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  1. The comparisons with 2010 are inevitable but there are differences which will put some theories to the test if this ends up being a prolonged cold spell like 2010 or 2009 with persistent -NAO, or just a short-lived anticyclonic wave break. A key difference are the SSTs and the Atlantic tripole - 2009 - 2010 - The Atlantic profile was fairly similar at this time of the year (unlike ENSO) and this has been the subject of a number of studies, eg - SSTs were linked to NAO in both winters in this paper - Re‐emerging ocean temperature anomalies in late‐2010 associated with a repeat negative NAO (Taws et al 2011) - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011GL048978 Whilst in the next, again SSTs were seen as important to 2010 - The Influence of Surface Forcings on Prediction of the North Atlantic Oscillation Regime of Winter 2010/11 (Maidens et al 2013) - https://journals.ametsoc.org/doi/abs/10.1175/MWR-D-13-00033.1 Finally, a third paper which suggests that SST response was not as important for 2009 which may have been more down to natural variation, but once again was conducive for -NAO in 2010 - North Atlantic SST Anomalies and the Cold North European Weather Events of Winter 2009/10 and December 2010 (Buchan et al 2013) - https://journals.ametsoc.org/doi/abs/10.1175/MWR-D-13-00104.1 This doesn't necessarily mean that the Atlantic temperature profile is required for similar conditions, but it doesn't appear as favourable this year - completely different to 2009 and 2010 -
  2. Maybe there should be some definition of a trop-strat disconnect because watching the animation in the link shows the linkage which exists between the two - the Scandi block is generating the wave 1 forcing which results in the strat Aleutian high pushing the vortex towards Eurasia. As the block weakens, so does the wave 1 forcing and the vortex returns to the pole.
  3. The thing is, the extreme cold period in Jan 87 occurred before the SSW which had nothing to do with it. In fact it was the repeated northern blocking causing the cold for the UK which also led to wave 1 forcing producing the displacement SSW. In the paper "Diagnostic Comparison of Tropospheric Blocking Events with and without Sudden Stratospheric Warming", Colucci & Kelleher (2015) highlight blocking centred at 62.5°N 355°E between 12-18/1/87 as preceding the SSW on 23/1/87. The chart below shows geopotential at 250mb with high pressure to the north of the UK with the easterly flow on the southern flank - source: https://journals.ametsoc.org/doi/pdf/10.1175/JAS-D-14-0160.1 This is the time of the record breaking UK cold. With regards to the MJO, 10mb zonal winds reached record levels at times during November 1986, and remained above average until the last 10 days of December. They only reduced significantly after the first third of January. Likewise November WAF was generally below average and only picked up towards the end of December. The time lag involved is far in excess of the accepted influence meaning that it was unlikely to be a direct factor - indeed another phase of Indian Ocean MJO initiated before the SSW occurred.
  4. Surprised nobody seemed to notice the crazy northern blocking on the 31/10 18z GFS. Anyway here is the stratospheric hydrostatic response -
  5. That is what matters - if following the SAI of course (and predominantly <60°N)
  6. -7.3°C for both Shap and Sennybridge last night.
  7. No surprise one of the authors was Yannick Peings, his earlier works have already shown that the data has brought into question the long term impact of the whole snow extent/advance of Cohen etc. edit: interesting that another author is Jason Furtado who collaborated with Cohen on "The combined influences of autumnal snow and sea ice on Northern Hemisphere winters" (2016) - https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL068108
  8. Last full SSW - at the end of November 1968! Not knocking it, but looking back this season here is a typical CFS forecast (posted by SM) - And here is how it panned out on today's weatheriscool plot - Are these CFS plots ever right?
  9. An alternative PDO - https://www.ncdc.noaa.gov/teleconnections/pdo/
  10. Yeah, I used around 18-18.5 to try to get it similar to the video.
  11. No, because this ice has similar microwave brightness temperature to any other ice but very different from seawater. So while it can be hard to determine optically, it is fairly obvious from passive microwave radiometry.
  12. Interitus

    Spain weather

    Further to the above, torrential rain was experienced in Malaga province of Andalucia with Alpandeire provisionally breaking records for totals between 3 and 6 hours (over 9 inches in 3 hours) - The earlier rainfall at Vinaros may have broken the totals up to and including one hour -
  13. Of course it's relative vorticity (positive) - Adding the negative vorticity shows a nice early season wavebreak -
  14. Nice stuff again Recretos. What is the value used to create the isosurface?