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Interitus

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  1. Interitus
    Of course this is from a narrow sample of SSW events for any particular day of the winter. So date records now are around 2 S.D. - a 3 S.D. event such as Jan 2009 would give a value today around -26 m/s.
  2. Interitus
    That doesn't contradict it at all
  3. Interitus
    Hehe, maybe the best way to visualise variability of model runs is by use of chiclet charts. Here is a form of chiclet covering the whole of the 2019 SSW in GFS forecasts - It's not annotated, so to explain - it is 10mb 60°N wind speed, red westerly, blue easterly. Y-axis represents the model time step, T0 analysis at the bottom - what actually happened. T384 forecast at the top. X-axis is the 6-hourly run, 4 times per day, advancing from left to right. So moving from left to right, forecast winds gradually advance diagonally down to the bottom of the graph and become the actual values. It can be seen that to the middle or just beyond of runs, accuracy is good and forecast winds progress downwards fairly consistently. But at the top of the graph, there are wild fluctuations in forecasts, from SSW to vortex intensifications, often from run to run giving the vertical stripiness, which don't materialise. At best it can be suggested that averaged over a number of runs, a weaker vortex and perhaps more particularly, a stronger vortex may be expected from the long range GFS values.
  4. Interitus
    Yes, they do! It may well have picked it at 384, it will also falsely pick many others that don't materialise.....
  5. Interitus
    Current events notwithstanding, for example here is a chart of forecasts over a few days last winter, inside 9-10 days the windspeeds progressed forward from run to run, at around 9-10 days they clustered without progressing, and beyond that they diverged all over the place - Of course not forgetting previous GEFS tendency to overcook wind reduction compared to GFS, here again from a portion of last winter, a day-10 comparison -
  6. Interitus
    Are they getting closer though? When consistently seeing peak warmings at 10 days or beyond they have a tendency to stay there, the strength of them doesn't matter so much.
  7. Interitus
    Reversals from MERRA data Date - days 01/03/84 - 34 24/01/09 - 29 06/01/13 - 22 31/01/87 - 22 26/02/99 - 21 21/01/06 - 19 02/01/19 - 17 12/02/18 - 17 22/03/92 - 15 07/03/89 - 15 11/02/01 - 14 12/03/05 - 12 05/01/04 - 10 27/03/14 - 10 21/02/89 - 9 08/12/87 - 9 22/02/79 - 8 18/03/88 - 7 17/03/80 - 7 22/02/08 - 6 13/03/08 - 6 15/12/98 - 6 23/01/87 - 5 01/01/85 - 5 19/02/10 - 5 24/02/07 - 4 11/02/06 - 4 24/02/84 - 4 30/03/05 - 4 30/12/01 - 4 09/02/10 - 3 29/02/80 - 3 24/03/10 - 3 29/03/08 - 3 20/03/00 - 3 29/03/98 - 3 14/03/88 - 3 05/01/21 - 2 20/01/19 - 2 20/03/18 - 2 25/03/89 - 2 04/12/81 - 2 18/01/03 - 1 29/01/87 - 1 01/02/17 - 1 05/02/95 - 1 25/02/87 - 1 28/03/15 - 1 26/03/05 - 1 04/03/81 - 1 25/03/80 - 1
  8. Interitus
    Y is u m/s, X is time steps of run, pretty obvious really,
  9. Interitus
    This is at 65°N, here is a rough and ready plot at 60°N
  10. Interitus
    Of course green is forecast and 100 hPa is in the strat. Here's an interesting chart a few days prior to Jan 87 SSW, posted a couple of times before - Of note, large anticyclonic wave break north of UK. Compare with this forecast for few days time -
  11. Interitus
    Nothing out of the ordinary there. From out of the chaos comes order - 3 of the 4 closest 30-day 10mb 60°N wind analogues to 31/12/20 feature an SSW in the following 3 week period -
  12. Interitus
    That's in the strat.
  13. Interitus
    No, not really. There is always some tropospheric blocking in advance of an SSW, usually Atlantic side for wave 1 like this.
  14. Interitus
    Weathercast data seems to be fixed now.
  15. Interitus
    Totally depends on definition of intensity and sustained period - 32°C on 15 consecutive days is the oft trotted out 1976 comparison.
  16. Interitus
    Bit of a downer that weathercast has not had any station data for a couple of days. Noticed that it also affects their app and other meteogroup sites (eg. meteoservices.be) and data from other countries.
  17. Interitus
  18. Interitus
    Very interesting, nice work! One question however, from near the end of the article re: North shoreline change from 1935 to 2018 on Peninsula Point - there is some variability between the time-samples but overall appears to show a fairly consistent rate of erosion which is at odds with a hypothesis of warming and reduced sea-ice? Ah: ok re-read your theory now.
  19. Interitus
    Iver Water Works 33.9°C at the same time (3pm). The significance? Nobody has seemed to notice that data is available from this other site, but it is barely 3 miles from Heathrow weather station and shows the difference of being semi-rural vs next to carparks, runways and apron.
  20. Interitus
  21. Interitus
    Maybe not, the 06z GFS today has +ve 10mb winds til April 28th, then a few days weak reversal then weakly +ve again. Normal reversal by about April 12th, so much for the theory that it happens earlier in years without SSW lol.
  22. Interitus
    Mentioned this before, basically the strength of the vortex is related to the temperature gradient between the pole and the mid-latitudes, so simply put, pole colder than mid-lats = stronger vortex and vice versa. But interestingly, the 10mb zonal wind is more sensitive to temperature gradient at lower levels than at 10mb itself. Using the difference between the 80 and 50°N temperatures from MERRA reanalysis, over all days since 1979 the zonal wind correlation to 10mb temperature is 0.80, but with 30mb temperature it is 0.97 and 50mb it's 0.96. So while seeing a warming appearing at 10mb may hint at an SSW, a wind reversal at 10mb is unlikely if the warming doesn't progress to the 30mb level or below and reversing the temperature gradient there.
  23. Interitus
    Yes, exactly this. Corralling people indoors in typical temperature and humidity is the perfect environment for virus transmission. Whilst they survive best in the liquid droplets from coughs/sneezes, it seems slightly counterintuitive but coronaviruses survive drying for some time and remain viable. Being outdoors in the open air reduces chance of transmission and also solar UV quickly inactivates them. Number of papers written but for example see research on original SARS CoV - https://www.hindawi.com/journals/av/2011/734690/ SARS dried of plastic survived 5 days at 22-25°C 40-50% RH with only slight loss of infectivity. Seriously should be hoping for some decent weather to help with this but of course dependent on measures on social distancing and self-isolation which come into force.
  24. Interitus
    The action has been higher up, this chart shows GFS 1mb zonal wind from 8/3 when the forecast splits occurred, to 13/3 and actually wave 1 displacement has been indicated. For a number of days wind reversal stuck around the 240+ hr uncertainty range, but today's 00z and 06z brought it down to 231 and 201 hours respectfully - Doesn't look like having large effect at 10mb or below at the moment. edit: Incidentally, does anybody else find those temperature charts slightly distracting with the multiple colour scales and repeated whites?
  25. Interitus
    Nah, his tweets are high quality, but splits in particular depend on fairly specific tropospheric patterns which are typically modeled wrongly at the end of a 16-day forecast. Of course it's more than reasonable to highlight the possibilities, but time and again when people make these forecasts in this thread they're invariably incorrect, Maybe because splits are seen as a bit of a holy grail by cold lovers, it's certainly not popular when it is suggested that it is an unlikely outcome!
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