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Showing content with the highest reputation on 23/12/15 in all areas

  1. 24 points
    Stratosphere forecasting is probably just as complicated as traditional weather forecasting and when you break things down there are both positive and negative factors which will affect whether a stratospheric warming will occur. Before I get into these factors lets just recap a few basics about stratospheric warmings. Warmings tend to come in three flavours. The first is a minor warming (wave 1) which tends to push the stratospheric vortex away from the pole and tend to be common. These warmings can often push the vortex towards the UK resulting in wet and windy weather while setting up blocked weather patterns elsewhere. This blocked pattern can often provide the conditions for a major warming to follow in two to three weeks time. A major warming (wave 2) will tend to split the vortex in two and tends to be a little less common than minor warmings. The result for the UK depends on where the two lobes of the vortex are at a particular point, but often you can expect a slowly moving blocked pattern giving a cold spell for the UK. Finally there is the final warming which indicates the break up of the stratospheric vortex and ultimately the polar vortex which can lead to a variable pattern and some cold out breaks over the UK. These warmings are caused by upward propagating planetary waves (Rossby Waves). OK so let me explain what I think these planetary waves are and how they work. Wave 1 represents a blocking pattern where there is a single major blocking high pressure in northern latitudes. Typically this blocking high is connected to the Siberian High or norther European high pressure in Winter. Wave 2 represents a blocking pattern where there are two major blocking high pressure areas in northern latitudes. Typically these might be North western Canada and Siberia. Wave 3 would represent three blocking highs in northern latitudes. Placement of the blocking high also seems to play a key role with a suggestion that Blocking Highs over the Euro-Atlantic sector tend to enhance the upward propagation of Planetary waves, whereas blocking highs over the western Pacific lead to a strengthening of the polar vortex. OK if you want to know more and see how these work follow the link below. http://www.sparc-climate.org/fileadmin/customer/5_Meetings/GA5_PDF/KazuakiNishii_SPARC_GeneralAssembly2014_14Jan.pdf So any old high pressure in winter will cause a stratospheric warming? No it is never quite that simple and there are precursor and conditions for these waves to propagate upwards into the stratosphere and affect the polar vortex. One source of precursors is possibly gravity waves in key areas with these smaller scale waves being able to penetrate above the stratosphere (mesosphere and ionosphere) to affect conditions there which will slow the winds slightly at the top levels of the stratosphere. These lowered winds then become susceptable to planetary waves disturbing them. Another link which sort of skirts around this. http://www.sparc-climate.org/fileadmin/customer/5_Meetings/GA5_PDF/PosterSessionB.pdf Now your head is probably totally confused about different waves I have better give a brief explanation of what gravity waves are as opposed to planetary waves. Gravity waves tend to result from either thunderstorms or low pressure systems crossing over mountain ranges. It turns out that particular mountain ranges and storms systems tend to have a large effect on whether planetary waves affect the stratospheric vortex. These gravity wave hot spots in the northern hemisphere winter include the mountains of Norway, Greenland and the UK. This might suggest that wet and windy weather in the UK and Norway might be a precursor to a stratospheric warming. Another link with some nice maps of where gravity wave hot spots occur. http://onlinelibrary.wiley.com/doi/10.1029/2012JD018658/full So we are starting to get a bit of a picture about how stratospheric warmings might come about. I have of course missed out on Kelvin Waves (particularly relevant to Tibetan plateau in winter) and solar tides. I am sure somebody here will go away and check up on these things to give an even clearer picture. Link explaining how all the different wave types combine together. http://arxiv.org/pdf/1412.0077.pdf Waves are part of the story but there is perhaps one more dimension that needs exploring a little and this is around ozone amounts over the pole. Ozone concentrations over the pole at high levels in the stratosphere alter the temperatures at those levels. Ozone depletion at the top of the stratosphere results in warming at this level and cooling through lower layers in the stratosphere. When temperatures go below -78 C Polar Stratospheric Clouds form which deplete the ozone further. This causes increased wind speeds in the stratospheric vortex which become ever harder to displace (i.e. No amount of planetary waves could shift it). One cause of ozone depletion in the top layer of the stratosphere is the pulling down of Nox from layers above due to Energetic Particles. What I think this means is that space weather or more particularly solar activity can play a part in whether stratospheric warmings occur (Note that EPP activity while related to the solar cycle can be slightly different). Gravity waves can off course play a part in excitation of the thermosphere and mesosphere changing ozone concentrations as well. A little bit of discussion about this at the following link. http://www.atmos-chem-phys-discuss.net/15/33283/2015/acpd-15-33283-2015.pdf Seems to me that Geomagnetic activity might play a part as well. http://www.swpc.noaa.gov/products/notifications-timeline So having said all that and knowing a little about the drivers are we any closer to understanding whether a stratospheric warming is likely this winter ? The answer I think is that there are some possibilities as energy is transferred from the troposphere into the stratosphere, but that we have a very strong stratospheric vortex which is going to take some shifting. After the current wave which we should not expect to shift the vortex much there is another wave forecast for around the 5th of January. I don't expect much from that one either but it might set up the conditions ready for a further wave. So I think we are looking at late January and into February as realistic windows of opportunity. Much will depend on ozone depletion due to cold stratospheric temperatures against ozone transport from lower latitudes.
