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  1. Ah yes, thanks, didn't think of looking in there. Looks like the sferics petered out just as the storm reached the Cumbrian coast.
  2. Thought there might've been a mention of night storms in Cumbria in the early hours of yesterday (Wednesday 3rd)? At around 2am could see sky lit up with lightning from southeast of Warrington to the northwest, was some surprise then to see that intense radar echoes were roughly midway between Blackpool and the Isle of Man about 70-75 miles away.
  3. A couple of observations, Rickmansworth is a renowned frost hollow which has been suggested may have been aided by early land use developments to help cold air pooling. However, subsequent urbanisation has meant that a similarly cold temperature as -8°C would be less likely now, as discussed some time back in a two part article in the journal Weather - Regarding polytunnels, if the plastic film covering is not opaque to infrared then the interior air is able to cool more effectively than outside because of lack of air movement. Assuming lack of insulation, supplementary artificial heat or sufficient daytime insolation this can surprisingly result in the inside being colder than the external environment.
  4. It may yet stick for a short while, it is affecting the M54 and this pic is just north of Shrewsbury at 100 metres asl -
  5. The Long Mynd gliding club is at 425 metres so this is Easthope near Much Wenlock at about 200 metres -
  6. Long Mynd, Shropshire -
  7. A tad premature - it may end up being the case, but the net radiative balance still slightly favours cooling and westerlies resume at the top of the stratosphere in the next few days.
  8. You are correct of course - the significant changes in geopotential height occurred in the stratosphere. To quote Steenburgh & Holton - So thinking of the atmosphere in terms of layers, warming of a particular layer increases the geopotential thickness of that layer which typically might increase the geopotential height at the top of the layer - but this depends on the sum of thicknesses of all the layers below as well. The height is proportional to the temperature of the whole atmosphere to a particular pressure level - warming aloft combined with cooling at the surface might mean there is no height change at the top of this depth of atmosphere. It also implies that change in geopotential height or thickness makes no difference to sea level pressure. The only way to change surface pressure is increase or decrease total atmosphere mass above by convergence/divergence - increased heights is not the same as high pressure. This can all be seen for example by looking at recent radiosonde data from the Polargmo Krenkelja station on Heiss Island, part of Franz Jozef Land in the Arctic, at 1/3/16 12z the height of the 20mb level was 25050m and -57.7°C and by 7/3/16 12z the height was 25990m with temperature -22.1°C. The majority of this 940 metre height rise came from an increase in the 50-20mb level of 720 metres. Afterwards the 20mb height rose further to 26550 metres by 13/3/16 12z but the temperature was back down to -46.3°C and the 50-20mb thickness fell 250 metres. Instead the bulk of the increase came from changes to 100-50mb and 250-100mb layers which were now 410m and 310m more than the start of the month. At the 500mb level, the next sounding on 14/3/16 0z saw a 500mb height of 5250m so also an increase from the initial 5140m, but with a 1000-500mb thickness of 5318m, a surface pressure of 988mb somewhat less than the 1012mb from the 1st. The temperature ranges of the 1000-500mb level increased from -18.9/-39.1°C to -0.7/-27.1°C with the arrival of low pressure into the region.
  9. Disagree - looking at the GFS 240h 10mb pattern shows vortex remnants over Scandinavia/NW Russia and northern US/ southern Canada with anticyclone over Pacific side of Arctic - This is a fairly good correlation for 500mb anomaly regions at that time - The charts by Hannah Attard show that at the moment, the strat vortex has only recently split and there is little correspondence between 10mb and 500mb levels, particularly Arctic stratospheric heights are opposite of the troposphere - But by 180h there is a coherent similarity between stratosphere and troposphere split vortices and Arctic height rises - For best effect visit the site and animate the charts - Obviously as with all forecasts the strength and duration of this likely coupling is open to question. Edit to add that it may become a final warming but it isn't at the moment as technically the FW is a radiative process of the stratosphere being warmed by the sun at which point the vortex cannot strengthen and dissipates.
