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Bring Back1962-63

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About Bring Back1962-63

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    Bring Back 1962-63

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    Everything weather related; glaciation; coin collecting; cricket; bridge
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  1. LOOKING AHEAD TO EASTER AND BEYOND After an exceptionally cold and snowy spell as we moved into March, followed by a brief return to similar conditions last weekend, many of us will be looking forward to some warmer spring weather or at least something more seasonal. Although a typical spring sees more frequent northerlies and easterlies than in any other season with a few colder spells, it also has some settled and warmer spells with an early taste of summer. We still have some time to see if there's a chance of the latter but the next few weeks seem set to provide further quite wintry weather. In this report I shall be focusing on the Easter holiday period in particular. My younger niece's wedding is on Saturday, March 31st and both families are hoping for some decent weather and have asked me what we can expect. Right now I'm not particularly optimistic. I'll examine the broader pattern and do one of my cross model analyses. I'll also look at potential upper and surface temperatures I'll finish with a more general look ahead to mid and late spring. I won't do one of my Arctic round ups (sea ice and temperature profiles) or my Eurasia round up (temperature and snow cover profiles) in this post but if I have time, I may cover them in another update early next week. . The Broader Pattern: I'll briefly go through the sequence of events that led up to the cold spells which I've covered in much more detail in earlier posts on here. In late January we saw a slight weakening in La Nina followed by a brief spike in atmospheric angular momentum (AAM) from mid January into early February with the usual time lags (of 10 to 14 days) leading to positive frictional torque and then positive mountain torque. This sent forcing "Rossby Waves" into the atmosphere which not only impacted on the jet stream but also on the lower stratosphere. Amongst other factors (still to be fully debated in the thorough post mortem which we shall see soon on both the strat thread and the teleconnections learning thread) this helped to trigger the very strong sudden stratospheric warming (SSW) during February. The SSW process itself was already underway but the final trigger for the impact is what I'm referring to (i go into much more detail on this in the final part of this post). This impacted on the surface with a full pattern reversal in the Arctic and HLB forcing much of the cold there down towards the middle latitudes. The combination of the slight weakening in La Nina with the positive AAM and the torques helped to produce a very high amplitude MJO (again the subject of debate) as it moved into the key phases 7, 8 and 1 (particularly phase 7 on this occasion) which also assisted with HLB. The strong Canadian PV which we had seen for much of the winter was weakened and displaced across the Arctic and towards Siberia. On this occasion the blocking pattern set up with a belt of high pressure (HP) from Siberia through Russia, Scandinavia and on to Greenland and towards north-east Canada. Exceptionally cold surface and upper air surged westwards from Siberia, through Europe, the UK and a long way across the Atlantic. The jet stream was forced way to the south, often tracking into the Mediterranean and even north Africa. The very strong long fetch easterly produced an unusually cold and snowy spell over the UK and Ireland in late February and early March. Then Storm Emma slowly moved in from the south creating blizzard conditions and then freezing rain in much of the far south followed by a thaw and milder conditions which slowly crept northwards. By this time, the weakening of La Nina had almost paused (temporarily - see the last part of this post), relative AAM and the torques went slightly negative and the MJO which barely entered phase 8, quickly lost amplitude and became relatively inactive (in the circle of death). The immediate impacts of the SSW weakened but still left its imprint on the lower atmosphere. We were left with a very odd pattern with the jet stream mostly continuing on a very southerly trajectory and a void between this and the HLB which became increasingly restricted to the very highest latitudes but the surface flow reversal was still evident to some extent. The void was filled for a while with further areas of slow moving low pressure systems (LPs). The strat specialists "had been" predicting a further (weaker) warming event which was likely to impact around or just after mid-March. The existing tropospheric signature from the initial SSW event meant that the surface layers were already primed for another and further cold blasts from the east (or the north) This produced another much briefer surge of exceptionally cold Siberian air which pushed rapidly across Europe and the UK. This time there was no additional assistance and also no interference (the opposite to earlier this winter) from AAM and the MJO both of which remained relatively benign. The SSW imprint has for a while become the more dominant driver. The second cold snap was very brief without that continuing (AAM/MJO) HLB support and we have entered another milder period. Please note that I have greatly oversimplified this explanation and a number of other factors were involved too - probably to at least some extent such as the east based QBO, record low Arctic sea ice build up this winter and the very weak solar influences (extremely low sun spot activity). I still have a lot to learn about the interaction of these drivers and will be fascinated by the ongoing debate into all the causes and relationships. I shall return to the "key" drivers shortly. Let's have a quick look at the current set up starting with the jet stream. I show the weekly changes for the last month: February 22nd March 1st March 8th March 15th March 22nd You can see that the main branch of the jet stream was mostly well to our south during the last four weeks with just occasional weaker more northerly streaks breaking off or looping around the UK. Right now, there is a slight break in the main pattern with the jet in the Atlantic taking a slightly more northerly route before meandering and buckling as it reaches the UK. Met O Fax 0600 Thurs Mar 22nd GFS 6z Pressure T+6 1200 Mar 22nd GFS 6z Pressure T+6 1200 Mar 22nd GFS 6z Pressure T+6 1200 Mar 22nd We are currently under an Atlantic flow with fairly weak LPs and frontal systems pushing into the UK during the next few days. The Azores HP is ridging slightly north-eastwards. There are also fairly weak LPs in the Arctic with a trough of LP extending from the north Russian side of the Arctic down into Scandinavia (this trough will be very important going further forward). There is a strong belt of HP over northern Canada and Alaska extending towards the North Pole. There is still a large pool of sub -16s to sub -24s 850 upper temps across almost all of the Arctic from northern Canada through to Siberia and Russia and a lobe of sub -8s to sub -12s remains across north-east Europe, northern Scandinavia and western Russia. There is a similar distribution of surface cold although values are not quite so low around north-eastern Europe and western Russia right now. Moving Into the Easter Weekend: During the next week to 10 days which takes us through to the Easter holiday period some slight but important changes for the UK are suggested in the broader pattern. Many of the key drivers will change very little. La Nina continues to weaken slightly, relative AAM and the torques are fairly neutral right now and the MJO is also pretty inactive. I will review all these drivers when I look beyond Easter and further ahead in the next section. I looked at the strat thread for the latest thinking and there is talk of an imminent "secondary warming" and/or a "final warming" (these may be the same event) and the demise of the strat PV. This change often (but not always) occurs during this time of the year and is the adjustment to the summer patterns and can occur at any time from later in February until well into April. It's uncertain how much "more" impact this secondary and/or final warming will have. The imprint from the initial SSW is still in the atmosphere. This is likely to be conducive to further bouts of cold being pushed towards Europe and the UK during the next few weeks. Just as I was writing this bit (currently around 1500) I noticed that @Blessed Weather posted on the strat thread. His last two excellent posts there as well as the very informative one from @ghoneym very much compliment what I have been saying. They are two of our "teleconnection team". I refer you to the page: https://www.netweather.tv/forum/topic/88772-stratosphere-temperature-watch-201718/?page=34&tab=comments#comment-3840387 