  2. 8 points
    Well with regards to last year it was actually a substantial warming setting some daily temperature records at some levels, though it appeared the wave forcing may have just tailed off too soon. Looking at a couple of current analogues for this year shows how similar set ups can give different results but also the potential forecastability of the stratosphere. The two closest 30-day analogues to the GEOS 10mb 60°N wind forecast for 31/12/15 are 09/01/1981 and 12/01/2000 - this is as calculated by way of mean square difference over 30 days. This is shown in the graph below, dark blue = 2015, orange = 1981, yellow = 2000, cyan = analogue average. Both analogues show a reduction in wind speed starting within the next couple of weeks, with 2000 almost achieving SSW - windspeed 0.6 m/s after 27 days - this shows the fairly typical amount of time required to get to a wind reversal from the current level, so eg 27th Jan 2016. 1981 didn't reverse till later in the season but what is remarkable firstly is the similarity in profile of the variation in wind speed between the two years, the correlation over the next 60 days is 0.857. But why the difference in wind speed? Maybe the forcing was different, however then remarkably again, the 60°N 10mb wave 1 geopotential height for the two years was almost identical - Remember, this match in wave 1 profile was not selected directly but by similarity of the previous 30 day wind speed to this year. Ultimately 2015/6 might not follow either of these years, but analogues for the other variables tend to give similar results of possibly end of January or start of February though certainly not guaranteed.
  3. 4 points
    If that really is the case then, how come the super duper US Homeland Security geniuses didn't pick it up earlier...Like when they first applied for visas?
  4. 3 points
    I have no sympathy whatsoever, It was just on the news In a Facebook post supposedly he said I'm a Taliban leader he's deranged - the FBI caught on it and he deserves refusal. I feel sorry for his wife & children. My mistake the 18 yr old son is being investigated potential young radicalisation concerning..
  5. 3 points
    Visa checks r different to the airplane checks.. Granting them visa is fantastic their then waste 6 thousand pounds of potential terror money with no chance of refund and then refuce them when go to board flight Its in their visa terms and conditions their only have their self to blame plus i now hope the USA trys to extradite them now their know their location
  6. 3 points
    I don't think there's been any outrage in the USA and they will probably just see it as a standard case. For some reason the UK was outraged despite not knowing the facts.
  7. 3 points
    I always pictured lassie more like this myself
  8. 3 points
  9. 3 points
  10. 3 points
    Heathrow's third runway to be built at Gatwick.
  11. 2 points
    ^^That, lfcd, is your biggest load of unsubstantiated nonsense, to date. Well done!
  12. 2 points
    Ah the LBC tweet says it all! Their terror suspects but free to walk in the UK
  13. 2 points
    Aye, they were two brown men with beards??
  14. 2 points
    how is it a disgrace? the visa terms and conditions say it can be cancelled at any time and does not guarantee entry, As the man said he always gets buzzed at going though customs.. clearly their is somthing more init then what is alleged.. I.e his name must pop up on a system America has the right to keep their citizens safe and denying entry to anyone she wishes two
  15. 2 points
    Trump is putting out a dangerous narrative. Do you honestly think the world would be a safer place with him as President? What happened to that Muslim family is an utter disgrace, just adds to more division and resentment.
  16. 2 points
  17. 2 points
    It's accurate even down to to the teeth although I'm more of a sewer rat I will look like that come Boxing day.
  18. 2 points
    Yes ,it's ugly and bald .......
