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