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Ruben Amsterdam

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Everything posted by Ruben Amsterdam

  1. Ruben Amsterdam
    Truly impressive upper strat warming at the end of the latest 18z!
  2. Ruben Amsterdam
    Lars from our Dutch/Belgian forum "weerwoord.be" made some interesting GEFS output again. The ensemble below shows zonal winds according to the 00z GEFS. The operational run is obviously one of the members with high mean zonal winds. Next update will be similar graphs of the (much better) 06z run. 06 GEFS 10 hPa - 60°N mean zonal wind 06 GEFS 10 hPa temperature over the north pole (90°N) Link to the forum thread (ancient set-up, scroll down for Lars' addition). http://www.weerwoord.be/includes/forum_read.php?id=1938536&tid=1938536&exp=1
  3. Ruben Amsterdam
    Yep, we need consistency! Looking good at 1hPa.
  4. Ruben Amsterdam
    06z shows what i mean: warm, warmer, warmest!
  5. Ruben Amsterdam
    I do not think the warming in this 00z is going to cut it. We need higher temperatures on every next chart. Warming seems to be subsiding already at the end of this run.
  6. Ruben Amsterdam
    Because this possible warming is troposphere driven (right?), runs will vary significantly. Yes, the 06z run is almost completed now. In this run warming is delayed, but the cold vortex core remains stretched. The last charts show a warming again. (Positioning and shape similar to yesterdays 18z, but warming is less pronounced.) Far too much inconsistency from run to run to draw any conclusions yet. Any news from the GEFS?
  7. Ruben Amsterdam
    Thank you so much for your great work, Recretos Interesting to see a strong correlation between NAO and 30hpa gph. I wanted to do this myself, but did not know how Such nice graphics! Between you and me, ~0.6 is regarded as pretty decent in ecology (for field data). And you are completely right, an important thing regarding correlations is that they do not (always) provide insight in causalities. I'am pretty sure I can strongly correlate (with correlation coefficient of >0.7) the number of posts in this thread with the time till onset date of a major warming. This does not mean that increasing the amount of posts in this thread increases our chances of an SSW, of course. A correlation coefficient is more valuable if the causalities are known, i.e.: there is supporting theory. By the way, those GEFS means, they look ok, don't they?
  8. Ruben Amsterdam
    Because we had a discussion last week on the relation between Sun Spot number/solar activity and the occurence of SSWs in the QBO west phase, I've been playing around with the data presented at the FU Berlin site. I am not a meteorologist or anything comparable (I'm an ecologist) and the analysis below is extremely simplified. I filtered for years with a WQBO phase and plotted mean February 30hpa temperatures against January average sun spot number. General linear model revealed a significant correlation (p=0.0029 and R2= 0.29) between Jan. sun spot numbers and 30hpa temperatures in February. The correlation coefficient is not particularly strong, but overall the result was significant. In the graph attached below, years with a Major Mid-Winter Warming in December are shown as circles, warmings in January are shown as squares and warmings in Febraury are shown in triangles. Years with no major warmings are shown in plus signs. I think the recent peak in solar activity and sun spot number (currently at 138 and flux at 175) is a good thing. Because I am not aware of the causal mechanism behind the relation I found by playing around in R (don't you just love that? ), these results should ofc. be taken wit a grain of salt. Cheers, Ruben
  9. Ruben Amsterdam
    It´s there again (at +348). Warming is also present in upper levels.
  10. Ruben Amsterdam
    The latest GFS runs were a variation on the same theme: a recovery of the vortex in combination with warming in the Asian sector. Good too see EC with simalar warmings at the end of the run. Could this grow into a potent wave-1 attack? Last chart of this 00z run.
  11. Ruben Amsterdam
    The original Labitzke paper from 1987 uses January sun spot numbers. http://onlinelibrary.wiley.com/doi/10.1029/GL014i005p00535/pdf
  12. Ruben Amsterdam
    I´m not too dissapointed by a R2 of 0.48. Certainly not when crude parameters like solar flux and QBO phase are used in a highly dynamical system. I actually think it's a quite decent correlation. I guess we can use it as a crude predictor. We have to be cautious as we do not know the underlying causal mechanism! Meanwhile, GFS06z shows a slight improvement with regard to previous runs. It shows renewed pressure on the vortex at the end of the run. Wave-1 action?