  19. 2 points
    I was going to say the first ever pic of Lassie23 (all tounge in cheek)
  20. 2 points
    Good Morning from sunny Austria. Pictures yesterday of the run into St Margaretten. First picture is of the A1 which is a super 7 km run. Note the fog in the valley. Second picture the final run into the village still shrouded in the freezing fog. Funny day yesterday , warmer at the top station 2200m than in the base station at 1000m. The snow on the piste is mostly man made prepared to perfection. An amazing result considering the snow drought over here and much of the Alps. C
  21. 2 points
    No, my question was genuine. I have a rough idea what your work is from your weather posts, so yeah. I've never insulted you HC. I'm kinda disappointed in your post as a result.
  22. 2 points
    Do you think I'd make this up for the fun of it? You really haven't a clue, have you?
  23. 1 point
    Thank you Interitus for the u and wave plots, very neat symmetry there. Also great post Brickfielder, some solid reading within. The EPF area is something I am just finding material on now and is of interest wrt to impacts and also the oscillations within. Following up on the wave descriptions- the W 1-2-3 at a visual quick glance is offered via JMA. http://ds.data.jma.go.jp/tcc/tcc/products/clisys/STRAT/ From the same page as these which you may have seen regularly over time. This page also plots EP Flux components and looking good as the current transfer across 100hPa busiest of season. From the first paper linked in Brickfielder's post - 100-hPa eddy heat flux ([V*T*]) is used as a measure of upward PW propogation into the stratosphere. Eddy Heat Flux plots are found in greater detail here http://acdb-ext.gsfc.nasa.gov/Data_services/Current/seasonal_strat/seasonal_strat.html Here is our current forecast, alongside this the 'what happens next' with respect to the zonal wind profile of the vortex...
  24. 1 point
    An Albion great, named in West Brom's greatest ever XI. RIP Don.
  25. 1 point
    Really I'm shocked. Its a shame this will just play into Trumps hands.
  26. 1 point
    what a stunning day weather wise today, unbroken sunshine, pleasent feel, certainly felt more like spring than winter, had a good few hours in the garden, daff bulbs comming up and the rubarb is well on it way, have not read anything on the model thread to say things are going to feel remotely wintry anytime soon.
  27. 1 point
    Out of interest, do you actually support new nuclear? I'm not specifically afraid of it in terms of safety. I just think its really messy waste-wise and eyewateringly expensive. Being a geologist originally, I'm particularly aware of the waste disposal problem (clays under London are the best site in the UK, but that's not going to happen). As I sit here listening to the wind picking up again looking at figures saying Scotland generated 50% from renewables in 2014, I'm struggling to justify the need for it.
  28. 1 point
    The status updates are a bit of a mess! The old system was better as a person's last statement would only show.
  29. 1 point
    You win the NW mars bar. A naked mole-rat.
  30. 1 point
    Iain Duncan Smith? Mole rat?
  31. 1 point
    Can you name this rodent?
  32. 1 point
    Things that tick me off; where to start? Children doing anything at all Village fetes; 3 a year here! Opposite my house Bold type randomly applied People being sorry for me living alone; I love it! Radio 2 - my boyfriend listens to it. Christmas
  33. 1 point
    That exert from the Cohen blog is interesting, a SSW sometime in Jan leading to some severe winter weather across NH is certainly a possibility by the sounds of it. In the mean time it would be nice if we could squeeze something more seasonable out of this pattern before the big one!
  34. 1 point
  35. 1 point
    Russia 'directly targets civilians' in Syria, killing at least 200 in possible war crimes, Amnesty report reveals http://www.independent.co.uk/news/world/middle-east/amnesty-report-russia-directly-targets-civilians-in-syria-killing-at-least-200-in-possible-war-a6783271.html Syria report https://www.amnesty.org/en/countries/middle-east-and-north-africa/syria/report-syria/
  36. 1 point
    Only way would be to abolish current planning laws and declare planning as a reserved matter to a department other than the Scotland Office. The council and Scottish Government could still use other powers to frustrate it - put tolls on roads for traffic involved in nuclear fission power plant construction etc. If HM government think they can build a new nuclear power station in Highland Scotland, they will be sent homeward to think again.
  37. 1 point
    Reading posts from the start of the winter, we are now entering the critical period so to speak when changes to the stratosphere need to start appearing to help engender a possible change in the northern hemisphere in time to produce a much colder spell of weather - but we have time on our hands still, as we are just at the start of that period. Conflicting signals it seems, MJO moving into Phase 7 could help, tropical convection being the end result, also heights building out of NW Russia which is what a number of forecasts were going for to help probe and weaken the PV - displacing it somewhat. We have signals for both this things occurring in the days ahead. We shall see..
