that nobody knows the outcome beyond today! I'll stick with the "normally" much more reliable (for 1 to 2 days ahead) Met O fax charts which were updated earlier this morning (and subject to updates soon but part of the Met O is slow to update due to the huge volume of viewers):. Met O Fax for 0600 Thur Mar 1st Met O Fax for 0600 Fri Mar 2nd Met O Fax for 1200 Fri Mar 2nd Met O Fax for 0000 Sat Mar 3rd The first chart has already passed but shows Emma off north-west Spain and Portugal and throwing up a succession of fronts towards the UK. The "ghost" (not blacked out) warm front) which is over riding the deep surface cold.is approaching us. That produced the first impact with the mixing of some "French" snow with our Channel streamer remnants (the barbed trough on the chart). There is a further pulse of snow pushing now and it looks like this will beef up the snow before the main event. In fact it's snowing steadily here now (1230). By tomorrow morning Emma has split into a complex group of LPs. The initial cell is now over the Breast peninsular. The very cold easterly flow is still entact and it looks like the less cold air has yet to penetrate down to the surface. The snow will probably be changing from dry and powdery to wetter with bigger flakes as the air aloft will be closer to freezing. So either more very heavy snow (blizzards with severe drifting in the strong winds) or possibly some freezing rain or even an alternating snow to rain to snow sequence but still sub zero at the surface (I should imagine). By later tomorrow (3rd chart) Emma has hardly moved and the fronts are stalling and queuing up in the Channel - perhaps an even more severe blizzard by then OR temps just above zero and some more rain or drizzle and a gradual thaw. By Saturday evening the now occluded front has pushed up to the Midlands with the flow over the south coming up through France from the south but this will still have a south-easterly wind blowing towards us. Will the less cold air have reached the surface by then? We'll need to watch the charts and monitor the temps etc.. Remember other models and solutions are available. I must get to the Post Office before I get snowed in - so I'll post this now and get on with part 4 later on. Enjoy David
  2. 24 points
  3. 22 points
    EARLY MORNING REVIEW Good morning and welcome to "Spring" everyone This is an "interim update". The big day is here. I've had my first settling snow since moving down here permanently 3 years ago. Here's a very modest pic. Many who missed out completely so far should have had a little overnight and right now. From Inside 0700 0705 Before I starting writing part 3 of my report (see part 1 on page 170 and part 2 on page 184 for loads of live charts) I will do a quick round up of current conditions and overnight developments. Most of these charts are at fixed times so that comparisons can be done later in the day but I'll start with the live radar and satellite ones for reference.. Before a few of you start panicking, this snow is NOT the main event which "should" develop later this afternoon and into this evening (as forecast yesterday) and we have our own "red" warning from 1500 today. There have been a few misleading local forecasts which seem to have suggested that this is the main event now and push it all through at breakneck speed (wrong!). The Met O seem to have a better handle on this and the BBC may well start to regret dropping their service. The red warning (and the previous amber warning) are totally at odds with the local BBC forecast. 0000 GMT 0600 GMT 0100 GMT 0500 GMT The snow that pushed eastwards and then northwards into France yesterday was quite well ahead of storm Emma. That initial band of snow over France has weakened and dispersed. The "all France" radar does not show the Channel snow properly. What happened was that the leading bands of snow from France moved across the Channel in the small hours and engaged with the remains of the streamer. This has introduced some additional moisture and the band has expanded and "may" become self sustaining and bridge the gap to the main event later today or we may get a lull as it pushes northwards. So look at it as an appertizer before things really wind up later on 0800 Round Up: France: Surface Temps Dew Points Windchill Wind UK: Surface Temps Dew Points Windchill Wind Euro: Surface Temps Dew Points Windchill Wind Wind Chart Explanations:This maps show the average wind in real time recorded by weather stations in France and neighboring countries. The red arrows represent the direction of the wind of the stations, and the white arrows (only on the all France chart) represent the direction of the wind calculated at any point of the map according to that of the stations. The colour represents the average strength of the wind. These are the most recent observations of the present time and not forecasts. Pressure: 0050 GMT 24 hours to GIF Live Fronts & Troughs 0700 Mar 1st Met O Fax for 0600 Mar 1st Brief comments: The milder air has made very little northward progress in France during the last 12 hours and the area of southerly winds is still confined to the south west of Biscay. The deep cold over us is still in place and today will see some March lowest max temp records broken.The Scandi HP has only declined slightly and remains in situ (for now), maintaining the block, holding off the northward progress of the LP. The flow has veered slightly more towards the east-south-east overnight with east-south-easterly to easterly winds continuing and strengthening. The Met O fax shows the "ghost" warm front ahead of the other fronts. This is only upper level less cold air climbing well over the surface cold - I discussed this in previous posts and will pick up on it in part 3 of my main report later this morning. Prepare to be snowed in David