There is a link there to a Met Office blog which has just been released today (Thursday) which is also very much on the same wavelength as my current thoughts. It's entitled "Will The Cold return?" I repeat the link here: https://blog.metoffice.gov.uk/2018/03/21/will-cold-conditions-return/ The comments there are rather oversimplified, nothing wrong with that but on this occasion it refers to the tropical forcing (which is the +veAAM/+veFT/+veMT and one of the triggers of the SSW "impact" (not the evolution of the SSW itself) that I've mentioned above (and pick up on in greater detail in the next part below). Adam Scaife says that this "is being exacerbated by the SSW" which is not quite right or at least somewhat misleading. There is reference to Judah Cohen's latest AER weekly report published on March 19th. I quoted Judah's reports a lot last winter and again in my last post on here about two weeks ago. Here's that link again now: https://www.aer.com/science-research/climate-weather/arctic-oscillation/ This is still very much in line with my current thoughts with a trough moving down from the Arctic in Scandinavia and more cold air being dragged in to Europe and the UK. I just quote one of his paragraphs in relation to our neck of the woods: ...."The PV is predicted to linger across Western Siberia over the next two weeks. This will contribute to persistent troughing/negative geopotential height anomalies across northern Eurasia including Europe. This will allow cold temperatures now stretching from Northern Asia to Europe and the United Kingdom (UK) to mostly remain in place with some fluctuation in intensity over the next two weeks".... Rather than a straight easterly, this time it'll be more from a northerly or north-easterly quarter. I'll now do one of my cross model analyses to see what the latest output looks like up to Good Friday and for Easter Saturday after that. Note that UKMO (to day 6) and Navgem (to day 7/8) do not go so far out. GFS 12z from 1900 Mar 22nd to 1300 Mar 30th GFS 12z for 1300 Mar 31st UKMO 12z for 1300 Mar 28th ECM 12z from 1900 Mar 22nd to 1300 Mar 30th ECM 12z for 1400 Mar 31st GEM 12z from 1900 Mar 22nd to 1400 Mar 31st GEM 12z for 1400 Mar 31st NAVGEM 12z from 1900 Mar 22nd to 0200 Mar 30th NAVGEM 12z for 1400 Mar 30th JMA12z from 1900 Mar 22nd to 1300 Mar 31st JMA12z for 1300 Mar 31st GEFS Control for 1400 Mar 31st GEFS Mean for 1400 Mar 31st There is now some pretty good consensus on the "broader" pattern amongst the 12z model output (JMA is from yesterday's 12z). They show HP moving down from the Arctic through and to the south of Greenland while a large trough of LP pushes down into Scandinavia and northern Europe. There are important minor variations in the finer detail in the position of the LP that is shown to be near the UK. Where available I've included the GIF chart to run through how we get from the current position to Easter Saturday. This shows the trajectory of the LP. One or more of the models show the following; dropping down just to our south-west; right over us; south or us or east of us. The timing will also be important. A little faster and a ridge of HP from the west might move in to dampen down any showery activity and produce more in the way of sunny intervals but still on the cold side. A little slower and we might be into a cold and showery pattern or even with more prolonged precipitation. It may well be cold enough for conditions to turn quite wintry once again. What is shown for Easter Saturday might end up coming through on Good Friday or somewhat later in the Easter weekend. The UKMO model only goes out to day 6 but we can judge their current thinking by the blog that I referred to above as well as their latest text forecasts which states: "The Easter weekend is too far away to be confident with any details. The most likely scenario currently is a spell of colder than average weather, with increased likelihood of overnight frosts, and a greater than normal chance of snow showers, especially in the north." They are right to state that the Easter weekend is still too far out to forecast the micro detail with any certainty. We may need to wait until we are less than 5 days out to home in on the precise position of the LP and even closer to the Easter weekend for the micro detail on how low temps might be and what type of (if any) precipitation we can expect over the UK. Well before I finish this post, the 18z output will have rolled out but as there are likely to be at least small changes from run to run, the cross selection of the 12z output is a good enough indicator at this stage. Let's have a look at predicted temperatures for Easter Saturday. This time I'll just take charts from GFS and ECM for the 850 upper temps and then GFS and GEM for the 2 m surface temps: 850 temps: GFS 12z from 1900 Mar 22nd to 1300 Mar 30th GFS 12z for 1300 Mar 31st ECM 12z from 1900 Mar 22nd to 1300 Mar 30th ECM 12z for 1400 Mar 31st . Both the GFS and ECM drop some sub -12c (to sub 20s) upper temps back into eastern Europe and Scandinavia during next week and towards Easter. The values for Easter itself are not quite so low with sub -2s to sub sub -8s moving into the UK on Easter Saturday. If that LP drifts a little further to the east into the near continent it's likely to drag in somewhat lower values. So the upper temps might also be on a bit of a knife edge in terms of rain or snow.. 2 m temps: GFS 12z from 1900 Mar 22nd to 1300 Mar 30th GFS 12z for 1300 Mar 31st ECM 12z from 1900 Mar 22nd to 1300 Mar 30th ECM 12z for 1400 Mar 31st Both the GFS and GEM (ECM 2 m surface charts of this type are not available) show that temps on Easter Saturday in the south may be around 8c to 12c in the afternoon. Not far to the north we see temps closer to 4c. It would only take a small shift southwards in the pattern to bring those much lower temps into southern and south-west England too. At 1400, these temps will be close to the maximums for the day. If it turns out to be a showery day, temps can fall sharply during the heavier showers. Until we can nail down greater detail nearer the time, it would be unwise to speculate further. I merely wanted to demonstrate the possibilities. if we are to see a flow more from a northerly or north-easterly direction then we need to take account of sea surface temperatures (SSTs) around the UK to see how much modification there might be: Sea Surface temps : March 21st 2018 February 21st 2018 March 21st 2017 SST Anomalies March 21st 2018 The first chart shows the current SSTs. Following the two exceptionally cold easterly spells, there are some very low values right now. The second chart shows the values a month ago just prior to the onset of the first cold spell. You can see that the temps in the North Sea fell by around 2c to 3c during this period and they have barely started to recover since the second cold snap finished during Monday. We should note that SSTs around our shores are usually at their lowest during March. This can vary from around as early as mid February (as in a few recent mild winters and early springs) to as late as early April (or even mid April following the long 2013 March/April exceptionally late cold spell). Much depends on the prevailing weather patterns, the temp of the lowest surface air layers and the strength and direction of the wind. Strong south-westerlies can quickly mix the top sea surface layers. Although these mid March SSTs are very low by recent standards, we have seen much lower values following previous severe winters. Back in the 1960s, Arctic sea ice extent was far greater than it is these days, often hugging the northern Iceland shores towards the end of winter. Following one of the most northerly months in the UK in February 1969, SSTs dropped from above average to well below. The north North Sea was still close to its average back then of around 4.5c (compared that to the 5c to 6c there right now, despite the recent cold spells). The SSTs in the Norwegian Sea were much lower and later on (into the spring melt) a few mini ice bergs were spotted off the northern Scotland shores and were a shipping hazard north of Shetland! The last chart (from the NetWeather suite) shows the current global SST anomalies (excluding the Arctic which I report on separately) compared to the 1971 to 2000 30 year mean. For the first time since March/April 2013, the SSTs surrounding most of the UK are below the mean. This is almost entirely due to the two exceptionally cold spells. Overall, the current low values will provide rather less modification than normal to an incoming air stream from a northerly (or easterly) quarter. Looking Beyond Easter: As there is still considerable uncertainty over the micro detail for the run up to the Easter holiday weekend, I will only look at the broader patterns and set up for this part of my report. There are a few indicators which I have not yet examined in any detail. Let's start with the El Nino Southern Oscillation (ENSO) state. The