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Ruben Amsterdam

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  1. Ruben Amsterdam
    This is the central theme of this entire thread. I think if you read back a couple of pages, you will find your question answered more than once. - The trop. response between SSWs differs between events. No guarantees given. - The stratospheric vortex will likely be out of business for a while - The standard time until the first trop. response is 10-14 days, but can be less, more, or the response may never come - EC shows a modest signal for downwelling at +240, but nothing convincing yet
  2. Ruben Amsterdam
    It's quite fascinating how the vortex shatters and basically ceases to exist at 10 hPa (GFS 12z FI). This translates to a pattern with relatively high geop. in the Canada/Greenland sector in the lower strat. Yet there is nothing (yet) to be seen in troposphere, not even a cute tiny baby polar high.
  3. Ruben Amsterdam
    So there you have it, EC more or less adopts the GFS-scenario
  4. Ruben Amsterdam
    Polar Stratospheric Clouds observed in the northern part of the Netherlands! Or? Dutch/Belgian weather forum
  5. Ruben Amsterdam
    That zonal wind at 1hpa used to be -40 in the previous runs though. But beggars can't be choosers
  6. Ruben Amsterdam
    But is GFS truly that different? Showing a modest split at 10hpa. The bigger differences are at the top of the strat I think.
  7. Ruben Amsterdam
    So, where do we find the current NAM100-300?
  8. Ruben Amsterdam
    That's bad news bears. But please note that the paper mentions the NAM at 100-300 hPa, not 1000.
  9. Ruben Amsterdam
    Cheers on your first post! For the record: the GEFS still shows a technical SSW but keeps pushing it back. Meanwhile, the hump in the short term is getting higher and higher (conform the operational runs).
  10. Ruben Amsterdam
    Thanks for the great feedback. I will try to MacGyver my way out using a 5W solar panel! :)
  11. Ruben Amsterdam
    So you take power from your Davis station? I'm sorry I do not quite understand. I'm building a diy version of a Stevenson screen and maybe I will add a fan (considering to use the Netatmo). What would be the best way to power the fan without having to run power cables into the yard?
  12. Ruben Amsterdam
    The problem is the small low of the Norwegian coast shown here at +96. This prevents fusion between the two area's of high pressure.
  13. Ruben Amsterdam
    Right I read you Most model ensembles are now hinting with blocks, just a lot of variation in position and timing. It's an interesting idea to think to what extend the models perform with stratospheric configurations that are several sigma's away from normal conditions. To what extend are models calibrated to handle (or to what extend do we understand strat-trop coupling?) vortex remnants moving from east to west like in the coming 72 hours?
  14. Ruben Amsterdam
    I do not quite see what you mean here. Surely, EC sees the reversal coming as it is output from the exact same model we look at in Berlin's Strat. plots vs. tropospheric output on meteociel. Perhaps, our current understanding of strat-trop dynamics limits our ability to accurately model responses to SSW events, but that's something different. And there is a possibility that the response is not as we all expect it (i.e. quick response, AO-), right? Not what we all hope for, but a possibility none the less.
  15. Ruben Amsterdam
    Would I be correct in stating this would also be a Canadian Warming? I.e. anomalies in early winter in the Canadian sector are Canadian Warmings, but only some of these also classify as a full-SSW?
  16. Ruben Amsterdam
    Still rather impressive output this morning (GFS 06z in FI). Does anyone have any info on December SSWs? I believe there are rare and FU Berlin reports such events only in '87, '98, and 2001. These were not exactly impressive winters...
  17. Ruben Amsterdam
    This is the WMO definition, yes. However, there is no real difference between using 60 and 65N when it comes to classifying SSW events. See: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-13-00173.1 "Poleward of 60°N, the local and coherent reversal requirements yield nearly identical numbers of SSWs; anywhere in this region, if the wind reverses from westerly to easterly at one latitude, it is also almost certain that the wind is reversing everywhere poleward of that latitude." This is also why Attard plots 65N and not 60N.
  18. Ruben Amsterdam
    I believe this is the first true reversal forecasted this season. The GEFS supports this to some degree, but we all know the model has the tendency to be too progressive.
  19. Ruben Amsterdam
    Nope, not here
  20. Ruben Amsterdam
    FYI: we are talking about the graph below? You may have uploaded the wrong image because the one in your post is very unexciting
  21. Ruben Amsterdam
    I was going to write that y'all are a bit too enthousiastic: I do not see it as abnormal to have some minor dents in the vortex before the season starts. (Remember last year's quiet start, followed by an unleashed vortex the rest of the season.) But after today's 12z one eye is officially open:
  22. Ruben Amsterdam
    Poof!
  23. Ruben Amsterdam
    First nacreous clouds spotted near Tromsø, Norway. Very spectacular sunset here in Oslo yesterday, also due to the cold stratosphere (although I personally did not observe any "classic" pearly clouds). All signs that the vortex is indeed displaced. Picture source is the twitter account of Yr.no, a collaboration between the Meteorlogical Institute and state broadcast NRK. Edit: picture I took from the sunset here yesterday
  24. Ruben Amsterdam
    Weird... But glad you agree haha
  25. Ruben Amsterdam
    I've been absent for a while now due to winter weather in early November (totally awesome!) and dark and mild "mørketid" weather (I hate it) for the last week or so. But, here's my two cents on the whole thing. After the initial dip in zonal winds related to the - I am quite sure it is one - Canadian warming this November, we see a strong uptick in zonal wind speed forecast. Or I should say, recovery to seasonally mean zonal wind speeds - note the very large spread in wind speeds around the average. The brief(!) reversal of zonal wind (at 65N at least) and the positioning of the whole thing makes this a CW for me. Yet, soon after the recovery of zonal wind speeds, we see a new area of higher geopotentials (and significant warming btw) in the GFS FI. This has been modelled consistently in the last consecutive runs, including todays 06z. It would be great if this develops further and could punch the vortex in the face once again. A '62-63/'76-'77/'80-81/'00-'01 scenario with a CW followed by a proper SSW would be the bees knees for stratonerds Regarding the effects of this CW event on lower levels, I think the displacement of the vortex and axis of "southward flow" could be very important. I think a pattern where the direction of this flow is parallel to the 0° meridional (or even 30° W) would generally favour a trough bringing cold air to Western Europe, whereas allignment with the 30° E meridional could trigger the Atlantic? Please correct me if I'm wrong (or my English terminology is crappy haha). So this is good regarding tropospheric responses, I would say. Edit: can's seem to get rid of the last image, shouldn't be there
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