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Ruben Amsterdam

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  1. Ruben Amsterdam
    This mornings ensemble looks very promising with about 50% of the members opting for a reversal at 10hpa @65N. Only one member shows an "increase" of zonal wind speeds but mind you, that is only just above todays zonal winds which are unseasonably low.
  2. Ruben Amsterdam
    I can't help but thinking that GFS outer FI is showing the onset of a proper SSW now. Ofcourse, very far away still, but not entirely unlikely given the persistent troposferic pattern. Edit: the GFS12z operational turned the warming signal slightly down, but it is still there. Meanwhile, we see the dipole pattern rotate somewhat, with main height anomalies over Canada and the cortex core over Northern Russia. I suspect we are very close to reversal at this point. The pattern is also present lower down (30hPa) and, if you would litteraly translate this down to the troposphere, one would expect the lowest gph to move slowly eastward over Scandinavia towards Russia while heights are rising over Greenland again. Do any of the more knowledgeable on the subject have any thoughts about this?
  3. Ruben Amsterdam
    First proper Canadian Warming modelled?
  4. Ruben Amsterdam
    I tend to disagree with the above re. recovery of the vortex and tightening of the ensemble members. Even in the "tightened" ensemble the strongest u mean winds do not even match the wind speeds from early October. Besides, I believe GFS's ultimate FI is tending towards a more displaced vortex in contrast to runs from a few days ago and, on top of that, todays ensemble shows that there are still options for a double dip-scenario (of course considering the limitations, 65NB only, of these graphs). .
  5. Ruben Amsterdam
    I guess in case of a split much depends on the actual positioning of the strongest part of the vortex (in the lower stratosphere). We should hope for the minor part to set up shop over Greenland with the bulk of all "blue and purple" concentrated over the Asian and Alaskan sector. If this works out well for us, I think we may have a good shot at it.
  6. Ruben Amsterdam
    I have been thinking about this again and I think it is a nice thought experiment to add the Southern hemisphere into the equation. The SH is completely different to our half of the globe as it lacks large landmasses and mountain ranges at middle latitudes. This results in far less wave breaking, and subsequently SSWs are very rare. I think this is one of the reasons that Antartica is not warming as fast as the Arctic: the tight vortex makes the continent actually more isolated to warmth from lower latitudes.
  7. Ruben Amsterdam
    Hei and welcome from neighbouring Norway I don't think science rules anything out per se, but a quick glance at the literature does not really yield any papers that directly address your question. I assume you mean cooling at the surface by the way? As far as I know IPCC assumes the stratosphere in general to cool down as a result of climate change. What comes to my mind is that, yes, stratospheric events can cause colder than average temperatures at lower latitudes but at the same time these events are usually accompanied by strong WAA that causes warmer than average conditions in other places, usually at high latitudes. For example, the average temperature yesterday in Longyearbyen, Spitsbergen, was +7.4°C in stead of the normal -6.5°C (winter has not arrived there at all so far, very concerning). Also, stratospheric events occur irregularly and are temporary in nature. I think that global warming/Arctic Amplification (snow, ice, and vegetation albedo feedbacks) is causing the arctic to warm so rapidly and to such extend that it far outweighs any possible effects of temporary stratospheric events.
  8. Ruben Amsterdam
    It's getting hard to hide excitement with the 06z ramping things up even further. I do not recall seeing charts like this so early in the season, 2010 was more modest, wasn't it?
  9. Ruben Amsterdam
    There is no direct answer to that question, although we would all like to know the answer, of course. For now all we can conclude is that the vortex may not develop uninhibited through early winter like last year, but could be displaced. Not all years with early or Canadian Warmings, or even SSWs, yield fierce winters. Some did ('62), others did not. A weaker vortex should theoretically allow more meridional flow and more blocking, but blocks need to be in the right place - and they very well may not be - to deliver cold to where we live (which is just a "pixel" if you look at the world wide scale of things).