  4. 21 points
    A POSSIBLE HISTORICAL WEATHER EVENT - PART 2: TEMPERATURES AND WINDS I think I'll break this into 4 parts, as it's so busy and if I take more than hour (or even 2 hours) the early "non live" charts are already out of date!. Part 1 was back on page 170, where I posted the live radar and satellite charts + pressure with an analysis of the current snow position and chances for tonight and tomorrow morning prior to the much anticipated arrival of the "big one"! I'll focus on temperatures and winds in this part. In part 3 I'll examine what we need to see and want we do not want to see and what is actually hinted at by any of the evidence available. I'll also look at the jet stream and broader pattern set up. In part 4 I'll draw it all together. These will both be tomorrow. Before I go any further, there are three Live charts which I'm going to repeat with each part. They are so important in monitoring developments and I can see them while I'm writing this - I don't want to miss anything. The snow shower activity is increasing steadily as the wind increases (I'm writing this part at 10 pm). Rather than die down in southern areas they are really getting going. The Channel streamer is healthier than ever and is once again moving closer to the coast and it's tail could be traced back to south-east Kent - longer than ever at 10pm. There's another line of quite beefy snow showers (which I'll nickname the A30 streamer for obvious reasons ) stretching from the Thames estuary though London and south-westwards through Hants, Wilts, Somerset, north Devon and Cornwall. Meanwhile I'm still sandwiched in between the two as I'm sure many others are too. The full France radar (doesn't pick up the Channel streamer so well) shows that the snow is making steady progress north and north-eastwards and turning to rain in south-west France. The infra red is simply remarkable, even more so than 2 hours ago. Just look at the enormous undercutting. Almost all that cloud and less cold air is been lifted well above the surface flow. If that profile continues as it tracks closer to us, something has to give and by then it'll be approaching the massive cold block. Can someone post a chart showing the temperature profile with altitude and the lapse rate? If I wasn't writing these reports, I'd be glued to these three charts I've just skimmed through the 12z model output and looked at the Met O fax charts and I'm none the wiser. What a mixture of outcomes. Even the GEFS ensemble panel starts to show a fair spread at T+72. I completely agree with what some on here have said, that even the T+0 nowcasts may not nail this one. Let's get a better idea of the progress of the less colder conditions. All times in headings adjusted to GMT. France temps: 1148 Feb 28th 2048 Feb 28th GIF 24 hours to 2148 Feb 28th Live We need to take account of the usual min/max changes in the GIF chart. The start period is around this time last night. The less cold green colours have reached southern France today. France winds: 1148 Feb 28th 2048 Feb 28th GIF 24 hours to 2048 Feb 28th Live Explanations:This map shows the average wind in real time recorded by weather stations in France and neighboring countries. The red arrows represent the direction of the wind of the stations, and the white arrows represent the direction of the wind calculated at any point of the map according to that of the stations. The color represents the average strength of the wind. These are the most recent observations of the present time and not forecasts. You can also see a ranking of the average wind values in France or see the wind information archive for the past hours or days by clicking on Classification or Archives above this map. You can also have more information about stations by hovering over the map. What we need to focus on is the point where the winds veer from the east or north-east to a milder more southerly or south-westerly point. We can see that at 2048 this evening that the winds over much of France were still more or less from an easterly point and only in the extreme south of France were they more south-easterly and then in north Spain and south-west Biscay they are due south. The winds are much stronger further north and in the UK. Now just a quick look through some UK and Europe view charts: UK Live: Surface Temps Dew Point Temps Windchill Temps GEFS 18z T+0 850 Temps for 2200 Feb 2th Euro Live: Surface Temps Dew Point Temps Windchill Temps With the stronger winds and cloudier skies the min temps may not be quite so low tonight but the maxes tomorrow will be well below zero in many parts, probably some sub -5s around - a