  13. Ruben Amsterdam
    Are you sure the conditions are all met? "This regionally conï¬ned temperature enhancement near 2 hPa in Figure 1 is part of an upper stratosphere and lower mesosphere disturbance that includes an unusually low-altitude stratopause near 42 km (2 hPa), a stratopause temperature in excess of 290 K (50 K above nominal conditions), a ~40 K cooling in the mesosphere near 75 km, and an undisturbed lower stratosphere [e.g.,Labitzke, 1972; von Zahn et al., 1998; Meriwether and Gerrard, 2004; Thayer and Livingston, 2008]. This thermal structure has been observed over the years and termed a “stratopause warming â€[ Duck et al., 2000; Braesicke and Langematz, 2000], "
  14. Ruben Amsterdam
    Sebastiaan, you recently asked (I can't find the exact post) what underlies the connection between EQBO/solar minimum vs. WQBO/solar maximum and the chances of Major Warmings under these conditions. With solar flux peaking over 200 today -and likely to stay high/increase over the coming days- I found this a very relevant question. Does anyone here know the exact mechanism? Sunspot number (#) is currently at 178. Similar years in terms of QBO and january sunspot number, ie. 57/58 (#203) and 78/79 (#167), featured major warmings in february. Labitzke ends the 2005 summary paper with the following conclusion: " The result of this paper is the introduction of the constructed annual mean of the solar cycle–QBO relationship. The differences of the solar signal in the two phases of the QBO are large and it is therefore necessary to stratify the data according to the phase of the QBO, in order to find the mechanism which transfers the direct solar signal from the upper stratosphere down to the lower stratosphere and to the troposphere. This new approach of an analysis of the solar signal may be useful for the interpretation of future model results." Before doing any extensive digging in the literature, is anyone familiar with more recent papers adressing the same question? Cheers, Ruben ps.: GFS12z indeed looks better. In the strat, at least.
  15. Ruben Amsterdam
    Well, it's a bit of a status quo. According to GFS, the vortex remains under wave-2 pressure at least the coming 240hrs. Chances are that it is allowed to breathe a bit more easily after this, and will ramp up temporarily in wind speed, gph, and temperature, like Chionomaniac said. I doubt it will ramp up to berserk-mode like we've seen last December.
  16. Ruben Amsterdam
    Let's hope for a knock-out in the third round According to NOAA, solar flux will increase the coming days (185-190). Penticton 10.7 cm FluxObserved 03 Jan 182Predicted 04 Jan-06 Jan 185/185/19090 Day Mean 03 Jan 146
  17. Ruben Amsterdam
    I agree. The double-sided (Asian and Atlantic) warmings we saw a while back are no longer as potent in recent runs. The attacks/warmings appear unable to penetrate the vortex (and get stranded in the surf-zone) and instead either subdue or circle around the vortex (conform the last two GFS runs; ofc. FI). Overall we can expect a reduction in mean zonal winds (except perhaps in the lower strat/trop at 70°NB, mentioned above), but I am less enthusiastic about our chances on a split/SSW within 14 days than I was at New Years Eve. Let's hope for January that the reduction in zonal wind is sufficient for some ML/HL blocking supported by the lower strat.
  18. Ruben Amsterdam
    After a rather underwhelming period around +144hrs, GFS12z is ramping up the warming from +216 onwards. Nothing is decided yet. At +300 the 1mb-split is back.
  19. Ruben Amsterdam
    EC (02-01) features a (short-lived/not-quite-there-yet) split at 10hpa at +168hrs with the vortex being able to recover afterwards. GFS00z (03-01) shows a similar picture. After the "split" the vortex reforms again, only to split again at the end of the run. EC looking pretty consistent at the end of runs. Only difference I can spot is the small warming near Greenland present in the most recent run (left). Now, Recretos, I know 2009 featured a really intense warming and split type SSW. To what extend is the current situation comparable to the situation in 2009?
  20. Ruben Amsterdam
    Well, the US-warming (let's refer to it that way) is already more pronounced in GFS06 at 120hrs then in GFS00z (may be wishfull thinking, tho). I think yesterdays 06z was too progressive, but we may still some large differences between ops. But maybe it's better to leave it to the experts The prolonged warming/pressure on the vortex at 1 hpa can only be a good thing, I guess. Edit: GFS06z downgraded the warming from +228 onwards. I do not like these downgrades/delays, Sebastiaan.
  21. Ruben Amsterdam
    Thanks Recretos, for your excellent post (please keep spamming ) I am aware that the GFS ENS is the same as the GEFS. That's why I mix them up. Perhaps better to be consistent with this terminology. Please excuse my English if it is not clear. By the way, I'm not that pleased with todays GFS0z. The small patch of warming over the American/Canadian sector does not amplify/intensify as we saw on the "good" runs (like yesterdays 06z). EC does not intensify this warming either. In the end, of course, these aren't bad charts, but I think we all prefer the agressive warming we saw on yesterdays 06z. It's good to see a significant reduction of zonal winds at 1hPa.
  22. Ruben Amsterdam
    Hi Aginob, Lars told us he will make these GEFS plots more often. Maybe it's also possible for him to make 30hpa plots I think they are usefull if we consider the limitations of the GFS ensembles (ie. model top and resolution).
  23. Ruben Amsterdam
    Reminds me of the song "One step forward, two steps back" by the Desert Rose Band. Luckily GFS06 makes a large step forward (one might even call it a leap at the end of the run). Cheers, Ruben
  24. Ruben Amsterdam
    GFS12z is not what I hoped for, unfortunetely. The vortex does get pushed towards the American Continent, though. But for now: happy 2014!
  25. Ruben Amsterdam
    Erm, guys? Lookin' good!
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