  38. 1 point
    In theory yes, it's mostly down to the number of variables to calculate. At the surface, you have to deal with all of the various elements of physics that make up 'the weather' and then add to it the thermal differences in oceans/landmasses, inland water, hills & mountains etc etc. In the stratosphere you're looking at a relatively flat 'landscape' so as to speak. But of course sometimes stratospheric events are reliant on things such as upwelling wave activity and perhaps even mountain torquing events (can be linked to one another) and so if we are saying things are more chaotic at the surface, and the stratospheric conditions are then reliant upon the outcome of these chaotic conditions at the surface, all of a sudden you probably have merit to question the stratospheric forecasts. So in theory - yes. In practice, not always. SK
  39. 1 point
    "Blow for Sturgeon as thousands of motorists need to change travel plans ahead of Christmas due to SNP reopening bridge." http://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-35160296 The Forth Road Bridge is to reopen on Wednesday after temporary repairs were completed ahead of schedule.
  40. 1 point
    Here we go folks. Back on the road to longer daylight hours and good times.
  41. 1 point
    I wonder if Trump realises that there are already about two and half million Muslims legally settled in the US and a sizable proportion of these are Sunni. His proposed policies are bound to alienate a number of these and in the more extreme cases radicalise some to the point they will commit acts of terror. The ordinary ones will be upset because they will not be able to receive visitors in the shape of their families and friends and because they are Muslim they well be more likely to attract attention from the various police and law enforcement agencies, who sometimes get a little paranoid in these situations, which will alienate them further. So many will be less co-operative in dealing with the authorities just at the time when their eyes and ears would be more needed. Many live beneath the radar because the US does not collect details of their religions of people and we do not know how many of these may already be 'sleepers' over there waiting for the call for martyrdom. Should it be, that in the unlikely event of Trump getting elected as president and with support from the Senate and Congress he puts his proposed policies into effect, he will open Pandora's box and escalate Jihad in his country. Also the US would lose a lot of credibility as far as international affairs are concerned. OK, this is a worst scene scenario but that's what could happen when a prominent politician opens his mouth and lets it all fall out.
  42. 1 point
    So, this thread is kinda pointless then?
  43. 1 point
    Aye, we can't even whip them, belt them or even hit them with sticks any more. PC gone mad!
  44. 1 point
    Tempting as it is with my own kids at times, I've been informed that it's looked on unfavorably by Social Services. Damn nanny state.
  45. 1 point
    Kids shouldn't have fun.. they should be locked away in a cupboard.
  46. 1 point
    That's a cracking shot from Rosehearty, PM! My best efforts - trying to dodge the rain showers, light pollution and moonlit clouds. First one from the front door.
  47. 1 point
    being a sub post office for the village at times, forever taking in parcels for the same people.
  48. 1 point
    This. https://www.youtube.com/watch?v=MqBF7TiyATo
  49. 1 point
  50. 1 point
    After record breaking mild so far this November, France is set for a big drop in temps this weekend. This from Meteo-France: Arrival of cold after an unusually mild period 11/20/2015 While maximum temperatures will likely drop by more than 10 ° C between Friday 20 and Saturday 21 at the passage of a very active front, the first 20 days of November saw unprecedented mild, since the early measures - close to 4 ° C above normal. If many records were broken, sometimes very significantly (especially during the weekend of 7 and , the mild was also exceptional in its duration. A record number of often mild days Maximum temperatures regularly reached levels worthy of a late September or early October, the minimum sometimes full summer levels. In Bordeaux and Toulouse, there have already been eight days since the beginning of the month during which the temperature reached 20 ° C (previous records: 6 and 5 times respectively the full month). In Nîmes, 20 ° C were achieved 15 times (previous record: 9 times). He made more than 15 ° C 12 times in Strasbourg (old record: 9 times), 14 in Paris (old record: 12 times) and 11 in Lille (old record: 9 times). Sudden cooling this weekend The cold front brings rains sustained over many areas Friday 20 is followed by a maritime polar air mass, cold and wet, that will bring significant amounts of snow on all massifs. Temperatures will drop significantly between Friday and Saturday, and this decline will be dramatic in the Southwest Auvergne. In areas near the Pyrenees, who received a veiled sun and a gentle yet time Friday, we will lose more than 10 ° C in 24 hours: 13 ° C (21 ° C to 8 ° C) Toulouse and 12 ° C (24 ° C to 12 ° C) to Perpignan. http://www.meteofrance.fr/actualites/30858898-arrivee-du-froid-apres-une-periode-exceptionnellement-douce
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