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Ruben Amsterdam

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    Ås, Norway
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    Alpine/arctic ecologist interested in weather and climate

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  1. 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.
  2. 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?
  3. 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.
  4. 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?
  5. 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...
  6. 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.
  7. 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.
  8. FYI: we are talking about the graph below? You may have uploaded the wrong image because the one in your post is very unexciting
  9. 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:
  10. 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
  11. 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
  12. 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.
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