  10. Tentatively, using the GEOS/MERRA data the SSW was marginally the strongest recorded at 10mb 60°N on 11/03/16 at -31.43 m/s just stronger than the -31.08 m/s from 2009 - tentatively because this is from the GEOS-FP assimilation, not yet from the MERRA reanalysis. The Berlin ECMWF analysis had it at -31. and both have today at about the same or a tad stronger before it begins to weaken. The GEOS forecast downwelling as measured by change in wind shear was initially quite strong - here the forecast from the 6th the day after onset shows the easterly wind shear predicted to propagate down from the 10mb level to the others one by one - and the forecast from the next day was quite dramatic with an actual wind reversal forecast all the way down to 150mb 60°N for today 15th - However the following day (8th) the wind propagation was minimal, and though subsequent forecasts have not been as weak a reversal has only been forecast as low as 70mb - This initial week from onset is when we would expect to see a rapid response if the atmosphere is well coupled but the CPC time series anomaly charts show polar stratosphere positive geopotential height anomalies propagating down due to increased thicknesses from the warming while most of the lower polar troposphere has a negative height anomaly reflecting a cold and fairly vigorous vortex - The wind anomalies tell a similar tale with weaker than normal flow gradually permeating throughout the strat so far but slightly stronger flow than normal below 500mb say (or the bottom half of the atmosphere by mass) - This situation looks likely to change with gradual downwelling continuing over the next few days with a rise in pressure and heights over the Arctic and a splitting of the troposphere vortex mirroring the stratosphere which has really only just started in the past couple of days. The differences we're seeing between a fairly benign and temporary northerly shot from the GFS and something perhaps more wintry and unseasonal from the ECM could be due to handling of the stratosphere. If we look at the 10mb 240 hour charts from yesterday lunchtime they are in generally broad agreement but the ECM has the vortices further west, with the European vortex remnant in particular closer and with lower heights more influential for the UK - charts courtesy Instantweathermaps & FU Berlin I get the impression that Recretos is slightly unimpressed and disillusioned with this SSW, but his animations might be quite illuminating right now!
  11. Interesting stuff, this one - A study of the properties of the Grand Solar Minima throughout the past 13,000 years and the implications for Space Weather - might not be popular here
  12. No, the temperatures are critical as I posted previously The two key points are that it is the meridional temperature gradient which is important (which is why it is used as one method for identifying SSW) and temperature at the 10mb level is not the best indicator of 10mb zonal wind. Further to the reference in the previous post, to quote J R Holton (of the Holton-Tan relationship between QBO and vortex strength) describing SSW - Here is a more recent description by Kornich - It doesn't matter if temperature is viewed as cause or effect because it is 'chicken and egg' depending on the frame of reference used to describe the processes. Looking at various equations eg - hypsometric for geopotential thickness, potential vorticity, EP-flux - they all have temperature related terms and it plays a role in any atmospheric kinetic energy, apart from some basic barotropic simplification. More than 98% of atmospheric motion is driven by horizontal heating gradients, the remainder by convection ie vertical heating gradients ( so I'm curious which other energies you refer to. The Kornich reference is actually topical with the potential for downwelling - Predictability of the coupled troposphere-stratosphere system
  13. Yeah, but never on the few occasions that they are really needed
  14. Yes as pointed out in the strat thread, wave 2 has been very weak this winter - Though there is some vortex splitting forecast, it is not unusual for daughter vortices to form during/following a displacement which causes confusion when classifying SSW type as seen in this table from Charlton & Polvani - But the current splitting is not by the classical wave 2 forcing and it may be that the underlying forcing mechanism helps determine how quickly and effectively the SSW downwells - a strong trop/strat wave 2 would be predisposed to a split vortex.
  15. Ah just dived into middle of thread and didn't read previous post about methodology change, my bad. It was obviously something to do with the baseline climatology and it would be stupid not interpolating the monthly mean but their brief description didn't mention it so without the climatology change it seemed the only explanation.