NOAA weekly reports are always useful to look at. Here's the link to their last report from March 19th: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf I've snipped a few key pages from there and post them below (the last chart is directly from the NOAA website): NOAA expect the La Nina to weaken further with ENSO neutral conditions likely (a 55% probability so by no means certain) during mid to late spring and predicted to last throughout the remainder of 2018. After a steady weakening of La Nina during the second half of January and into February particularly from the lowest values in the eastern tropical Pacific, there was a pause in the warm up but this has resumed again in the last couple of weeks. Anomalies in "all four" Nino Pacific regions are now less than 1 c below the neutral level. The values are between -0.1c (in the west) and -0.7c (elsewhere) and not seen since last summer (compare the values to those in the fifth chart for previous 3 month periods in earlier years). There has been an upwelling of warmer sub surface currents in the central and eastern Pacific during the last few weeks. NOAA also refer to a weakening of the tropical easterlies and an "eastward propagating kelvin wave" . This is somewhat above my pay grade but I have just been consulting on this and it seems that this can be an early precursor to a change to El Nino conditions and one to look out for as the year progresses. The is an ongoing (smaller) risk of a return to stronger La Nina conditions and the next few months may be critical in deciding where we go from here. I will return to this towards the end of this post. Next up, the MJO. Again NOAA's weekly report makes for useful reading. Here's the link: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf ...and here's the summary + two charts from the NOAA site: NOAA Report Summary GEFS forecast from Mar 18th to Apr 1st GEFS forecast from Mar 22nd to Apr 5th ECM forecast from Mar 22nd to Apr 5th Well this is interesting. The NOAA report "was" forecasting a weak MJO remaining in the circle of death (COD). Today's forecasts bring it to life again. The GEFS plot takes it out of the COD into phase 6 during the next few days at increasing amplitude and then on into phase 7 at higher amplitude early next week and through Easter and then on to phase 8 during week 2. The ECM plot takes it on a similar path at the same times but at rather lower amplitude. This is a somewhat surprising turnaround and "may" be quite significant in favouring or assisting with further HLB patterns after Easter (more later). Now onto AAM and the torques. Here we have an excellent new source of data for the GWO (global wind oscillation) plots with an alternative to the GEFS output and also with the GEFS negative biases ironed out. I'll start with the excellent and new Victor Gensini free to view educational site - here's the link: http://atlas.niu.edu/gwo/ This site is still under construction with further developments planned including torque "forecasts" - something we have not had since the two NOAA scientists retired 2 year ago. Here are some of the current charts for March 22nd: Relative AAM By Latitude Relative AAM Anomaly By Latitude Global AAM Anomaly for last 90 days CFS Global Relative AAM 30 Day Forecast GEFS Global Relative AAM 30 Day Forecast CFS GWO Ensemble Mean 30 day Forecast GWO Annotated Phase Chart Looking at the third chart with the AAM anomaly for the last 90 days (these charts are available to go back over a full year) we can clearly see the spike from the low point mid January until the high point in early February that I referred to as the chain of events that helped to trigger the SSW (more after the torque charts). AAM is predicted to remain relatively neutral for the next month. The CFS ensemble members are mostly slightly negative whereas the GEFS members are mostly slightly positive but with no significant spikes for the time being. Frictional Torque (FT) Mountain Torque (MT) Global Calculated AAM Tendency Relative AAM Tendency Global AAM Anomaly Again you can see the spike in the torques which occurred during February. Quite a few people get confused by the timing and impacts of these processes, as did I until a few months ago. If you refer to the annotated GWO phase chart you can see that the process actually starts when AAM spikes from a negative or even a strongly negative position not just when it has gone positive. So in mid January AAM was shown as close to -3 with east Indian Ocean "maritime convection" or around GWO phase 3. Then the chain of events begins. As AAM rises into phase 4 (still negative) FT starts to rise. Then as AAM continues to rise it starts to become positive and moves towards the GWO phase 5 and this is when MT starts to rise. This chain of events has a usual time lag of around 10 to 14 days (in this case from just after mid January to very early in February). The different colour lines on the lower section of the MT chart represent the different torques (the key to these is immediately above that lower section). The black line represents the global torque which was strongly positive for a short while. With this phase of positive MT it was the EAMT (East Asian Mountain Torque) that was the main northern hemisphere influence. As this energy forcing circumvented the globe (known as Rossby Waves which impact on the jet stream causing it to meander) it interacted with the Himalaya mountain range. This sent up energy waves high into the atmosphere, through the troposphere and into the lower stratosphere. This involved a further time lag. Other factors in the strat were already initiating the earlier stages of the warming. Think of the MT energy waves as giving the process a violent nudge. Sometimes warming events do not propagate effectively down to the surface layers. The MT forcing was definitely one of the key contributory factors in triggering the final stages of the SSW and its impact on the surface. These processes and interactions are only beginning to be understood. AAM probably always plays its part in this process. It is not always EAMT that has the largest impact on the strat. Sometimes it is NAMT (North American Mountain Torque over the Rockies) but not on this occasion (it had been positive in January but was slightly negative during the key period in early February). There have been a few papers on the impacts of MTs on the strat in relation to earlier SSW events. The term is also known as "orographic forcing". As part of the post mortem and debate on the teleconnections learning thread into the causes, timing, triggering and impacts of the SSW, we intend to examine past MT forcing types and the links with previous SSW events. It will also be fascinating to see when previous potential SSWs came close but failed to reach the surface. I'm wondering if there was little or no AAM/FT/MT assistance in these years. This should also give us all a better idea of the degree of AAM influence and whether or not it must be an essential ingredient to the overall process. I am very grateful [email protected] for spending so much time during the last few months patiently taking me through the angular momentum learning curve. Whilst I still have much to learn, this has already enabled me to include some of this new found knowledge in my posts on the MOD and particularly on the Teleconnections Learning Thread. There are more detailed explanations of the AAM processes on that thread and I'll remind you of the link at the end of my post. To sum up this section so far, we may well be seeing La Nina move into an ENSO neutral phase. The MJO, which has been inactive for some time since early to mid February shortly before "Beast 1), is just starting to show signs of coming to life and in the key phases of 7, 8 (and perhaps onto 1) for assisting HLB. The SSW has left its imprint on the atmosphere and the secondary and/or final warming (I'll let the strat specialists agree or argue over that one) may help to extend the blocking and colder patterns for longer. AAM and the torques are forecast to be relative benign for the next few weeks. I would say that after the Easter holiday period the Scandinavian trough of LP may start to weaken as further HLB may replace it. This and other factors (partly discussed above) may either prolong the cold spell or allow for further cold bursts with brief milder interludes. Then what many of us want to know is will we see any decent spring weather? What I outlined above may well take us through to mid April. By then, assuming the trend continues, we may well see the demise of La Nina and an ENSO neutral phase. I'm still learning about AAM impacts through the summer half of the year but Tamara has already given me some of the lowdown. With AAM very quiet, the longer lasting impacts of the initial SSW are likely to have continuing impacts for the next few weeks and will still override other factors for some time. This would be in line with what I said above. What we need is something to jolt the tropospheric pattern. We do not know