nippy start to Spring We should beat the UK's lowest max record set on 2nd March 2001 (at Cassley in Sutherland) with a max temp of -4.6c. The lowest in England was -3.3c at Spadeadam on 2nd March 1965 matching that on 5th March 1942 at Buxton (-4.4c in Wales and -1.2c in N.Irleand). The lowest min temp of -22.8c was on March 14th 1958 (at Logie Coldstone, Aberdeenshire) may survive unless we get some calm clear conditions over the Scottish snowfields. The coldest 850s are just about over us right now. Sub -14s everywhere and pockets of sub -16s just north of our region. This is an amazingly deep and extremely cold block. There is plenty of very cold air over Europe to continue to tap into. Finally tonight - I promised to give my take on tomorrow's snow event and I will now, trying to take wishful thinking out of the process. After some snow in many parts of our region tonight and tomorrow morning - the main event should kick off some time tomorrow afternoon. The snow will start off as the dry powdery stuff for several hours with temps falling even further initially - perhaps below -5c even in our neck of the woods. Then as the flow comes more and more from the south-east it will warm up closer to -1c or even a balmy 0c and the snow will become much wetter and very sticky. There will be widespread blizzard conditions for quite a few hours but perhaps not for the 48 hours suggested by some. I also see a period of freezing rain for some hours as the milder air aloft just cannot penetrate the dense surface cold. Then I see the LP stalling and splitting but no really less cold air making it in. One LP cell will run east under the block and bring back the cold on a north-easterly. The Scandi HP will re-build and the cold spell continues but not quite so extreme as right now. On the other hand we might see some early Spring warmth . Frankly, it's pretty ridiculous to make any forecast in the most uncertain set up we've (perhaps) ever had. I'll examine all the pros and cons in part 3 tomorrow morning and give a few reasons why I really do think that the cold will continue. .
  5. 20 points
    The next person to use an App forecast and go into one in here will be banned ! How many times can you say the same thing, apps are useless , automated forecasts are crap. The weather doesn’t behave according to an app. Will people please stop checking apps every 10 minutes and just wait and see what happens . Moan over ! NS newly assigned App moderator !
  6. 19 points
    Morning all Obviously, focus on the immediate both in terms of snowfall and the complex LP moving WNW and its interaction with the cold air over the British Isles. That's for others - I'll look further ahead to where we might be by Sunday March 11th or Mother's Day or Mothering Sunday or Jackpot Day for a pub with a carvery. Starting as always with the ECM 00Z OP at T+240: A shallow LP is over the north east of the British Isles and winds are light here but further south and west winds are from a NW'ly direction. The LP is part of a complex trough elongated north-south across Europe with centres to the north west of Norway and over Romania. HP to the Azores is trying to ridge north (as yesterday) to residual heights over Greenland. Uppers below zero everywhere so temperatures still struggling and below average. GEM 00Z OP at T+240: Very different or is it simply more progressive? A developing HP over Biscay with a ridge to the north is crossing the British Isles so light winds for most but a residual NNW'ly over eastern areas. Pressure remains high over Scandinavia with a ridge westwards from an intense HP and the jet is lifted north. Uppers remain below -4 for most of the British Isles so temperatures remain below average with frost likely at night. GFS 00Z OP at T+240: Different again and even more progressive ? Perhaps but it's a hint of spring for the British Isles with a southerly flow as a HP moves east and intensifies with the cell now centred over the Low Countries and ridging north. LP is in mid-Atlantic but going nowhere slowly. Further into FI and as expected the HP moves into Scandinavia and intensifies ridging back west allowing pressure to drop over Europe as an E'ly sets up over the south of the British Isles. While lacking the potency of the current spell, -8 uppers in mid March would certainly deliver snow for many and especially so at altitude. GFS 06Z OP at T+234: A very different and flatter evolution. Plenty of colder air over Scandinavia and a weak ridge coming SE from heights over Greenland. The Azores HP is ridging east into Iberia but not really moving north. It's a messy chart and with uppers between -4 and -8 across the British isles still very much on the cold side for the time of year. Further into FI and the jet stays well to the south with shallow LP areas crossing southern areas periodically bringing rain. Looking at the uppers, there are periodic incursions of milder air into the south but the north remains in cold or very cold uppers so any precipitation could well be topping up the snow cover. GFS 06Z Control at T+240: A clear distinction between the colder air-mass over Scandinavia and something milder coming off the Atlantic as the cold trough pulls away far enough east to allow