  10. Ruben Amsterdam
    I was just about to post the same graphs, haha. Very interesting indeed, especially because runs are getting more progressive. Great to see the thread reopened this year and thanks to all who contribute!
  11. Ruben Amsterdam
    Crewcold, I would not call it a split (yet). However, the blue "tail" does show the vortex is not happy as could be
  12. Ruben Amsterdam
    To me it shows that, in contrast to last year and I would say "normal" circumstances, the stratospheric vortex is not in a state of uninhibited intensification, centered over the north pole. On the contrary, we see heights rising over the Eastern Russian/Canadian sector and as a result the vortex is displaced. This might (!!) cause mean zonal mean winds at 60NB to come close to reversal. I strongly believe it is this that could support blocking at high latitudes. That being said, I should probably add that the vortex is not yet being "ripped apart" as would often be the case with mid-winter Sudden Stratospheric Warmings. It is displaced, but the core does not warm all that significantly and heights continue to drop. This - as far as I know - is in agreement with what we call Canadian Warmings (an early winter stratospheric event) but I am no expert in these definitions.
  13. Ruben Amsterdam
    GFS inching closer to a reversal in zonal mean winds at 10hPa? Most interesting chart of the suite I would say.
  14. Ruben Amsterdam
    Thanks a bunch and the most important conclusion I think is that none (!!) of the members go for increasing mean zonal wind speeds!
  15. Ruben Amsterdam
    Maps like these this early on in the season: one eye open for me! Anyone info on zonal mean wind predictions (GFS ENS)?
  16. Ruben Amsterdam
    Split yes, but SSW...?
  17. Ruben Amsterdam
    06z close to a technical?
  18. Ruben Amsterdam
    If this is the map shown along with it, it does not show a technical SSW
  19. Ruben Amsterdam
    So? Trop. driven split in the lower stratosphere, as expected given current tropospheric model output. The upper and middle strat. thusfar do not show a similar pattern. Yet.
  20. Ruben Amsterdam
    This mornings run (note that this is for the eastern part of the Netherlands, close to the German border, De Bilt is in central the Netherlands and is a bit warmer, usually) shows some colder members indeed. Mostly inversion weather in a slow continental flow, would be my guess. I also included an ensemble with wind directions which shows a tendency towards more south/easterly winds instead of south westerly wind, but this is not all convincing yet. From top to bottom: T2m, dew point, precip., wind 10m, wind 10m gusts, cloud cover.
  21. Ruben Amsterdam
    Tendency towards a split in the lower vortex on the Berlin charts (+240 at 50hPa shown) this morning. Ofc. following yesterdays impressive tropospheric developments, but maybe there to stay in the next runs?
  22. Ruben Amsterdam
    Haha, looks like GFS12z has found a slightly bigger fish to hit with. Mostly trop. driven, though. Looking similar to the excellent exp. charts posted above by Recretos.
  23. Ruben Amsterdam
    Slap in the face yes, knock-out blow no. All forecasts seem to let this wave subside at the +240-300 timeframe. At the outer reaches of FI the wave may revive but its strength is as yet unknown. If no renewed and stronger activity is in the forecast at new year, I fear we have to surrender to this almighty vortex.. I still feel EC is a bit more progressive at the upper strat but that remains to be seen. I'm not very optimistic at this point.
  24. Ruben Amsterdam
    It's funny how some interpret the fact that averages result from high and low values as an almost supernatural "power of compensation".
  25. Ruben Amsterdam
    15.3 is the max. at the official station De Bilt so far. I do not expect it to rise any further given the cooling trend in the last hour. Some other parts of the country reached temperatures of >16ºC. Highest max. temp recorded at an amateur station (stations that meet national standards, but are not official stations of the Dutch met. service) is 18.9ºC in the south-east of the country. That's mad! So, not a new Tmax record, but ex equo score. We can still break some all-time winter daily average and minimum temperature records though.
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