whether we'll see a final warming - it doesn't occur in every year. May be the Nina to neutral changes will help. May be the very recent suggestion of a more active MJO will help. Perhaps we'll see another spike in AAM during April. Quite often the Nina to neutral phase at this time of the year can produce some fine, dry and warm late spring and early summer weather. Positive AAM then will help to push the jet stream back onto a much more northerly track with LPs being driven well away from the UK. For this to happen we do need this jolt I mentioned above. If the broader pattern favoured further easterlies (rather than flows from a northerly quarter) then the continent does start to warm up rapidly during late March and into April. There is still a chance that the La Nina will strengthen again but this does seems fairly unlikely right now. So, although this might seem that I'm saying that all options are possible, what I've attempted to demonstrate are some of the signs to look out for going forward. Finally, I said last time that my MOD posts would be becoming far less frequent as I increasingly focus on developing the teleconnections learning thread. Our bolt on library should be set up soon. The fascinating SSW debate will be underway shortly after Easter and there will be a lot of other activity on there. So why not take a look through now and ensure that you come back to visit us soon. I'll post an update on here when the debate really gets underway. Here's the link: https://www.netweather.tv/forum/topic/89161-learning-about-teleconnection-science-and-background-signals/ or just click on the chart below:
  2. I really do need to wade in here. I believe that you are over simplifying this to the extent you are missing the point and quoting out of context as well as picking holes in something that does not merit this treatment. My teleconnection friends @Blessed Weather and @ghoneym are certainly not jesting and we have been thoroughly researching and consulting on this and taking it all extremely seriously. I am currently in the middle of preparing a very long post for the MOD (to go live later tonight) and I go through this in rather greater detail. What you need to realise is this relationship: The slight weakening in La Nina/ the spike in AAM (that's the start of the tropical forcing reference) in early Feb/ the time lag to +veFT/then +ve MT which helped to trigger the SSW*** along with other influences. Adam Scaife refers to the forcing but does not go into the key detail. This same process was also partly the cause of the MJO to go into a very high amp phase 7 to further assist with HLB. There is still a lot for "all" of us to learn about the interaction of all these influences but you "must" take on board that some of the very recent thinking is starting to accept the vitally important role of AAM in this whole process. ***EDIT: Yes the SSW processes were underway earlier but the main (or one of them) trigger for the impact was the AAM cycle and sequence that followed.
  3. Yes, it's a fascinating pattern and overall set up with repeated cold incursions to come for a few more weeks yet until a "likely" big change later in April to a mostly dry, fine and warm finish to spring and into early summer. The general pattern is entirely plausible and very much in line with my recent thoughts which will be included in my long MOD post for late tomorrow to be entitled "Looking Ahead to Easter and Beyond".. I do think that GFS are over egging the low temps and the snow a little. The SSTs are extremely low for late March but they are usually at their lowest during March (sometimes late Feb and sometimes early April - depending upon prevailing winds and near surface air temps). We have seen lower ones following all our severe winters and mid-April 2013 matched these values). Unfortunately, the Meteooceil archive charts only go back for 3 years but I'll see if I can find another source. From my personal records (taken from weather reports at the time) March 1962, 1963, 1965, 1969 and 1970 all saw much lower values. The Arctic sea ice extent was over 50% greater back then and hugged the north Iceland shores by the end of most winters. In late March and early April 1969 following a very cold and mostly northerly February, mini ice bergs were seen off the north Scottish coast and endangered shipping north of Shetland. The north North Sea had SSTs close to 0c then! David
  4. APRIL 2000 You really must stop distracting me as I've got a huge back log in my work I've noted all the posts re: the 4th April 2000 snowfall and the very wet year that followed. Here are a few charts for that day: If you go to these reanalysis sites you can find so much more. You can check every day and then run through the charts which include northern hemisphere and other views. Here are the links NCEP Archives - Reanalysis of Daily Charts from 1871 to Date: http://www.meteociel.fr/modeles/archives/archives.php?month=4&day=1&year=2000&map=0&hour=0&mode=2&type=ncep ECM Archives - Reanalysis of Daily Charts from 1979 to 2017: http://www.meteociel.fr/modeles/archives/archives.php?mode=1&month=4&day=4&year=2000&map=5&type=era&region=uk Here are some Met O reports: https://www.metoffice.gov.uk/climate/uk/interesting/apr2000recordrain.html https://www.metoffice.gov.uk/climate/uk/interesting/apr2000wintry.html https://www.metoffice.gov.uk/climate/uk/interesting/apr2000wet.html The Met O library contains a vast amount of archive data. I often quote from the monthly weather reports. Unfortunately there is a 7 year gap (including 2000) when the old style reports ceased until the new system started. Here are the links: Jan 1884 to Dec 1993 - monthly: https://www.metoffice.gov.uk/learning/library/archive-hidden-treasures/monthly-weather-report Jan 1994 to Dec 2000 - monthly: There is a gap in the Met Office records - they stopped the old reports and didn't replace them until 2001 Jan 2001 to date - monthly: https://www.metoffice.gov.uk/climate/uk/summaries/2001 Better still we have the "Daily Weather Reports" for the whole period from as far back as 1860 without gaps. These take a little longer to find. They're in their digital archive library and you need to search, refine details and wait for pdf files to load up. Here's the link to all the 2000 charts - stored for each month: https://digital.nmla.metoffice.gov.uk/archive/sdb%3AdeliverableUnit|2e7a0c97-8ed9-4b8d-95b3-22d0d4b2d2ed/ ....and the link to April 2000: https://digital.nmla.metoffice.gov.uk/file/sdb%3AdigitalFile|e303e6c1-6800-494c-b85d-86e000051a2f/ which will download to this: file:///C:/Users/David/Downloads/DWS_2000_04.pdf The month has 124 pages of daily data and 4 pages for each day. Here are those 4 pages snipped: and close ups of a couple of sections: Finally. I feel that I should slightly disagree with those who are likening the weather that we might see this Easter - quite probably with cold winds from a northerly quarter with some wintry showers around or perhaps some more widespread snow (but "probably" less cold and less snowy than "Beast 1" or "Beast 2") to 2000. I'll be doing a MOD report on this in a week or so. That's where the analogue ends. The broader patterns and set ups were very different in 2000 to 2018. A mostly mild and very dry March in 2000, gave way to that Arctic outbreak followed by very wet conditions during April and further very wet weather in spring and summer 2000. Once we get over the effects of the sudden stratospheric warming and the final warming which is likely to produce these further cold spells into early April, there is "likely" to be some significant improvements later in April and through the rest of spring and early summer. The La Nina is weakening to ENSO neutral during the next few weeks. This period is "usually" associated with very weak jet streams. In spring this is likely to produce some dry and settled weather and probably some pleasantly warm conditions. Once we get over the repeating cold patterns with some wet weather in between, we are likely to see a rapid change and warm up. I would be very surprised to see a wet and cool early summer. Nothing is certain but the broad indications are there. I provided all the links so that anyone who is interested in spending hours or days going through this vast amount of data and archive records and reports can do so. I use it regularly but I must have a break now for a few days to catch up with work. David