the Azores HP to ridge in. Further into FI and "normal service" is resumed with a broadly SW flow with heights to the south and SE and LP to the north and NW. The 06 GEFS at T+240: http://www.meteociel.fr/cartes_obs/gens_panel.php?modele=0&mode=1&ech=240 Plenty of options but I can only see the odd Member that screams "spring". Most keep winter very much in charge with air flows from the north or east. It's also trough dominated so rain or snow looks likely and with very low 850s especially in the north, I'd argue more snow for many and especially so to altitude. IN summary, the transition from winter to spring looks sluggish at best on today's medium term output. The south seems set to see milder air on occasions as LP pass over or close by and uppers come back nearer zero (which would only denote average temperatures for the time of year). Further north, the air stays cold and temperatures remain below or indeed well below what you would expect. Plenty of rain and snow on offer with the onus on the former in the south and on lower ground and on the latter in the north and to elevation. One evolution I am interested in is seeing a lobe of the Azores HP transfer east and then NE into Scandinavia. This ties in to suggestions I've picked up from GP and others of a further phase of blocking into mid month and beyond. The 00Z OP took that and ran with it and it's been hinted at elsewhere while others keep the trough and the colder air over Scandinavia and as that fades east, the Atlantic comes in. The plethora of options across the models this morning illustrates the uncertainties out there and the hugely unusual environment we are enjoying or enduring currently.
  7. 18 points
  8. 18 points
    I’m from Liverpool but have been based in Spain since the start of the year. I used to spend a lot of my holidays in Scotland , I love the place and the people. I’m really enjoying seeing these pictures and amazing snowfall your all getting. Continue with the videos and pictures they’re making me smile after feeling a bit home sick. Your a good bunch on here. Wish I was up there now and not in this boring 20 degree heat. Hope you all enjoy the snow and obviously all stay safe out there!!! Keep this great thread going!!!
  9. 18 points
    Morning All 2 key items of note this morning * All models agree on the Eastern track of the PPN today -still with varying degrees of moisture - however London is certainly now in the game as well as all the original areas * UKMO 00z now follows the ECM in terms of 500MB profiles & extending the cold all the way through the run, whats interesting ( almost incredible ) is the now, solid continuation of the E / SE convective flow for the N / NE part of the UK ( accompanied by low heights ) as well as the continued risk of frontal weather pushing in from the S / SW turning to snow- The GFS will more than likely follow very soon...
  10. 18 points
    If you are still up and able to do so and it is safe to do so you should get out a wee walk just now, it's beautiful. Very rare to have the streets to myself and unlike anything I've ever seen in Motherwell before.
  11. 17 points
    Please get some pics- Ive seen some old historic pics of dartmoor when houses have snow up to the roofs Best of luck everyone but stay safe-
  12. 17 points
    As I look out the window snow? - check radar show snow - check more incoming? - check I’m up to date -
  13. 16 points
    Interloper from the frozen north here, we've had a foot of snow and drifting and widespread chaos ! . so hope you get yours in the SW - good luck today and stay safe !
  14. 15 points
  15. 15 points
    How are my often forgotten sw coldies doing? Remember folks this snow now isn’t in relation to the main low !
  16. 15 points
    Freezing with a chance of hydrated iron(III) oxides Fe2O3·nH2O and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3).
  17. 13 points
    Couple more from earlier. Wind-scoured Calton Hill 5 minutes up the road from me, and The Mound.
  18. 13 points
    Snow getting heavier now in downgrade central On the plus side Fred Flintstone made it to work this morning
  19. 13 points
    There are some awesome drifts now, the farmer has dug out the road to the main road but it's filling back in. Main road is a 3ft deep 12ft wide snowplough shaped channel through the snow drifts, also filling back in.
  20. 13 points
    Icicles like I've not seen since 2010
  21. 13 points
  22. 13 points
  23. 13 points
    Look, this snow now is bonus snow if you have it! Light snow on and off all day across the region, then the main course later So can you please stop the frankly wrong posts of non event, it’s if nothing else pessimistic, but actually dangerous if people look in here see a post and head out!
  24. 13 points
    Just wanted to say thanks again to Knocker for his extremely informative and well written updates. For those very much in the minority such as myself who regularly read these pages simply to acquire accurate information as to the forecast itself, they really are greatly appreciated.
  25. 13 points
    After being trolled by almost every streamer and blob going, I now have snow! Thin layer getting going.
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