  5. You people just cannot keep me away I cannot access Knocker's site which seems to have the most impressive images. The first two images are from the pay to view site where (I do not subscribe to) I have special permission to copy images but I cannot disclose the source. The next one (3rd image) is from the free-to-view Meteo Group site: http://meteoradar.co.uk/BewolkingDagZonderFilter The bottom three are from Meteoceil which we all have access to and I know that you (Karlos) and others use regularly. I've been showing their EuroSat and Infra Red images (and their radar charts) in many of my posts on here. I just fiddled around there and used their tools to focus on the UK and filter, animate etc. For those that have not used the Meteoceil site - they have an enormous amount of data on there apart from the standard model output. One can spend many hours on there if you have the time. Here's the link directly to their satelitte page: http://www.meteociel.fr/observations-meteo/satellite.php?mode=image-visible-europe The fourth "live" image will look great in an hour or so, when the remaining high cloud clears southwards. I'm sorry that I cannot get a good close up of the snow. Knocker or someone else should be able to do that for you Karlos. David EDIT: Two more that I snipped and edited for a close up UK view:
  6. OK, just one more thing. Some impressively low dew points - this will dry things out rapidly where there's any melting. My icicles are still growing in the shade but melting in the sun. I'm still at 0c - the "albedo effect" of the deep snow cover reflecting the sunlight is really working hard today. Snow on the grass, even in the sun will only sublimate and evaporate but barely melt if the air temp remains below 4c. With these dew point reading and with clear skies tonight, I expect almost everyone to see below -3c tonight, -4c to -5c over the snowfields (including Exmouth as the winds will be a lighter north-easterly overnight) and -6c or even lower in the frost hollows such as around Liscombe and near Dunkeswell Aerodrome + many others. This may be setting an new record low min for second half of March in the south-west. Dew Point Temps: Live UK UK Last 24 hours to 1050 GMT Mon Live Euro Last 24 hours Euro 0910 GMT Mon Live UKTemps Live Euro Temps Finally, I'll sound the "all clear" Goodbye for a few days, at least. Thanks for putting up with me David
  7. A QUICK FINAL ROUND UP AND SOME MORE PICS Well that was all a real treat for those that love the snow and did not suffer any hardship or disasters. I'm snowed in at the moment as I live at the top of a low hill and I do not have snow chains or winter tyres. The warm ground should melt the snow in the road during today especially if we get a little sunshine but the temp is still -1c here. I expect it'll get up to 2c or 3c by lunchtime unless that small area of light snow reaches south Devon. Just one final look at a few charts: Live UK Radar Live France Radar Live Satelitte Live Infra Red Satelitte Live UK Pressure Live Euro Pressure Last 24 hours Euro Pressure Fronts & troughs at 0600 GMT Mon Live UK Temps Last 24 Hours UK Temps Last 24 Hours Euro Temps Last 24 Hours UK Ground Temps at 0900 GMT Mon There is still a little mostly light snow shower activity revolving around in the LP circulation coming out of France and in the Channel and some of this on its northern edge is brushing the far south. Here's a snip of the NetWeather radar at 1015: it's moving south-westwards and the whole area of precipitation is being dragged away southwards and south-westwards leaving the UK. Apart from that there may be the odd snow flurry but I feel that the proper snow in "this" spell is now over. Those, like me, who saw a lot of snow, would have seen it finally accumulate on the roads and pavements yesterday. Apart from the power of the sun, the ground temps are still around +2c to +3c throughout our region (see the last chart). So, apart from anywhere that saw some larger drifts, the roads and footpaths will be clear later today. With the temp only rising slightly above zero for a few hours, the general thaw will be quite slow today in shaded parts and on grass. As in the last "beast" spell, we've had very dry, powder snow. This contains less than 10% of the moisture compared to our usual wet snow. So, it will disappear quite quickly, especially tomorrow and will add very little melt water to those areas that were seeing some flooding last week. Tonight will see some particularly dangerous conditions when the temp falls well below zero with a very hard frost - I predict a -6c somewhere in the snow fields (near Liscombe for example). Any melt water will freeze and leave a lot of black ice patches from around 1900 onwards. I should all be clear again by 1000 tomorrow. Now for a few pics: It was difficult to measure the depth. There had been some sublimation overnight (sinking and compacting of the snow cover under its own weight). Maximum level depth were 18 cm to 20 cm. More like 15 cm now. There are some drifts down the road of over 50 cm (no pics). I must dig out my car later on. The daffs are buried with just one bravely poking through - looks like it's regretting that Should I have put the bins out? Icicles everywhere - some are over a foot long now. There is one outside my bedroom window which is about 30 cm long. I couldn't get out there with a ruler but I've annotated two chart s(very crudely). From the same window you can see my faithful lamp post. So it has been watching snow overnight and watching iclcles grow in the day light I do need to catch up with a lot of work now. So, I'll sign off until the next extreme weather event. There's likely to be some northerlies, north-easterlies or even a beast 3 in about 10 days time. Any beast will be tamed as the source region of Russia and Siberia will warm up rapidly during the next few days. A north-easterly from the Arctic and tracking over Scandi can still produce unusually cold weather as it did in late March and early April 2013. I'm not predicting a repeat of that but it's possible. With La Nina steadily weakening, ENSO neutral conditions usually favour some settled spring weather with very weak jet streams. So it might be a quick change during April from cold to warm. David
  8. UPDATE ON THIS EVENING'S SNOW PROSPECTS Having done a comprehensive post on our snow chances for this evening 6 hours ago, I see that I might have been a little too cautious! I did spot the small breakaway area of snow and I stated that it might brush the south-east. I also said that "unless there were further developments" we could probably ignore looking east. The band of snow over western Germany and northern France "was" fizzling out as it spread westwards towards Belgium at the time I started writing that post (1130). Just as I was finishing off the post and was proof reading it, I noticed that the band of snow was re-invigorating again. Hence my edit at the bottom. I also said that I would be back with an update if there were any developments. Well there have been and here I am again So, let's have another good look. Please refer to my post on page 94 for some of the details and I'll pick it up from there: Live Radar - UK view Live Radar - NW France view Live Radar - NE France view Live Radar - All France view Live Radar - Germany view Firstly, the current south-west snow. There have been some interesting changes this afternoon. The main snow area continued its westward progression. It reached east Devon around 0800, here in Exmouth at 0930, south-west Devon around 1030 and into east Cornwall by 1130 and westwards since then. Meanwhile it cleared west Dorset and the far east of Devon around 1400 to 1500. At 1600 it stopped here and I took a few pics (see at the end of this post) but by 1630 it started again and has been moderate at times. I have about 16 cm to 18 cm now, almost matching "Beast 1" and it's still snowing - temp is still -1.5c and it has been an "ice day"! What has happened is that the snow which was always being enhanced by being pumped up on the eastern side in the circulation of the minor LP disturbance (now centred in the middle of the western Channel has developed a couple of snow streamers. One is running from Cherbourg towards central southern Devon with Exmouth and Exeter near its eastern edge and South Hams on its western edge with Torbay in the centre. The second one, which is not so well defined, runs on a roughly parallel route about 50 miles further west into the Lizard and down to Land's End. The whole snow area is beginning to weaken and break up very slightly and it is also pivoting within the circulation. It's still making some north-west progress but is moving out of south Wales. The circulation of the minor LP shows up very well in the second chart. The snow shower activity further north is gradually dying out as the HP pushes down towards northern Scotland. Now this evening's snow. The band of snow that is moving out of Belgium and north-west France is not only spreading into south-east England but it's showing sings of developing and expanding. It doesn't look very potent in France or Germany but the very cold dry air is picking up some moisture and instability as it cross the extreme south of the North Sea and the eastern Channel. it's now extended northward to Essex and Suffolk, the south Midlands, through London and and it's on a westward journey (EDIT: 1915 - it has now reached Hants and just east of the IOW and it's still expanding and intensifying slightly). It's actually being dragged into the wider circulation of that minor LP in the western Channel as well as the general circulation of the main LP which was centred over central France but is now over northern Italy - you can see the mini and the wider revolving patterns when you view the whole of the European view in the first two charts below. The last three images show the depth of the cloud and the areas of snow and snow showers around and over the UK. Live Satelitte Live Infra Red Satelitte Pay To View Satelitte Images (I have permission to copy these but cannot provide the source or the link) Met O Fax 1200 at Sun Met O fax for 1200 Mon Fronts & Troughs at 1200 GMT Sun Live NW France View Pressure 24hr to 1648 GMT France View Pressure There have been minor changes in the position of the fronts and troughs. The wriggling front is now shown to be closer to the south coast and even by 1200 tomorrow the front is not as far south as it was shown for this time on the last fax update. The live pressure chart shows what I was describing above with that small LP gradually slipping southwards into the Brest Pensinular but a trough is extending north-westwards towards the Lizard. The 24 hours chart shows all this very nicely. Now we need to look slightly ahead. The Arpege 12z has changed slightly from the 6z run. The minor LP in the western Channel deepens a little more and holds its north-westward and then westward trajectory a little longer. That change was probably sufficient to set up the two streamers. The LP then dives southwards and links up with another centre intensifying over Biscay and looks set to merge later on with the LP centre over Italy. There is still not much that shows the minor changes in the flow further east. The upper flow on the jet chart does now match rather more the surface flow. The upper LP and cold pool moves from SW England to the south of France during tonight and tomorrow. There is a further revolving pattern to the north (the white area). In fact you can now see all this wider circulation in all four charts below. The surface pressure, the upper flow, the wind direction and convergence and finally in the precipitation chart. So, I would now say, that some (at least) light to moderate snow looks likely to spread from the south-east and east into our region later this evening. The exact extent, timing and intensity will be very difficult to pin point. If there's any snow left in the south-west the new feed might invigorate that briefly too. This still may not come to that much or it could develop further. Nowcasts, radar and satelitte charts at the ready again! Arpege 12z - Pressure 30 hrs to 1800 Mon Arpege 12z - Jet 30 hrs to 1800 Mon Arpege 12z - Wind 30 hrs to 1800 Mon Arpege 12z - Wind 30 hrs to 1800 Mon It's still snowing lightly here (1930) and still 1.5c. I'll close with the pics that I took at 1600: it was (at 1600) about 14 cm deep on my front path. The paths, pavements and the road got less due to the earlier melting (above zero ground temps) and the depth on the grass was around 17 cm to 18 cm but my pic of that measurement did come out (I'll get another one tomorrow when it may be over 20 cm!). There are some 40 cm to 50 cm drifts which I'll photograph tomorrow too. The last three were taken by my brother who lives about a mile away from me. He had similar depths but it looks snowier than here - I'm further inland and about 10 m higher. btw that's not me - it's a snowman
  9. LOADS OF MEMBERS ARE ASKING - WILL WE GET MORE SNOW THIS EVENING? Quite apart from the posts on here, I've now had 7 PMs enquiring about the prospects for later today. Well, I'm still enjoying the current snow band which has already produced another 12 cm in 90 minutes and it's almost white out conditions right now (currently 1130) and down to nearly -2c. I want to get out in the snow soon to get some pics. I also run a full time online business from home and I have some work to do. I'll have a quick look now and give it my best shot. I need to keep posting the radar, infra red and temp charts to keep an eye on things and then I'll examine the micro pattern: Live Radar - UK view Live Radar - France view Live Radar - Germany view Live Satelitte Live Infra Red Satelitte Live UK Temps Live Euro Temps Live Euro Pressure Live NW France View Pressure 24hr to 1148 GMT NW France View Pressure Firstly we need to focus on the current and live charts. Right now most of central southern England, the south-east and east are pretty clear of any snow. The snow in the south-west will continue for about another 12 hours (Devon) and up to 24 hours (Cornwall). There is a small patch of snow drifting westwards from Belgium which may hit the far south-east this afternoon. This was linked to a wider band of snow over northern France and Germany. It does seem to be fizzling out and I do not believe that we need to bother too much by looking east (unless further developments show up out there later on); those deeper colours on the infra red are starting to fade but keep checking for renewed developments - the chart represents deeper and thicker cloud which is not always producing precipitation but usually is. The snow shower activity in the east and north of the UK will continue but should gradually weaken as the HP to the north slowly sinks towards northern Scotland. A few lighter snow showers may develop again over East Anglia this afternoon. So we can discount any more of those showers reaching our region (except perhaps a few in north Oxon if those East Anglian ones develop). Most of today's snow has been developing in the circulation of the minor LP over the mid Channel. There is a small centre that shows up just north of the Brest Peninsular and a bulge (or slight trough) of LP north-west from there. Several model runs have been showing (on and off) further small developments in the air stream in the eastern Channel - so we need to focus on that area. I always like the Met O fax charts and the excellent Arpege model which has been almost spot on with the Channel disturbance so far: Met O Fax at 0600 Sun Mar 18th Met O Fax for 0600 Mon Mar 19th Arpege 6z - Pressure 30 hrs to 1200 Mon Arpege 6z - Jet 30 hrs to 1200 Mon Arpege 6z - Wind 30 hrs to 1200 Mon The Met O are showing the wriggling frontal system (the one that cleared south through us on Saturday morning and brought in the very cold air) to push southwards into France by 0600 Monday (shown as a cold fornt again on the second chart). So unless a further wave develops on the front, we can probably discount any more activity from this source. Next we need to keep an eye on that circulation in the Channel. The third charts shows that the bulge (or trough of LP) in the air stream pointing north-west does develop a temporary minor cell of LP. I've already accounted for this in yesterday's and this morning's updates. It move westwards just south of the south coast from roughly south-west of the IOW right now to just off the Lizard Pensinular by late this evening. Then it dives back southwards and merges back into the main LP centred over Biscay by Monday morning. This is enhancing the snow over south-west Dorset and south Devon now and then, more especially, over Cornwall later today and this evening. Unless this feature changes course, stalls or deepens slightly further (all fairly unlikely in my view but by no means impossible) other parts of our region cannot expect any further action from this feature. Next we need to look for other waves, disturbances and/or minor features developing further upstream towards the eastern Channel. Given the exceptionally cold surface and upper temperatures and the easterly flow (with east-north-easterly winds blowing the cold air off the land and not in from the sea at the surface) and the large temp contrast with the Channel (sea surface temps there are 5c to 6c in the east and nearer 7c in the west near to the coast) as well as some instability in the upper and middle flows, we cannot rule out anything turning up unexpectedly. There is another very minor bulge or kink in the easterly flow showing up at around 0200 Monday on the pressure chart. This may come to nothing, may produce a little light snow or it may develop a little further. The latter two scenarios are not suggested on their 6z run (12z run due out around 1600 or so GMT). Next we need to look at the upper flow. A lot of the enhanced snow activity in the south and now south-west was caused by an upper cold pool moving from Poland westwards across southern England and then south-west over Cornwall. This is an upper LP and helped to drag in the sub -10s 850s last night. If you look at the jet chart you can see the upper LP pushing south-westwards through Cornwall right now. Then it's predicted to move out into the western Channel this afternoon before pushing south and then south-eastwards into central France by Monday morning. There is a minor or shallower upper LP or shallow cold pool showing up over Denmark and pushing south-westwards but this seems to be steadily weakening and is probably nothing to be excited about. Finally, the wind chart tells us more than just the strength and direction of the wind. It shows minor kinks and waves in the flow. That slight wave that I mentioned showing up in the pressure chart is even clearer on the wind chart. It shows up later this afternoon and early this evening moving over south-east England. Then it moves south-westwards in the flow out into the mid Channel. You can see a convergence zone developing for a short while there at about 0800 on Monday but rather than moving towards southern England it rapidly slides south-south-westwards and then down into Biscay. From all this, I think I'll predict some heavy rain for Biscay early tomorrow morning Overall, I am not very optimistic about new snow prospects for this evening. We need to stay glued to the live radar, satelitte images and the pressure charts. The 12z and 18z Arpege and other high res models will be interesting. Something might develop out of the blue or one of the minor disturbances I mentioned might become more significant. The snow is temporarily lighter right now (1320) but there's over 15 cm out there and I'll get some pics later. It's -1.5c and the radar suggests some more to come before it all clears westwards later this afternoon or early this evening. Right now the snow depth is not far off the early March depth and the temp is only slightly higher than then but no freezing rain in sight. Pretty impressive. EDIT: in the last half hour or so the activity to our east does seem to have increased again slightly. So definitely keep an eye on the live satelitte and radar charts. I'll be back soon if this develops further.
  10. A SHORT UPDATE FROM A VERY SNOWY EXMOUTH Well I spent the last two days telling all of you that almost all of us will see a lot of snow and sticking my neck out by giving depths well above most of those that have been forecast and yet some in my area must have been thinking that I'm just an excitable child ramping it all up. Until half an hour ago, I might have agreed with them....not The snow has swept in and it became heavy almost immediately. Mostly the very fine flakes swirling around but occasionally switching to big flakes with drifting. I had about 2 cm from yesterday and last night but this has already doubled. I would say that at this rate it'll be at least 3 cm to 4 cm per hour. The temp had risen to -0.5c before the snow arrived and it's now back to -1.5c. The snow IS settling on the road and pavements. For Exmouth to have an ice day at all is rare but this will be the 4th one this month There is a stiff breeze here (I'm at the top of a low hill and 2 miles inland from the coast on the north-east outskirts of Exmouth). Judging by the radar, the satelitte and all my other charts - I expect this to last for up to 12 hours - perhaps longer with 15 cm at the very least and drifts of 30 cm to 50 cm. So, the moors should see 2 to 3 times this amount! I'll get a few pics this afternoon. In the meantime a few more charts - without comments this time (to add to all those that I posted on page 83). David NW Radar at 1015 (snipped) Live Rain/Snow Radar Live Satelitte Live Infra Red Satetelitte Fronts & Troughs at 0700 Sun Jet Stream at 0900 GMT Sun 850s at 0900 GMT Sun 2 m Temps at 0900 GMT Sun Dew Point Temps at 0900 GMT Sun GroundTemps at 0900 GMT Sun Wind Speed & Direction at 0900 GMT Sun Selection of (4) Pay to View Satelitte Images (I have permission to copy them here but I cannot disclose the source or animated them)
  11. Yes - 1148 this morning, give or take a few seconds Seriously, it should reach you around lunchtime and I would expect you to get at the very least another 10 cm - 15 cm, as will much of Devon and Cornwall. David
  12. A QUICK ROUND UP NW Radar (snipped) 0800 Live Rain/Snow Radar Live Infra Red Satelitte Live Temps Live Dew Points Pressure 24 hours to 0648 GMT Sun Live Pressure Pressure 30 Hour Forecast from 0000 GMT Sun Met O Fax at 0600 Sun Met O Fax for 0000 Mon Good morning everyone I managed 4 hours sleep to recharge my batteries for today. Many of us have seen some decent snow accumulations overnight, particularly those in the east, north and north-west of our region - probably anything from 2 cm to 15 cm (or more) with some impressive drifting. Some of us, including me, in south Devon and south Cornwall have only seen 1 cm to 2 cm ( 2cm here and -1 5 c) so far but we will see a lot more this morning. The wave disturbance and the minor LP have developed/are developing and moved/moving westwards more or less as expected in terms of intensity and timing. You can still see the strong "upper" circulation from this system on the radar. It's currently centred over the mid Channel about 30 miles south-west of the IOW and 30 miles north-west of Cherbourg. This is continuing to generate more and more snow mostly on its eastern flank. This is being pumped northwards and north-westwards. The IOW and Hants, Wilts, north Somerset, parts of Gloucestershire, the Bristol area, the south west Midlands and much of Wales have seen much of the heavier stuff so far. There was some in north Devon and north Cornwall a little earlier too. There is a clear patch south-west of this area over much of Deon and Cornwall. The whole snow area is slowly moving westwards. Much of Dorset and Somerset are now the centre of attention and then east and south Devon will be within an hour or so (circa 0900). You can see on the pressure forecast chart that the tiny LP develops a little more this morning. So as the snow area moves westwards it should intensify somewhat. The Met O 0600 fax chart shows the frontal systems and troughs associated with this LP. Yesterday's cold front that cleared our region in the morning and brought in the very cold air, is wriggling around with a wave close to the IOW now. The "ghost" warm front (the one that is not filled in) is shown clearly. I coined this term when we had the initial impact from Storm Emma. It's where the warmer air in the system is uplifted and cannot penetrate the the deep cold surface (easterly) layer. In fact the warmer/moist air generates far more precipitation. Unlike last time, this layer is much higher, so there should be no danger of freezing rain. So, all the west of our region (from Dorset and Somerset westwards will see a lot of heavy snow this morning. It will reach Cornwall by lunchtime and will not clear Devon until this evening. South Wales, which has already done well, should see quite a bit more too. There are still signs of a little, probably lighter and more patchy snow further east and this set up might produce one or two more surprises today. Meanwhile the snow showers continue from the north Midlands northwards. Some of these will feed back further south this afternoon before they gradually reduce in intensity. The temps are well below zero and many parts, especially in the centre and west of our region, should see an ice day. All the snow will continue to be the dry, powdery type. Some of us are still seeing little snow settling on the roads and surface concrete and tarmac. I gave a detailed account and explanation of this with a series of charts around 2300 last night - so please refer to my "ground temps" post for that. Right, I can see that the snow area is just a few miles east of here and now into east Devon. So, I'll prepare to enjoy it. More later on. David
  13. Beast 1: The air circulating around the Scandi HP only reached our shores very slowly, initially on a dry and rather cold south-easterly. The Siberian surge of very cold air moved in, along with the very low 850s, took about 3 days to cross Russia, Europe and push out across the North Sea and the UK and Ireland. Then the exceptional low level convection started producing a few days of snow showers. Then storm Emma engaged with the deep cold and produced blizzard conditions in the south, before a period of freezing rain for many and then less cold air gradually moving up from the south. Beast 2: The deep cold air was never pushed away very far. Europe warmed up but northern Russia and northern Scandi remained very cold. This Scandi HP drifted down from the eastern Arctic and pulled in the very cold air back across north-east Europe and Scandinavia. Then, late on Friday and into early yesterday, the HP pivoted from a north to south axis to an east to west axis. This opened the floodgates and the very cold air (surface and uppers) surged westwards across Europe and into the UK. The low level convection formed almost instantly and snow showers started early yesterday just behind the cold front. Now we have a minor disturbance engaging with the old cold front that cleared the south coast on Saturday morning with heavy snow developing as I speak. Live Rain/Snow Radar Live Infra Red Satelitte Rapid developments now (0130) with some very heavy snow in many parts of our region. Will peak in the next few hours - so SNOW, SNOW, SNOW My lamp post has gone out and there's over 2 cm lying now, including the road and pavements. I keep sticking my head out of the window - still snowing heavily. David. EDIT: Yes, time for several hours sleep. Goodnight all.
  14. TIME FOR AN UPDATE My long posts on here with all the charts take an hour or two to prepare. They're quickly out-of-date. So, I'll break them down into much shorter ones covering a few different angles each time. Live UK Rain/Snow Radar Live Infra Red Satelitte These 3 Satelitte images are from a restricted site; I have special permission to copy them but I cannot disclose the source Jet Stream showing upper low/cold pool 48 hour Pressure forecast 48 hour wind direction & speed Live 2 m Temps Live Dew Point temps You can clearly see the rotation in the Channel centred between the Cherbourg Peninsular and the Isle of Wight. This is evident in the radar, satelitte, pressure and wind charts. Arpege was again almost spot on. You can see the initial bulge in the pattern moving from the eastern Channel westwards and a small LP cell develops on that wave and pushes along close to the south coast from IOW westwards. The jet chart shows the upper LP pushing southwestwards through southern England. This has moved in all the way from eastern Europe and some of the lowest uppers (sub -12s) were dragged into the east with it (sub -10s over all of our region). The circulation in the mid Channel is not at the surface - so the very cold easterly is maintained. With the winds only coming off the land (east-north-easterlies) there should be no danger of any modification from the sea. Instead the moisture there will get into the middle level circulation and enhance the precipitation. The snow area has been moving from south east England and intensifying in the circulation. It's taking a slightly north-west route before turning south-westwards towards our region. It also engages with the shower activity on its northern edge. The snow in the western Channel is from the cold front that cleared our region earlier yesterday morning. It stalled and the LP is actually linking with it and reinvigorating it as it wriggles around as an occluded front (I'll show the fax chart on my next update). Most of the very heavy snow will develop rapidly over the Channel and merge with the snow moving westward. This is almost a three-pronged attack. I'll stick to what I suggested earlier. 5 to 10 cm in the south-east, 10 to 20 cm further west and potentially 30 cm + in parts of the south-west, locally more especially over the moors. Potential for a strong blizzard and even a red warning for the far south (IOW westwards and up to 20 to 50 miles inland) and much of Devon and Cornwall. Still some good accumulations further north, perhaps up to the south Midlands and south Wales. The snow is already growing heavier and the main event should be peaking within 3 hours. A lot more white (heavy snow) should be appearing on the radar within an hour or so. My lamp post goes off at 1 am but I'll be up for quite a few hours yet (at least).
  15. NO NEED TO BE SO GLOOMY - THINGS ARE BREWING NICELY! SNOW NOT SETTLING YET - WHY? Some of you seem to be getting quite worried. Everything has been moving in the right direction during the last few hours and by around midnight some heavy continuous snow will be showing up in our region for many of us. Some of us are already seeing snow turning steadily heavier (2230 at the time of writing this bit). I've had steady moderate snow here for the last hour and yes, it's starting to settle on the road and pavement. I'll do a general round up in an hour or so but right now I'll address the query about why the snow in some parts isn't settling on the roads and footpaths (yet). I did mention this in several of my posts yesterday and this morning and showed some charts but I'll explain it properly now. We need to focus on the ground temperatures. In the last cold spell most places down here had 1 or 2 ice days prior to any significant snow falling. The ground was frozen solid to quite a depth - perhaps to over 10 cm. All the snow settled immediately and swirled around on all surfaces. This time around we have almost as low uppers and 2 m surface temps with very low dew points and an even stronger easterly wind blowing off the land not off the Channel. The one ingredient that is missing is that the ground temps are well above freezing. I've dug out the ground temp charts from the GFS archive runs at T+3, so barely forecasts and as close as I can find for broadly accurate values. Then I've taken tonight's 18z run and gone slightly further ahead but these are forecasts but still provide a reasonable idea of what to expect.: 18z for Fri Mar 16th at 2100 GMT 0z for Sat Mar 17th at 0300 GMT 6z for Sat Mar 17th at 0900 GMT 12z for Sat Mar 17th at 1500 GMT 18z for Sat Mar 17th at 2100 GMT 18z Sun Mar 18th at 0300 GMT 18z Sun Mar 18th at 0900 GMT 18z Sun Mar 18th at 2100 GMT These charts show the ground temps down to a depth of 10 cm. You can see that most of our region had ground temps of around 7c at 2100 last night and they were still at 6c by 0300 this morning. Then the very cold air started to move in during the early morning. By 0900 the ground temps had fallen back to around 5c. By 1500 they were down to 4c. By 2100 this evening they were closer to 3c or 4c. They are predicted to fall very slowly to mostly 2c to 3c by tomorrow evening. Remember these are the average temps for the full 10 cm depth. The surface and the top 1 cm or so will be very close to zero already. While the surface is being cooled by the melting snow and the strong drying sub zero wind, the underlying warmth is still radiating upwards. Right now I would estimate that most surfaces are actually dropping just below zero - probably down to 1 cm or so. With the average down to 3c or lower, I would expect that the top 1 cm layer will be sufficiently low enough to cancel out the rising warmth from below. Any heavier snow will readily settle and even lighter snow will settle on all surfaces during Sunday. Roads and pavements retain their warmth for longer than soil. Grass is always one of the first surfaces to see snow accumulate as the blades are not affected by the warmer ground. It settled on trees and hedgerows around here from late morning. The wetness of the surface is always a red herring. It's the ground and 2 m surface temps which are critical. Even wet snow will settle if the air temp drops close to zero, initially forming a slushy surface and then accumulating. There is one saving grace from having snow settling on unfrozen ground. It forms a blanket and protects the ground from sharp frosts. Many plants are starting to come into bud and the snow may actually prevent them from being damaged or killed by the freezing conditions!